Girl delinquency A study on sex differences in - VU-dare
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Girl delinquency A study on sex differences in - VU-dare
Girl delinquency A study on sex differences in (risk factors for) delinquency Photography and cover design: Viewtography || www.floorknaapen.com Cover model: Lotte van der Vleuten Author: Thessa Wong ISBN: 978-90-8891-394-5 Printing: Proefschriftmaken.nl || Printyourthesis.com Published by: Uitgeverij BOXPress, Oisterwijk © 2012 Thessa Wong VRIJE UNIVERSITEIT Girl delinquency A study on sex differences in (risk factors for) delinquency ACADEMISCH PROEFSCHRIFT ter verkrijging van de graad Doctor aan de Vrije Universiteit Amsterdam, op gezag van de rector magnificus prof.dr. L.M. Bouter, in het openbaar te verdedigen ten overstaan van de promotiecommissie van de faculteit der Rechtsgeleerdheid op woensdag 18 april 2012 om 15.45 uur in de aula van de universiteit, De Boelelaan 1105 door Thessa Margaretha Loisie Wong geboren te Zeist promotoren: copromotor: prof.dr.mr. C.C.J.H. Bijleveld prof.dr. J.M. Koot dr. A. Slotboom Leescommissie: prof.dr. M. Dekovic prof. C. Kruttschnitt prof.dr. P.H. van der Laan prof.dr. N.W. Slot dr. F.M. Weerman Voor tante Karin TABLE OF CONTENTS Chapter 1 Introduction 9 Chapter 2 Prevalence of juvenile delinquency 25 Chapter 3 Risk factors for delinquency in adolescent and young adult females: A European review 41 Chapter 4 The sex difference in delinquency explained? Differential exposure and vulnerability in the parent and peer domain 63 Chapter 5 The sex difference in delinquency: Do girls need a bigger push? 89 Chapter 6 Sex and age differences in the risk threshold for delinquency 115 Chapter 7 General discussion 139 References 157 Publication list 173 Samenvatting (summary) 175 Dankwoord (acknowledgment) 179 Curriculum Vitae 181 7 Chapter 1 Introduction 9 10 For a long time, researchers generally neglected criminal behaviour of girls, most probably because committing crimes was seen as a male phenomenon with males outnumbering females in official statistics. However, the last decades the arrest rates for females have gone up in Western countries, like the United States and The Netherlands (Steffensmeier & Schwartz, 2009; Wong, Blom & Van der Laan, in press). This has led to more attention for girls’ crime involvement by scholars. As the number of arrested and adjudicated girls is rising, there is an increasing need for knowledge how to effectively cope with these delinquent females. After all, only when interventions target adequate criminogenic needs (i.e. important risk factors), will they be successful in reducing recidivism (Dowden & Andrews, 1999). Although researchers only recently became more interested in girl delinquency, there has been some research in the past about sex differences in delinquency (e.g. Bontekoe, 1984; Bruinsma, & Lissenberg, 1987; Dijksterhuis & Nijboer, 1987; Mertens, Grapendaal, & Docter-Schamhardt, 1998; Rutenfrans, 1989). However, this previous research had many limitations and therefore not much is known yet about the development and correlates of delinquent behaviour of girls. Without a doubt, most of the research on juvenile delinquent behaviour has focused on boys and much more is known about the origin of their behaviour. Theories about juvenile delinquency and interventions to diminish it are for that reason mostly based on research about males’ delinquent behaviour. And since the risk and promotive factors for girl delinquency are not decisively identified yet, it is not clear whether these theories and interventions are suitable for female delinquency. The first aim of the current dissertation is therefore to examine which factors are related to delinquency of girls and which of these are similar to those for boys. Furthermore, since the sex difference in the prevalence of delinquency is so prominent, but so little understood, a second aim of this dissertation is to search for explanations why girls are less involved in criminal behaviour than boys. How to study girl delinquency? Different approaches have been used to study girl delinquency. In the current paragraph three approaches (i.e. the add-and-stir, the female-only-focused and the cumulative risk approach) will be described and related to girl delinquency research in general. Add-and-stir approach The first approach, the so-called add-and-stir approach, is embraced by most researchers and studies the contribution of mainstream theories – mostly developed in research about male delinquency – to account for delinquent behaviour of girls (Hoyt & Scherer, 1998). In other words, this approach assumes that girls become delinquent for the same reasons as boys. 11 According to the control theory of Hirschi (1969), for instance, everybody is inclined to commit crimes, boys as well as girls. The reason that most people do not, is that they have learned that they might jeopardize the bonding they have with society when they become delinquent. This bonding consists of four elements: attachment to parents, teachers and peers; commitment to conventional institutions such as school or work; involvement in conventional activities such as sports; and belief in the validity of moral values and social norms. Although all four elements have a unique influence on delinquent behaviour, they also appear to be related to each other (Chapple, McQuillan, & Berdahl, 2005). Hirschi claims that these mechanisms can be applied to both males and females, but that girls, compared to boys, have higher quality relationships with friends and parents and achieve better in school. Because of their stronger bonds, girls have a lower tendency to commit offences. Another example of a mainstream theory often used to explain girl delinquency – also originally developed to explain delinquent behaviour of boys – is Moffitt’s developmental taxonomy (1993). According to Moffitt, at least two different types of offenders can be distinguished: life-coursepersistent delinquents and adolescence-limited delinquents. Life-coursepersisters, on the one hand, are thought to have behavioural problems already early in life and commit offences from early ages through adulthood. Their criminal behaviour is not only persistent, but also severe. The explanation for their behaviour is that they suffer from neurological deficits that are originated in pregnancy or were incurred during birth or after birth. These deficits can be manifested in cognitive, physical or behavioural problems. Furthermore, these juveniles are generally born in a high-risk environment that interacts cumulatively with their neuropsychological problems. Adolescence-limited offenders, on the other hand, show less severe delinquent behaviour and only commit offences during puberty when they experience a gap between their social and biological maturity, the so-called ‘maturity gap’. During this maturity gap, these adolescents want to be independent from their parents and show rebellious behaviour, such as committing (minor) offences. Delinquent behaviour can thus be explained by situational risks, not by background or personality risks. The group of adolescent-limited offenders is therefore much bigger than the life-coursepersistent group. Moffitt claims that these developmental trajectories can be found among males as well as among females. Females less often suffer from neuropsychological problems and therefore relatively few females follow the life-course-persistent trajectory (Moffitt, Caspi, Rutter, & Silva, 2001). A limitation of the add-and-stir approach is that researchers assume that girl delinquency can be explained in the same way as boy delinquency, without being sensitive to the possible differences between boys and girls in 12 terms of pathways to delinquency and context of crimes (Steffensmeier & Allan, 1996). The focus of theories in this approach is on gender neutrality and as such they preclude sex-specific mechanisms. Female-only-focused approach The second approach in female delinquency research, the female-onlyfocused approach, states that existing mainstream theories are not adequate to explain delinquent behaviour of females. Girls are thought to have different risk factors and hence need different theories that can explain their delinquent behaviour. Therefore, not mainstream, but female focused theories are used (Chesney-Lind, 1989; Hoyt & Scherer, 1998; Miller & Mullins, 2009). Such theories claim that patriarchal power relations are a reason for the sex difference in delinquency. In addition, researchers taking this approach, believe that it is the reality that males and females have different experiences in life because of their gender (Daigle, Cullen, & Wright, 2007). For instance, females are at larger risk of being victimized then males (Holsinger, 2000) or of being depressed (Calhoun, 2001). Also, they are supervised more closely than boys (Leaper, Anderson, & Sanders, 1998). For this reason, the pathways to crime of females are different from those of males. Also, it is thought that females who commit crimes are usually forced to do so through victimization by males, because of their economic disadvantage or because of other manifestations of gender inequality (Chesney-Lind, 1989; Gaarder & Belknap, 2002). A shortcoming of the female-only-focused approach is that researchers are only interested in unique female factors and assume that there are no shared factors and therefore do not examine these. These researchers even believe that studies should focus only on delinquent females and ignore delinquent males. In their point of view females are different from males anyway and therefore there is no need to compare findings with those for males. However, in order to know whether females are indeed different from males, males should be used as a comparison group. As a result, the femaleonly-focused view of female delinquency is, just like the add-and-stir approach, selective: it precludes gender neutral theorizing. Since the add-and-stir approach is not very informative regarding femalespecific pathways to crime and the female-only-focused approach neglects resemblances between males and females, girl delinquency should be examined through the integration of these two approaches. Especially while delinquent behaviour of girls is still less understood, it is essential in girl delinquency research to study as many possibly related factors, either shared or sex-specific and not to preclude any explanations. 13 Cumulative risk approach In line with this broad focus, a third approach is needed to supplement the discussed approaches. This is the so-called cumulative risk approach which asserts that it is a not a single risk factor that affects delinquency, but instead a whole range of factors that influence whether adolescents become delinquent or not. The more risk factors adolescents experience, the more likely they are to be delinquent, for boys as well as girls (Johansson & Kempf-Leonard, 2009; Loeber, Slot, & Stouthamer-Loeber, 2008; Van der Laan & Van der Schans, 2010). Because the cumulative risk approach is very flexible, it is an adequate approach to study girl delinquency. As a consequence of its flexibility, it is possible within this approach to integrate the add-and-stir and the femaleonly-focused approach. The cumulative risk approach thus allows to include shared as well as sex-specific factors in the study on girl delinquency. Furthermore, this approach captures the intrinsic covariation of risk factors (Luthar, 1993). The present dissertation investigates which factors are related to girl delinquency by considering those factors that are shared with boys, as well as factors that may be sex-specific. Factors are taken into account in the individual, family, peer and school domain. This cumulative risk approach provides the stepping stones for the development of theories on specific domains and factors to analyze through what mechanisms these domains and factors influence delinquent behaviour of girls. Previous research This dissertation is not the first one to study girl delinquency and sex differences in risk factors of delinquency. A number of previous studies have examined risk factors for delinquent behaviour of females. However, these studies did not integrate the discussed approaches. Studies either examined whether known risk factors for males could be applied to girls – and mainly found similarities between boys and girls – or they focused only on sexspecific factors – and found differences between boys and girls. In any case, no comprehensive picture is provided yet about delinquent girls. The studies of Rowe, Vazsonyi, and Flannery (1995), Moffitt et al. (2001), and Junger-Tas, Rbeaud, and Cruyff (2004) are examples of studies that examined whether known risk factors for males were related to girls’ delinquency. In the study of Rowe et al. (1995), 499 10-to-16-year old boys and girls were analyzed, but no sex differences were found in risk factors. Delinquent behaviour of both boys and girls was related to sexual experience, parental affection, parental encouragement, school achievement, anger, emotionality, impulsivity, deceitfulness, rebelliousness, and delinquent peers. Also Moffitt et al. (2001) concluded that the same risk factors predicted delinquency in girls as in boys (i.e. a young mother, a low 14 intelligent mother, deviant mother-child interaction, harsh or inconsistent discipline, living with a single parent, low socio-economic status, low school involvement, low intelligence, difficult temperament, hyperactivity, being rejected by peers, delinquent peers). Their conclusions were based on longitudinal analyses of delinquent behaviour from the age of 13 to 18 of adolescents in the Dunedin study. Some sex differences were found (that is, a higher vulnerability of boys for family risk factors), but according to the researchers these were not very consistent if different measurement strategies or statistical procedures were used. Junger-Tas et al. (2004), who carried out research among juveniles from eleven different countries, also concluded that no large sex differences could be found in the relations between delinquency and important risk factors such as family bonding, parental knowledge, the bond with teachers, school commitment, truancy, and number of friends. Hence, these studies found that boys and girls have similar risk factors for delinquency. However, the studies might have missed the unique risk factors for boys and girls, because they only focused on risk factors previously identified for boy delinquency. Not many studies are carried out yet that focused on sex-specific factors of delinquency. The ones that did examine sex-specific factors, mostly compared characteristics of delinquent girls with those of delinquent boys. They found some differences in characteristics between boys and girls. Delinquent girls appeared to have lower levels of self-esteem, lower quality parent-child relationships, lower family climates, to be more often raised in a household with a single parent or with domestic violence, and to be more often physically or sexually abused than delinquent boys (Belknap & Holsinger, 2006; Emeka & Sorensen, 2009; Gavazzi, Yarcheck, & ChesneyLind, 2006; Gover, 2004; Johansson & Kempf-Leonard, 2009). However, non-delinquent comparison groups were mostly not included and the samples were probably biased and it is therefore unclear whether these characteristics are indeed risk factors for delinquency. A more detailed discussion of these and other limitations of previous research will be discussed in a later paragraph. In any case, previous research is limited and therefore it is difficult to draw conclusions yet about risk factors of girl delinquency. The explanation of the sex difference in the prevalence of delinquency Next to knowledge about girl delinquency, it is important to gain knowledge about the nature of the sex difference in the prevalence of delinquency. Being able to explain why girls are less often delinquent than boys can facilitate our understanding of girl delinquency. Although the add-and-stir, female-only-focused and the cumulative risk approach have their limitations, they contain elements that can be used to generate hypotheses to explain the sex difference in the prevalence of delinquency: the differential risk exposure hypothesis, the differential risk vulnerability hypothesis and the 15 differential threshold hypothesis. All these hypotheses will be examined in this dissertation. The differential risk exposure hypothesis The differential risk exposure hypothesis assumes that the origin of delinquency is similar for both sexes, but that boys are exposed to higher levels of these similar risk factors than girls and are therefore more likely to become delinquent (Keenan, Loeber, & Green, 1999; Lahey et al., 2006; Moffitt et al., 2001; Murray, 2002). For the sake of simplicity, the hypothesis will be referred to as the exposure hypothesis in the rest of this dissertation. Differential exposure regards the level of risk and not the presence of risk. For instance, adolescents are at little risk to become delinquent if they have only one delinquent friend, but if all of their friends are delinquent, their risk for delinquency is much higher. The exposure hypothesis states that girls are exposed to lower level of risks and are therefore less likely to become delinquent. To illustrate this, let us go back to the developmental taxonomy of Moffitt (1993). Girls were found to have less (i.e. were less exposed to) neurological deficits than boys and, according to Moffitt, therefore there are fewer girls who follow the life-course-persistent trajectory. Along the same line of reasoning, girls are thought to be less often delinquent because they have higher levels of so-called promotive factors than boys: Hirschi (1969) claims that girls have (i.e. are exposed to) stronger attachment to their family and stronger bonds to school than boys, and are therefore more likely to be withheld from delinquency. Girls thus are exposed to more protection in terms of bonds and are therefore less often delinquent. In this dissertation, it is examined whether sex differences in exposure can explain the sex difference in the prevalence of delinquency. The hypothesis is confirmed if the association between sex and delinquency is not significant anymore when differences in exposure are taken into account. Previous research indeed found that differential exposure could partly explain the sex difference in delinquency. Moffitt et al. (2001), for instance, found that because boys were exposed to higher levels of harsh parental discipline, neuro-cognitive risk, hyperactivity and peer influences than girls, part of the sex difference in the prevalence of delinquency was explained. Messer, Goodman, Rowe, Meltzer, and Maughan (2006) found as well that higher exposure of boys to harsh punishment, neuro-cognitive risk and peer problems accounted for the sex difference in delinquency, as well as lower reading performance of boys and higher prosocial behaviour of girls. These factors were all assessed through parents and teachers though, and therefore may contain gender bias. Differences in parental supervision (i.e. girls were controlled more by their parents than boys) could also partly explain the difference between boys and girls in delinquency (Junger-Tas et al., 2004). Sex differences in school problems and in the quality of relationships with parents did not contribute to the explanation though. Differential exposure 16 regarding the quality of the parent-child relationship (i.e. girls higher quality than boys) did seem to partly explain sex differences in serious delinquency (Fagan, Van Horn, Hawkins, & Arthur, 2007). Findings regarding the parent-child relationship appeared to be more consistent when mothers and fathers were considered separately: boys were found to receive more paternal affection than girls, whereas girls were found to receive more maternal affection (Fagan et al., 2007; Rowe et al., 1995). The differential risk vulnerability hypothesis Another possible explanation for the sex difference in delinquency, the differential risk vulnerability hypothesis, states that girls and boys are differently vulnerable for risk and promotive factors (Lahey et al., 2006; Moffitt et al., 2001; Murray, 2002). This indicates that different associations exists between risk and promotive factors on the one hand and delinquency on the other. Vulnerability can be different in two ways. First, factors can be associated with delinquency for one sex, but not for the other. This would imply that boys and girls have completely different risk and promotive factors for delinquent behaviour. In addition, differential vulnerability can signify differences in terms of the strength of the association between factors and delinquent behaviour. This is when factors are related to delinquency of both boys and girls, but have a stronger relationship to delinquency for one of the sexes. In other words, even if delinquency of boys and girls is affected by the same risk factors, these may still have a different effect on them. For instance, it might be that delinquency of both boys and girls is affected by having delinquent peers, but that boys are more sensitive to peer influences than girls. This would result in differential vulnerability towards delinquent peers. It should be noted that the two types of vulnerability are actually similar to each other, because a non-significant relationship between a factor and delinquency is similar to an extremely weak relationship. The consequences are different, however: in case of the first type of vulnerability, the factor is uniquely related to delinquency of one sex, whereas in case of the second type of vulnerability, the factor is a risk for both boys and girls, even though it is more relevant for one of them. According to the vulnerability hypothesis, girls are less likely to be delinquent than boys, because boys are more vulnerable for risk factors than girls, or have more risk factors they are vulnerable for (Lahey et al., 2006; Moffitt et al., 2001; Murray, 2002). The same goes for promotive factors: girls might be more susceptible for promotive factors than boys or might be sensitive to more promotive factors, and therefore are less inclined to commit offences. In this dissertation an attempt is made to test whether differential vulnerability could explain the sex difference in the prevalence of delinquency. If differences in vulnerability are taken into account and sex cannot predict delinquency anymore, the vulnerability hypothesis is confirmed. 17 In the previous paragraph, prior findings about differences in risk factors between boys and girls were already discussed. However, none of the studies that examined whether boys and girls had different risk factors, tested the vulnerability hypothesis: whether differences in the effect of risk and promotive factors can explain the sex difference in delinquency. In this dissertation, the exposure hypothesis and the vulnerability hypothesis are also tested concurrently. That is, it is very well possible that girls are less exposed to risk factors than boys and at the same time are less vulnerable for the risk effects, or not vulnerable at all. In that case one of the hypotheses may not by itself be able to account for the difference in delinquency between boys and girls, but in unison the two hypotheses have more explanatory power. The two explanations should therefore be examined concurrently. As far as we are aware, no previous study has done so. The differential threshold hypothesis The third hypothesis to be tested that aims to explain the sex difference in delinquency is the differential threshold hypothesis. Please note that for the sake of simplicity the hypothesis is referred to as the threshold hypothesis. This hypothesis claims that the more risk factors someone has, the more likely he or she is to become delinquent (Eme, 1992). This implies that people will only commit offences if they have a certain number of risk factors. This particular number has been identified as the ‘threshold’ for delinquency. A threshold is a cut-off value from which point onwards the probability to be delinquent is larger than the probability not to be delinquent. The threshold hypothesis asserts that this threshold is higher for girls, which explains why delinquency is less common among girls. Not many studies have examined whether girls indeed have a higher threshold than boys. Existing studies suggested that more risks are needed for girls to become delinquent, but they have used select samples and did not operationalize the threshold properly. Alemagno, Shaffer-King, and Hammel (2006), for instance, considered the number of risk factors of 250 boys and girls who were incarcerated and found that detained girls had more risk factors than detained boys. The same was found by Van der Laan and Van der Schans (2010) regarding family risks. They showed that arrested girls appeared to be exposed to more risk factors in the family domain than arrested boys. They also found that arrested boys had a higher number of risky lifestyle factors compared with arrested girls though. Prior studies did not investigate the threshold as such, but instead compared the number of risk factors of delinquents with those of nondelinquents. In order to adequately examine (sex difference in) the threshold, it is essential to assess the threshold itself. Put differently, the exact ‘tipping point’ should be identified for boys and girls. 18 In addition, it is possible that the threshold differs by age since the delinquency prevalence of boys and girls varies by age and criminal careers also develop differently for boys and girls (Junger-Tas, Haen-Marshall, & Ribeaud, 2003; Wong et al., in press). As Moffitt (1993) suggested, during adolescence boys and girls often commit crimes, as an expression of the maturity gap they experience. Therefore, during puberty, delinquent behavior is almost normative behavior, also for girls. Besides, since girls’ delinquency peaks earlier than that of boys, i.e. at age 15 versus at age 16 (Junger-Tas et al., 2003; Slotboom, Wong, Swier, & Van der Broek, 2011), the age at which delinquent behavior is relatively most common, differs between the sexes. Limitations of previous research about girl delinquency Previous studies about girl delinquency and about explanations for the sex difference in delinquency had a number of methodological limitations. First, many girl delinquency studies – especially those that considered sex-specific factors and those that considered the threshold hypothesis– were carried out in juvenile justice institutions or with a sample of arrested or adjudicated girls. Since it is very likely that girls who are arrested or incarcerated are a select group, results from these studies probably suffer from selection bias. Investigating the characteristics of these girls therefore only resulted in knowledge about girls that are involved in the juvenile justice system (i.e. risk factors for delinquency, getting arrested, and incarcerated), but not in knowledge about delinquency per se. Whether arrested, adjudicated or incarcerated girls are indeed a special group of girls is not verified yet, but indications in this direction can be made if we consider the juvenile ‘prosecution gap’, i.e. the difference between the number of offenses committed and the number of offenses prosecuted (Rouwette, Van Hooff, Vennix, & Jongebreur, 2007). A longitudinal study from Farrington et al. (2003) showed with data from the US that according to self-reports, 85.9% of the juveniles had committed a crime at least once as a 11 to 17 year old, whereas only 34.0% of them was referred to court for at least one offence. For females the prosecution gap appears to be even bigger than for males (for more details, see Chapter 2) and, compared to their male counterparts, the arrested and prosecuted females seem to be a group even more select. For instance, Sealock and Simpson (1998) found that juvenile females were relatively less often arrested than juvenile males for crimes. Also, if they were arrested, they were relatively less often prosecuted compared to males, even if it was taken into account that females commit less serious crimes than males (Jeffries, Fletcher, & Newbold, 2003; Spohn & Beichner, 2000; Williams, 1999). Also in the Netherlands, the prosecution gap of girls appeared to be bigger than of boys. Van der Geest and Bijleveld (2008) examined characteristics of institutionalized boys and found that according to self-report 78% of the boys had committed one or more offences before 19 admission to the institution, whereas 62% of the boys was convicted for an offence before admission. Girls from the same institution were examined by Megens and Day (2007) and showed that while 75 per cent had committed at least one offence before admission, only 41% was prosecuted for an offence. These results all suggest that the juvenile justice system is more ‘lenient’ towards girl offenders than towards boy offenders. However, there are also indications that girls receive a harsher punishment for minor offences; especially in the US where juveniles are adjudicated for status offences, such as truancy and running away (Hoyt & Scherer, 1998; Rosenbaum & Chesney-Lind, 1994). In any case, research that involves only arrested or incarcerated girls is not suitable to investigate all delinquent behaviour of girls. A better way of examining girl delinquency might be by using selfreported delinquent behaviour of a population-based sample. Second, in many studies there was a lack of a non-delinquent comparison group. Without such a comparison group it is difficult to conclude whether certain factors are indeed risk factors, since it might be that all girls (and not only delinquent girls) score high on these factors. This can only be tested with a comparison group. Third, previous research on girl delinquency and on explaining the sex difference in delinquency was often based on small samples. With small samples, it is difficult – if not impossible – to detect effects. However, since delinquency among girls has low prevalence, studies have difficulties finding a group of delinquent females that is large enough to research girl delinquency with enough power. In order to be certain to have a sufficient number of delinquent girls, researcher therefore often focused on samples of juvenile justice females. Fourth, many studies do not include both boys and girls. Many studies that only contained girls in their samples, compared their results with previous boys’ studies. However, with such a comparison it is not clear whether differences found between girls and boys are actual differences or are caused by method differences between the studies. To accurately examine sex differences in risk and promotive factors, information about boys and girls should be assessed in the same manner, preferably within the same study. Fifth, studies that include girls in their samples, usually have no or only a short follow-up period. Without longitudinal data, however, no conclusions can be drawn about causal relations of factors (Singer & Willett, 2003). Moreover, it is known that the prevalence of offending varies greatly by age and different domains and factors can be important for delinquency at different age periods. Much research has been carried out with large selfreport studies that have followed males for a (long) period of time, with studies such as the Pittsburgh Youth Study, the Cambridge Study, and the Montreal Longitudinal Study. Although there also exist some large studies that include females (i.e. the Pittsburgh Girls Study, the Rochester Youth 20 Study, The Denver Youth Study, RADAR, the Dunedin Study, Trails), not much research has been done yet with longitudinal self-reported female delinquency data. Sixth, and this applies actually to delinquency research in general, much attention has been paid to risk factors, but hardly any attention has been paid to promotive factors or to the cumulative effect of risk and promotive factors. However, although risk factors can increase the likelihood of becoming delinquent, promotive factors can decrease this likelihood. Risk and promotive factors can thus be of similar importance and should therefore receive the same amount of attention in research. Most delinquency studies define their factors in such a way that they all represent risk factors. For instance, not supervision, but lack of supervision is examined, assuming a risk effect of low supervision. However, whether delinquency is related to high supervision, low supervision or to both (i.e. whether supervision has a risk effect, a promotive effect, or both) is generally never tested. Aims and overview of the thesis The central objectives of this dissertation are twofold. The first objective is to establish an overview of factors related to delinquent behaviour of adolescent girls and to identify which of those factors are unique for girls and which of them are shared with boys. To start, a summary is given of risk factors for girl delinquency found in previous European research and a comparison is made with risk factors for boy delinquency. Subsequently, it is empirically tested whether adolescent boys and girls differ in factors related to delinquent behaviour. The second objective is to explain the sex difference in delinquency during adolescence. Why is it that girls are less likely to commit offences than boys? This will be examined by testing three hypotheses that might explain the sex difference in delinquency: the exposure hypothesis, the vulnerability hypothesis and the threshold hypothesis. To demonstrate the extent of the sex difference in delinquency, chapter 2 will start with an outline of how the prevalence of delinquency differs between boys and girls in the Netherlands. Because it is rather difficult to measure the prevalence of offending behaviour, both official records as well as self-reported data are used. In presenting the prevalence, a distinction is made by type of offence and by age. In addition, the trends of self-reported delinquency between 1996 and 2005, and for official records until 2007, will be displayed. Chapter 3 reviews European research on risk factors for delinquency in adolescent and young adult females. All research carried out in European countries between 1984 and 2009 will be reviewed that examined delinquent behaviour of females aged 12 to 25 and that included a comparison group of non-delinquents. For inclusion in the review, it is essential that males and females were examined separately. To analyze whether the factors are 21 unique risks for girls or not, risk factors are compared with those for male delinquency. In chapter 4, it is shown which factors in the parents and peer domain are related to boy and girl delinquency. Furthermore, two hypotheses to explain the sex difference in the prevalence of delinquency are tested: the exposure hypothesis – sex differences in exposure to factors explain the difference in delinquency – and the vulnerability hypothesis – sex differences in associations between factors and delinquency explain the difference in delinquency. It is not only examined whether differential exposure and sensitivity can indeed explain why girls are less often delinquent than boys, but also whether these operate simultaneously. Data of the first measurement of the RADAR study is used, an ongoing Dutch prospective cohort study, to examine the hypotheses. Adolescents were then 12 or 13 years of age. Chapter 5 investigates the third explanation for the sex difference in delinquency: the threshold hypothesis, that is whether more risk factors are present for girls to increase the probability to be delinquent than for boys. Previous research suffered from many limitations and therefore never adequately tested the threshold hypothesis. In this chapter the threshold is assessed in a similar way, by comparing the risk level of delinquent girls with those of delinquent boys, but improves previous research by taking into account risk and promotive factors and a non-delinquent comparison group. Again, data of the RADAR study will be used, only now data of the second and third waves when adolescents were aged 13 to 15. Chapter 6 goes a little further into the threshold research by identifying the exact location of the threshold (i.e. the tipping point) for boys and girls and by including sex-specific factors in determining the risk level. Furthermore, age-graded effects are studied in the sense that it is examined whether there are sex differences in this threshold for delinquency at two different age periods: in late childhood (ages 10 to 12) and in adolescence (ages 13 to 16). The chapter will again provide an overview of unique and shared risk and promotive factors for girls at the developmental stages. Now, data of two studies from the US are used: the Pittsburgh Youth Study and the Pittsburgh Girls Study. Finally, chapter 7 presents an overview of the results found in the previous chapters. In addition, it shows what the unique and shared risk factors are for girl delinquency in adolescence and to what extent the three hypotheses could explain the sex difference in delinquency. The chapter also reflects on the methodological strengths and on limitations of the dissertation and implications for practice and theory. This final chapter will also provide an agenda for future research. 22 What this dissertation adds to the literature on girl delinquency Not much research has been carried out on girl delinquency and on the explanations for the sex difference in the prevalence of delinquency. Existing research was, as explained, limited. This dissertation will improve on many of these limitations. To make sure that results are not biased because of selected samples, randomly selected population samples are used in the empirical chapters and a non-delinquent comparison group is included. Also, boys and girls are compared without any methodological disparities. Furthermore, longitudinal data are used whenever possible. Moreover, this dissertation is the first in examining the exposure hypothesis and the vulnerability hypothesis concurrently and by testing directly whether they can explain the sex difference in the prevalence of delinquency. In addition, this dissertation is the first in examining the threshold properly by including risk and promotive factors, a non-delinquent comparison group and, lastly, by identifying the exact location of the threshold. 23 Chapter 2 Prevalence of juvenile delinquency An extended version of this chapter was published as ‘Wong, T. M. L., Blom, M., & Van der Laan, A. (in press). De inhaalslag van vrouwen? Omvang, aard en trends in criminaliteit onder meisjes en vrouwen. In A. Slotboom, M. Hoeve, M. Ezinga & P. van der Helm (Eds.), Criminele meisjes en vrouwen: Achtergronden en aanpak. Den Haag: Boom Juridische Uitgevers.’ 25 26 This chapter describes the prevalence and time trends of delinquency of 12to-18-year old boys and girls in the Netherlands. Because every method of determining the prevalence of delinquency has limitations it is difficult to establish how many juveniles offend. Therefore, it is wise to use more than one method to determine this prevalence. In this chapter, two methods are considered: official records and self-reports. Data sources and limitations Official records Official records pertain to juveniles who were arrested because they were suspects of a crime. Absolute numbers as proportions related to subgroups (e.g., the proportion of 12-to-18-year old males versus females who were arrested) are presented here. These relative numbers can be used to compare groups (such as boys and girls) with each other, as well as to make comparisons with prevalence numbers from self-reports of delinquency. To make an optimal comparison possible with self-report, the 2005 records will be used in this study. A serious limitation of official records is that not all offences that are actually committed become known to the police. For instance, those offences that involve victims who do not report to the police, or offences without victims are not visible in official records. Moreover, for many crimes, the police is not able to identify the offender. The average proportion of crimes that are solved by the police in the Netherlands is 22 per cent (Eggen, 2009). Besides, police records reflect the priorities and effort of the police and therefore offenders who commit those offences that are within these priorities are probably more likely to be identified and arrested than others (Blom, Van der Laan, & Huijbregts, 2005). Because of all this, there is a large so-called dark number of crimes. The dark number refers to those crimes that are committed but not known to the officials. Self-reports One way to get a grip on this dark number is to use so-called self-reports of criminal behaviour. In self-reports, people report themselves which crimes they have committed in a particular time period. The self-reported information used in this chapter is obtained from the WODC Youth Delinquency Survey (WODC YDS). This is a cross-sectional survey, conducted every three years amongst a representative sample of Dutch juveniles aged 10 to 17. We used the information gathered in the first three months of 2005. The sample was randomly selected from the General Municipal Personal Records Database (GBA). Of all the juveniles approached, 68 per cent were willing to participate. This resulted in 1,460 juveniles interviewed. The analyses are weighted by a number of background characteristics (i.e. gender, age, ethnic background, education level, degree of urbanization, and region) to make the results representative 27 for all juveniles in the Netherlands (for more details, see Van der Laan & Blom, 2006). For a total of 33 offences, the juveniles reported whether they had committed them or not in the previous twelve months. Note that the reference period is the twelve months prior to the first quarter of 2005 and therefore not completely similar to that of the official records. Two rule violations (i.e. dodging and using fireworks) are not taken into account in this chapter, since these are not as serious as the other offences and their prevalence is relatively high so that their influence on the prevalence numbers would be (too) large. Furthermore, this way the numbers are more comparable to those in the official records. Only the prevalence of the remaining 31 offences will thus be reported on. The self-report method also has limitations. Firstly, the validity of selfreport is dependent on the honesty and may seriously be jeopardized by social desirability of the respondents (Farrington, 1973). Also, respondents might be afraid that their anonymity is not ensured which may lead to underreporting (Hessing & Elffers, 1995). However, some respondents might also overreport because they like to brag or because they report about offences outside the reference period (Nijboer, 1995; Sudman, Bradburn, & Schwarz, 1996). However, several researchers have shown that self-report is a sufficiently reliable and valid method for obtaining prevalence data on delinquency (Thornberry & Krohn, 2000; Van der Heijden, Sijtsma & ’t Hart, 1995). Another limitation of self-reports is that these are mostly focused on common crimes and less on serious crimes. Therefore, many serious offences be under assessed with this method. In the WODC YDS this limitation is considered by taking more serious crimes into account. However, the focus is still on more common (less serious) offences. Prevalence of different offences In Table 2.1 the prevalence of the 31 self-reported offences is presented. Of all girls, 37.6% reported to have committed at least one offence in the previous year. The prevalence of public order, property and minor violent offences is about equal (around 20%). The offences mostly committed by 12-to-18-year old girls were hitting without injury (13.4%) and spoiling walls and public transport (12.7%). More boys than girls reported to have committed an offence, that is 52.3 per cent of the boys indicated to have committed one offence or more. The prevalence of offending in boys was therefore 1.5 times the prevalence in girls. Also in case of separate offences, the prevalence in boys was higher than in girls for almost all offences. For some offences the prevalence in boys and girls was similar; regarding changing price tags and shoplifting up to 10 euros, the prevalence in girls was higher. Just like girls, most boys reported that they have hit somebody without injuries (19.8%). Besides, many boys reported to have stolen at school or work (17.9%) in the reporting period. 28 Table 2.1 Prevalence of self-reported delinquency in 2005 in the previous twelve months amongst 12-to-18-year olds in the Netherlands, by sex (%) Girls Boys (n = 552) (n = 572) 19.5 29.4* Vandalism and public order offences Damaged or destroyed a vehicle 1.1 2.7* Damaged or destroyed a house 0.9 2.0 Damaged public transport 1.4 2.3 Damaged something else 3.8 8.0* Soiled walls or public transport 12.7 12.2 Miscall regarding color 8.1 15.8* Miscall gay 2.7 7.0* 20.6 29.9* Property offences Changed price tags 8.0 4.5* Shoplifting < 10 euro 7.5 4.8* Shoplifting > 10 euro 0.9 0.3 Stole anything from school or work 9.0 17.9* Bike or scooter theft 1.7 3.8* Stole anything from outside car 0.2 1.9* Stole anything from car 0.0 0.0 Purse snatching 0.4 0.6 Burglary 0.6 1.5 Buying stolen goods 4.0 9.2* Selling stolen goods 1.8 3.5 20.8 29.6* Minor violent offences Threatened somebody 11.0 13.8 Hitted somebody, no injury 13.4 19.8* Hitted somebody, with injury 6.3 12.9* 0.9 1.6 Serious violent offences Threatened to steal 0.0 0.2 Robbery 0.0 0.0 Hurt somebody with weapon 0.9 0.5 Forceful sex 0.0 0.9* 2.6 7.8* Possession of weapon Weapon when going out 2.6 7.8* 2.2 2.9 Drug offences Dealing softdrugs 2.1 2.5 Dealing partydrugs 0.4 0.5 Dealing harddrugs 0.0 0.0 6.5 8.9 Internet offences Sending viruses 1.0 3.0* Threat through internet 5.9 7.3 Total offences One of more offences committed 37.6 52.3* * p < .05 In 2005 more than 5,300 girls aged 12 to 18 were arrested as crime suspects. This is about 1 per cent of all 12-to18-year old girls in the Netherlands (See Table 2.2). Relatively speaking, many girls were arrested because they were suspected of committing a property offence (0.4% of all Dutch girls). Most often this was because they had committed aggravated 29 thefts (such as burglary or theft with a group of people), although girls were also arrested for simple thefts. Violent and public order offences were less common among girls (respectively 0.3% and 0.2%). Regarding the separate offences, girls appeared to be most often arrested as a suspect of a violent offence against a person. The number of boys who were suspects of a crime was much higher than that of girls, independent of the type of offence. In general, four times as many boys are as girls were arrested. Differences were most obvious regarding public order offences: the number of boys who were suspects of a public order offences was six times bigger than the number of females arrested for this. With regard to property and violent offences, four times as many boys as girls were arrested. Within the group of boys, the number of boys suspected of committing a public order, a property or a violent offence is almost equal. Table 2.2 Arrested suspects aged 12 to 18 in 2005, by sex (absolute and %) Girls Boys abs. % abs. % 1,329 0.2 8,440 1.4 Vandalism and public order offences Public order 921 0.2 5,088 0.8 The authorities 136 0.0 657 0.1 Other vandalism and public order offences 327 0.1 3,613 0.6 2,402 0.4 9,140 1.5 Property offences Simple theft 884 0.2 2,892 0.5 Aggravated theft 1,333 0.2 5,949 1.0 Other property offences 423 0.1 2,070 0.3 1,751 0.3 8,122 1.3 Violent offences Sex offence 13 0.0 622 0.1 Threat 350 0.1 1,873 0.3 Violence against persons 1,433 0.2 5,191 0.8 Robbery 132 0.0 1,570 0.3 470 0.1 3,477 0.6 Other offences Traffic offence 107 0.0 960 0.2 Drug offence 117 0.0 621 0.1 Weapons 47 0.0 858 0.1 Other 204 0.0 1,163 0.2 5,341 0.9 23,130 3.8 Total (at least one offence) Note. The sum of the sub categories can be larger than the total of the sub subcategories, since one person can be arrested for more than one offences. Many differences appear between data obtained from the official records and those obtained from the self-reports. Although almost 40 per cent of the girls reported in 2005 to have committed at least one offence in the previous year, not even 1 percent was arrested in that year. Even though the self-report survey asked after a number of less serious offences, this still illustrates the extent of the dark number, as the police only knows about a very small part of girl delinquency. It has to be noted, however, that self30 reports are especially adequate to measure frequently committed crimes that are less serious. The numbers therefore may not fully reflect criminal offences, but the less serious offences less frequently lead to an arrest. Regarding the type of offences, not many differences were found between self-reported public order, property and violent offences. Twenty per cent of the girls reported to have committed at least one such offence. Arrest rates for these crimes did differ, however. It appeared that more girls were arrested for a property offences than for a violent offence. Arrest rates for violent offences were higher though than those for public order offences. This comparison shows the difference between the two methods. From the police data, it appears as if girls less often commit violent or public order offences. The self-reports show, however, that girls are also quite likely to commit violent and public order offences. An explanation for this might be that girls are most often arrested for a property offence, since this is seen as a typical ‘girl offence’. In case of a violent of public order offence, the police might be less inclined to expect girls to be involved. Age The prevalence of delinquency for girls appears to be highest among 15year-olds, according to self-reports (see Figure 2.1). Almost half of the girls aged 15 in the sample reported to have committed an offence in the previous twelve months. To see whether there were age differences regarding various types of offences, a distinction will be made between public order, property and minor violent offences. It was not possible to look into all separate offences, since the prevalence then became too low to test for age differences. For every offence type the prevalence was also highest among 15-year-olds. Girls who were 12 years of age most frequently reported minor violent offences; those 15 years old minor violent and property offences and those aged 17 most frequently reported property offences. In comparison with boys, at every age, fewer girls reported to have committed an offence, also for separate kinds of offences. At age 12, differences between boys and girls were small. For boys, the prevalence was highest among 16-year-olds, which indicates boys have a later prevalence peak age than girls. Figure 2.2 shows the percentage of female and male juveniles arrested in 2005 by age. The curve for girls is in line with the general age crime curve (Farrington, 1986; Junger-Tas, 1992): the prevalence of delinquency increases with age, peaks in late adolescence and then decreases. Apart from level differences, the curves are similar for every type of crime. For every type of crime, the prevalence was highest among 15-year-olds, except for property crimes where the number of suspects was highest among 18-yearolds. There are a number of noteworthy differences between females and males. The most apparent sex difference is that, across all ages, the number of arrested males is much higher than that of females. Furthermore, while the peak age for females is at age 15, most boys were 19 years old when they 31 Figure 2.1 Prevalence of self-reported delinquency, by age Boys 80 70 Prevalence (%) 60 50 40 30 20 10 0 12 13 14 15 16 17 15 16 17 Age Girls 80 70 Prevalence (%) 60 50 40 30 20 10 0 12 13 14 Age Public order Property Minor violence Total got arrested. In addition, there at not many differences between the different types of offences for which boys were arrested, whereas there are differences for girls: at every age females were most often arrested for property offences. Thus, the higher arrest rates for girls regarding property crimes mentioned before are present regardless of age. 32 Number of suspects per 100 peers Figure 2.2 Arrest rates per 100 peers, by age Males 8 6 4 2 0 Number of suspects per 100 peers Age Females 2 1,5 1 0,5 0 Age Public order Property Violence Total Girl offending peaks at the age of 15. This finding is rather certain, since it was found in the self-reported data as well as in the official records. After the age of 15, the prevalence of delinquency among women declines. For the different types of offences it was also found, in both data sources, that the peak age was 15 years. The one exception was regarding property crimes in official records which peaks at the age of 18 whereas in selfreported data it peaks at the age of 15. The biggest difference between selfreported data and official records was found for 12-year-old girls: although 33 there are hardly any girls arrested at the age of 12, almost 30 percent of these girls reported to have committed an offence. A noteworthy difference between boys and girls is that delinquency peaks at an earlier age for girls than for boys. This appeared from selfreported data as well as from official records. Although the peak age for girls is 15 years, the peak age for boys is 19 years according to official records and 16 years according to self-reported data. Since no self-reported data existed beyond the age of 17 it cannot be determined what the development of the prevalence is after this age and therefore there might be another peak age than 16 years. The difference in official records is rather large. An explanation might be that because girls have an earlier puberty than boys and reach adulthood at an earlier age, they might be younger when they start offending, but also when they desist from delinquent behaviour (Haynie, 2003). Time trends After considering sex differences in the prevalence of different (types of) offences and at different ages, trends in delinquency prevalence over time will be described. For the trends in self-reported delinquency the prior measurements of the WODC YDS were used from 1996, 1998 and 2001 (for more details, see Van der Laan & Blom, 2006). In Table 2.3 the delinquency prevalence can be seen for these years and for 2005 for girls as well as boys. The prevalence numbers only consider native Dutch juveniles, since the measures are not well comparable for juveniles with a different ethnicity, as for immigrant juveniles non-random samples had been drawn. In addition, the table only contains those offences that are measured in a consistent way across years. Only small differences appear between the prevalence numbers over time. The prevalence of delinquency among girls varies to some extent between 1996 and 2005. The prevalence of damaging and soiling objects seems to increase from 1998. The prevalence of changing price tags or of having injured somebody increased between 2001 and 2005 (please note that this is only an increase between two measurement points) among girls. Regarding shoplifting and buying or selling stolen goods the prevalence seems stable: no clear increase or decrease can be identified. Hence, for some offences there was a small increase in prevalence, for others it 34 35 15,4 2005f (N=424) 11,7 13,2 5,3 5,8 9,7 Note. From Jeugddelinquentie: Risico’s en bescherming (p.100), A. M. van der Laan en M. Blom, 2005 , Meppel: Boom Juridische Uitgevers. a One of the offences in the sub category damaged objects. From 1998 to 2001 this category contained six different question, in 2005 four. All questions consider damaging a car; public transport; windows; a lamppost; phone booth; bus shelter. b One of the offences in the sub category shoplifting. In 1996 and 1998 juveniles reported on shoplifting of something with a value lower or higher than 10 guilders; in 2001 on shoplifting in general; in 2005 on shoplifting of something with a value lower or higher than 10 euros. c In 1998 to 2001 one question about buying or selling something that has been stolen; in 2005 these were two separate questions. d One of the offences in the subcategory to injure. In 1996 and 1998 it was not assessed. In 2001 and in 2005 two questions were asked: hitted somebody with injury; hurt somebody with weapon. e In the previous year. f In the previous 12 months. Table 2.3 Prevalence of self-reported delinquency in the previous 12 months amongst 12-to-18-year olds, by year (%) Girls Boys 1996e 1998e 2001f 2005f 1996e 1998e 2001f (N=413) (N=506) (N=410) (N=411) (N=477) (N=525) (N=432) Damaged objecta 4,4 3,5 3,9 4,6 18,4 14,9 12,4 Soiled objects 9,4 7,8 10,8 10,9 9,7 13,1 9,2 Shopliftingb 7,5 5,1 9,4 6,8 11,5 10,1 7,6 Changed price tags 5,9 8,2 4,3 Buying or selling stolen 4,2 3,3 3,8 3,6 12,0 8,2 6,9 goodsc Injured somebodyd 7,1 8,0 14,6 remained fairly stable. In general, the prevalence of delinquency thus increased slightly over time for girls. Delinquency prevalence is always smaller for girls than for boys, regardless of the assessed year. However, the prevalence of shoplifting decreased for boys, even below the level of that of girls. The prevalence of damaging objects also decreased over time. The prevalence of changing price tags or of injuring somebody increased between 2001 and 2005 among boys. It thus depends to a great extent on the type of crime how the prevalence has developed over time for boys. However, although for girls the prevalence of delinquency appeared to either increase or remain stable between 1996 and 2005, for boys the prevalence of some offences decreased over time. In Figure 2.3 it is shown how the percentage of girls who is arrested developed between 1996 and 2007. For every year, the increase or decrease in terms of percentages with reference to 1996 was presented.1 The number of arrested girls seems to be stable between 1996 and 2000 and to strongly increase from 2001. In comparison to 1996, the number of arrested girls in 2007 has almost doubled. The strongest increase can be found among the number of girls arrested for a public order offence: two and a half times more arrests in 2007 compared to 1996. Although the prevalence of public order offences is relatively low, the proportionate increase throughout the years was strong and therefore the difference with other types of crime has decreased. The number of girls that is arrested on suspicion of a violent offence more than doubled and of a property offence increased with more than half between 1995 and 2007. The number of arrested boys also increased after 2001, but less so than the increase among girls. This indicates that the sex difference in delinquency according to official records has decreased in this period. This is especially so for property offences. The number of boys arrested on suspicion of a property crime hardly changed in the period between 1996 and 2007 (i.e. -9%), whereas the number of girls increased with 66%. Many differences can be found between the time trends in delinquency according to self-reports and according to official records. Although the selfreported delinquency prevalence only slightly varied over time for girls, the official records show a strong increase of arrested girls between 2001 and 2005, that continues in 2006 and 2007 (years that were not available for self- 1 Official record in a particular year are gathered twice: once several months after the years has passed (the preliminary numbers) and once a year later (the final numbers). In case of preliminary numbers, there can be errors in registration and therefore numbers might be incomplete or over complete. For the period 1996 to 2000 only preliminary numbers were available and therefore a dotted line is used to display the delinquency prevalence in this period. 36 36 Figure 2.3 Time trends in the number of arrested 12-to-18-year olds per 100 residents from 1996 to 2007, by year (increase or decrease in comparison with 1996) Boys 260 240 220 200 180 160 140 120 100 80 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 Year 260 240 220 200 180 160 140 120 100 80 Girls 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 Public order Year Property Violence Total reported delinquency). Regarding specific types of crime, some similarities were found between the data sources. Although conclusions should be drawn with care given the fact that the self-reported data regard a (small) sample, the results imply that the prevalence of public order offences among girls somewhat increased between 1996 and 2005. This trend is in line with official records, although the latter show an increase much larger than the self-reported increase. It might be that the policy towards female suspects has been changed, especially from 2001. From 2003 the Dutch government 37 strongly focused on reducing juvenile nuisance (TK, 2002/2003a). It might very well be that this partly generated the rise in the number of arrested girls on suspicion of a public order offence. The increased attention for domestic violence, a policy program that started in 2002 (Ministry of Justice, 2002), may also be related to the rise in arrest rates of girls. Although this program started from the idea that females are often victims of domestic violence, the program might also have led to more female suspects of crime, since research suggests that violent crimes of girls are often committed within their own houses (Putallaz & Bierman, 2004). More attention for domestic violence could therefore have resulted in more female arrests. Since official records pertain to a select group of delinquents and this dissertation aims to gain knowledge about delinquent girls in general, in the following self-reported data will be used, collected in randomly selected population samples. Data has shown that the prevalence of delinquency among girls is lower than among boys. This dissertation attempts to explain this difference between boys and girls. 38 39 Chapter 3 Risk factors for delinquency in adolescent and young adult females: A European review Wong, T. M. L., Slotboom, A., & Bijleveld, C. C. J. H. (2010). Risk factors for delinquency in adolescent and young adult females: A European review. European Journal of Criminology, 7, 266-284. 41 This study reviews 30 European studies on risk factors for delinquency of adolescent and young adult females. Risk factors are compared with those for (adolescent) male delinquency. Risk factors unique for females are identified as well as risk factors shared by males and females. Sex differences in risk factors are mainly found for individual and family factors. Females and males differ less in school and peer risk factors. As studies zoom in more at specific domains of risk factors or specific types of delinquent behaviour, more differences emerge between males and females. Limitations of studies examining female delinquency are discussed and future research areas proposed. 42 Introduction Juvenile delinquency and its causes have been studied extensively. Many factors that put adolescents at risk of becoming delinquent have been identified, such as parental monitoring, physical abuse and neglect, having delinquent friends and low school achievement (Loeber, 1990; Thornberry & Krohn, 2003). However, such risk factors have been identified predominantly for males. Much less is therefore known about adolescent female offending and its aetiology. One reason often put forward for this is that female offending is generally less serious – so that there would be a less pressing need to study it – and its prevalence lower – which makes it more difficult to study. There are different explanations for the sex difference in delinquency. First, it is often assumed that female delinquency can be explained in the same way as male delinquency (Moffitt et al., 2001), but that females are less exposed to risk factors than males. A second explanation states that male and female delinquency have different causes. A third explanation is that females have a higher threshold for becoming delinquent than males. This means that, while they may be affected by the same risk factors as males, females have to experience more risk factors in order to start offending. When the threshold is passed by females, however, it is believed that the manifestation of delinquency is more severe than in males, the so-called ‘threshold effect’ (Loeber & Keenan, 1994). A number of meta-analyses and reviews of risk factors of (adolescent and young adult) female offending (Hoyt & Scherer, 1998; Hubbard & Pratt, 2002; Simourd & Andrews, 1994; Tankersley & Rycraft, 2007) have been carried out. These generated evidence for individual risk factors such as an antisocial personality, low intelligence, substance abuse, physical or sexual abuse, mental health problems, pubertal timing and low levels of self-worth. In the family domain, important risk factors are the quality of parent-child relationships, conflicts within the family, parental control, family violence and having caregivers with a history of substance abuse or delinquency. Mixed results were found for single parenthood and school achievement. Delinquent friends, gang membership and the quality of peer relationships were found to affect female delinquency. However almost all these reviews and meta-analyses were based on American studies. It is unlikely that risk factors found for US females can be generalized to European females. In the US, serious violence rates and gun use are higher than in Europe (Haen-Marshall, 1996; Junger-Tas et al., 2003), as is gang involvement (Hill et al., 1999; Klein et al., 2001). Furthermore, drug law violations figure more prominently in US official statistics (Tonry, 1999) and contrary to most European countries, in the US juveniles can be prosecuted for status offences like running away (ChesneyLind, 1999). Moreover, the income distribution in the US is much more skewed than in Europe, and the US does not have social welfare systems as 43 most European countries do, leading to greater income inequality and to more poverty (Alesina & Glaeser, 2004). This paper will provide a systematic overview of studies on adolescent and young adult female delinquency in Europe. The overview will list risk factors shared by males and females, as well as risk factors unique for genders. In that sense, the study aims to provide information that may shed light on the first and second explanation for the sex difference in offending. Whereas previous meta-analyses and reviews generally combined specific risk factors into larger clusters, we will examine risk factors separately. Method Sample of studies Computer searches of the databases Google Scholar, Psych Info and Science Direct were conducted to locate relevant studies, using the following key words: female delinquency, female offenders, female juvenile offenders, girl delinquency, risk factors, juvenile delinquency, gender and sex differences. We also traced the reference lists of studies. To make sure that every published and unpublished study considering female delinquency was included, we also contacted (developmental) criminologists from many European countries (the Netherlands, Belgium, The United Kingdom, France, Italy, Germany, Denmark, Finland, Sweden, Poland, Spain, Switzerland, Slovenia and Hungary) and asked them to refer us to any published or unpublished studies in their countries with at least an abstract in English, French or German (or Dutch). Various criteria were used for the selection of studies. First of all, studies had to assess delinquency, i.e. behaviour penalized by criminal law, and not simply ‘risky’ behaviour. Furthermore, if males were also addressed in the studies, it was essential that females were analyzed separately. Additionally, it was necessary that studies also considered non-delinquent females. Another criterion was age: only studies that sampled adolescents and young adults were selected (aged 12-25). Some studies pertained to adult females, but these were included if delinquency in adolescence or young adulthood was explicitly addressed. A last criterion was the year of publication: only studies published during the last 25 years (from 1984 to 2009) were selected. The search and selection resulted in 30 European studies (see Table 3.1). 44 45 10. 9. 8. Hoeve, 2008 The Netherlands Honkatukia, 1998 Finland Jolliffe & Farrington, 2007 England N = 330 (54.8% females) Age 13-22 N = 1254 (47.5% females) Age 15-19 N = 720 (47.8% females) Age 13-17 Table 3.1 European studies on female delinquency and its risk factors Authors Sample 1. Bijleveld & Wijkman, 2009 n = 1540 (48.1% females) The Netherlands Average age 20 2. Campbell, 1987 n = 64 (100% females) England Age 15-16 3. Farrington & Painter, 2004 n = 1013 (51.2% females) England Age 40 (risk factors from age 8) 4. Graham & Bowling, 1996 n = 1648 (about 50%) England Age 14-25 5. Hartjen & Priyadarsini, 2003 n = 387 (62.3% females) France Age 13-18 6. Hauber et al., 1987 n = 308 (57.1% females) The Netherlands Age 12-18 7. Hodgins et al., 2001 n = 13852 (48.7% females) Sweden Age 30 Odds ratio χ² Pearson correlations Hierarchical regression T-tests and χ² Official records Self report (23 items) Self-report (50 items) Self-report Official records 4 groups: non-offenders (*), offenders, violent offenders, persistent early starters (*) Self-report (28 items) Self-report (15 items) Self-report Zero-order correlations Self report (43 items) Unclear, most likely correlations t-tests ANCOVA Strategy of analysis Odds ratio Assessment delinquency Official records 46 Landsheer & Van Dijkum, 2005 The Netherlands Mansel, 2003 Germany Martens, 1997 Sweden McAra, 2005 England Oberwittler 2003 Germany 18. 17. 16. 15. 13. 14. n = 270 (58.1% females) Age 12-14 at T1 n = 2086 (48.2% females) Age 12-16 n = 502 (43.8% females) Average age 14 n = 4299 (50% females) Age 13 n = 5819 (52.1% females) Age 12-14 Study 2 n = 4500 (about 50% females) Age 14-15 n = 5056 (100% females) Age 16 n = 13852 (48.7% females) Age 30 The Netherlands Kemppainen et al., 2002 Finland Kratzer & Hodgins, 1999 Sweden Study 1 n = 10996 (48.4% females) Age 14-21 Sample Junger-Tas et al., 2004 3 different cultural clusters: Anglo-American (England and Wales, Northern Ireland, USA); north-west Europe (Finland, Germany, Belgium, the Netherlands, Switzerland) (*); southern Europe (Spain, Portugal Italy)(*) 12. 11. Authors Self-report (18 items) Self-report (18 items) Self-report Self-report (violence) Official records. 4 groups: early starter (*), adolescent limited (*), adult-onset, discontinuous, no crime (*) Self-report (28 items) Official records Study 2 Self-report Study 1 Self-report (30 items) Assessment delinquency χ² and hierarchical regression Correlation Hierarchical regression Longitudinal Hierarchical regression Correlation Logistic regression – Odds ratio T-tests Study 2 Logistic regression – Odds ratio Study 1 Gamma’s Strategy of analysis 47 Authors Piko et al., 2005 Hungary Rantakallia et al., 1995 Finland Riley & Shaw, 1985 England and Wales Ritakallio et al., 2005 Finland Scholte et al., 2007 The Netherlands Slotboom et al., 2005 The Netherlands Smith & McAra 2004 England Svensson 2004 Sweden Torstensson, 1990 Sweden Sample n = 1240 (47% females) Age 11-20 20. n = 11764 (48.9% females) Age 25 21. n = 751 (49.7% females) Age 14-15 22. n = 50569 (49.9% females) Age 14-16 23. n = 214 (49.5% females) Age 13-17 24. n = 1978 (45% females) Average age 13 25. n = 4144 (about 50% females) Age 15 26. N = 979 (48.4% females) Average age 14 27. n = 6825 (100% females) Age 30 4 groups: non-delinquents (*), delinquents from Child Welfare Committees (*), females with police-recorded crimes or serious drug use and females with police records ánd records of hard drug use 28. Van der Rakt et al., 2005 n = 932 (43.1% females) The Netherlands Age 12-14 at T1 29. Van de Schoot & Wong, in press n = 873 (66% females) The Netherlands Age 18-24 (*) In our review we only focused on these groups of the study (**) Test results are calculated ourselves with the available information 19. Logistic regression – Odds ratio χ²-test Logistic regression – Odds ratio Longitudinal Hierarchical regression Correlation Correlation Correlation t-tests (**) Longitudinal Logistic regression – Odds ratio Bayesian approach: various theories tested Official records Self-report (21 items) Self-report (6 items) Self-report (10 items) Self-report (18 items) Self-report (10 items) Official records Self-report (12 items) Self-report (13 items) Self-report (11 items) Strategy of analysis Hierarchical regression Assessment delinquency Self-reported (8 items) Variables We distinguish four clusters of factors related to delinquency: individual, family, school and peer factors. The individual factors are: birth complications, negative life events, personality, moral development, attitudes towards delinquency and other problem behaviour. Family factors are: parenting, family relationships and family situation. School factors are: school achievement, attachment and commitment. The last group of factors is peer factors: delinquent friends, number of friends and quality of relationships with peers. Analytic strategy To examine the risk factors of female delinquency adequately, the studies should be as comparable as possible. Therefore, we attempt to focus on results from bivariate analyses and avoid results from multiple regression analyses as this type of analysis cannot reveal the independent effects of risk factors, but instead the effect of a risk factor given the effects of other risk factors in the model. Results from a regression analysis are therefore only considered if no other results were reported, and we will indicate whenever this is the case. If hierarchical regression analyses were used, we will always discuss the results of the final model with all risk factors. If factors were inconsistently related to delinquency, in the sense that one bivariate analysis found an effect for a risk factor but another study did not, we report this inconsistency but leave the factor out of our summary tabulations. If however, a large number of studies reported a finding, and only one study deviated from this, we do report the factor as a risk factor, noting the diverging study. If a bivariate result for a risk factor in one study was not replicated in another study in a multivariate regression analysis, we do report the risk factor as the disappearance of the effect may be due to multicollinearity. These choices imply that if only one study included a certain risk factor and found an effect, we do include this risk factor in our final tabulations. Although this review focuses on overall delinquency, we have included results from studies that distinguish between different types of delinquency as well. We do not include them in our summary tabulations but do report them in the text. To discuss differences between risk factors for male and female delinquency, results for males and females within the same study are compared with each other, based on the p-value. Factors are considered similarly relevant to male and female delinquency if the factors are significantly related, in the same direction, to both male and female delinquency in the same study. Strictly speaking, we can only decide so after 48 the regression weights have been statistically tested against each other. Almost none of the studies have carried out such tests, though.2 Results The studies and a number of their properties are listed in Table 1. On average, the studies had considerably large sample sizes, ranging from 64 to over 50,000. Studies used either official records or self-reported delinquency. Most studies used population-based samples and most of these contained both female and male respondents; only two had a female-only sample. Some studies carried out multivariate (regression) analyses, most employed bivariate analyses. The studies came from 13 mainly West European countries. In discussing results, we first consider, for every cluster of factors, the risk factors found for female delinquency, followed by the differences found with factors for male delinquency. Individual factors Birth complication. No study found an association between birth complication and female delinquency (Hodgins et al., 2001; Kemppainen et al., 2002; Rantakallia et al., 1995). Male delinquency, however, was related to birth complications (Hodgins et al., 2001; Rantakallia et al., 1995). Negative life events. The number of negative life events predicted female delinquency (Junger-Tas et al., 2004 study 2). More specifically, female delinquency was related to crime victimization (Junger-Tas et al., 2004 study 2; McAra, 2005; Smith & McAra, 2004) and to having been harassed3 by an adult (McAra, 2005; Smith & McAra, 2004). Male delinquency is similarly related to certain negative life events (Junger-Tas et al., 2004; McAra, 2005; Smith & McAra, 2004); although the number of negative life events was not related to male delinquency (Junger-Tas et al., 2004). Personality. Low levels of self-control (Slotboom et al., 2005) and low intelligence (Kratzer & Hodgins, 1999; Rantakallia et al., 1995) were found to be related to female delinquency. Additionally, female delinquency was associated with high levels of aggression and disobedience (Hauber et al., 1987). Varying results were found for the relation between female delinquency and the level of impulsiveness (Hauber et al., 1987; McAra, 2 A complete overview of all results of all studies is available from the authors. Adult harassment was assessed by questioning: number of times in past year an adult stared at you so that you felt uncomfortable; followed you on foot; followed you by car; tried to get you to go somewhere with them; indecently exposed themselves to you (McAra, 2005). 3 49 2005; Smith & McAra, 2004) and risk-taking behaviour (Hauber et al., 1987; Smith & McAra, 2004). Findings for self-esteem were inconsistent, both high (Piko et al., 2005) and low self-esteem (McAra, 2005; Smith & McAra, 2004) were related to female delinquency. This is possibly due to the finding by Van de Schoot and Wong (submitted) that both low and high self-esteem were related to female and male delinquency. Regarding male delinquency, a relation was found with low general self-esteem (McAra, 2005; Smith & McAra, 2004) but not with high general self-esteem (Piko et al., 2005). Otherwise, delinquent males have the same personality characteristics as delinquent females (Hauber et al., 1987; Kratzer & Hodgins, 1999; McAra, 2005; Rantakallia et al., 1995; Slotboom et al., 2005; Smith & McAra, 2004), except for disobedience on which delinquent females scored higher than their male counterparts (Hauber et al., 1987). In addition, the relation between delinquency and low self-control was stronger for males than for females (Slotboom et al., 2005). Moral development. Svensson (2004) studied feelings of shame about delinquency towards friends, parents and teachers (i.e. the level of shame adolescents would feel towards others if they were caught committing an offences) and found that it was negatively related to female delinquency as well as male delinquency. Jolliffe and Farrington (2007) also distinguished between different types of delinquent behaviour (i.e. violence, fighting, theft from person, serious theft, shoplifting, vandalism and drugs use). They found that total empathy was related to violence and theft from a person, but not to overall delinquency. Low affective empathy was associated with theft, violence and shoplifting; low cognitive empathy was associated with theft only. For males, contrary to females, total and affective empathy were related to overall delinquency. These factors were also related to violence, fighting and vandalism. In addition, affective empathy was related to serious theft and shoplifting amongst males. Cognitive empathy was related to fighting, serious theft and vandalism. These results show that disaggregating by types of delinquency and by types of a certain factor can generate complex results about sex differences. Therefore, no conclusions on unique or shared factors can be drawn about empathy and delinquency. Attitudes towards delinquency. A positive attitude towards delinquency increased the risk of becoming delinquent for females as well as for males (Hartjen & Priyadarsini, 2003; McAra, 2005; Oberwittler, 2003; Smith & McAra, 2004; Riley & Shaw, 1985). Other problem behaviour. Delinquent females were more often depressed (Piko et al., 2005; Ritakallio et al., 2005), suicidal and substance abusing 50 (Piko et al., 2005) than non-delinquent females. For males, results regarding the relations between depression and delinquency are inconsistent (Piko et al., 2005; Ritakallio et al., 2005). Psychological wellbeing was related to male delinquency, but not to female delinquency (Junger-Tas et al., 2004 study 1). Male delinquency was related to substance abuse, but not to being suicidal. Figure 3.1 presents an overview of the unique and shared individual risk factors consistently related to male and female delinquency. It appears from this figure that quite a number of factors are shared by males and females. Victimization, a positive attitude towards delinquency as well as low selfesteem appear to be factors found repeatedly over studies. At the same time, some differences do emerge as well: females have a marked set of risk factors regarding internalizing problems. Also, the high number of life events for females is notable. Finally, only delinquent boys are marked by birth complications, possibly signalling increased risk for neurological damage. Figure 3.1 Unique and shared individual risk factors consistently related to female or male delinquency Unique factors for females High number of life events (1r) Disobedience (1r) High self-esteem (2+r) Depression (2r) Suicidal behaviour (1r) Shared risk factors Victimization (3+r) Being harassed by an adult (2) Low self-control (1) Aggression (1r) Low IQ (2+r) Low self-esteem (3) Being unashamed for parents, friends and teachers (1) Positive attitude towards delinquency (5) Substance abuse (1r) Unique factors for males Birth complications (2) Psychological wellbeing (1r) Note. The numbers between brackets indicate the number of studies that took the risk factor into account. Superscript r: results from all studies come from a regression analysis; superscript +r: results from some of the studies come from a regression analysis; superscript l: results from all studies come from a longitudinal analysis. superscript +l: results from some of the studies come from a longitudinal analysis Family factors Parenting. Inadequate parenting was found to be associated with female delinquency (Hodgins et al., 2001; Mansel, 2003). Hoeve (2008) took four different parenting styles into account and found that maternal and paternal 51 parenting styles affected female delinquency. Females with a permissive, poorly responsive mother, father, or both (i.e. moderately attached to adolescent, little response to adolescent’s needs, low demands on conformity) had the highest rates of delinquency. Looking more specifically into parenting practices, we can see that parental monitoring – parenting behaviour that considers the child’s whereabouts, activities and friends – was negatively related to female delinquency (Campbell, 1987; Farrington & Painter, 2004; Graham & Bowling, 1995; McAra, 2005; Piko et al., 2005; Riley & Shaw, 1985; Smith & McAra, 2004). Decreasing parental control through adolescence was positively associated (Honkatukia, 1998). Low parental involvement with school also puts females at greater risk to become delinquent (McAra, 2005; Smith & McAra, 2004). Inconsistencies were found for parental knowledge about activities (Junger-Tas et al., 2004 study 1; Martens, 1997), knowledge about friends was unrelated to female delinquency (Junger-Tas et al., 2004 study 1). Parental monitoring is closely linked to what adolescents and young adults actually tell their parents, i.e. child disclosure (Stattin & Kerr, 2000). Low child disclosure appeared to be related to delinquency of females (Riley & Shaw, 1985; Svensson, 2004). Females who are seldom at home, a factor reflecting parental monitoring, were found to be more likely to be delinquent (Martens, 1997). Monitoring also involves rules at home, which was negatively related to female delinquency (Slotboom et al., 2005) and with harsh discipline positively related (Campbell, 1987; Farrington & Painter, 2004; Mansel, 2003). Inconsistent results were found for rules about the time until when adolescents are allowed to go out. Physical abuse by parents was positively related to female delinquency (Piko et al., 2005) as was low parental trust towards children (McAra, 2005; Riley & Shaw, 1985). Some parenting factors were differently associated with male delinquency. First, males’ delinquency was affected by paternal, but not by maternal parenting styles. Neglectful, rather than permissive, parenting (i.e. unattached to adolescents, punish often, lowest demands on conformity) appeared to be positively related to male delinquency. Males having a father, or both parents, with a neglectful parenting style were most likely to be delinquent. Second, high parental knowledge about friends (Junger-Tas et al., 2004) was related to male delinquency, in contrast to female delinquency. Third, opposed to their female counterparts, males who were seldom at home were not more likely to become delinquent (Martens, 1997), nor were males who had been physically abused by their parents (Piko et al 2005). Inconsistencies were found for the relations between male delinquency and low child disclosure and low parental trust. Scholte et al. (2007) examined different types of delinquency and differential parental treatment among siblings. They found no predictive 52 value of differential parental treatment in their longitudinal analysis on theft, vandalism and violence. However, males’ vandalism and violent behaviour could be predicted by a less favourable treatment (compared to their siblings) by mothers. Quality of relationship with family members. Low parental warmth was found to be related to delinquency (Mansel, 2003; Slotboom et al., 2005). Landsheer and Van Dijkum (2005) longitudinally analyzed parental support, and found that female delinquency is related to low support of mothers, but not to that of fathers. The extent to which adolescents and young adults go out or spend time with family was not consistently related to female delinquency (Hartjen & Priyadarsini, 2003; Honkatukia 1998; Junger-Tas et al., 2004 study 1; McAra, 2005; Riley & Shaw, 1985). Low attachment and commitment to parents is related to female delinquency if studied bi-directionally (Graham & Bowling, 1995; Slotboom et al., 2005; Svensson 2004). However, in studies in which the predictive value of attachment or commitment on delinquency was examined in a multiple regression analysis, effects always disappeared (Hauber et al., 1987; Martens, 1997; Van der Rakt et al., 2005). The extent of conflicts that females have with their parents was related to delinquency (Mansel, 2003; McAra, 2005; Smith & McAra, 2004; Riley & Shaw, 1985). When relationships with mothers and fathers were examined separately, it appeared that both low quality mother-child and father-child relationships were related to female delinquency (Campbell 1987; Junger-Tas et al., 2004 study 1; Riley & Shaw, 1985). The associations between male delinquency and family relationship factors were partly similar to those of females. However, low support from mothers was not associated with male delinquency (Landsheer & Van Dijkum, 2005). Furthermore, the quality of mother-child relationship was inconsistently related to male delinquency. Disaggregating by type of delinquency, the quality of adolescent sibling relationships was related to female property offending. No relation was found with vandalism and violence (Scholte et al., 2007). In addition, no relation was found between sibling relationships and male offending. Family situation. Having a convicted father (Bijleveld & Wijkman, 2009; Farrington & Painter, 2004) or a delinquent sibling (Graham & Bowling, 1995; Farrington & Painter, 2004) was related to delinquent behaviour of females. Conviction of the mother, however, was not associated with female delinquency (Bijleveld & Wijkman, 2009; Farrington & Painter, 2004). Single parenthood was inconsistently associated with female delinquency as was socio-economic status. Living in a disadvantaged neighbourhood was related to female delinquency (McAra, 2005). No association was found between family size and female delinquency (Graham 53 & Bowling, 1995; Martens, 1997; Rantakallia et al., 1995; Riley & Shaw, 1985; Svensson 2004). Males differ in their family situation risk factors. Having a convicted father, a delinquent sibling and a convicted mother were related to male delinquency (Bijleveld & Wijkman, 2009; Farrington & Painter, 2004). Furthermore, single parenthood was related to male delinquency in almost all of the studies (except McAra, 2005). Associations with family size and low SES were comparable with those for females. Figure 3.2 presents an overview of the unique and shared family risk factors consistently related to male and female delinquency. We see that there are numerous differences between males and females, that have been replicated over several studies. The mother appears to play a unique role in female delinquency, for both males and females neglect, discipline and conflicts appear to be prominent. Figure 3.2 Unique and shared family risk factors consistently related to female or male delinquency Unique factors for females Maternal parenting style (1) Low child disclosure (2) Being seldom at home (1r) Physical abuse by parents (1r) Low parental trust (2) Low maternal support (1r,l) Low quality mother-child relationship (3) Shared risk factors Inadequate parenting (father or both parents) (3) Paternal parenting style (1) Overall parental monitoring (7 +r) Decreasing parental monitoring (1) Low involvement parents in school (3) Small number of rules at home (1) Harsh discipline (3) Low parental warmth (2) Conflicts within family (4) Low quality father-child relationship (2) Convicted father (2) Delinquent sibling (1) Living in a disadvantaged neighbourhood (1) Unique factors for males High parental knowledge about friends (1) Convicted mother (2) Single parenthood (9) Note. The numbers between brackets indicate the number of studies that took the risk factor into account. Superscript r: results from all studies come from a regression analysis; superscript +r: results from some of the studies come from a regression analysis; superscript l: results from all studies come from a longitudinal analysis. 54 School factors School achievement. School level and its relation with female delinquency had inconsistent results. The same was found for school achievement – within school levels. Concerning males, all studies found low school achievement to be related to delinquent behaviour (Hartjen & Priyadarsini, 2003; Hauber et al., 1987; Junger-Tas et al., 2004 study 2; Rantakallia et al., 1995; Riley & Shaw, 1985), except one (Piko et al., 2005). Attachment and commitment to school. Low attachment to school – whether adolescents like going to school – was related to female delinquency (Graham & Bowling, 1995; Junger-Tas et al., 2004; Mansel, 2003; Slotboom et al., 2005; Smith & McAra, 2004). Some studies failed to find an association though (Hauber et al., 1987; Piko et al., 2005; Van der Rakt et al., 2005), but these studies all used a regression analysis to test the association. Low quality of the relationship with teachers (as an indicator of school attachment) was related to female delinquency (Junger-Tas et al., 2004; Mansel, 2003; McAra, 2005; Smith & McAra, 2004), as was low commitment to school – whether adolescents are willing to put effort in school (Hartjen & Priyadarsini, 2003; Mansel, 2003; McAra, 2005; Riley & Shaw, 1985; Slotboom et al., 2005; Smith & McAra, 2004; Torstensson, 1990). No large differences existed in the associations of school factors with male delinquency compared to female delinquency, although it appeared that the negative associations of attachment and commitment with delinquency were somewhat stronger for males (Slotboom et al., 2005). Inconsistent results were found for the relation between the quality of the relationship with teachers and male delinquency. Figure 3.3 presents an overview of the unique and shared family risk factors consistently related to male and female delinquency. The figure shows that low school commitment was a shared risk factor for males and females and a poor relationship with teachers was uniquely related to female delinquency. These findings have been replicated over many studies. Peer factors Delinquent friends. Female delinquency was related to having delinquent friends (Graham & Bowling, 1995; Hartjen & Priyadarsini, 2003; Riley & Shaw, 1985; Slotboom et al., 2005) as well as to the extent of these friends’ delinquency (Van der Rakt et al., 2005) and to having ‘negative’ friends, characterized as having had contact with the police, low school achievement, and being problematic according to their parents (Hauber et al., 1987). Problematic youth group membership is also related to female delinquency (Piko et al., 2005) and more specific, if disaggregated by type of delinquency, to robbery, assault and severe property offences (Oberwittler, 55 Figure 3.3 Unique and shared school risk factors consistently related to female or male delinquency Unique factors for females Low quality relationship with teachers (4+r) Shared risk factors Low school commitment (7) Unique factors for males Low school achievement (6+r) Note. The numbers between brackets indicate the number of studies that took the risk factor into account. Superscript +r: results from some of the studies come from a regression analysis. 2003). According to Riley and Shaw (1985), having friends who are positive towards delinquency was positively related to female delinquency. The relationship disappeared in a multiple regression analysis (Hauber et al., 1987). Male delinquency was comparably and consistently related to delinquent friends. Only Van der Rakt et al. (2005) found no association between the extent of delinquency of friends and male delinquency. Results from this study may deviate from those of other studies not only because the extent of friends’ delinquency was assessed instead of having delinquent friends, but also because this was the only study that assessed friends’ delinquency not indirectly through the adolescents but directly through friends. Number of friends. The relationship between the number of friends and delinquency was not clear for females, probably because it depends on whether these friends are delinquent or not. The number of opposite-sex friends was related to delinquency (Smith & McAra, 2004). If a regression analysis was used, the association disappeared (Van der Rakt et al., 2005). Having a romantic partner was consistently found to be positively related to delinquency (Smith & McAra, 2004; Riley & Shaw, 1985), as was the extent to which adolescents and young adults hang out with their friends, or go out (Hartjen & Priyadarsini, 2003; Honkatukia 1998; McAra, 2005; Smith & McAra, 2004; Riley & Shaw, 1985). Males’ delinquency was similarly inconsistently related to the number of friends. The number of opposite-sex friends was consistently related to male delinquency (Smith & McAra, 2004; Van der Rakt et al., 2005), but findings on the direction of this relation were inconsistent. Quality of relationship with peers. No relation was found between quality of relationships with peers, or peer support and female delinquency (Junger-Tas et al., 2004; Landsheer & Van Dijkum, 2005; Slotboom et al., 2005), 56 possibly because no distinction was made between antisocial and prosocial peers. Friends disliked by parents were a risk factor for female delinquency (Riley & Shaw, 1985). For male delinquency, the same associations were found except regarding the quality of peer relationships for which inconsistencies were found. Figure 3.4 presents an overview of the unique and shared peer risk factors consistently related to female and male delinquency. Here, it appears as if risk factors are similar as well as unique, replicated over a number of studies. Figure 3.4 Unique and shared peer risk factors consistently related to female or male delinquency Unique factors for females Extent delinquency of friends (1r, l) Shared risk factors Unique factors for males Having delinquent friends (3) Having negative friends (1) Problematic youth group member (2r) Having a romantic partner (2) Many activities with friends (5) Having friends disliked by parents (1) Note. The numbers between brackets indicate the number of studies that took the risk factor into account. Superscript r: results from all studies come from a regression analysis; superscript l: results from all studies come from a longitudinal analysis. Discussion The purpose of this study was to generate an overview of risk factors related to female delinquency as found in Europe and to identify factors that are promising as distinctive explanations for offending in females as opposed to males. This review contains most, if not all, European studies on risk factors of female delinquency. Given that these number 30, female delinquency appears definitely understudied. Overall, many similarities in factors were found between males and females, although clear differences emerged as well. Females seem to be more affected by social context factors, such as negative life events and physical abuse by parents. Also, internalizing problems were more prominent. The role of mothers in their daughters’ delinquency is noteworthy. Maternal support, mother-child relationship and maternal parenting styles 57 were uniquely associated with female delinquency. However, for males, having a convicted mother was uniquely related to their delinquency. Unique female delinquency factors seem to be mainly in the relational domain. A bad relationship with the mother seems to put adolescent and young adult females at risk of becoming delinquent, but good relationships protect them. It has to be kept in mind, though, that results have been derived from crossectional, mostly bivariate results. It is therefore not apparent whether quality of maternal relationship is a cause or effect of female delinquency (or both). Also, only for girls it is the relationship with the school teacher that plays a role. School factors seem to have affect male delinquency more than female delinquency. An explanation for this may be that when males fail at school they may feel they have to compensate by showing delinquent behaviour: through this compensation they may (re)gain their status (Warr, 2002). For females, status might be regained by other types of behaviour. School attachment and commitment might be mediating factors between achievement and delinquency. If adolescents achieve badly at school they will probably be less attached and committed to school, leading to more compensating behaviour. Another explanation for the sex difference may be that low intelligence is more strongly related to male than to female delinquency (Moffitt et al., 2001). This might be reflected in stronger relationships of school achievement, attachment and commitment with male delinquency. Even though we reported the delinquency of friends as a risk factor as it has been established as such repeatedly, it is important to stress that the relation between friends’ delinquency and delinquency may in fact be spurious. Most studies assess friends’ delinquency indirectly by asking respondents and not the friends themselves, and adolescents’ belief about their friends’ delinquency may be perceived as more similar than it actually is. The only study that asked the friends directly about their delinquent behaviour (Van der Rakt et al., 2005), did not find any relation with male delinquency, although it has to be taken into account that their interest was different, as they examined the extent of friends’ delinquency, instead of having delinquent friends. As studies focused on more specific sub-domains (e.g. of empathy, disaggregated domains of self-esteem, parental monitoring) or on different types of offences (e.g. violent, property, public order), more sex differences emerged. Thus it appears, that females do have a number of different risk factors for delinquency than males, supporting the second explanation put forward in the introduction. While our study found clear overlaps as well as differences in risk factors for males and females, further systematic research needs to uncover whether overlapping risk factors also have the same predictive value for male and female delinquency. 58 Additionally, our findings might indicate that females have a higher threshold to become delinquent; the number of negative life events in particular affected female delinquency and not male delinquency. Related to this, the extent of friends’ delinquency was found to be uniquely related to female delinquency. These findings imply that females may be more resilient to particular risk factors than males, and that only once females pass a certain threshold they become delinquent. Previous research on the higher threshold for females, in which mixed results were found, examined only the number of risk factors (Baker et al., 1989; Eme 1992; Loeber & Keenan, 1994; Moffitt et al., 2001; Robins, 1966). The current study indicates that perhaps the level or severity of risk factors might be of importance as well. Thus, our findings offer some support for the third explanation for the sex difference in delinquency as well. Our findings differ from some of the findings from existing (mostly American) reviews. More extensively studied in the US reviews were variables such as sexual and physical abuse (Hoyt & Scherer, 1998; Hubbard & Pratt, 2002; Tankersley & Rycraft, 2007), criminal family members, substance abuse, mental health problems (Hoyt and Scherer; Tankersley & Rycraft, 2007) and living in a disadvantaged neighbourhood (Tankersley & Rycraft, 2007). These variables all appeared to be associated with female delinquency in the US. In addition, Tankersley and Rycraft (2007) had different conclusions about single parenthood compared to our findings, as they found it to be consistently related to female delinquency. This shows that associations between risk factors for (female) delinquency may indeed not be generalizable from the US to Europe. An explanation may be that single parenthood in the US is more strongly associated with poverty than in European countries, because of the lack of a social welfare system. Remarkably, neighbourhood effects are less often studied in Europe – possibly because social disadvantage is less clustered within neighbourhoods in Europe than in the US. Other factors were not at all studied in European studies: family substance abuse, family violence and pubertal timing (Hoyt & Scherer, 1998; Tankersley & Rycraft, 2007). Whether this is coincidental or whether European studies structurally neglected some factors is not clear. The current review contained many more variables, on the other hand, to which previous reviews did not pay attention: birth complications, empathy, self-control, shame, disclosure, differential parental treatment, going out and spending time with family, quality of relationship with teachers, number of (opposite-sex) friends, quality of relationship with friends and whether parents disliked friends of the adolescent. Crosscontinental studies would be needed to gather evidence on the applicability of risk factors in European and US contexts. 59 Limitations of the study and need for further research Due to our choices, it occured that we labelled a factor a risk factor if it had been identified as such in only one study. As such, risk factors identified by us should be regarded as ‘not inconsistent’ rather than as ‘consistent’. Secondly, we were not able to properly compare studies when they used different methodologies or multivariate models. To make the studies as comparable as possible, we discussed bivariate results if available. However, relationships between risk factors and delinquency are obviously more complicated in reality, and more realistic models, incorporating males as well as females, are needed to arrive at a comprehensive test of differences. The selected studies that examined delinquent females were also often limited in several ways. Overall, there are not many longitudinal studies yet on female delinquency. More specifically, only three studies were found in Europe that investigated female delinquency longitudinally; all were from the Netherlands (Landsheer & Van Dijkum, 2005; Scholte et al., 2007; Van der Rakt et al., 2005). Longitudinal studies are essential in drawing conclusions about causality. Therefore, it should be kept in mind that it is uncertain whether the risk factors identified here are causes, effects or both. What is more, most studies did not report on the effect sizes of their results. We could therefore only discuss the significances. Given that many sample sizes were large, if not huge at times, this also limits the relevance of our findings. In most studies, delinquent females were considered as one group. There can, however, be many differences within groups of offenders, and therefore it is important to make a distinction between those groups. Not only in terms of types of offences, but also in terms of developmental pathways of delinquent behaviour. Females showing delinquent behaviour only in adolescence, presumably have different risk factors from females who persist to be antisocial throughout life (Moffitt et al., 2001). These differences are neglected when all types of offenders are analyzed together. Given that delinquency is less prevalent in females, more studies concerning high risk female samples seem warranted. Furthermore, sex differences in associations of factors with delinquency were almost never tested as such. Only one study actually performed such a test (Slotboom et al., 2005). In this review, we had no other option but to consider factors significant for one sex but not for the other, as being sex different. There was almost no overlap in factors that were taken into account in the self-reported and criminal record studies. This can be explained by the fact that studies with official records mostly obtain their variables from existing documents, like obstetric or school files, whereas self-reported studies are able to choose their own variables. So even if there were enough studies to compare studies using self-reported delinquency with those using 60 criminal records as an outcome measure, there would be little to compare since both types of studies cover different risk factors. Clearly, in order to be able to shed light on the possibly different mechanisms through which female and male adolescent and young adults start, continue to and desist from offending, more comprehensive, longitudinal studies are needed. Such studies would have to include males as well as females, so that method differences can be disregarded as an explanation for any sex differences. Ideally, as this review shows, they would have to include many tentative risk factors not identified previously found in male-only studies. Such studies would also have to enable explicitly to model differential exposure to risk factors as an explanation for the difference in male and female offending. This review shows that it is likely that females do have a number of unique risk factors for delinquency and that threshold effects exist. That does not preclude that differences in exposure further help to explain how females have different pathways into delinquency. 61 Chapter 4 The relationship between the sex difference in delinquency and differential exposure and vulnerability in the parent and peer domain Wong, T. M. L., Slotboom, A., Zahn, M., Bijleveld, C. C. J. H., Van Lier, P. A. C., Frijns, T., Meeus, W. H. J. & Koot, J. M. (submitted). The relationship between the sex difference in delinquency and differential exposure and vulnerability in the parent and peer domain. 63 This study is an attempt to gain insight in the aetiology of the sex difference in delinquency by testing the risk exposure hypothesis, which states that sex differences in exposure to risk factors are related to the sex difference in delinquency, the risk vulnerability hypothesis, which states that sex differences in associations between risk factors and delinquency are related to the sex difference in delinquency, and the combination of the two. The hypotheses are tested by using innovative methodological analyses on a broad range of factors in the parent and peer domain. A sample of 480 Dutch juveniles from the RADAR study, a prospective cohort study, is analyzed. Sex differences in exposure and vulnerability were found, but only differences in exposure were related to the relationship between sex and offending behaviour. A reason why girls are less often delinquent than boys is that their mother is more involved in their lives and that they have less delinquent friends. 64 Introduction Delinquent behaviour peaks in adolescence. Although this has been widely acknowledged for both boys and girls, the prevalence of girl delinquency is always lower than that of boys (Junger-Tas, Marshall, & Ribeaud, 2003; Van der Laan & Blom, 2006, Steffensmeier & Schwartz, 2009). An explanation broadly accepted for the peak in adolescence is that adolescents experience a gap between their biological and social maturity (Moffitt, 1993). Delinquency is a way of displaying their discomfort about this gap and demonstrating their autonomy towards their parents. Also, (status among) peers become(s) more and more important in adolescence and empirical research has shown that delinquent friends are imperative in explaining delinquent behaviour (Warr, 2002). As we know, however, not all adolescents engage in delinquent behaviour. Important factors that affect whether they do or not are the previous mentioned peer factors, and factors in the parent domain (Moffitt, Caspi, Rutter, & Silva, 2001; Wong, Slotboom & Bijleveld, 2010). Parents can affect their children in two ways, through parenting practices and through the relationship they have with their children. The link between parent factors and delinquency can be understood through the social control theory of Hirschi (1969). This theory claims that good relationships between parents and children can keep adolescents from committing crimes. Since adolescents do not want to jeopardize the strong bond they have with their parents and do not want to go against the wishes of their parents they will not engage in offending behaviour. Adolescents with a low quality parent-child relationship do not have this fear of losing the strong attachment to their parents and are therefore more likely to be delinquent. Peers, on the other hand, can influence adolescents’ delinquency because adolescents imitate each other’s behaviour. An important theory about the influence of peers on delinquency is the differential association theory of Sutherland (1947) which states that delinquency is behaviour learned from others. People learn attitudes, techniques and motives within intimate personal relationships. As friends are very important during adolescence, adolescents especially learn behaviour from their friends. Adolescents who have delinquent friends, are therefore likely to show the same type of behaviour. However, it can also be a selection effect that explains why adolescents often show the same behaviour. In other words, adolescents might also choose their friends because they show similar (delinquent) behaviour (Weerman, 2007). Sex differences in parent and peer factors From a theoretical perspective it can be expected that there are differences between boys and girls regarding the influence of parents and peers. It has been postulated, for instance, that girls are more family-oriented than boys 65 (Gecas & Seff, 1990; Gilligan, 1982). Furthermore, parents seem to socialize their daughters differently than their sons and use gender specific parenting practices (Hoeve, 2008; Lytton & Romney, 1991): boys are thought to receive harsher punishment and less supervision than girls, whereas girls are found to receive more parental warmth (Leaper, Anderson, & Sanders, 1998; Lytton & Romney, 1991; Zahn-Waxler & Polanichka, 1994). This familyfocused nature of girls and differences in parenting can result in higher levels of social control in girls compared to boys and therefore may lead to a higher prevalence of delinquency among boys than among girls. It can also result in sex differences in exposure and vulnerability regarding parent factors. Differential exposure implies that there are differences between boys and girls in mean levels of risk and promotive factors. Risk factors are those factors that “have proven or presumed effects that can directly increase the likelihood of a maladaptive outcome” (Rolf & Johnson, 1990: 387). Promotive factors are those factors that decrease the likelihood of becoming delinquent. Promotive and risk factors are actually the opposite end of each other within the same variable. That is, the same variable may constitute a risk as well as a protective condition for adolescents (Stouthamer-Loeber, Loeber, Wei, Farrington, & Wikström, 2002). In general, it is thought that girls are exposed to fewer risk factors and to more promotive factors than boys, the so-called risk exposure hypothesis (Moffitt et al., 2001; Murray, 2002). The stronger focus of girls on the family and the different parenting strategies towards daughters may indeed result in a higher exposure to promotive factors of girls than of boys. More specifically, girls might experience more promotive parenting behaviour such as higher levels of supervision (Leaper, Anderson, & Sanders, 1998), and high quality parentchild relationships (Hoeve et al., 2009). This may lead to higher levels of social control in girls and therefore in a lower prevalence of delinquency. Differential vulnerability implies that there are differences in the association of delinquency with risk and promotive factors between boys and girls. The risk vulnerability hypothesis states that girls are less vulnerable for risk factors and more receptive for promotive factors than boys (Lahey et al., 2006; Moffitt et al., 2001; Murray, 2002). It means that for girls risk factors less often result in delinquent behaviour as for boys and that promotive factors have a stronger deterrent effect on girls. This makes sense if we take into account the family-oriented nature of girls. Compared to boys, girls may be more afraid to endanger a good bond with their parents and they might be more compliant towards them (i.e. girls have higher levels of social control). Parents are therefore expected to have a stronger promotive effect on girls. Exposure and vulnerability regarding peers may also be gender specific. To start with exposure, adolescents tend to make friends of the same sex, so girls have more female friends and boys have more male friends (Rose & Rudolph, 2006). Since girls are less often delinquent than boys (Junger-Tas, 66 Ribeaud, & Cruyff, 2004; Steffensmeier & Schwartz, 2009; Van der Laan & Blom, 2006), girls had less delinquent peers than boys. Girls therefore have less role models from who they can learn delinquent behaviour. Regarding vulnerability, the nature of boys’ friendships is different from that of girls which may lead to different influences. While boys focus more on common activities, competition and status within the group, girls find communication, social support and taking care of each other more important in their friendships (Giordano, Cernkovich & Pugh, 1986; Rose & Rudolph, 2006; Heimer, De Coster & Ünal, 2006). Because girls are less involved with competition and obtaining status, they seem to be less susceptible for group pressure and therefore less vulnerable for the (bad) influence of delinquent peers. Furthermore, boys likely internalize ideas that favour being aggressive or delinquent, because male peer groups reinforce the idea of masculinity through competitiveness and physical strengths. Female peer groups, on the other hand, emphasize the importance of emotional bonds. Therefore, girls are less likely to favour behaviour that includes harming others and violating the law (Heimer et al., 2006). In the present study, sex differences in exposure and vulnerability were examined in the parent and peer domain. Not only is examined whether these differences exist, but also whether these differences are related to the lower prevalence of delinquency in girls. Previous Research A number of previous studies have examined whether boys and girls differ in exposure to and vulnerability for risk and promotive factors regarding parents and peers. Regarding exposure, sex differences seem to be especially apparent in the peer domain. It was consistently found that boys had more delinquent peers than girls (Fagan, Van Horn, Hawkins, & Arthur, 2007; Liu & Kaplan, 1999; Mears, Ploeger, & Warr, 1998; Moffitt et al., 2001; Murray, 2002; Rowe, Vazsonyi, & Flannery, 1995). Peer attachment and peer popularity were higher for girls (Moffitt et al., 2001; Rowe et al., 1995). In the family domain, sex differences in exposure particularly emerged when mothers and fathers were considered separately. Moffitt et al. (2001), who made no distinction between mothers and fathers, showed equal levels of boys and girls regarding the quality of relationships with parents. However, when examined more closely, sex differences in the parent-child relationship appeared to emerge. Boys were found to receive more paternal affection than girls, whereas girls were found to receive more maternal affection (Fagan et al., 2007; Rowe et al., 1995). Furthermore, as indicated before, boys and girls were exposed to different parenting practices (Hoeve, 2008; Leaper, et al. 1998; Lytton & Romney, 1991; Zahn-Waxler & Polanichka, 1994), i.e boys were exposed to harsher punishments than girls, less supervision and less parental support. 67 Regarding vulnerability, previous studies also suggested that sex differences existed. In the family domain, physical abuse by parents appeared to have a stronger relationship to girl delinquency than to boy delinquency (Piko, Fitzpatrick, & Wright, 2005). Boys’ delinquency was found to be more strongly related to inconsistent parental discipline and years with single parents (Moffitt et al., 2001; Wong et al., 2010). Family conflict had a stronger relationship to antisocial behaviour of boys than to that of girls, but it was related similarly to serious delinquency of both sexes (Moffitt et al., 2001). The relation between delinquency and maternal factors seem to be more important for girls than for boys (e.g. low quality motherchild relationship, low maternal support, inadequate parenting and authoritative parenting; Blitstein, Murray, Lytle, Birnbaum, & Perry, 2005; Blum et al., 2003; Wong et al., 2010). Parenting of fathers and the quality of the relationship between father and adolescents appeared however to have a similar effect on girls’ and boys’ delinquent behaviour (Blitstein et al., 2005; Wong et al., 2010). Fagan et al. (2007) found the opposite effect between delinquency and the parent-child relationship of both parents for boys and girls: attachment to mother had an equal negative effect on boys’ and girls’ delinquency, but attachment to father appeared to be more strongly related to boys’ delinquency. This might be because, contrary to the other studies that examined the parent-child relationship, Fagan et al. (2007) examined serious delinquency instead of general delinquency. Regarding peers, many studies have shown that boys were more strongly affected by delinquent peers than girls (Fagan et al., 2007; Giordano et al., 1986; Mears et al., 1998 Steffensmeier & Haynie, 2000). In addition, peer rejection appeared to affect boys’ delinquency to a greater extent than girls’ delinquency (Moffitt et al., 2001). Van der Rakt, Weerman, and Need (2005) studied self-reported delinquent behaviour of a Dutch school sample and showed that the extent of friends’ delinquency was uniquely associated with girl delinquency, but not with boy delinquency. Their results might be inconsistent with other studies, because they had operationalized peer delinquency differently. In their study, they had asked all respondents to list their friends within their school. Since these friends had also participated in the study and had reported on their delinquent behaviour, the authors could construct accurately how many delinquent friends all respondents had. It is therefore not yet understood how and whether peer delinquency differentially influences boy and girl delinquency. Limitations in research on differential exposure and vulnerability Previous studies were limited in some important ways and it is therefore not clear whether differential exposure and vulnerability is indeed related to the sex difference in delinquency. Firstly, the few studies that examined differential vulnerability, mostly did not test whether factors were actually differently associated with boy and girl delinquency, but only compared the 68 levels of significance. This can lead to wrong conclusions about sex differences. Although a factor might be related to both boy and girl delinquency, the influence may still be sex different if the effect is stronger for one of the sexes. Secondly, the fact that differences between girls and boys are found in mean levels of risk and promotive factors and in vulnerability, does not necessarily mean that differential exposure and vulnerability are related to the sex difference in delinquency. To test the risk exposure and risk vulnerability hypotheses properly, it must be shown that these differences in risk and promotive factors between boys and girls are actually related to the sex difference in delinquency. So far, four studies have examined whether differential exposure is related to the gap between boys and girls in delinquent behaviour. To our knowledge, this has not been investigated for differential vulnerability. Moffitt et al. (2001) tested the risk exposure hypothesis on the Dunedin sample, which contained approximately 1000 juveniles, by comparing the sex difference in antisocial behaviour before and after controlling for sex differences in mean levels of risk factors. They showed that the sex difference in antisocial behaviour could be partly explained by differential mean levels of risk factors such as harsh parental discipline, neuro-cognitive risk, hyperactivity and peer influences. Messer, Goodman, Rowe, Meltzer, and Maughan (2006) used the same procedure and found as well, among preadolescent juveniles, that the higher exposure of boys to harsh punishment, neuro-cognitive risk and peer problems accounted for the sex difference in delinquency, as well as lower reading performance of boys and higher prosocial behaviour of girls. These risk factors were all assessed through parents and teachers though, and therefore can be already sex biased. Junger-Tas et al. (2004) tested the risk exposure hypothesis by examining a large European sample of juveniles and also used the same analytical strategy. They showed that sex differences in parental supervision could partly explain the difference between boys and girls in delinquency. Sex differences in school problems and in the quality of relationship with parents did not contribute to the explanation though. Fagan et al. (2007) examined whether sex differences in serious delinquency were mediated by sex differences in exposure to factors such as the parent-child relationship and found only partial mediation, indicating, again, that differences in quality of parent-child relationship between boys and girls could only partially explain the sex difference in delinquency. Thirdly, previous research focused on separate factors whereas it is also important to see whether boys and girls are differently exposed to or vulnerable for domains of risk factors. That is because it is often a accumulation of risk factors that affect delinquency (Sameroff, Seifer, Barocas, Zax & Greenspan, 1987). To capture the imperative concurrent effects of risk and promotive factors on delinquency, that is neglected in previous univariate analyses, it is necessary to do multivariate research. 69 Fourthly, no study has ever investigated the combination of differential exposure and vulnerability. The Current Study In the current study, we will test the risk exposure and the risk vulnerability hypotheses, where we deal with the limitations of previous studies. Both hypotheses will be tested separately, as well as combined. In addition we investigate whether the hypotheses are related to the sex difference in delinquency by examining whether the sex difference in delinquency is related to differential exposure and/or differential vulnerability. Since previous studies suggested that differential exposure and differential vulnerability might exist in the family as well as the peer domain, we will examine a broad range of risk and promotive factors in each of these domains. Obviously, the exposure and vulnerability hypotheses may hold for different risk and promotive factors, i.e. it may be that for some factors, differences in exposure are associated with the sex difference in delinquency, while for others differences in vulnerability play a larger role. The two hypotheses and the combination of the two will be analyzed univariately, as well as multivariately. Method Sample Data for this study come from the RADAR study (Research on Adolescent Development and Relationships), an ongoing prospective cohort study aimed at understanding the interplay between adolescent relationships and their development in many domains (Van Lier et al., submitted). In this study, adolescents, both their parents, a sibling (between the ages of 10 and 20), and a best friend are followed across adolescent ages 12-17 years. Assessments began in 2006 when the adolescents were in the first grade of secondary school. The current study used data from this first annual wave, which contained 480 adolescents for whom data on delinquency were available. The RADAR study focuses on delinquency development in particular. Therefore, adolescents at high risk of developing delinquent behaviour were oversampled. To indicate high risk, teachers in the sixth grade of primary school rated behaviour problems of the adolescents (See Van Lier et al. (submitted) for detailed information about this procedure). Of the sample, 200 children were at elevated risk of developing problem behaviour and 280 children were at average risk. The sample contained 56% boys (n = 269) and 44% girls (n = 211). The mean age was 13 years (SD = 0.52). All respondents were asked to fill in an annual questionnaire during a home visit by trained interviewers. The questionnaires contained questions about the adolescent’s behaviour, personal characteristics and relationships between family members and between the adolescent and the best friend. 70 Measures Delinquency was measured with a questionnaire covering 25 delinquent acts, based on the ISRD (Junger-Tas et al., 2003). The items included public order offences (i.e. destroying means of transport; destroying somebody’s house; destroying the school building; destroying property; arsony), property offences (i.e. shoplifting less than five euro’s and more than five euro’s; theft at school less than five euro’s and more than five euro’s; theft at home less than five euro’s and more than five euro’s; stealing a bike; theft from/out of car; burglary; other theft; selling stolen goods), violent offences (i.e. threatening somebody to scare somebody or to get something; robbery; hurting with weapon; beating up without injury; beating up with injury; sexual offences) or drug offences (i.e. soft drug selling; party drug selling; hard drug selling). For each of the offences, respondents indicated how often they had committed them in the previous year. We computed a dichotomous delinquency scale (0 = not delinquent, 1 = delinquent) based on whether or not the adolescent had committed at least one offence in the previous year. The same delinquency scale was used for the adolescent’s best friend’s delinquency, filled in by the best friend him/herself (see also Table 4.1). Measures of risk and promotive factors are described in Table 1. The factors comprised five sub domains: 1) mother-child relationship (motherchild conflict, involvement in peer relations, negative interaction, power, support), 2) father-child relationship (father-child conflict, involvement in peer relations, negative interaction, power, support), 3) maternal parenting (parental knowledge, adolescent disclosure, parental solicitation, parental control), 4) paternal parenting (parental knowledge, adolescent disclosure, parental solicitation, parental control), 5) peers (extent of best friend’s delinquency, number of delinquent friends, best friend’s truancy). All the measures were filled out by the adolescents except for extent of best friends’ delinquency and best friends’ truancy, which were filled out by the best friend. 71 72 Parental direct interference in peer relations Knowledge of parents about the child’s whereabouts The extent to which parents actively ask their children about their whereabouts Parenting Practices (Kerr & Stattin 2000) Parenting Practices (Kerr & Stattin 2000) Parental knowledge Parental solicitation Mean of 6 5-Point Likert items (for both parents) Mean of 9 5-Point Likert items (for both parents) Mean of 6 4-Point Likert items Sum of 25 items and dichotomized total into not delinquent versus delinquent Whether adolescents had committed particular offences in the previous 12 months Parental Management of Peers Inventory (Mounts, 2002) How created? Description Involvement in peer relations Table 4.1 Description of constructs used in this study Instruments Constructs International SelfDelinquency (of adolescent and best reported Delinquency Study (Junger-Tas, friend) Haen-Marshall, & Ribeaud, 2003). mother = .74; father = .75 mother = .80; father = .82 .69 Reliability (alpha) NA - How often does your mother/ father talk to your friends? - How often does your mother/father start a conversation about school? - Does your mother/father know what you do in your spare time? - Does your mother/father know how you spend your money? - I tell my child sometimes which friends are good for him/her in my opinion - I want my child to associate with peers who work hard at school - How often have you damaged the school in the previous twelve months? - How often have you stolen a bike in the previous twelve months? Example of item 73 Controlling the child’s freedom by setting rules and restrictions Parenting Practices (Kerr & Stattin 2000) Whether the bond between parent and child is based on affection, admiration, alliance, intimacy, and companionship The control parents have in the relationship with their child Network of Relationships Inventory (Furman & Buhrmester 1985) Network of Relationships Inventory (Furman & Buhrmester 1985) Parental support Parental power The extent to which children spontaneously tell their parents about their whereabouts Description Instruments Adolescent disclosure Parenting Practices (Kerr & Stattin 2000) Constructs Parental control Mean of 6 5-Point Likert items (for both parents) Mean of 8 5-Point Likert items (for both parents) Mean of 6 5-Point Likert items (for both parents) Mean of 6 5-Point Likert items (for both parents) How created? mother = .88; father = .82 mother = .84; father = .86 mother = .70; father = .75 Reliability (alpha) mother = .84; father = .83 - How often does your mother/father have his/her way when you disagree? - How often does your mother/father take a decision for the both of you? - Does your mother/father admire and respect you? - How often do you have fun with your mother/father? - How often do you talk with your mother/father about school subjects? - Do you have many secrets for your mother/father about what you do in your spare time? - Do you need permission of your mother/father to get home late on a school night? - Does your mother/father demand to tell how you spend your money? Example of item 74 Description Whether the parent-child bond is characterized by punishment and irritation Frequency conflicts between adolescents and mother/father Instruments Network of Relationships Inventory (Furman & Buhrmester 1985) Parent-child conflicts Interpersonal Conflict Questionnaire (Laursen, 1993) Number of friends they thought had committed an offence in the previous three months How often truant in the previous three months Basic questionnaire peers School achievement questionnaire Delinquent friends Truancy of best friend Parental Negative interaction Constructs 1 5-Point Likert item Summing 5 items Sum of 10 5-Point Likert items (for both parents Mean of 6 5-Point Likert items (for both parents) How created? NA .72 mother = .84; father = .82 mother = .88; father = .86 Reliability (alpha) - How often have you been truant in the previous three months? - How many of your friends have damaged something on the streets - How many of your friends have injured somebody by hitting or with a weapon? - How often have you had conflicts with your mother/father about money in the previous week? - How often have you had conflicts with your mother/father about relationships in the previous week? - How often do you disagree and argue with your mother/father? - Are you and your mother/father irritated by each other’s behavior? Example of item Analytic Strategy Multiple group path analyses were performed in MPlus version 6.1 (Muthén & Muthén, 1998-2010). In our multiple group comparisons, means and association paths of the model, depending on the research question, were set equal or set free across the sexes. To test our hypotheses, a series of models were run. We started with a null model in which mean levels of risk and promotive factors as well as the regression paths of each factor on delinquency were set equal for boys and girls. This model simply represents that girls and boys differed neither in exposure nor in vulnerability. In a second model, Model A, we tested the exposure explanation by setting the mean levels of risk and promotive factors free across sexes; the regression coefficients on delinquency of each factor were kept equal for boys and girls. If this model fitted the data better than the base model, this confirmed that boys and girls differed in mean levels of the factor. In our third model, Model B, we tested the vulnerability hypothesis. Mean levels of the factors were set equal for boys and girls, but the regression coefficients of the factors were allowed to differ across sexes. If this model fitted the data better than the base model, this would imply that boys and girls are differently influenced by the risk factor. Finally, we analysed a model, Model C, in which both mean levels and regression coefficients were allowed to differ for boys and girls. If this model had a better fit than the former models, this would imply that boys and girls were concluded to differ in exposure as well as in vulnerability to that factor. In all of the models described above (see also Figure 4.1), the probability4 for delinquency was allowed to differ for boys and girls, because it is well established that this differs across sexes. All these models were run for each factor but also multivariately. We carried out the multivariate analyses in two ways: per domain (by grouping factors together that belonged to a particular domain) and based on the univariate results (by grouping factors together for which sex differences were found in the univariate analyses). After the multivariate analyses, the best model was tested against a model, the Final Model, with the same restrictions except regarding the probability for delinquency, which was now set equal for boys and girls (see Figure 4.2). If this model performed equally well as the model in which the probability was allowed to differ across sexes, the sex difference in delinquency was related to differential exposure and/or vulnerability. If the model performed significantly worse than the 4 In reality, we allowed the threshold for delinquency to differ across sex. The threshold for delinquency is the statistical cut-off point from which the delinquency scale changes in value from 0 (not delinquent) to 1 (delinquent). You can compare this to the intercept of equations concerning continuous outcomes. For a fuller understanding of the meaning of thresholds, see Long (1997). Thresholds actually reflect probabilities. Since this term is much easier to understand, we use probabilities instead of thresholds. 75 model with sex different probabilities, this indicates that the sex difference in delinquency was not related to differential exposure or vulnerability. Goodness of fit of the models was evaluated through the comparative fit index (CFI; acceptable values > .90) (Bentler, 1990) and the root-meansquare error of approximation (RMSEA; acceptable values < .08) (Browne & Cudeck, 1993). To compare the difference in fit of the different nested models, we used the chi-square difference test. Results Sex differences in delinquency More boys than girls in our sample had committed at least one offence in the previous year (respectively 54.6% and 38.9%, p<.05), the boy to girl ratio is 1.4 : 1 (see Table 4.2). Many of these boys and girls reported to have committed only one type of offence (respectively 40.4% and 53.7%). Most offences were committed by more boys than girls. The offence committed mostly by both boys and girls was beating up somebody without injury followed by shoplifting for items worth less than 5 euros (approximately US $7). Sex differences in exposure and vulnerability Univariate multiple group analyses were carried out for each of the factors. These results will only be discussed shortly, but the detailed results can be found in the Appendix. Girls and boys appeared to differ in mean levels regarding several factors: girls had higher means of adolescent disclosure to mother and parental solicitation of mother, whereas boys had a higher number of delinquent friends. Differential vulnerability was found for maternal support, parental control of mother and the extent of best friends’ delinquency. Maternal support was more strongly related to girl delinquency than to boy delinquency. Regarding parental control of mother it was found that it was negatively related to delinquency for boys, but positively for girls. Additionally, girls but not boys appeared to be affected by the extent of delinquent behaviour of their best friend. For the other variables boys and girls no differential exposure or sensitivity was found. 76 77 ≠ = ≠ Probability delinquency Extraversion Probability delinquency Extraversion ≠ ≠ = Probability delinquency Extraversion Differential vulnerability to factors ♂ ♀ Probability delinquency Extraversion ≠ ≠ ≠ Probability delinquency Extraversion 77 Differential exposure and vulnerability factors ♀ ♂ Note. ‘=’ between squares indicate that the means are equal for boys and girls, ‘≠’ that they are unequal. ‘=’ between arrows indicate that the association between the factor and delinquency are equal for boys and girls, ‘≠’ that they are unequal. Probability delinquency Extraversion Differential exposure to factors ♂ ♀ Figure 4.1 Nested model types of differential level and differential vulnerability Figure 4.2 The sex difference in delinquency explained? The sex difference in delinquency explained ♂ ♀ Extraversion ? Extraversion ? Probability delinquency = Probability delinquency Note. The best model out of the three models in Figure 1 was tested against the model in Figure 2 in which the mean score of delinquency in boys and girls is equal. Since the other restrictions are similar to those of the best previous model, we have printed ‘?’ in the model. 78 Table 4.2 Prevalence of offences, by sex (%) Destroying means of transport Destroying somebody’s house Destroying the school building Destroying property Arson Shoplifting less than five euro’s Shoplifting more than five euro’s Theft at school less than five euro’s Theft at school more than five euro’s Theft at home less than five euro’s Theft at home more than five euro’s Stealing a bike Theft from/out of car Burglary Other theft Selling stolen goods Threatening somebody to scare somebody or to get something Robbery Hurting with weapon Beating up without injury Beating up with injury Soft drug selling Party drug selling Hard drug selling Sexual offence Total One or more offences committed * sex difference at p < .05 Girls (n = 211) 0.9 0.5 1.4 2.4 5.7 10.9 0.9 3.3 0.0 6.2 2.4 0.5 0.5 0.0 1.4 0.5 6.2 Boys (n = 269) 8.9* 4.5* 8.2* 10.1* 11.9* 15.2 3.4 10.0* 2.2* 11.2* 3.4 3.7* 1.9 2.6* 5.2* 4.5* 9.7 0.0 0.0 22.3 4.7 0.9 0.0 0.0 0.5 1.1 1.9 31.7* 12.3* 0.7 0.4 0.7 0.7 38.9 54.6* Consecutively, we carried out multivariate multiple group analysis of the five sub domains (see Table 4.3) For peers, none of the multivariate models had an acceptable fit and these are therefore not discussed and not displayed in Table 3. For most of the other domains (mother-child relationship, father-child relationship and parenting of father) the best fitting model was the Null Model in which mean levels and associations were set equal across sex. So for these factors, boys and girls did not differ in mean levels or vulnerability. For the sake of simplicity, only the fit indices for the Null Model are displayed in Table 3 for these models. 79 Table 4.3 Fit indices for multivariate models Model Mother-child relationship Null Model: Fixed χ2 df CFI RMSEA 11.54 11 .99 .01 Father-child relationship Null Model: Fixed 10.03 11 1.00 .00 26.54* 11.34* 9 5 .95 .98 .09 .07 16.63* 5 .96 .10 1.70 1 .99 .05 4.92 2 .91 .08 Maternal parenting Null Model: Fixed Model A: Differential exposure Difference with Null Model Model B: Differential vulnerability Difference with Null Model Model C: Differential exposure and vulnerability Difference with Model A Difference with Model B Final Model: No sex difference in delinquency Difference with best previous model (C) Δχ2 15.81* 10.46* 10.46* 15.81* 6.62 Paternal parenting Null Model: Fixed 11.37 8 .99 .04 Note. CFI = Comparative Fit Index; RMSEA = Root Mean Square Error of Approximation. * p < .05. Regarding maternal parenting the best model appeared to be the one in which boys and girls differed in mean levels and vulnerability. Girls had higher mean levels of maternal parenting than boys. Additionally, girls were protected in general more strongly from delinquency through maternal parenting than boys. Parental knowledge was negatively associated with delinquency of both boys and girls, but more strongly with delinquency of girls (see also Table 4.4). However, maternal control was not related to boys’ delinquency, but positively related to girls’ delinquency, indicating that delinquent behaviour of girls correlated with higher levels of maternal control. The fit worsened significantly by setting the probability for delinquency equal for boys and girls. This means that differential exposure to and sensitivity for maternal parenting factors are not related to the sex difference in delinquency. Next to the multivariate analyses per domain, we have done some multivariate analyses based on the univariate results. The fit indices for these models are displayed in Table 4.5. First, we took all factors to which boys and girls were differently exposed univariately and put them in one model. These were the number of delinquent friends, adolescent disclosure to mother and parental solicitation of mother. Then we followed the same analytic strategy as before by comparing different models that represented differential exposure and vulnerability. As expected, the model in which boys and girls had different mean levels of these factors had the best fit. 80 Table 4.4 The maternal parenting model with sex differences in mean levels and vulnerability Means (SD) B (se) Boys Girls Boys Girls Parental knowledge M 8.05 8.03 -0.17* -0.25* (1.51) (1.66) (0.06) (0.10) Adolescent disclosure M 7.11 7.56 -0.13 -0.03 (1.52) (1.67) (0.08) (0.10) Parental solicitation M 5.16 5.67 0.07 0.03 (1.73) (1.82) (0.05) (0.06) Parental control M 6.47 6.48 -0.06 0.15* (2.46) (2.26) (0.04) (0.06) * significantly related to delinquency (p < .05) This model was compared with the same model where the probability for delinquency was set equal for boys and girls. It appeared that the model in which boys and girls had different mean levels on the factors, but an equal probability for delinquency was the best model. This indicates that the sex difference in delinquency is related to sex differences in exposure towards the number of delinquent friends, adolescent disclosure to mother and parental solicitation of mother. More specifically, the fact that girls are less likely to be delinquent is related to girls have higher levels of adolescent disclosure with mother and parental solicitation of mother and less delinquent friends than boys. Second, we took all factors for which boys and girls showed differential vulnerability in the univariate analyses (i.e. maternal support, maternal control and the extent of best friends’ delinquency), put them in one model, and ran again a series of models. The best model was the model in which boys and girls were differently vulnerable for the risk factors, but the model did not improve by setting the probability for delinquency equal among boys and girls. This indicates that the sex difference in delinquency was not related to differential vulnerability. Third, we put all factors in a model boys and girls were differently exposed to or differently vulnerable for in the univariate analyses. The best fitting model indeed appeared to be the one in which boys and girls showed differential exposure to and vulnerability for the factors. However, the model did not improve if the probability for delinquency was set equal for boys and girls. In other words, the sex difference in delinquency is not related to this model of differential exposure and vulnerability. 81 Table 4.5 Fit indices for multivariate models Model All differential exposure factors Null Model: Fixed Model A: Differential exposure Difference with Null Model Model B: Differential vulnerability Difference with Null Model Model C: Differential exposure and vulnerability Difference with Model A Difference with Model B Final Model: No sex difference in delinquency Difference with best previous model (A) All differential vulnerability factors Null Model: Fixed Model A: Differential exposure Difference with Null Model Model B: Differential vulnerability Difference with Null Model Model C: Differential exposure and vulnerability Difference with Model A Difference with Model B Final Model: No sex difference in delinquency Difference with best previous model (B χ2 df CFI RMSEA 28.38* 2.59 7 4 .92 1.00 .11 .00 24.68* 4 .92 .15 1.72 1 1.00 .06 5.02 5 1.00 .00 17.77* 14.05* 7 4 .78 .80 .08 .10 5.02 4 .98 .03 1.14 1 1.00 .02 6.95 5 .96 .04 Δχ2 23.48* 0.74 0.74 23.48* 2.74* 4.44 14.26* 14.26* 4.44 2.06 All differential exposure/vulnerability factors Null Model: Fixed 45.85* 13 .92 .10 Model A: Differential exposure 17.18* 7 .97 .08 Difference with Null Model 26.93* Model B: Differential vulnerability 28.15* 7 .95 .11 Difference with Null Model 17.17* Model C: Differential exposure and vulnerability 1.14 1 1.00 .02 Difference with Model A 17.17* Difference with Model B Final Model: No sex difference in delinquency 3.39 2 1.00 .05 Difference with best previous model (C) 3.48 Note. CFI = Comparative Fit Index; RMSEA = Root Mean Square Error of Approximation. * p < .05. Discussion It is a fact that there are sex differences in offending behaviour. However, the origin of these sex differences is not yet understood. To better understand the sex difference, this study addressed the risk exposure hypothesis – whether the sex difference in delinquency is related to sex differences in mean levels of parent and peer factors – and the risk vulnerability hypothesis – whether the sex difference is related to differences in vulnerability of parent and peer factors. Factors were considered in the sub domains motherchild relationship, father-child relationship, maternal parenting, paternal parenting, and peers. In addition, we examined the risk exposure and risk 82 vulnerability hypotheses concurrently. Innovative was that we not only tested whether differences in mean levels or vulnerability between boys and girls (co-)existed, but also whether these were related to the sex difference in the prevalence of delinquency. We used an eminently suited data set with rich and relevant data for the research question at hand. Data had been gathered – without method differences – for both boys and girls. Sex differences in Mean Levels and Vulnerability The sex ratio in delinquency in our sample (i.e. 1.4 : 1) was comparable to that of 12-and-13-year olds in a Dutch nationally representative self-report survey (Van der Laan & Blom, 2006). Our study showed that this sex difference disappeared when differences in mean levels of adolescent disclosure to mother, parental solicitation of mother, and number of delinquent friends between boys are taken into account. Put differently, a reason why boys are more likely to commit offences than girls appears to be that girls talk more with their mothers than boys, that mothers are involved more with their daughters than with their sons, and that boys have more delinquent friends than girls. It makes sense that girls’ involvement with their mother and vice versa is higher than that of boys, since girls are much more social and more family oriented. That this is reflected in the reciprocal behaviour towards their mother and not towards their father is most likely because mothers are also female and have this same social tendency. The lower number of delinquent friends of girls was also expected since, as discussed before, girls more often have female friends whereas boys hang around more often with male friends. In light of the social control theory (Hirschi, 1969) and the differential association theory (Sutherland, 1947) these results might imply that girls are less likely to be delinquent because they do not want to endanger their high involvement with their mothers by going against their mothers will and therefore they have less difficulties with resisting the influence of delinquent friends. Furthermore, girls do not happen to have a lot of delinquent friends which makes it even less difficult to get affected by them. This indicates that if girls had both similar levels of involvement with their mothers as boys ánd a similar number of delinquent friends, there might not have been a sex difference in delinquency. We could speculate that to decrease the gender gap in delinquency, preferably by reducing delinquent behaviour of boys, both the boys’ level of disclosure towards mothers and the interest of mothers towards sons should be improved, but boys should also be encouraged not to hang around with (same sex) delinquent peers anymore. Then again, we found for maternal parenting, that sex differences existed in mean levels as well as in vulnerability. This shows that parenting behaviour of mothers is not only different for boys and girls, but it also has different effects on boys and girls. Mothers appeared to be involved more with their daughters than with their sons, in terms of parental solicitation. 83 Moreover, the higher level of adolescent disclosure for girls towards mothers shows us that girls tell their mothers more than boys do. Girls are therefore protected more from delinquency than boys. Besides, mother who had higher levels of parental knowledge protected their daughters more than their sons. This indicates that girls probably not only absent themselves from delinquency because they have more to lose in terms of maternal involvement than boys, but also because they are more vulnerable for the influence of maternal parenting. The reason for this higher vulnerability might be that girls are more family-focused than boys and are taught to care for others. This may result in higher levels of social control: girl do not show delinquent behavior since they do not want to risk losing the good bond with their mothers. A finding that could contradict this suggestion is that girls’ delinquency was found to be related to high levels of maternal control, indicating that maternal control is a risk factors for delinquency in girls. However, it should be noted that these are cross-sectional results and therefore, it might very well be that mothers control their daughters more when they show delinquent behaviour and not the other way around. Interestingly, while mothers had a differential influence on boys and girls, the influence of paternal parenting on delinquency was similar across sexes. This is in line with the studies of Blitstein et al. (2005) and Wong et al. (2010). Hence, an important addition to previous studies that displayed that mothers can have different influences on boys’ and girls’ delinquency development (Moffitt et al., 2001; Pedersen, 1994) is that girls are more exposed to the influence of mothers. Strengths and Limitations This study was limited because of its cross-sectional nature; we could not distinguish cause and effect or reciprocal effects like in longitudinal studies. Parenting practices, for instance, might be influenced by the delinquent behaviour of the adolescent, or the other way around (Kerr & Stattin, 2003). Also, note that cross-sectional results are generally stronger than longitudinal results. In addition, it has to be taken into account that respondents in this study were 12 to 13 years of age and that results cannot be generalized to adolescents of all ages. It might for instance be that results are different for older adolescents, for whom parents become less important and peers more important. Replications for other age groups are therefore necessary. A strong point of this study was the direct measurement of best friends’ delinquency. Most studies assessed friends’ delinquency by asking respondents about their friends. In this way, it is likely that similarity with friends’ delinquency is overestimated, because adolescents’ belief about their friend’s delinquency is based on their own assessment. Another strong point was that not only differences in mean levels and vulnerability were 84 examined, but also whether they co-existed and whether these were actually related to the sex difference in offending. Hoyt and Scherer (1998) identified several approaches for explaining delinquent behaviour of girls. One of these approaches claims that there is no need for a different theoretical framework to account for female delinquency, but that existing theories, mostly based on research on males’ delinquent behaviour, can be used to explain female behaviour. The reason that girls are less often delinquent than boys is simply that they are less exposed to risk factors than boys are. Another approach states that existing theories are not adequate for the explanation of female delinquency. Girls are thought to have different risk factors and therefore need other theories to clarify their delinquent behaviour. Hence, this approach assumes that girls and boys differ in their vulnerability for risk factors. Our results indicated that girls have many similar risk factors as boys, although to some of these risk factors they were less exposed, but also that girls and boys have some different risk factors. These results imply that existing (male) theories can be used to explain girl delinquency, but that these are not sufficient; gender specific adaptations are probably needed. 85 86 Appendix None Vulnerability Power M Support M None None NAF None Involvement in peer relations F Negative interaction F Power F Support F None None Negative interaction M Father-child relationship Father-child conflict None None Model (sex difference in) Involvement in peer relations M Mother-child relationship Mother-child conflict Univariate multiple group analyses 2.99 (1.75) 2.52 (2.02) 1.21 (1.34) 5.12 (1.91) 5.12 (1.78) 3.21 (1.89) 2.78 (2.07) 1.75 (1.56) 4.89 (1.76) 5.71 (1.93) 3.01 (1.63) 2.78 (1.93) 1.31 (1.41) 3.04 (1.66) 2.95 (2.03) 1.57 (1.34) 5.05 (1.61) 5.48 (1.77) Means (SD) Boys Girls B (se) Girls -0.21* (0.04) -0.05* (0.01) 0.10* (0.03) 0.10* (0.04) 0.16* (0.03) -0.11* (0.04) -0.04 (0.03) 0.14* (0.04) 0.10* (0.04) 0.16* (0.03) Boys 87 Vulnerability Parental control M NAF Parental control F 7.19 (1.81) 6.75 (1.71) 4.46 (1.74) 8.05 (1.51) 7.11 (1.52) 5.16 (1.73) 6.47 (2.46) 7.11 (1.78) 6.88 (1.94) 4.46 (1.93) 8.03 (1.66) 7.56 (1.67) 5.67 (1.82) 6.48 (2.26) Means (SD) Boys Girls B (se) Girls 0.09* (0.05) -0.09* (0.03) -0.18* (0.03) -0.16* (0.03) -0.09* (0.04) -0.07* (0.03) -0.20* (0.03) -0.22* (0.03) Boys 0.41* (0.03) 1.77 0.67 (2.42) (1.12) Best friends delinquency (scale of Vulnerability 1.10 1.18 0.04 0.15* variance) (1.37) (2.12) (0.03) (0.04) Truancy best friend None 0.87 0.56 0.12* (0.05) (1.50) (1.11) Note. Means in bold refer to means that are significantly different for boys and girls. When boys and girls do not differ in their B’s, the single B is shown in the table. When B’s are not equal, two separate B’s are shown. * p < .05 NAF = model is not of acceptable fit Mean levels None Parental solicitation F Peers Number of delinquent friends None Adolescent disclosure F None Mean levels Parental solicitation M Paternal parenting Parental knowledge F Mean levels None Adolescent disclosure M Maternal parenting Parental knowledge M Model (sex difference in) Chapter 5 The sex difference in delinquency: Do girls need a bigger push? Wong, T. M. L., Slotboom, A., Bijleveld, C. C. J. H., Van Lier, P. A. C., Meeus, W. H. J. & Koot, J. M. (submitted). The sex difference in delinquency: Do girls need a bigger push? 89 This study is an attempt to gain insight in the aetiology of the sex difference in delinquency by testing the threshold hypothesis which states that girls have a higher risk threshold for delinquency than boys. In examining the hypothesis the authors dealt with methodological problems of previous research by focusing on self-reports of delinquency instead of arrest or incarceration as indicator of delinquency, by studying general delinquency as well as serious delinquency, and by taking risk factors and promotive factors into account. A sample of 495 Dutch juveniles from the RADAR study, a prospective cohort study, is analyzed. This study did not find evidence for the threshold hypothesis, but did find some interesting results regarding the dose-response relationship. 90 Introduction The sex difference in adolescent delinquency is widely acknowledged. Girl offending is generally less serious than boy offending and its prevalence is lower (Junger-Tas, Marshall, & Ribeaud, 2003; Van der Laan & Blom, 2006, Steffensmeier & Schwartz, 2009). An explanation often brought up for this sex difference is that girls are being socialized against delinquent behavior, whereas boys are socialized towards it. Boys are taught that it is a good thing to be competitive and take risks and therefore they may hold positive beliefs about aggressive and delinquent behavior. In contrast, girls are taught to care for others, be passive and prudent, which is more likely to result in negative attitudes towards aggression and delinquency (Agnew, 2009; Mears, Ploeger, & Warr, 1998; Moffitt, Caspi, Rutter, & Silva, 2001). In other words, the aggressive and delinquent behavior repertoire of girls is likely to be constrained by their environment through socialization or modeling. As a result, it is a much bigger step for girls to become delinquent than for boys, leading to a lower prevalence of delinquency among girls. In line with this reasoning, it is thought that girls have a higher threshold than boys for delinquency, the so-called threshold hypothesis, i.e. that girls pass a higher critical ‘risk level’ in order to become delinquent (Eme, 1992). This risk level that defines the risk threshold can be operationalized in two ways : 1) the risk level indicates the severity or level of a single risk factor, and 2) the risk level considers the number of risk factors. This last way of operationalizing risk level is derived from the cumulative risk approach (Rutter, 1979; Sameroff, Seifer, Barocas, Zax & Greenspan, 1987) : the more risk factors someone experiences, the more likely he or she is to be delinquent. There is evidence for such a doseresponse relationship between the number of risk factors and the likelihood of delinquency for boys and girls (Johansson & Kempf-Leonard, 2009; Loeber, Slot & Stouthamer-Loeber, 2008; Van der Laan & Van der Schans, 2010; Wong et al., submitted). However, the threshold hypothesis states that for girls it requires more risk factors than for boys to start offending. If girls are exposed to the same number of risk factors as boys, they are less likely delinquent. Differences between boys and girls in such a threshold for delinquency, while often posited, have hardly been studied empirically. In the current study, we tested the threshold hypothesis following the cumulative risk approach, since it has been found in general population studies that it is rather the amount of risks than the level of risk that affects the development of deviant behavior (Rutter, 1979; Sameroff, Seifer, Barocas, Zax & Greenspan, 1987). Furthermore, this approach has been noted for its potential to capture the natural covariation of risk factors (Luthar, 1993). A few studies used the same approach to sex differences in delinquency. In the study by Alemagno, Shaffer-King, and Hammel (2006) the overall number of risk factors in relation to delinquency was compared 91 among 250 incarcerated boys and girls. In accordance with the cumulative risk hypothesis they found that detained girls were exposed to more risk factors than detained boys. However, Van der Laan and Van der Schans (2010) showed that the sex difference in thresholds may vary by risk domain. They found that arrested girls were exposed to a higher number of family risk factors than arrested boys, but that by contrast arrested boys appeared to have a higher number of risky lifestyle factors compared with arrested girls. Thus the threshold model may not apply to all risk domains. Also, since females and males are not equally likely to show delinquent behavior at different age periods (Junger-Tas et al., 2003; Van der Laan & Blom, 2006), the sex variant threshold for displaying delinquency may also be age variant. As Moffitt (1993) suggested, during puberty, it is almost normative to show delinquent behavior as an expression of the discomfort experienced due to the discrepancy between biological and social maturity that is typical for adolescence. If so, it may be that girls in this period, like boys, are more liable for delinquency and the threshold effect does not show during this particular age period. The studies that examined the threshold hypothesis according to the cumulative risk approach only investigated adjudicated or incarcerated juveniles. Without a non-delinquent comparison group however, it is difficult to conclude whether one of the sexes indeed has a higher risk threshold for delinquency, since it might be that one sex always (also in case of non-delinquency) has higher risk levels than the other sex. Therefore, differences in number of risk factors found in samples of delinquent boys and girls alone are not enough to conclude on a higher threshold for girls. Another limitation of the studies addressing the threshold hypothesis so far is that it has been studied in youth who were regarded delinquent based on being arrested or convicted while the hypothesis was not tested using self-reports of delinquency. Girls and women, however, are often treated differently in the juvenile justice system than boys and men (e.g. Daly, 1994). This is illustrated for instance by the bigger gender gap in official records than in self-reported delinquency, which may result from the fact that girls are less likely to be arrested than boys (Slotboom, Wong, Swier, & Van der Broek, 2011). Therefore, the threshold for delinquency in such studies cannot be separated from the threshold to be arrested, prosecuted or convicted. Thus it is problematic to attribute sex differences in the number of risk factors in officially delinquent samples to the threshold for delinquency. Furthermore, adjudicated or incarcerated adolescents are mostly serious delinquents, while researchers suggest a higher threshold for girls across the whole range of delinquency. It should therefore be examined more directly whether the threshold effect applies to general delinquency, to serious delinquency or to both. As Moffitt (1993) argues, delinquent behavior seems to be more normative for adolescents. Therefore, it might be that the threshold hypothesis only holds for serious delinquency in adolescence. 92 In this study, we try to contribute to the literature on the threshold hypothesis by focusing on self-reported delinquency, and by considering general as well as serious delinquency. However, there is one additional issue that has to be taken into account in threshold research that regards promotive factors. In examining the threshold, it is essential to include promotive factors, next to risk factors, since adolescent delinquency is not only affected by risk factors, but also by promotive factors. Promotive factors are those factors associated with a decreased probability of delinquency (Sameroff, Bartko, Baldwin, Baldwin, & Seifer, 1998; Stouthamer-Loeber, Loeber, Wei, Farrington, & Wikström, 2002). Promotive and risk factors are actually the opposite end of each other within the same variable. That is, the same variable can constitute a risk as well as a protective condition for juveniles. Having a bad relationship with parents, for instance, can be a risk for the development of adolescent delinquency, but having a good relationship with parents can serve as protection against it. The relationship between this factor and delinquency is not necessarily linear and the relative importance may differ for risk and promotive factors (Sameroff, et al., 1998; Stouthamer-Loeber et al., 2002). Since the number of promotive factors can neutralize the influence of the number of risk factors (Stouthamer-Loeber et al., 2002; Van der Laan & Blom, 2006), not only the number of risk factors should be considered to identify the risk level in threshold studies, but also the number of promotive factors. This important neutralization effect is ignored if promotive factors are not considered, which might result in overstating the risk and in getting any threshold effect wrong. To examine the threshold hypothesis properly, we therefore analyze the relative risk level (i.e., the number of risk factors minus the number of promotive factors) of boys and girls in relation to delinquency. Research questions In this study we tested to what extent 1) the threshold for delinquency is different for boys and girls; 2) the threshold for serious delinquency is different for boys and girls; 3) these differential thresholds vary across different domains. In examining these research questions we dealt with the methodological problems of previous research by analyzing delinquent as well as nondelinquent boys and girls, by taking into account promotive factors next to risk factors, by focusing on self-reported delinquency instead of arrest or incarceration as indicator of delinquency, and by studying general delinquency as well as serious delinquency. A broad array of factors are considered that were shown to predict delinquency in previous studies (Hoeve et al., 2009; Hubbard & Pratt 2002; Lipsey & Derzon, 1998; Maguin & Loeber, 1996; Pratt & Cullen, 2005; Simourd & Andrews, 1994; Wong et al., 2010; Zahn, 2009). These included individual (problem) factors (i.e. personality characteristics, prosocial behavior, empathy, pubertal timing, 93 levels of self-worth, victimization), family factors (i.e. the quality of parentchild relationships, conflicts within the family, parenting practices, having caregivers with a history of delinquency), school factors (i.e. school achievement, truancy) and peer delinquency. Methods Sample Data for this study come from the RADAR study (Research on Adolescent Development and Relationships), a Dutch ongoing prospective cohort study aimed at understanding the interplay between adolescent relationships and their development in many domains (Van Lier et al., submitted). In this study, adolescents, both their parents, a sibling (between the ages of 10 and 20), and a best friend are followed across adolescence at the age of 12 to 17 years. Assessments began in 2006 when the adolescents were in the first grade of secondary school (n = 497). The current study used data from the second and third wave, which contained 495 Dutch adolescents for whom data on delinquency were available. The RADAR study focuses on delinquency development in particular. Therefore, adolescents at high risk of developing delinquent behavior were oversampled. To indicate high risk, teachers in the sixth grade of primary school rated behavior problems of the adolescents (for detailed information about this procedure, see Van Lier et al., submitted). Of the sample used in this study, 41.4% of the children were at elevated risk of developing problem behavior. The sample contained 56.6% boys (n = 280) and 43.4% girls (n = 215). In the elevated risk sample, there were 57.1% boys and 42.9% girls. The mean age was 13.5 years (SD = 0.61) at the second wave. All respondents were asked to fill out questionnaires during an annual home visit by trained interviewers. The questionnaires contained questions about the adolescent’s behavior, personal characteristics and relationships between family members and between the adolescent and the best friend (for other published papers that used data from the RADAR study, see Eichelsheim et al., 2010; Eichelsheim et al., in press; Hale et al., 2011; Klimstra et al., 2010; Schwartz et al., in press; Yu, Branje, Keijsers, & Meeus, 2011). Delinquency measurements Delinquency was measured in Wave 2 and 3 with a questionnaire covering 30 delinquent acts, among which were five minor offences, based on the International Self-Reported Delinquency Scale (Junger-Tas et al., 2003). These minor offences are not taken into account in the analyses, since the severity of these offences is very low, but the prevalence relatively high and therefore they would influence the delinquency scale disproportionately high (see the Appendix for an overview of the 25 included offences). For each of the offences, respondents and their best friends indicated how often 94 they had committed them in the previous year. For this study we summed all offences and dichotomized the total of the sum into 0 (no offence committed – not delinquent) and 1 (1 or more offences committed – delinquent). Delinquency was not only measured annually in the RADAR study, but also every three months through internet assessments. In the internet assessments (of which there were three between the annual measurements) respondents were asked whether they had committed offences in the previous three months. During the annual assessments, however, it was asked whether respondents had committed the offences in the previous twelve months. It appeared that many adolescents filled out in the annual assessment that they did not commit any offence while they had reported to be delinquent some of the three monthly internet assessments. Since it was clear that they had at least committed one of the offences in the previous year, regardless of the exact period, these adolescents were assigned to the delinquent category. Serious delinquency was defined as all offences carrying a maximum prison sentence of four years or more in the Netherlands (an overview of all those offences can be found in the CBS Standaardclassificatie Misdrijven 1993). However, the seriousness of some of the offences was not clear and therefore we did not include them in the serious delinquency scale5. The items that were included were (attempt of) arson, theft of a bike, theft from a car, burglary, handling stolen goods, robbery, weapon injury, violence with injury, and sex offences. We dichotomized the total sum of all the items into 0 (no serious offence committed) and 1 (at least one serious offence committed). Other measurements The factors used in this study are described in Table 5.1. All the risk and promotive factors were measured at Wave 2. Previous studies were limited because most of them were cros-sectional: risks and delinquent behavior were measured at the same time. By contrast we used risk and promotive factors of the data preceding the data wave in which delinquency was assessed. The factors comprised six domains: individual, negative life events, parent-child relationship, parenting, school, and peers. Most of the constructs were assessed through the adolescents. However, mothers had indicated whether there were family members with contacts with the police or justice. Besides, adolescents’ best friends reported about their own delinquent behavior. 5 These included the items: theft with a value of more than five euro’s, threatened somebody to scare that person or to let him do something. 95 96 The extent to which a person is trustworthy, altruistic, kind and affectionate The extent to which a person is thoughtful, has good impulse control is goal-directed behaviors The extent to which a person is emotional instable, anxious, moody, and sad The extent to which a person has imagination, insight and broad range of interest Big Five Big Five Big Five Conscientiousness Neuroticism Openness to experience .72 .85 Sum of 6 7-Point Likert items Sum of 6 7-Point Likert items .82 .78 .79 Reliability (alpha) Sum of 6 7-Point Likert items Sum of 6 7-Point Likert items Sum of 6 7-Point Likert items The extent to which a person is sociable, talkative, assertive and expressive Big Five How created? Description Agreeableness Table 5.1. Description of factors used in this study Instruments Constructs Individual Big Five Extraversion - Versatile - Innovative - Irritated - Nervous - Punctial - Neat - Pleasant - Kind - Reserved - Talkative Example(s) of item 97 Description Difficulties to remain in control of behavior when experiencing negative emotions Behaviour that regards helping others with no thought of reward or compensation The tendency to experience feelings of sympathy and compassion for unfortunate others The tendency to spontaneously adopt the psychological point of view of others in everyday life The extent to which a persons’ self-concept is clear, confident, internally consistent and stable over time Instruments Difficulties in Emotion Regulation Scale (Gratz & Roemer, 2004) Prosocial behavior Interpersonal Reactivity Index (Davis, 1983) Interpersonal Reactivity Index (Davis, 1983) Self-Concept Clarity Prosocial behavior Empathic concern Perspective taking Self-concept clarity Constructs Impulse control difficulties Sum of 12 5-Point Likert items Sum of 7 5-Point Likert items Sum of 7 5-Point Likert items Sum of 11 7-Point Likert items Sum of 5 5-Point Likert items How created? .84 .66 .70 .93 Reliability (alpha) .76 - My ideas about myself are often contradictory - Sometimes I have the feeling I know other people better than myself - I am often worried about people who are worse off than me - If I see that someone is taken advantage of, I tend to protect this person - Sometimes I try to better understand my friends by imagining myself in their position - During a disagreement, I try to understand all positions before taking a decision - I am in general nice to other people - I try to involve other people in conversations - When I’m upset, I lose control over my behaviors - When I’m upset, I cannot concentrate anymore Example(s) of item 98 Victimized or not in the previous year by 5 different offences Victim of relational of physical aggression Whether a family member was ever in contact with the police Whether a family member was ever in contact with justice Proactive/Reactive Aggression NA NA Victimization aggression Family member with police contact Family member contact with justice The extent to which the adolescents had noticed own physical changes Pubertal Development NA Description Instruments Victim offence Negative life events Pubertal development Constructs 1 dichotomous item 1 dichotomous item Sum of 7 7-Point Likert items Dichotomized the sum of 5 dichotomous items 1 5-Point Likert item How created? NA NA .84 NA NA Reliability (alpha) Theft Threat of violence Threat with a weapon Violence with assault Sexual offence Other people try to let me do things by physically intimidating me - If other people are angry with me, they exclude me from common activities - - How long is het ago that you noticed that your body changed Example(s) of item 99 Description Whether the parent-child bond is based on affection, admiration, alliance, intimacy, and companionship The control parents have in the relationship with their child Whether the parent-child bond is characterized by punishment and irritation Frequency conflicts between adolescents and mother/father Instruments Network of Relationships Inventory (Furman & Buhrmester 1985) Network of Relationships Inventory (Furman & Buhrmester 1985) Network of Relationships Inventory (Furman & Buhrmester 1985) Interpersonal Conflict Questionnaire (Laursen, 1993) Parental power Parental Negative interaction Parent-child conflicts Constructs Mother/father Parental support Sum of 10 5-Point Likert items (for both parents Mean of 6 5-Point Likert items (for both parents) Mean of 6 5-Point Likert items (for both parents) Mean of 8 5-Point Likert items (for both parents) How created? mother = .84; father = .82 mother = .88; father = .86 mother = .88; father = .82 mother = .84; father = .86 Reliability (alpha) - How often have you had conflicts with your mother/father about money in the previous week? - How often have you had conflicts with your mother/father about relationships in the previous week? - How often do you disagree and argue with your mother/father? - Are you and your mother/father irritated by each other’s behavior? - How often does your mother/father have his/her way when you disagree? - How often does your mother/father take a decision for you both? - Does your mother/father admire and respect you? - How often do you have fun with your mother/father? Example(s) of item 100 Description Knowledge of parents about the child’s whereabouts The extent to which children spontaneously tell their parents about their whereabouts The extent to which parents actively ask their children about their whereabouts Controlling the child’s freedom by setting rules and restrictions Instruments Parenting Practices (Kerr & Stattin 2000) Parenting Practices (Kerr & Stattin 2000) Parenting Practices (Kerr & Stattin 2000) Parenting Practices (Kerr & Stattin 2000) Parental knowledge Adolescent disclosure Parental solicitation Parental control Constructs Mean of 6 5-Point Likert items (for both parents) Mean of 6 5-Point Likert items (for both parents) Mean of 6 5-Point Likert items (for both parents) Mean of 9 5-Point Likert items (for both parents) How created? mother = .84; father = .83 mother = .74; father = .75 mother = .70; father = .75 mother = .80; father = .82 Reliability (alpha) - Do you need permission of your mother/father to get home late on a school night? - Does your mother/father demand to tell how you spend your money? - How often does your mother/father talk to your friends? - How often does your mother/father start a conversation about school? - How often do you talk with your mother/father about school subjects? - Do you have many secrets for your mother/father about what you do in your spare time? - Does your mother/father know what you do in your spare time? - Does your mother/father know how you spend your money? Example(s) of item 101 Peers Delinquent friends Truancy Constructs School School achievement How often truant in the previous three months School achievement questionnaire Number of friends they thought had committed an offence in the previous three months How well performed at school in previous week compared to class mates School achievement questionnaire Basic questionnaire peers Description Instruments Summing 5 items 1 5-Point Likert item 1 10-Point Likert item How created? .72 NA NA Reliability (alpha) - How many of your friends have damaged something on the streets - How many of your friends have injured somebody by hitting or with a weapon? - How often have you been truant in the previous three months? - - In comparison to your class mates, how well did you perform at school? Example(s) of item Strategy of analysis We performed preliminary analyses to identify the risk versus promotive nature of the factors. To examine whether the factors were risk factors, promotive factors or both we partly used the same method as StouthamerLoeber et al. (1993; 2000) and Van der Laan and Blom (2006). All factors were trichotimized into a promotive, a neutral and a risk component using the sex-specific 25th and 75th percentiles of the variable distributions as cutoffs, if applicable. For some variables it was more appropriate to trichotimize according to the categories (see notes of Table 2). All these factors were recoded into two dummy variables: a risk variable and a promotive variable. The reference category in each variable was the neutral component. For some other variables it was only possible to dichotomize the values (i.e., victimization of delinquency, family members with police contacts, family members with justice contacts, having a delinquent best friend) given the content of the variable. These were all considered to be risk factors and had therefore only risk variable. The risk and promotive variable that were computed for each factor were analyzed in a logistic regression. If the risk variable was related to delinquency (p less than 0.05), we considered the variable to be a risk factor. If the promotive variable was related, the variable was considered to be a promotive factor. If both variables were related to delinquency, the factor was both a risk as well as a promotive factor. To examine whether girls have a higher threshold for delinquency than boys, we created three types of variables: one that indicated the number of risks, one that indicated the number of promotive factors, and one that indicated the relative level of risk. The relative risk level indicated the number of risk factors minus the number of promotive factors. These variables were created for each domain. All the previous mentioned preliminary analyses were carried out for general delinquency as well as for serious delinquency. After these analyses we carried out a logistic regression to investigate whether the risk level variable, sex and the interaction between risk level and sex could predict delinquency (to avoid multicollinearity, the interaction terms were constructed with the centered version of the risk level variable). In the regressions we controlled for delinquency at Wave 2. If the interaction term significantly predicted delinquency, this would indicate that there is a different relation between the number of risk (or promotive) factors and delinquency for boys and girls. All these analyses were performed for the number of risk factors, the number of promotive factors, and for the relative risk level. Furthermore, we carried out the analyses for all the factors together and for the separate domains of factors. The same analyses were performed for serious delinquency. 102 Results Delinquent behavior In Wave 3 48.2 per cent of the boys and 38.1 per cent of the girls reported to have committed at least one offence in the previous year, while 14.6 per cent of the boys and 7.5 per cent of the girls reported at least one serious offence. Risk and promotive factors In Table 5.2 the risk and promotive factors for delinquency and serious delinquency are presented. Empty cells in this table indicated no risk or promotive effect. All the risk factors were summed to indicate the number of risk factors for each adolescent. The same was done with the promotive factors. For general delinquency, the risk domain of school and peers consisted of only one factor. For serious delinquency, both the school and peer domain consisted of only one risk and one promotive factor. In Table 5.3 the descriptive statistics of the risk and promotive factor counts are presented. Girls in general had more promotive factors than boys. Boys showed to have more peer risk factors than girls. Threshold for general and serious delinquency Table 5.4 shows the results of the logistic regression of Wave 3 general and serious delinquency on sex, the risk level, and the interaction between sex and risk level, controlling for delinquency at Wave 2. These analyses were carried out for the number of risk factors, for the number of promotive factors, and for the relative risk level (number of risk factors minus the number of promotive factors). The general number of risks (OR = 1.47), as well as the number of specific risks of the negative life events (OR = 2.69), father (OR = 1.62) and peer (OR = 3.39) domain were associated with an increased risk of general delinquency. However, none of the levels of promotive factors were significantly related to general delinquency. Regarding the relative risk levels, the general risk level, as well as the negative life events risks and the peer risks were related to delinquency (OR = 1.15, 2.69, and 3.01, respectively). All associations were similar for boys and girls, as indicated by non-significant sex by risk level interaction terms. For serious delinquency we found an increased risk originating from the number of risks in the individual domain (OR = 3.74). The number of promotive factors (general nor in specific domains) was not associated with serious delinquency. Finally, the relative level of risk in the individual domain was positively associated (OR = 3.74). As was the case for general delinquency, all associations again were similar for boys and girls, as indicated by non-significant sex by risk level interaction terms. 103 Table 5.2 Significant risk and promotive factors for general delinquency and for serious delinquency General delinquency Serious delinquency Factors Risk Promotive Risk Promotive Individual Extraversion Agreeableness Low Conscientiousness High Neuroticism Openness to experience Impulse control difficulties Prosocial behavior Low Empathic concern Low Low Perspective taking Low High Low Self-concept clarity Low High Low Pubertal developmentc Negative life events Victim offence (theft, Yes Yes violence, threat, sexual)d Victimization (physical or High High relational) aggression Family member with police Yes Yes contactsd Family member contact with justiced Mother Support mother Low Low Power mother High Negative interaction mother High Low High Low Conflict with mother Higha Lowa Higha Lowa Parental knowledge mother Low High Low Adolescent disclosure mother Lowa Higha Lowa Parental solicitation mother Parental control mother Father Support father Low High Low High Power father High Negative interaction father High Low High Conflict with father Higha Lowa Higha Low b Parental knowledge father Low High Low Adolescent disclosure father Lowa Higha Lowa High Parental solicitation father Parental control father Highb School School achievementc Truancyc High Low High Low Peers Delinquent best friendd Yes Delinquent friendsc Many None Many None 104 Note. Cell entries indicate whether the factor constituted a risk or protection based on logistic regressions with general and serious delinquency, respectively. High = highest level; Low = lowest level; Yes = factor present; Many = many delinquent friends; None = no delinquent friends; Most factors were trichotimized based on the sex specific 25 th and 75th percentiles of the variable distributions as cut-offs. Factors with a superscript d were already dichotomous, and only represented risk dummies. Factors with a superscript c had cut-offs based on the existing response categories. Regarding puberty, adolescents were at risk if their body was mature already or when it had started changing more than a year ago. No body changes were regarded as a promotive factor. For school achievement, it was classified a risk when adolescents responded that they achieved worse to much worse than their peers and as a promotive factor when they achieved better to much better. Regarding truancy it was a risk if adolescents had stayed away from school at least once a month and a promotive factor if they had never been truant in the last three months. With regards to delinquent friends, it was a risk factor if adolescents responded about at least one of the offences that most of their friends had committed them or about at least two of the offences that some of their friends had committed them. It was a promotive factor if none of their friends had committed any of the offences. Superscript a indicates that the factor was too highly correlated with factors from the same domain and therefore excluded from all risk and promotive analyses. Superscript b indicates that the factor was too highly correlated with factors from other domains. Therefore they were included in the analyses where separate domains were analyzed and excluded from the risk and promotive analyses in which the overall risk level was examined. 105 106 Table 5.3 Risk level means of delinquent and non-delinquent boys and girls All Non-delinquent Delinquent Boys Girls Boys Girls Boys Girls (n = 280) (n = 215) (n = 145) (n = 133) (n = 135) (n = 82) Risk General (all factors) 3.44a (2.60) 3.51a (2.94) 2.47a (2.02) 2.58a (2.32) 4.45b (2.76) 5.05b (3.21) a a a a b Individual 1.03 (1.14) 1.14 (1.17) 0.81 (1.03) 0.91 (1.04) 1.26 (1.20) 1.54b (1.28) Negative life events 0.61a (0.75) 0.57a (0.80) 0.36a (0.61) 0.40a (0.65) 0.86b (0.79) 0.88b (0.93) a a a a b Mother 0.84 (0.97) 0.85 (1.06) 0.62 (0.86) 0.64 (0.94) 1.06 (1.02) 1.20b (1.16) a a a a b Father 0.94 (1.00) 0.85 (1.14) 0.64 (0.81) 0.60 (0.99) 1.26 (1.09) 1.27b (1.26) School 0.05a (0.21) 0.07a (0.26) 0.02a (0.14) 0.03a (0.17) 0.07ab (0.26) 0.15b (0.36) a b a a b Peers 0.87 (0.67) 0.67 (0.69) 0.64 (0.55) 0.50 (0.62) 1.11 (0.70) 0.97b (0.72) Promotive General (all factors) 3.10a (2.01) 3.49b (2.22) 3.74a (2.03) 4.14a (2.14) 2.43b (1.75) 2.41b (1.91) Individual 0.70a (0.85) 0.64a (0.78) 0.84a (0.93) 0.75ab (0.85) 0.55bc (0.73) 0.46c (0.59) a a a a b Mother 0.52 (0.67) 0.50 (0.67) 0.64 (0.70) 0.64 (0.73) 0.40 (0.61) 0.27b (0.50) a b ac b a Father 0.61 (0.73) 1.04 (0.96) 0.70 (0.75) 1.15 (0.98) 0.53 (0.70) 0.84bc (0.89) School 0.65a (0.48) 0.64a (0.48) 0.74a (0.44) 0.77a (0.42) 0.56b (0.50) 0.53b (0.50) a a a a b Peers 0.58 (0.49) 0.64 (0.48) 0.86 (0.43) 0.79 (0.41) 0.39 (0.49) 0.39b (0.49) Risk minus promotive General (all factors) 0.43a (3.94) 0.06a (4.56) -1.16a (3.36) -1.53a (3.78) 2.09b (3.84) 2.70b (4.55) a a a a b Individual 0.33 (1.65) 0.51 (1.59) -0.03 (1.16) -0.15 (1.48) 0.71 (1.61) 1.09b (1.60) Negative life events 0.61a (0.75) 0.57a (0.80) 0.36a (0.61) 0.40a (0.65) 0.86b (0.79) 0.88b (0.93) a a a a b Mother 0.32 (1.36) 0.36 (1.47) -0.01 (1.29) 0.01 (1.40) 0.66 (1.35) 0.94b (1.42) Father 0.32a (1.36) -0.19b (1.72) -0.07a (1.20) -0.55b (1.56) 0.73c (1.39) 0.43ac (1.81) School -0.61a (0.58) -0.57a (0.62) -0.72a (0.49) -0.74a (0.50) -0.48b (0.63) -0.28b (0.71) a b a a b Peers 0.17 (0.97) -0.06 (0.98) -0.22 (0.73) -0.34 (0.86) 0.59 (1.02) 0.40b (1.00) Note. Means of total group of boys and girls are compared with t-tests. Means of non-delinquent and delinquent boys and girls are compared with ANOVA’s. Within each domain, for both the total group of boys and girls, as for the non-delinquent and delinquent boys and girls, means with similar superscripts are equal to each other. In between brackets are the standard deviations. Discussion This study examined the threshold hypothesis, which states that girls have a higher risk threshold for delinquency than boys. Accumulated risk levels in general and in several of the risk domains under study (individual, father, peers) were related to general delinquency. However, associations were not different for boys and girls, thus disconfirming the threshold hypothesis. Serious delinquency was only related to the risk level in the individual domain with, again, no differences in associations between boys and girls. Roughly the same results were found when levels of risk were corrected for levels of promotive factors, with the exception that the risk level in the father domain was not related anymore to delinquency. The fact that despite careful analyses no differences in risk-delinquency associations for boys and girls were found, thereby refuting the proposed threshold hypothesis, suggests that other mechanisms might account for the always found sex difference in levels of delinquency. An explanation more consistently found is that girls are less exposed to risk factors than boys. For example, girls seem to be less exposed to risk in the peer domain (Moffitt et al., 2001; Murray, 2002; Wong et al., submitted), which was confirmed in the present study. So although girls and boys have the same risk threshold for delinquency, girls may to be less likely than boys to reach this threshold, and therefore they are less likely delinquent. Regarding the dose-response relationship, there were some interesting findings. We found that the dose-response relationship for general delinquency existed in other domains than for serious delinquency. General delinquency was affected by the general risk level and the risk level in the domains of negative life events, father and peers, whereas serious delinquency was only affected by the risk level in the individual domain. These results imply that risk factors from the environment increase the risk for delinquency in general, but individual risk factors (such as low empathy, low perspective taking and an unclear self-concept) increase the risk for serious delinquency. Results on serious delinquency seem to be in line with Moffitt’s taxonomy (1993) in which she states that seriously delinquents (defined as life course persistent offenders) become delinquent because they have neurological deficits manifested as problems in the individual domain, such as low self-control, hyperactivity and difficult temperament. The difference between our findings and previous investigations, where girls were found to have a higher threshold for delinquency than boys (Alemagno et al., 2006; Van der Laan & Van der Schans, 2010), might be explained by the fact that previous studies examined a population that was already arrested or incarcerated for committing an offence. It could very well be that girls do not have a higher threshold for delinquency than boys, but that girls do have a higher threshold for being arrested. Because of the high prevalence of problems among arrested and convicted girls (e.g. Chamberlein & Reid, 1994; Emeka & Sorensen, 2009), it seems like girls 107 108 Table 5.4 Logistic regression of general and serious delinquency on sex, risk level and the sex x risk level interaction Risk Promotive B SE Odds ratio B SE Odds ratio (95% CI) (95% CI) General delinquency General (all factors) Sex 0.38 0.22 1.47 (0.95 – 2.26) 0.27 0.22 1.29 (0.84 – 2.00) Risk level 0.31* 0.14 1.37 (1.12 – 1.89) -0.38* 0.18 0.68 (0.48 – 0.98) Sex × Risk level -0.04 0.09 0.96 (0.81 – 1.14) 0.06 0.12 1.06 (0.84 – 1.36) Individual Sex 0.30 0.22 1.35 (0.89 – 2.06) 0.28 0.22 1.32 (0.87 – 2.01) Risk level 0.18 0.29 1.20 (0.68 – 2.12) -0.39 0.41 0.68 (0.30 – 1.51) Sex × Risk level 0.10 0.19 1.10 (0.76 – 1.60) 0.05 0.29 1.05 (0.60 – 1.84) Negative life events a Sex 0.30 0.22 1.35 (0.88 – 2.09) Risk level 0.99* 0.47 2.67 (1.08 – 6.70) Sex × Risk level -0.28 0.30 0.75 (0.42 – 1.34) Mother Sex 0.29 0.21 1.34 (0.88 – 2.03) 0.31 0.22 1.36 (0.89 – 2.07) Risk level 0.41 0.33 1.50 (0.78 – 2.89) -0.46 0.51 0.63 (0.24 – 1.71) Sex × Risk level -0.03 0.21 0.97 (0.64 – 1.46) -0.01 0.35 0.99 (0.50 – 1.98) Father Sex 0.28 0.22 1.32 (0.86 – 2.03) 0.21 0.22 1.24 (0.81 – 1.90) Risk level 0.77* 0.35 2.15 (1.09 – 4.25) -0.44 0.42 0.65 (0.28 – 1.49) Sex × Risk level -0.17 0.21 0.83 (0.54 – 1.26) 0.19 0.26 1.21 (0.73 – 2.02) Peers b Sex 0.18 0.23 1.19 (0.76 –1.87) Risk level 1.22* 0.55 3.39 (1.16 – 9.91) Sex × Risk level -0.23 0.35 0.79 (0.40 – 1.58) 0.22 0.10 0.06 0.22 0.21 0.14 0.22 0.47 0.30 0.22 0.24 0.16 0.22 0.25 0.15 0.22 0.38 0.24 0.32 0.16 0.07 0.30 0.99* -0.28 0.32 0.33 -0.02 0.17 0.57* -0.19 0.18 1.10* -0.27 1.20 (0.79 – 1.83) 3.01 (1.43 – 6.31) 0.77 (0.48 – 1.23) 1.19 (0.87 – 1.82) 1.77 (1.09 – 2.89) 0.83 (0.62 – 1.12) 1.37 (0.90 – 2.09) 1.39 (0.86 – 2.23) 0.98 (0.72 – 1.32) 1.35 (0.88 – 2.09) 2.67 (1.08 – 6.70) 0.75 (0.42 – 1.34) 1.38 (0.90 – 2.11) 1.17 (0.78 – 1.75) 1.07 (0.81 – 1.42) 1.39 (0.90 – 2.16) 1.28 (1.06 – 1.55) 0.96 (0.85 – 1.09) Risk minus promotive SE Odds ratio (95% CI) 0.33 0.25* -0.04 B 109 SE Risk Odds ratio (95% CI) B Promotive SE Odds ratio (95% CI) B 2.03 (0.87 – 4.37) 1.19 (0.57 – 2.45) 1.12 (0.67 – 1.86) 1.60 (0.76 – 3.39) 1.27 (0.56 – 2.89) 1.09 (0.61 – 1.95) 1.38 (0.62 – 3.07) 2.57 (0.77 – 8.57) 0.81 (0.36 – 1.84) 1.48 (0.71 – 3.06) 3.74 (1.05 – 13.35) 0.52 (0.21 – 2.30) 2.27 (0.85 – 6.05) 1.27 (0.92 – 1.74) 1.02 (0.82 – 1.26) Risk minus promotive SE Odds ratio (95% CI) Serious delinquency General (all factors) Sex 0.69 0.45 2.00 (0.82 – 4.86) 1.21 0.62 3.37 (0.99 – 11.41) 0.82 0.50 Risk level 0.35 0.21 1.42 (0.94 – 2.14) -0.05 0.49 0.95 (0.36 – 2.50) 0.24 0.17 Sex × Risk level -0.03 0.14 0.97 (0.74 – 1.28) -0.45 0.39 0.64 (0.30 – 1.38) 0.02 0.11 Individual a Sex 0.39 0.37 1.48 (0.71 – 3.06) 0.39 0.37 Risk level 1.32* 0.65 3.74 (1.05 – 13.35) 1.32* 0.65 Sex × Risk level -0.66 0.47 0.52 (0.21 – 1.30) -0.66 0.47 Negative life events a Sex 0.32 0.41 1.38 (0.62 – 3.07) 0.32 0.41 Risk level 0.94 0.61 2.57 (0.77 – 8.57) 0.94 0.61 Sex × Risk level -0.21 0.42 0.81 (0.36 – 1.84) -0.21 0.42 b Mother Sex 0.57 0.39 1.77 (0.82 –3.79) 0.47 0.38 Risk level -0.09 0.52 0.92 (0.33 – 2.53) 0.24 0.42 Sex × Risk level 0.27 0.36 1.31 (0.65 – 2.66) 0.08 0.30 Father Sex 0.67 0.41 1.95 (0.88 – 4.35) 0.71 0.44 2.03 (0.85 – 4.84) 0.71 0.41 Risk level 0.29 0.51 1.33 (0.49 – 3.61) 0.08 0.84 1.08 (0.21 –5.55) 0.17 0.37 Sex × Risk level 0.09 0.35 1.09 (0.55 – 2.16) -0.43 0.65 0.65 (0.18 – 2.33) 0.12 0.26 Note. In all the analyses we controlled for delinquency at Wave 2. * p < .05. Superscript a: there were no promotive factors in this domain. Superscript b: there was only 1 promotive factor in this domain. B are not arrested if they do not have many problems. The threshold of risks may be even bigger for being convicted. Previous research indeed has shown that juvenile females are relatively less often arrested than juvenile males for crimes (Sealock & Simpson, 1998). Also, if they are arrested, they are relatively less often prosecuted compared to males (Jeffries, Fletcher, & Newbold, 2003; Spohn & Beichner, 2000; Williams, 1999). It would be interesting to examine in a future study if there indeed are different thresholds for being arrested or convicted between boys and girls. Our results do not necessarily have to implicate that the threshold hypothesis is not true. It might be, for instance, that girls do have to exceed a different risk level than boys for delinquency, but not at all ages. The sample in our study was 13 to 15 years old when they were examined and as Moffitt et al. (2001) suggest, in this age period delinquent behavior might be sort of normative, also for girls. It may be that girls in this period, like boys, are therefore more liable for delinquency and as a result do not need such a big push anymore in terms of risk factors. Also, the peak age of delinquent behavior is earlier for girls than for boys (15 and 16 years, respectively) (Slotboom et al., 2011). This indicates that delinquency is relatively seen even more common for girls than for boys at the age of our sample. Future research should examine the threshold hypothesis at different ages, preferably before, during, and after adolescence. Another possibility is that girls do have to surmount a higher threshold for serious delinquency, but that there were not enough seriously delinquent boys and girls included in our study. Because of the low prevalence of serious delinquency, especially among girls, self-reported data may not be truly suitable to examine risk for serious delinquency. Therefore, most studies that intend to investigate these delinquents analyzed adjudicated or incarcerated samples. However, with these samples there is the problem that one cannot disentangle the threshold for arrest from the threshold for delinquency. In this study we considered promotive factors next to risk factors to specify the risk level. Although our results did not find large differences in results regarding the number of risk factors alone or regarding the relative risk level, the results in the father domain did differ. This indicates that it is important to take into account promotive factors. The current study was limited in some ways. A relevant limitation of this study is that in the preliminary analyses, we determined whether a factor was a risk (or promotive) factor for delinquency by analyzing the entire sample and not by distinguishing between girls and boys. However, previous studies (Wong et al., 2010) have shown that girls and boys share many risk and promotive factors, but also have some different risk and promotive factors. Also, we regarded each risk or promotive factor as equally important, whereas it is possible that some factors are more strongly related to delinquency than others. We have chosen not to make a distinction 110 between risk factors for boys and girls or – when aggregating risk factors within domains - between less and more important factors, as no a priori assumptions could be made to guide such choices. As studies on the threshold hypothesis are very limited, we decided to deal with the issues of promotive factors, overlapping effects of factors and different risk domains first. It would be interesting for future studies to additionally consider different risk factors for boys and girls and/or weight them in their study on the threshold hypothesis. Furthermore, the study was limited by the sample size. If the sample would have been bigger, there would have been more power to carry out the complicated analyses of this study. To conclude, this study showed that there is a clear dose-response relationship between the number of risks – overall and in several different domains – and general as well as serious delinquency. However, we could not demonstrate that girls need a higher number of risks than boys for (serious) delinquency. Thus, for now, the threshold hypothesis does not seem to provide an adequate explanation for the always demonstrated sex differences in levels of delinquency. 111 Appendix Delinquency items General delinquency (included serious delinquency) Destroying means of transport Destroying somebody’s house Destroying the school building Destroying property Shoplifting less than five euro’s Shoplifting more than five euro’s Theft at school less than five euro’s Theft at school more than five euro’s Theft at home less than five euro’s Theft at home more than five euro’s Other theft Threatening somebody to scare somebody or to get something Beating up without injury Soft drug selling Hard drug selling Party drug selling 112 Serious delinquency Arson Stealing a bike Theft from/out of car Burglary Handling stolen goods Robbery Hurting with weapon Beating up with injury Sexual offence 113 Chapter 6 Sex and age differences in the risk threshold for delinquency Wong, T. M. L., Loeber, R., Slotboom, A., Bijleveld, C. C. J. H., & Koot, J. M. (submitted). Sex and age differences in the risk threshold for delinquency. 115 This study examines sex differences in the risk threshold for adolescent delinquency. Analyses were based on longitudinal data from the Pittsburgh Youth Study (n = 503) and the Pittsburgh Girls Study (n = 856). The study identified risk factors, promotive factors, and accumulated levels of risks as predictors of delinquency and nondelinquency, respectively. The risk thresholds for boys and girls were established at two developmental stages (late childhood: ages 10-12 years, and adolescence: ages 13-16 years) and compared between boys and girls. Sex similarities as well as differences existed in risk and promotive factors for delinquency. ROC analyses revealed only small sex differences in delinquency thresholds, that varied by age. Accumulative risk level had a linear relationship with boys’ delinquency and a quadratic relationship with girls’ delinquency, indicating stronger effects for girls at higher levels of risk. 116 Introduction Many girls involved in the juvenile justice system – those who are arrested, adjudicated or incarcerated – have been exposed to trauma or abuse, have mental health as well as academic problems, and come from multi-problem families (Chamberlain & Moore, 2002; Kataoka et al., 2001; Lederman, Dakof, Larrea, & Li, 2004; Slotboom, Wong, Swier, & Van der Broek, 2011). Compared to arrested, adjudicated, or incarcerated boys, girls in the juvenile justice system have more problems and are exposed more to known risk factors (Belknap & Holsinger, 2006; Emeka & Sorensen, 2009; Gavazzi, Yarchek, & Chesney-Lind, 2006; Gover, 2004; Johansson & KempfLeonard, 2009). This has been interpreted as delinquent girls having a more problematic background than delinquent boys, which has also been rephrased as the ‘threshold’ hypothesis, i.e. that girls pass a higher critical ‘risk level’ in order to become delinquent. This hypothesis was initially defined for antisocial personality disorder (Cloninger & Gottesman, 1987) and later expanded to other developmental disorders (Eme, 1992). A threshold has been defined as the point that must be exceeded to begin producing a given effect or result (www.thefreedictionary.com). Thresholds are encountered in many areas of (social) science and generally denote a critical value, under which a certain effect is not present and above which it is, such as the absolute hearing threshold in medicine, or the extinction theshold in ecology. In the manner in which the ‘threshold’hypothesis has been phrased in criminology, it denotes the ‘risk level’ above which the probability to be delinquent is larger than the probability not to be delinquent. This ‘risk level’ that defines the risk threshold can, however, be operationalized in two ways. Firstly, it can be operationalized as the severity or level of a single risk factor: having a problematic relationship with parents is a risk factor for delinquency, and only those youth with a very problematic parent-child relationship have a risk level that is high enough to pass the threshold to offend. The other way of operationalizing risk level is derived from the cumulative risk approach (Rutter, 1979; Sameroff, Seifer, Barocas, Zax & Greenspan, 1987) and defines the risk level as the number of risk factors. Thus, according to this operationalization the more risk factors someone experiences, the more likely he or she is to be delinquent. There is evidence for such a dose-response relationship between the number of risk factors and the likelihood of delinquency for boys and girls (Johansson & Kempf-Leonard, 2009; Loeber, Slot & Stouthamer-Loeber, 2008; Van der Laan & Van der Schans, 2010; Wong et al., submitted). A key issue, that is unresolved in the literature and that is the focus of this study, is whether there are sex differences in the risk threshold for delinquency: differences between boys and girls in such a threshold for delinquency, while often posited, have hardly been studied empirically.. 117 Sex difference in risk thresholds Alemagno, Shaffer-King, and Hammel (2006) examined the number of risk factors of 250 detained boys and girls and found that incarcerated girls were exposed to more risk factors than their male counterparts. Van der Laan and Van der Schans (2010) showed, using a similar analytical strategy, that arrested girls were exposed to more risk factors in the family domain than arrested boys. Although the results of these studies concur with the differential risk threshold hypothesis, they do not show that such a differential threshold exists for delinquency, since all studies investigated samples of adjudicated or incarcerated juveniles. Given that girls and women are often treated differently in the juvenile justice system, the threshold for delinquency cannot be separated from the threshold to be arrested, prosecuted or convicted (e.g., Daly, 1994). Thus it is problematic to attribute sex differences in the number of risk factors in officially delinquent samples to the threshold for delinquency. This may also explain seemingly incompatible findings, such as that arrested boys have in fact a higher number of risky lifestyle factors compared to arrested girls (Van der Laan & Van der Schans, 2010). Self-reported delinquency studies tend not to have the confounding effect of justice processing. Wong et al. (submitted) investigated sex differences in the delinquency threshold using self-reported data of a Dutch population-based sample, and did not find support for a sex-related threshold. The use of a comparison group is necessary, as without such a group it is impossible to determine whether delinquent girls have a higher risk level than delinquent boys or vice versa. In contrast to the previously mentioned studies, the authors included such a comparison group of nondelinquents, and in addition to risk factors, the authors also examined the extent to which promotive factors influenced the risk of later delinquency. Promotive factors are those factors associated with a decreased probability of delinquency (Sameroff, Bartko, Baldwin, Baldwin, & Seifer, 1998; Stouthamer-Loeber, Loeber, Wei, Farrington, & Wikström, 2002). Since promotive factors can neutralize risks (StouthamerLoeber et al., 2002; Van der Laan & Blom, 2006), ignoring these factors might result in overstating the importance of risk factors and might make it impossible to assess any accurate threshold effect. Although the study by Wong et al. (submitted) had fewer limitations than previous studies, the authors did not investigate the threshold as such as they compared risk levels of delinquents with those of nondelinquents. The present study will improve upon previous research firstly by actually assessing the threshold itself, i.e. identifying the exact cut off value, for boys and girls. Secondly, this study will improve on previous studies by investigating whether the threshold varies with age and/or sex. Boys’ and girls’ involvement in delinquency changes with age, and criminal careers develop differently for boys and girls (Junger-Tas, Haen-Marshall, & Ribeaud, 2003; Wong, Blom & Van der Laan, in press). Girls’ delinquency 118 tends to peak earlier than that of boys, i.e. at age 15 versus at age 16 (JungerTas et al., 2003; Slotboom, Wong, Swier, & Van der Broek, 2011). It remains to be seen whether delinquency thresholds vary with age for each sex. As Moffitt (1993) suggested, during puberty, it is almost normative to show some delinquent behavior. Thirdly, this study will add to previous research by incorporating sex-shared as well as sex-specific risk factors for delinquency (Wong, Slotboom, & Bijleveld, 2010; Zahn, 2009). We will address the following research questions: 1) Is the age-crime curve for girls lower than that of boys? 2) Which shared and sex-specific risk and promotive factors measured in middle childhood (ages 7 to 9) and late childhood (ages 10 to 12), respectively, predict self-reported delinquency in late childhood (ages 10 to 12) and adolescence (ages 13 to 16)? 3) Are there sex differences in exposure to risk and promotive factors? 4) Are there linear or quadratic differences in the relationship between cumulative risk and protective factor score and delinquency for each sex? 5) Are there differences by sex and age in the optimal cumulative threshold to predict delinquency? The questions are addressed using data from the Pittsburgh Youth Study (PYS) and the Pittsburgh Girls Study (PGS) using self-reported delinquency as outcomes at late childhood and adolescence. The studies contain a broad array of risk and promotive factors known to predict delinquency in previous studies (e.g., Hoeve et al., 2009; Hubbard & Pratt 2002; Lipsey & Derzon, 1998; Maguin & Loeber, 1996; Pratt & Cullen, 2005; Simourd & Andrews, 1994; Wong et al., 2010; Zahn, 2009). These include individual (problem) factors (i.e., birth problems, early disruptive behavior disorder, callous unemotional behavior, anxiety, early puberty), family factors (i.e., poor education of parents, single parent household, physical punishment, communication with parents, positive parenting, supervision, parent-child relationship), school factors (i.e., truancy, school motivation, school achievement), peer delinquency, and neighborhood problems. Methods Sample The PYS is a longitudinal study that started in 1987 (Loeber, Farrington, Stouthamer-Loeber, & White, 2008), consisting of three samples of boys who were in grades one, four, and seven, respectively, at the start of the study. Boys who attended public schools in Pittsburgh participated in the study. In the initial screening assessment, information about the boys’ antisocial behavior was collected through the boys themselves, the caretakers, and their teachers. On the basis of this information, a risk score was calculated and all of the boys with the highest scores on antisocial behavior (n = c. 250, for every sample) were selected for follow-up, while a random sample of the remaining boys (N = c. 250) were also included in the follow-ups. Only boys from the youngest sample (n = 503) were included in 119 the present study. In the first four years of the follow-ups, interviews were conducted by trained interviewers every half year with the boys and one or both caretakers. In the same period, one of the boys’ teachers was asked to rate the boys’ behavior. Subsequently, interviews were held every year. For the current analyses, information about grades was transformed in agespecific data. The PGS is also a longitudinal study, but is based on a stratified, random sample from all households in Pittsburgh with a girl between the age of 5 and 8 (Keenan et al., 2010). Disadvantaged neighborhoods were oversampled. The final sample consists of 2,451 families. To make the samples of PGS and PYS youth comparable, the current study included only girls aged 7 or 8 at the initial assessment, who attended public schools at the first assessments in 2000 (n = 856). Follow-ups in the PGS consisted of yearly interviews with the girls, their caretaker and teacher ratings. Measurements To achieve comparability between the sexes, only measurements were included that were comparable across the PYS and the PGS. Delinquency. Delinquency was measured at ages 11-16 through the 40-item Self-Reported Delinquency Scale (SRD; Loeber, Farrington, StouthamerLoeber, & Van Kammen, 1998) which was based on an adaptation of the the National Youth Survey (Elliott, Huizinga, & Ageton, 1985). For each of the offenses, respondents indicated whether they had committed a delinquent act, and if so, how often in the previous year. For this study we focused on moderate to serious delinquency (see details in Loeber et al., 1998), which included breaking-and-entering, stealing things worth more than 5 dollars, purse snatching, stealing from a car, dealing in stolen goods, joyriding, vehicle theft, attacking with intent to injure, forcible robbery, and gang fighting. All offences were summed and dichotomized into 0 (no offence committed – nondelinquent) and 1 (1 or more offences committed – delinquent). At age 11 the dealing in stolen goods item was accidentally not assessed in the PGS, so we did not include this item in the delinquency construct for both boys and girls. The SRD was judged to be too difficult to understand for the youngest respondents. For that reason, the Self-Reported Antisocial Behavior Scale (SRA) instead of the SRD was administered at age 10. Since boys were selected in the first wave by grade and therefore had different ages, and since the switch from SRA to SRD was made in one phase for all boys, some of the 10-year-old boys filled out the SRA en some the SRD. For girls, the switch was made after the age of 10 and therefore all 10-year-old girls reported on the SRA. The SRA consisted of 27 items of delinquent behavior that were appropriate to younger children (Loeber et al., 1989). For the current study, only those items were used to construct the delinquency scale 120 that were comparable to the SRD items used in the construct: theft from building, theft from a car, and purse snatching. After the creation of the moderate and serious delinquency constructs for each age, we prepared summary constructs for age blocks in late childhood (ages 10 to 12) and adolescence (ages 13 to 16), contrasting nondelinquents with delinquents (1 or more offences committed at this age). Risk and promotive factors. Table 6.1 lists all constructs used in this study based oncomparable measures in the PYS and PGS. For most factors, we created two age blocks: for late childhood and adolescence. Birth problems and early disruptive behavior disorder were only assessed in the first assessment and regarding early pubertal development only the measurements prior to the delinquency age blocks were included (i.e. age 9 and age 12). In the PGS, no information about single parent households was available at the age of 7, so the late childhood age block regarding single parent households only contained age 8 and 9. Truancy was only measured at age 11 and 12, so the late childhood age block was not created. In creating the constructs from reported waves, missing constructs were coded as missing if more than 33% was missing. If fewer were missing, the mean of the available responses was substituted for the missing data. In creating the age blocks, only the non-missing ages were used to calculate the age blocks for a respondent. The age block was set to be missing if the construct was missing at all ages. To identify the risk versus promotive effect of the factors we used the same method as Stouthamer-Loeber et al. (1993). All age blocks were trichotimized into a promotive, a neutral and a risk component using the sexspecific 25th and 75th percentiles of the age block distributions as cut-offs. The age blocks were recoded into two variables: a risk variable and a promotive variable. The reference category in each variable was the neutral component (the 26th to the 74th percentile of the distribution). The exceptions were birth problems, early disruptive behavior disorder, poor education of the parents, and child’s truancy, because these were inherently dichotomous. Another exception was the age block for single parent households. In this case, it was more appropriate to trichotimize according to the number of years the household consisted of a single parent (i.e. risk: single parent in all years of age block; promotive: both parents in all years of age block; neutral see Table 6.1). 121 122 Psychopathy Screening Device Child Behavioral Checklist (CBCL) Callous unemotional behavior7 Parent Parent Assessed by Parent 7-9, 10-12 First assessment Ages First assessment 32 items (alpha from .90 to .93) ADHD: 27 items; ODD: 18 items; CD: 18 items 6 items (alpha from .56 to .69) ADHD: 14 items; ODD: 8 items; CD: 12 items Reliability Boys Girls 15 items 7 items Highest 25% At least one of the following disorders: ADHD, ODD, CD Risk Any pre- or perinatal birth problem Lowest 25% NA Promotive NA Due to the time of the assessment, the diagnoses of ADHD, ODD, and CD in the PYS were based on the DSM-III-R, whereas the diagnoses in the PGS were based on the DSM-IV. To make diagnoses comparable, we only included those symptoms that were assessed in both studies. For ADHD, the age of onset, that is usually part of the diagnosis, could not be taken into account since it was not assessed in the PGS. To reach the diagnosis of ADHD, boys and girls had to have 9 symptoms or more. For the diagnosis of CD, 3 or more symptoms were required, and for the diagnosis of ODD, 4 or more symptoms. 7 In the PYS a construct is created that measures psychopathic features in childhood, assessed by the CBCL. Examples of items are ‘lying or cheating’ ‘sudden changes in mood or feelings’, and ‘behaving irresponsibly’. In the PGS, items from the PSD were used to create a similar construct for girls. The following items are included: concerned about school or tasks, keeps promises, feels bad about doing wrong, concerned about others’ feelings, shows feelings and emotions, keeps the same friends. 6 Child Symptom Inventory (CSI) Diagnostic Interview Schedule for Children (DISC) Instruments Boys Girls Birth and Pre and Perinatal developmental Risk Factors history Early disruptive behavior disorder6 Constructs Birth problems Table 6.1 Constructs used in this study 123 Girls Scared Highest degree of education Petersen Pubertal Development Scale (PPDS) How many caretakers? Parent-Child Conflict Tactics Scale (CTSPC) Highest degree of education Petersen Pubertal Development Scale (PPDS) How many caretakers? Discipline Poor education of parents Early pubertal development Single parent household Physical punishment of both parents Instruments Boys CBCL Constructs Anxiety Child Parent Child Parent Assessed by Parent 7-9, 10-12 8-9, 10-12 9, 12 7-9, 10-12 Ages 7-9, 10-12 1 item 1 item 5 items (alpha from .56 to .75) 1 item 1 item 1 item 5 items (alpha from .50 to .69) 1 item Reliability Boys Girls 7 items 29 items (alpha (alpha from .54 to from .90 to .61) .92) Highest 25% Living with one parent at all ages Highest 25% No diploma or a General Education Diploma (GED) for both parents at all ages Risk Highest 25% No physical punishment at all ages Living with both parents at all ages Lowest 25% NA Promotive Lowest 25% 124 SIS Parent-Child Relationship Survey (PCRS) SRD Teacher Works not hard compared to peers SIS Parent-Child Relationship Survey (PCRS) SRD Works not hard compared to peers Low supervision Bad quality relationship with primary caretaker Truancy Low school motivation Child Child Child Child Parent Practices Scale (PPS) Child Assessed by Parent Practices Scale (PPS) Girls Low positive parenting of both parents Instruments Supervision and Involvement Scale (SIS) Boys Low communication Supervision and about activities with Involvement Scale (SIS) both parents Constructs 7-9, 10-12 11-12 7-9, 10-12 7-9, 10-12 7-9, 10-12 7-9, 10-12 Ages 1 item 1 item 16 items (alpha from .83 to .91) 4 items (alpha from .54 to 70) 14 items (alpha from .71 to .97) 10 items (alpha from .64 to .84) 1 item 1 item 16 items (alpha = ) 4 items (alpha from .45 to .61 ) 14 items (alpha from .71 to .97) 10 items (alpha from .52 to .87) Reliability Boys Girls Highest 25% Truant at both ages Highest 25% Highest 25% Highest 25% Highest 25% Risk Lowest 25% NA Lowest 25% Lowest 25% Lowest 25% Lowest 25% Promotive 125 Parent Your Neighborhood Your Neighborhood Neighborhood problems 7-9, 10-12 7-9, 10-12 Ages 7-9, 10-12 17 items (alpha from .93 to .96) 17 items (alpha from .94 to .96) Reliability Boys Girls 9 items 9 items (alpha (alpha = ) from .64 to .71) 5 items 7-9: 5 (alpha items from .68 to (alpha .84) from .78 to .80); 1012: 6 items (alpha from .75 to .78) Highest 25% Highest 25% Risk Highest 25% Lowest 25% Lowest 25% Promotive Lowest 25% For 7-to-9-year-olds, exactly the same offences were included (vandalism, shoplifting, stealing at school, stealing from building, violence against adult) in the PYS and the PGS. For 10-to-12-year-olds, the peer delinquency scale was similar in the PGS, but included more serious offences in the PYS. Therefore, we only took those offences of the PYS into account that were comparable to those of the PGS (and which are also similar to the offences considered at earlier ages), i.e. vandalism, stolen something up to $100, stealing from building, and hitting someone with intent to hurt. We corrected for the number of possible items. 8 Child Peer Delinquency Scale (PDS) Assessed by Parent and teacher Peer Delinquency Scale (PDS) Instruments Boys Girls CBCL & TRF CBCL & TRF Peer delinquency8 Constructs Low school achievement Analyses First, we established which risk and promotive factors predicted delinquency at late childhood and adolescence, respectively. These analyses were carried out separately for boys and girls and separately for the two age periods. If a factor predicted delinquency (p < 0.05), this was regarded as a risk effect; if a factor predicted low or nondelinquency, this was regarded a promotive effect. If both variables were related to delinquency, this was regarded both a combined risk and a promotive effect. Some risk factors predicted delinquency in boys and girls and were labeled shared risk factors. The same applied to factors predicting nondelinquency in boys and girls and were labeled shared promotive factors. Factors that were only related to delinquency in either boys or girls were labeled sex-specific risk and promotive factors. Odds Ratios were calculated for the risk and promotive factors: an Odds Ratio larger than 1 with a p-value < .05 indicates that the presence of the risk factor significantly increased the prediction of delinquency, while an Odds Ratio smaller than 1 with a p< .05 indicates a promotive factor that significantly predicted nondelinquency. Next, we created three types of cumulative risk level indexes. The first index consisted of the number of significant risk factors in the data set. A second index indicated the number of significant promotive factors in the data set. The third, called the combined risk index indicated the number of significant risk factors minus the number of significant promotive factors. Because the three risk indexes were created by taking into account shared factors as well as sex-specific factors, each risk index consisted of slightly different risk and promotive components for boys and girls. Thresholds were studied at two levels. First, we studied whether the distribution of the relationships between cumulative risk were similar for boys and girls; for this we carried out a curve fitting analysis to see whether cumulative risk indexes predicted delinquency in a linear or quadratic way for boys and girls. If, for example, a quadratic function applied to one but not the other sex, this indicated that the risk of future delinquency accelerated faster for one sex compared to the other. In a second set of analyses, we examined whether a threshold could be empirically established by means of signal detection theory (Swets, 1964). Receiver Operating Curves (ROC) were calculated with Area Under the Curve (AUC) indicating how well a cumulative risk index predicted delinquency. The analyses also allow the identification of optimal prediction thresholds in which, for every possible cut-off, the trade-off between the false negative and false positive rates is calculated. AUC values can range from 0 (total inaccuracy) to 1 (perfect accuracy). A value of 0.5 indicates that the model is not better than chance, a value between 0.5 and 0.75 is regarded as fair, between 0.75 and 0.92 as good, between 0.92 and 0.97 as very good and between 0.97 and 1 as excellent (McFall & Treat, 1999). The Youden’s index, a function of sensitivity (number of true positives) and 126 specificity (number of true negatives), was used to identify the optimal cutoff point (Youden, 1950). The optimal cut-off is the value with the highest combination of sensitivity and specificity. This cut-off point is the threshold for delinquency. We carried out these analyses separately for late childhood and adolescence and for boys and girls. Results Table 6.2 shows the descriptive results. The average number of measured risk and promotive factors are presented for boys and girls in middle and late childhood as well as the number of delinquents in late childhood and adolescence. Girls appeared to have on average more promotive factors than boys. No other sex differences were found regarding the average number of measured risk and promotive factors. The prevalence of delinquency differed by gender in both late childhood as well as in adolescence. Table 6.2 Descriptive results Boys Girls Average Middle childhood Average number of risk factors Average number of promotive factors 3.43 (2.33) 2.92 (2.11) 3.29 (2.28) 3.00 (2.37) 3.34 (2.30) 2.97 (2.28) Late childhood Average number of risk factors Average number of promotive factors* 3.41 (2.24) 2.95 (2.17) 3.19 (2.34) 3.42 (2.51) 3.27 (2.31) 3.24 (2.40) % delinquent* 24.5% 9.7% 15.2% Adolescence % delinquent* 42.6% 21.2% 29.2% Note. Standard deviations are in parentheses. With t-tests it was tested whether boys and girls differed in number of risk and promotive factors. Crosstabs were used to test the difference in delinquency prevalence. * significantly different for boys and girls at p < .05 The first question we addressed was: Is the age-crime curve for girls lower than that of boys? Figure 6.1 shows that at age 10 there was only a small, although significant (3.6% vs. 1.8%; p<.05) sex difference in the prevalence of moderate to serious delinquency, but at all other older ages the prevalence of delinquency was higher for boys than girls (for all ages p<.01). However, the peak age of the age-crime was the same for the two sexes (age 14). 127 Figure 6.1 Age crime curve for moderate to serious delinquency by sex 25% % delinquents 20% 15% 10% 5% 0% 10 11 12 13 Age % delinquent boys 14 15 16 % delinquent girls The second question that we posed was: Which shared and sex-specific risk and promotive factors measured in middle childhood (ages 7 to 9) and late childhood (ages 10 to 12), respectively, predict self-reported delinquency in late childhood (ages 10 to 12) and adolescence (ages 13 to 16) Table 6.3 shows the odds ratios of the risk and promotive factors for boys and girls in the two age periods. An empty cell indicates that there is no statistically significant risk (or promotive) effect of a given factor. The results showed that delinquent behavior of boys and girls is related to many different factors. As Table 6.3 shows, many risk and promotive factors are shared by boys and girls, but some differences were found between boys and girls, and between age periods as well. Next we asked: Are there sex differences in exposure to risk and promotive factors? Table 6.4 shows the average number of (significant) risk factors and (significant) risk minus promotive factors for nondelinquent and delinquent boys and girls during middle and late childhood. Delinquent boys and girls averaged higher risk scores than nondelinquent boys and girls, respectively. Furthermore, delinquent girls averaged a higher number of risk factors than delinquent boys at each age period. When average of risk and promotive factors were considered, delinquent girls compared to delinquent boys scored higher at middle childhood only. At late childhood, average exposure to risk and promotive factors was similar for of delinquent boys and girls. 128 129 Table 6.3 Odds ratios of risk and promotive factors for delinquency at ages 10 to 12 and ages 13 to 16, by sex Delinquency (10 to 12 years) Delinquency (13 to 16 years) Risk Promotive Risk Promotive Boys Girls Boys Girls Boys Girls Boys Girls Factors Birth problems 1.82** Disruptive behavior 3.22** 2.64** Callous unemotional behavior 2.39** 3.21** 0.35** 0.18** 2.15** 3.16** 0.41** 0.35** Anxiety 0.62* 2.28** 0.47** Early pubertal development Poor education of parents 3.37** Single parent household 0.64* 0.62* 0.53** Physical punishment of parents 0.37** 1.82* 0.64* Positive parenting 1.88* 1.63* 0.55* Supervision 1.83* 0.41* 2.44** 2.31** 0.41** 0.35** Relationship with primary caretaker 2.20** 2.80** 0.20** 2.83** 2.86** 0.44** 0.29** Truancy 4.18** 6.10** School motivation 2.59** 2.32** 0.35** 0.44* 2.29** 2.13** 0.46** 0.28** School achievement 1.93** 2.20** 0.48* 0.38* 1.93** 0.50** 0.42** Peer delinquency 2.19** 2.57** 0.32** 0.12** 3.78** 4.96** 0.23** 0.18** Neighborhood problems 1.97** 0.52* 1.60* 1.79** 0.54** 0.58* * p < .05, ** p < .01 130 Delinquent Difference within boys Non delinquent Girls Delinquent Difference within girls Sex difference between delinquents Middle childhood Average Number of risk 1.15 (1.27) 1.95 (1.41) 2.19 (1.76) 3.82 (1.81) t (468) = 5.66** t (804) = 7.85** t (192) = 8.11** factorsa Average Number of risk -0.89 (2.41) 0.65 (2.40) 0.61 (2.61) 2.91 (2.11) t (468) = 4.96** t (804) = 7.58** t (192) = 6.77** minus promotive factorsa Late childhood Average Number of risk 1.13 (1.25) 2.32 (1.62) 1.63 (1.50) 3.39 (1.89) t (444) = 8.83** t (747) = 12.39** t (347) = 5.70** factorsa Average Number of risk -1.39 (2.72) 0.92 (2.69) -1.68 (3.18) 1.43 (2.61) t (444) = 8.91** t (747) = 11.35** t (347) = 1.80 minus promotive factors Note. Standard deviations in parentheses. Means of nondelinquent and delinquent boys and of nondelinquent and delinquent girls are compared with T-tests as well as those of delinquent boys and girls. * p < .05, ** p < .01 Non delinquent Table 6.4 Means and standard deviations of risk levels for nondelinquent and delinquent boys and girl Boys The fourth question we asked was: Are there linear or quadratic differences in the relationship between cumulative risk and protective factor score and delinquency for each sex? Curve fitting analyses showed that for both age periods positive linear relationships between the risk levels and delinquency were found for boys (with R² of .07 and .15 respectively; other relationships had a worse fit to the data), but positive quadratic relationships for girls (with R² of .06 and .17 respectively, again other relationships had a worse fit to the data; see the modeled relationships in Figures 6.2 and 6.3). This indicates that, regardless of sex, the more risk factors boys and girls are exposed to, the more likely they are to be delinquent. However, for boys the increase in likelihood for delinquency is similar across risk levels, whereas for girls the increase in likelihood is amplified at every next risk level. More specifically, for boys every increase in the number of risk factors results in 5.2% more delinquents in late childhood and 7.3% more delinquents in adolescence. For girls, this increase depends on the risk level. An increase from 3 to 2 promotive factors (in middle and late childhood respectively), for instance, leads to 0.6% more delinquents in late childhood and to 3.3% more delinquent in adolescence, whereas an increase from 3 to 4 or more risk factors (in middle and late childhood) results in 5.4% and 10.5% more delinquents in late childhood and adolescence. Thus, for girls we see that the effect of a one-step risk increase becomes ever stronger: the higher the risk level, the larger the corresponding shift in delinquency of an increase in risk. The final question concerned: Are there differences by sex and age in the optimal cumulative threshold to predict delinquency? The results regarding the predictive power of the combined risk levels on late childhood delinquency for boys and girls are in Figure 6.2: girls have slightly higher AUC values than boys (0.74 vs. 0.68). Furthermore, the optimal cut-off point for girls is higher than for boys (1 vs. 0 risk factors) which indicates that girls have a higher threshold for delinquency in late childhood than boys. Next, adolescent delinquency was predicted from risk levels at the age of 10 to 12 (see Figure 6.3). Girls had slightly higher AUC values (0.77 vs. 0.72), but boys had a higher optimal cut-off point than girls (1 vs. 0 risk factors). Boys therefore have a higher threshold than girls to become delinquent in adolescence. Thus, we see that there are no consistent differences in the delinquency threshold for boys and girls: the thresholds differ by age period. The differences are also small; however, as the threshold is a group-value and not the average of a set of individual-level values, we cannot test whether it differs significantly for boys and girls. 131 Figure 6.2 Combined risk levels (number of risk factors minus number of promotive factors) at the age of 7 to 9 predicting moderate to serious delinquency at age 10 to 12, for boys and girls. 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% % delinquent boys (AUC: 0.68) Prevalence of boy delinquency Modeled relationship Threshold Promotive risk factors 100% % delinquent girls (AUC: 0.74) 90% 80% 70% Prevalence of girl delinquency 60% Modeled relationship 50% 40% Threshold 30% 20% 10% 0% Promotive 132 risk factors Figure 6.3 Combined risk levels (number of risk factors minus number of promotive factors) at the age of 10 to 12 predicting moderate to serious delinquency at age 13 to 16, for boys and girls. 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Threshold Promotive 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% % delinquent boys (AUC: 0.72) Prevalence of boy delinquency Modeled relationship risk factors % delinquent girls (AUC: 0.77) Prevalence of girl delinquency Modeled relationship Threshold Promotive risk factors 133 Discussion This study examined whether boys and girls had different risk thresholds for delinquency at two age periods (late childhood and adolescence). Using data from the PYS and PGS studies, we first tested which factors (at ages 7 to 9 and 10 to 12) had a risk effect, a promotive effect, or both. Boys and girls appeared to share many risk and promotive factors, but sex differences and differences between age periods were found as well. Not surprisingly, boys and girls who were delinquent appeared to have higher risk levels than their nondelinquent counterparts. Within the delinquents, girls on average had higher number of risk factors than boys when only risk factors were considered. When promotive factors were taken into account as well, girls compared to boys had on average a higher risk levels in middle childhood. In late childhood, the risk level of delinquent boys and girls was similar. The relationship between the risk level and delinquency was linear for boys, indicating that every extra risk factor resulted in a similar step-wise increase regarding delinquency probability. For girls, however, this relationship turned out to be non-linear, with the increase in the probability of delinquency larger at the higher risk level ranges than in the lower part. Thus, at low risk levels, an additional risk factor gives but a small increase in the delinquency probability. However, at higher risk levels, one additional risk factor augments this probability substantially. Due to this amplification, delinquent girls would – even with a same delinquency threshold - have higher average risk levels than boys. Therefore, previous studies that focused on the average risk level for boys and girls found higher risk levels among delinquent girls than among delinquent boys (Alemagno et al., 2006; Van der Laan & Van der Schans, 2010. While higher risk levels are associated with a stronger increase in likelihood of delinquency in girls than in boys, this study has shown that girls do not have a higher threshold for delinquency, and that any differences in the threshold are small and fluctuate with age. All in all, in this study – that was appropriately designed with a control group, and sex-specific risk as well as promotive factors – no evidence for a sex-specific delinquency threshold emerged. The threshold hypothesis was examined using two complementary approaches: curve fitting and ROC analyses. The curve estimation analyses showed a linear association between risk level and delinquency for boys and a curvilinear relationship for girls. The ROC analyses examined the location of the threshold and did not show sex differences. While there appears to be no different threshold as such, increases of the risk level beyond this threshold impact differently on girls than on boys. That is, from the threshold onwards, risks contribute more and more to the delinquency risk for girls, but not for boys. 134 Differences with previous studies Several explanations can be put forward for the fact that most previous studies on the threshold had such different results than the present study. These explanations regard differences between previous studies and the present study regarding the sample, the definition of the threshold, and regarding the operationalization of risk. With regard to sample differences, previous studies mainly examined adjudicated or incarcerated samples. In these samples the threshold for delinquency is confounded with the threshold for criminal justice system involvement. The fact that our study showed that the threshold for delinquency differs minimally for boys and girls, these studies probably picked up on arrest, prosecution or incarceration thresholds. Concerning differences in the definition of the threshold, previous studies based their conclusions about sex different thresholds on risk levels of delinquent boys and girls (Alemagno et al., 2006; Belknap & Holsinger, 2006; Emeke & Sorensen, 2009; Johansson & Kempf-Leonard, 2009; Van der Laan & Van der Schans, 2010), whereas the current study identified the location of the threshold. Because delinquent girls had on average higher risk levels than boys and because delinquency is less prevalent in girls, previous studies concluded that girls have a higher threshold for delinquency. However, the threshold as such was not assessed. Regarding the operationalization of risk, there are two main differences between previous studies and the present study. First, previous studies did not include promotive factors to measure risk. However, since the number of promotive factors can buffer the influence of risk factors only (StouthamerLoeber et al., 2002; Van der Laan & Blom, 2006), it is inadequate to examine only risk factors. To see how the results would differ if we would have considered risk factors only, the analyses of the present study were carried out as well for the risk index that only considered the number of risk factors9. Just like in previous studies (Alemagno et al., 2006; Van der Laan, & Van der Schans, 2010), we found a higher threshold for girls when we focused solely on risk factors, for both age periods. Slightly better AUC values showed, however, that models that included both risk factors and promotive factors were more adequate than models that considered risk factors only. Not including promotive factors can lead to overestimation of the risk and therefore of the threshold. This indeed turned out to be the case for girls. Second, the present study included sex-specific factors while other studies did not (see Moffitt, Caspi, Rutter, & Silva, 2001; Junger-Tas, Ribeaud, & Cruyff, 2004). Again, for the sake of comparison, the analyses of the present study were also carried out with models that only considered 9 For reasons of simplicity, these results are not presented here, but are available from the author. 135 shared factors10. Models that considered sex-specific factors as well resulted in better predictions of delinquency at puberty for girls than models with solely shared factors. In these latter models, that were utilized in previous studies, girls’ risks are underestimated and their risk threshold cannot be examined properly. Our study showed that girls and boys do not differ in their delinquency ‘threshold’, i.e. the risk level beyond which the probability to be delinquent is greater than the probability to be not delinquent. It is likely that the threshold that was picked up in previous studies among criminal justice samples may actually have been a criminal justice-involvement threshold. Difference in the average risk levels of delinquent boys and girls are generated by the increasing impact of risk factors on girls beyond the delinquency threshold. Strengths and limitations This study had several limitations. First, only moderate to serious delinquency was taken into account. It might be, however, that although no sex differences were found in the threshold for delinquency in general, boys’ and girls’ thresholds do differ for violent or serious delinquency. As Moffitt (1993) claimed, during puberty, delinquent behavior is more normative, which as we argued may explain the lack of a clear differential threshold. For less normative behavior, such a threshold may well emerge. This is difficult to test, however, since serious (violent) delinquent behavior is a rare phenomenon in juvenile females and therefore such analyses would have suffered from a lack of power. Another limitation is that not all factors that have an important risk or promotive effect on delinquency could be taken into account. This is because two different studies (the PYS and the PGS) were combined and we were strict in our decision not to consider factors that were not conistently measured in both studies. For instance, negative life events (i.e. crime victimization, abuse, neglect), that have been shown to be important in predicting delinquency especially for girls (Wong et al.. 2010), could not be included because of assessment differences. Despite these limitations, the present study improved on previous studies by identifying thresholds for delinquency, and by taking into account promotive factors. Furthermore this study focused on self-reports of delinquency, and included shared as well as sex-specific risk and promotive factors, and examined thresholds longitudinally at two age periods. Moreover, we showed that some of our design improvements actually improved predictions compared to previously studies. 10 See footnote 13. 136 137 Chapter 7 General discussion 139 140 This dissertation aimed to increase our understanding of the correlates of girls’ delinquency, how these differ from those of boys’ delinquency and how the sex difference in the prevalence of delinquency can be explained. As we showed in chapter 1, quite a number of theoretical frameworks have been proposed to explain differences in the prevalence of offending and the criminal careers of girls and boys, but very few of these explanations have been properly tested. The practical importance of gaining knowledge about factors related to girl delinquency lies in the fact that increasingly more girls enter the juvenile justice system the past years. Although it is the question whether girls are indeed becoming more delinquent than in the past or whether the police is more focused on (offences usually committed by) girls nowadays, there is an increasing group of girls present in the juvenile justice system to deal with. If girls have similar risk factors as boys, it is likely that interventions used to handle boys’ delinquency and theories to explain it, can also be applied to girls. If not, however, different programs and theories should be developed for girls. The first aim of this dissertation was therefore to generate an overview of risk factors related to delinquent behaviour of adolescent girls and to see which of these were shared with boys and which of them were sex-specific. The second aim of this dissertation was to test explanations for the difference in prevalence between boys and girls. Using these risk factors, the exposure hypothesis, the vulnerability hypothesis and the threshold hypothesis were examined. The results regarding the first aim are described and discussed first, followed by the results regarding the second aim. Subsequently, the implications for interventions are discussed, limitations and strengths of this dissertation are outlined and an agenda for future research is proposed. Unique and shared risk factors of delinquency In Table 7.1 the risk factors found in chapter 3 and those that appeared to be univariately related to delinquency in chapter 4 are combined. Note that in these chapters it was not directly tested whether the factors related to delinquency were risk factors, promotive factors or both. For the sake of simplicity, the factors in the table are defined or rephrased in such a way that they all had a positive relationship with delinquency and therefore referred to as risk factors. The results of chapter 5 and 6 were not included in the table, since in chapter 5 no distinction was made between risk factors of boys and girls and since chapter 6 measured risk and promotive factors before adolescence during childhood. There was an overlap between the factors found to be related to delinquency in chapter 3 (that provided a synthesis from previous research) and those examined in chapter 4 (that analysed new data). It should be noted that these included only factors from the parent (i.e. mothers and fathers separately) and peer domain. Almost no inconsistent results were found 141 between chapter 3 and chapter 4, but also not many findings from chapter 3 were replicated by chapter 4. This is because previous studies mainly examined parents in general, whereas chapter 4 distinguished between mothers and fathers. Therefore, results from this dissertation are more detailed than previous studies. Findings that were replicated concerned maternal support and the number of delinquent friends. Low levels of maternal support and having many delinquent friends were consistently found to be unique factors for girls. Taking all the results together, boys and girls appeared to have many risk factors for adolescent delinquency in common, especially regarding personality, specific parenting characteristics (such as parental monitoring, harsh discipline, number of rules at home, negative interaction, parental solicitation and involvement of parents in school) and peers. However, some factors were uniquely associated with either boys’ or girls’ delinquent behaviour. Regarding the individual domain, unique factors for boys were mainly birth problems, whereas for girls unique risk factors referred to mental health problems. In the family domain, unique factors – for both boys and girls – were found with regard to maternal factors in particular though not with regard to paternal factors. Furthermore, it is noteworthy that unique factors for girls often reflected the severity of risks, such as the number of life events, the extent of friends’ delinquency and the extent of best friend’s delinquency in specific. Implications for the girl delinquency approaches A first conclusion of this thesis is therefore that some unique risk factors for girl delinquency exist, but that boys and girls predominantly share risk factors. Moreover, it should be noted that, for boys as well as for girls, a wide range of factors is related to delinquent behaviour. This indicates that a theoretical framework that only includes specific risk domains cannot offer a complete explanation for delinquent behaviour. This also implies that the cumulative risk approach – which claims that delinquency is not caused by a single risk factor, but that multiple factors are always involved – is necessary for the study on boy and girl delinquency and thus for the development of theories. A further reason for the inclusion of multiple factors or risk domains is that only then it is possible to integrate the add-and-stir and the female-only focused approach. As we integrated the approaches in this dissertation shared as well as sex-specific factors could be identified. Otherwise, important results would probably have been overlooked. For instance, interesting sex differences about maternal factors and mental health problems would not have been noticed if the focus had been on factors from existing theories. Besides, in mainstream theories, the distinction between mothers and fathers is never made and differences between maternal and paternal factors – that fathers have a similar effect on boys’ and girls’ 142 delinquency, but that mothers had different effects – could thus not have been detected. Focusing on sex-specific factors only, on the other hand, would have been poor as well, since all the risk factors that boys and girls share would not have been detected. Therefore, factors and domains from existing theories as well as sex-specific factors must be included in order to include the relevant factors for girl delinquency. The cumulative risk approach seems a suitable approach to do so. Explanations for the sex difference in the prevalence of delinquency Chapter 2 showed that girls are clearly less likely to commit offences than boys. The second aim of this dissertation was to explain this sex difference in the prevalence of delinquency. Three different possible explanations were examined for this universal phenomenon: the exposure hypothesis, the vulnerability hypothesis and the threshold hypothesis. The exposure hypothesis The exposure hypothesis – which states that girls have lower levels of risk factors and higher levels of promotive factors than boys and are therefore less likely to be delinquent –was to a large extent confirmed in this dissertation. Girls reported higher levels than boys of adolescent disclosure towards mothers and of parental solicitation from mothers. These were both factors that had an inhibiting effect on delinquency. On the other hand, boys were exposed to more delinquent friends than girls, while having many delinquent friends was a risk factor for juveniles to be delinquent themselves. It was demonstrated that sex was not a predictor of delinquency anymore when differences in exposure regarding these three factors were taken into account. Differential exposure to adolescent disclosure towards mother, regarding parental solicitation of mother and regarding peer delinquency together therefore appeared to be related to – and might even explain – the higher prevalence of delinquency among boys than among girls. Future research should examine why the sex difference in the prevalence in delinquency is associated with the sex differences in exposure regarding the two mother factors and peer delinquency. In addition, causal effects should be investigated. The study on differential exposure used crossectional data and therefore it is uncertain whether girls are less often delinquent than boys because they are differently exposed to particular factors or that differential exposure to these factors was a result of differences in delinquent behaviour. As previous longitudinal research has already shown that parenting and peer factors can influence antisocial behaviour or delinquency of girls over time (Landsheer & Van Dijkum, 2005; Neumann, Koot, Barker, & Maughan, 2010; Van der Rakt, Weerman, & Need, 2005), it is likely that the first explanations will have more 143 144 Table 7.1 Shared and sex-specific factors related to delinquency Shared risk factors Victimization Individual Being harassed by an adult Low self-control Aggression Low IQ Low self-esteem Being unashamed for parents, friends and teachers Positive attitude towards delinquency Substance abuse Inadequate parenting Family Overall parental monitoring Decreasing parental monitoring Low involvement parents in school Small number of rules at home Harsh discipline Low parental warmth Conflicts within family Delinquent sibling Mother Low parental knowledge* Low involvement in peer relations* Low parental solicitation* Mother-child conflict* Negative interaction* Low adolescent disclosure* Unique factors for boys Birth complications Psychological wellbeing High parental knowledge about friends Single parenthood Low support (but less strong than for girls)* Convicted mother Unique factors for girls High number of life events Disobedience High self-esteem Depression Suicidal behaviour Being seldom at home Physical abuse by parents Low parental trust Parenting style Low support** Low quality mother-child Relationship 145 Shared risk factors Inadequate parenting Parenting style Low parental knowledge Low involvement in peer relations* Low parental solicitation* Low quality father-child relationship Father-child conflict* Negative interaction * Low adolescent disclosure* Convicted father* Having delinquent friends Truant best friend* Having negative friends Problematic youth group member Having a romantic partner Many activities with friends Having friends disliked by parents Low commitment Low child-teacher relationship Many delinquent friends** Highly delinquent best friend* Unique factors for girls Disadvantaged neighbourhood Community *Factor added by this dissertation to the results of previous European studies **Replicated by this dissertation School Peers Father Low achievement Unique factors for boys predictive strength, although a (partial) reverse association cannot be outruled. The vulnerability hypothesis The vulnerability hypothesis was not confirmed in this dissertation. According to this hypothesis, boys and girls have different associations between risk factors and delinquency (i.e. they are differentially vulnerable to risk factors) and these differences are associated with the sex difference in delinquency. More specifically, girls are supposed to be less vulnerable for risk factors and more ‘vulnerable’ for promotive factors than boys and therefore less likely to be delinquent. Although our study found that boys and girls were differentially vulnerable for some factors, these differences were not always in the direction expected by the hypothesis. As expected, support from mothers appeared to have a stronger promotive effect on girls than on boys. Nevertheless, maternal control had a promotive effect on boys but a risk effect on girls. Also, the level of delinquency of best friends was positively related to girls’ delinquency whereas no relation was found with boys’ delinquency. It should be kept in mind though that – again - results were based on cross-sectional data and therefore no inferences could be drawn about causal relationships. As with our data girls were not found to be less vulnerable for risk factors than boys, but instead more vulnerable for risks, therefore differences in vulnerability could not explain the sex difference in delinquency. In chapter 6 it was found as well that girls’ delinquency was in general related to more risk factors than boys’ delinquency. However, in line with the vulnerability hypothesis, girls had more promotive factors than boys. It might therefore be that the reason for the sex difference in delinquency is not that girls are less vulnerable for risk factors, but only that they are more vulnerable for promotive factors than boys. This should be examined by future research, since it was not examined in chapter 4 whether factors had a risk or a promotive effect on delinquency. Differential exposure and vulnerability appeared to operate concurrently, at least regarding maternal parenting factors. The higher exposure of girls in terms of promotive maternal parenting factors (i.e. especially to adolescent disclosure and parental solicitation) than boys coincided with differential vulnerability for maternal parenting (i.e. especially for maternal knowledge and control). This combination of differential exposure and vulnerability for maternal parenting factors did however not appear to be able to explain why girls less often commit offences than boys. Again, this was not surprising, given the direction of the previous mentioned vulnerability differences (i.e. the risk effect of maternal control for girls and the promotive effect for boys). 146 146 The threshold hypothesis The threshold hypothesis – claiming that girls compared to boys become delinquent only after they are exposed to a higher number of risks – was also not confirmed in this dissertation. In the first study (i.e. chapter 5) on the threshold hypothesis, the threshold for adolescent delinquency was examined using the same analytical strategy as previous studies (Alemagno et al., 2006; Van der Laan & Van der Schans, 2010), that is, comparing the risk levels of delinquent girls with those of delinquent boys. However, the study improved on previous studies by taking into account a non-delinquent comparison group, by examining self-reported data of a random populationbased sample and by considering risk as well as promotive factors. With these improvements, no differences in risk levels appeared to exist between delinquent boys and girls, suggesting that there was no sex difference in thresholds for delinquency in adolescence. It is important to realize though that in order to examine the threshold, it is not entirely accurate to analyse the average risk level of delinquent juveniles. This way, conclusions can only be drawn about the average number of risk factors of already delinquent boys and girls, but not whether girls actually have a higher threshold to become delinquent. The second threshold study of this dissertation (i.e. chapter 6) therefore attempted to examine the threshold itself by identifying a ‘tipping point’ for boys and girls. This was studied for two age periods: for delinquency in late childhood (ages 10-12) and in adolescence (ages 13-16). For delinquency in late childhood a higher threshold was found for girls than for boys, whereas for delinquency in adolescence boys appeared to have a higher threshold. In addition to this fluctuation, the threshold differences were small. The differences would most probably be insignificant if there was any way to test it. Therefore, as in chapter 5, it can be concluded that no true sex differences in thresholds exist. This indicates that it is not a difference in thresholds for delinquency between boys and girls that accounts for the sex difference in the prevalence of delinquency. However, chapter 6 also showed that the relationship between the probability to be delinquent and the level of risk is quadratic for girls – indicating that the probability of delinquency amplifies when girls have higher levels of risk – whereas for boys the probability had a linear relationship with the risk level. Because of this amplification, delinquent girls on average have more risk factors than boys once they are delinquent. This might be one reason that previous research found higher levels of risk among delinquent girls than among delinquent boys. Another reason is that previous studies examined official records of crime. Therefore, the threshold that was picked up in previous studies was mostly a criminal justiceinvolvement threshold. This is in line with what was found in chapter 2: the sex difference in delinquency appeared much larger in official records, than in self-reported data. This illustrates that the police are relatively less 147 focused on delinquent girls than on delinquent boys. Besides, chapter 2 suggested that official records strongly reflect the priorities and effort of the police. This was demonstrated in the increase of arrest of particularly those offences that gained attention in policy programs of the Dutch government. The reason for the higher threshold to be arrested for girls, might therefore be related to the policy of the police. Implications for interventions Since increasing numbers of girls are involved in the juvenile justice system, there is more and more demand for suitable interventions for girls. The studies in this dissertation have given some important indications for such interventions. Firstly, interventions should consider many different factors and domains. Girl delinquency (but boy delinquency as well) appeared to be related to many factors from the individual, parent, school, and peer domain. Secondly, interventions may focus on risk factors that are also important for boys. These include mainly factors in the peer domain and regarding personality and specific parenting factors. In the Netherlands, the interventions currently offered to delinquent girls are similar to those offered to delinquent boys. As the studies in this dissertation have shown that girls share many risk factors with boys, these interventions are probably partly effective for delinquent girls. ‘Probably’, because no effect studies have been carried out yet in the Netherlands for these interventions for delinquent girls. Thirdly, this study identified a number of unique factors for girls that interventions should take into account, such as maternal factors and mental health problems. In line with the studies in this dissertation, a recently published report of Slotboom, Wong, Swier, and Van der Broek (2011), that examined the suitability of interventions now offered to Dutch delinquent girls, also concluded that broad-focused interventions for girls are most likely to be successful. In addition it was recommended that mental health problems, traumatic experiences and sexuality are of importance in tackling girl delinquency. Sexuality was not investigated in this dissertation, but the number of negative life events was indeed found to be a unique risk factor for girls. Before it can be concluded with certainty, however, that boys’ interventions can be applied to girls as well, research should examine the effectiveness of interventions for girls. In addition more research should be carried out regarding the mechanisms behind the association between risk factors and delinquency. If it is known how risk factors affect delinquency exactly, interventions could focus on these mechanisms in particular which can enhance the effectiveness of interventions. More detailed recommendations for future research are given in a later paragraph. 148 Limitations and strengths of the studies in this dissertation Limitations As with all research, a number of limitation to the studies in this dissertation must be noted. One limitation is the sole reliance on self-reported data. As mentioned in chapter 2, self-report is limited to some extent. Delinquency concerns a sensitive topic. Most adolescents are too aware that committing offences is not desirable behaviour and might therefore be reluctant to report it (Farrington, 1973). In addition, respondents might have forgotten about committed offences (Glasner & Van der Vaart, 2009; Tourangeau, Rips, & Rasinski, 2000) or they might conceal criminal behaviour because they fear that their anonymity is not ensured (Hessing & Elffers, 1995). On the other hand, respondents may overreport because they like to brag about their behaviour or because they report about offences outside the reference period (Nijboer, 1995; Sudman, Bradburn, & Schwarz, 1996). However, it has been shown that self-reports are a sufficiently reliable and valid means to measure delinquency (Thornberry & Krohn, 2000; Van der Heijden, Sijtsma & ’t Hart, 1995). It may also be that differences in accuracy or honesty exist between boys and girls. Piquero, MacIntosh, and Hickman (2002) have shown that males and females vary in the way they report on delinquency items. Males and females had different items on which they found it easier to report positively on. Males had less difficulty, for instance, to admit that they had broken into a house or carried a hidden weapon, whereas girls more easily reported about being loud or unruly in public place or about hitting their parent. Differences might thus exist in the way boys and girls report about various items. However, also in general sex differences might exist regarding reporting behaviour. It might be, for example, that girls are more hesitant to admit that they had committed offences than boys, since this might not match with their idea of feminity. On the other hand, it might also be that girls, obedient as they usually are, (too) honestly fill out every question. If girls were overreporting, this implies that the differences between non-delinquents and delinquents are not that clear-cut and therefore the effects found in the studies of this dissertation would likely be underestimated. The consequence of underreporting of girls depends on which of the delinquent girls underreport. If only serious delinquent girls underreported, this would have the same consequence as overreporting, since there would then be relatively little serious delinquents among girls leading to fewer differences between non-delinquents and delinquents. If only minor delinquent girls underreported, differences between non-delinquents and delinquents are exaggerated leading to overstated effects. In any case, we are not sure whether there are differences between boys and girls in how they report on delinquency questionnaires and it is therefore uncertain whether our results are confounded with reporting biases. However, as will be 149 discussed in the next paragraph, the use of official records is even more problematic; the use of self-reported data are therefore most adequate. Another limitation of this dissertation was that it was not examined consistently whether the factors related to delinquency of girls were risk factors, promotive factors, or both. Without testing whether factors had a risk effect, a promotive effect, or both, factors were either considered as risk or as promotive factors, depending on how the factor was defined and on the direction of the association. For instance, the negative relationship between adolescent disclosure and delinquency as found in chapter 4was presumed to represent a promotive effect of adolescent disclosure. Put differently, we assumed that higher levels of adolescent disclosure would protect adolescents against becoming delinquent. However, it might very well be that it is not a promotive factor, but instead a risk factor, which would imply that low levels of adolescent disclosure put adolescents at risk for becoming delinquent. One more limitation, particular to the study on differential exposure and vulnerability in particular (see chapter 4), was the use of cross-sectional data. Using such data, it is not clear whether a factor that is related to delinquency is a cause of delinquency, an effect, or both. To disentangle these effects, longitudinal data are essential. However, longitudinal data were not available in the period that the study was carried out. Moreover, the exposure and vulnerability hypotheses were only examined in early puberty (when the adolescents were aged 12 to 13). It might very well be that different results regarding exposure and vulnerability will be found at later ages. After all, the older adolescents become, the more important peers become and the less important parents. This may have an influence on the level of exposure to parent and peer factors, but also on the associations between the factors and delinquency. As the RADAR study from which we analysed data was on going as the research was carried out, we had to make do with the waves that were available. Furthermore, in the studies that addressed sex differences in the threshold no attention was paid to the differential importance of various factors in measuring the threshold. Instead, every risk and promotive factor was considered to have an equal impact on delinquency. As we know that some factors are more important than others (and these may differ for males and females), future research should examine the threshold by considering the relevance of each factor. Strengths Despite of these limitations, the studies in this dissertation also had clear strengths. First of all, self-reported measures of population-based samples were used. Regardless of the previous mentioned possible drawbacks of selfreported measures, it is the least problematic method to examine girl delinquency in such a way that results can be generalized to all delinquent 150 girls. Another way to measure delinquency is to use official records. However, this will always result in a select sample. As already discussed, not all delinquents are arrested or incarcerated and therefore official records only represent those delinquents the (policy of the) police is focused on. These are usually the most serious or obvious delinquents. The measures used in this study - self-reported data of population samples – are therefore the least biased and thus the most adequate. A second strength of this study is the inclusion of a non-delinquent comparison group. Including such a group is very difficult or even impossible in studies using official records and this possibility is therefore another advantage of population-based samples. Without such a comparison group no proper claims can be made about risk or promotive factors. Third, boys and girls were compared without method differences. To be able to conclude anything about sex differences in delinquency and its correlates, this is essential. Otherwise, differences found can be due to dissimilarities in the methods and not to actual differences. Fourth, it was directly tested whether differential exposure and vulnerability were related to the sex difference in the prevalence of delinquency. Previous studies only examined whether differences in exposure and vulnerability existed, but not whether these could account for the difference in prevalence. The studies in this dissertation have shown that if boys and girls are differently exposed to or vulnerable for factors that this did not necessarily mean that this was related to the sex difference in delinquency. Furthermore, this dissertation concurrently tested whether differential exposure and vulnerability were related to the sex difference in delinquency. Fifth, if possible, maternal and paternal factors were separated instead of merged into parental factors. The finding that mothers had a unique influence on boys and girls whereas fathers played a similar role regarding delinquent behaviour of the two sexes, shows that it is important to disentangle mother and father influences on delinquency. However, most previous studies – also on boys’ delinquency – combined maternal and paternal factors or only examined factors in the mother domain, since mothers are often the main caregiver. Sixth, attention was paid to promotive factors in examining the threshold hypothesis. Since the threshold is contingent on the level of risk, and promotive factors can neutralize risks, considering promotive factors in threshold research is essential. This has – to our knowledge – not been implemented before. Lastly, the threshold hypothesis was studied extensively, with the exact location of the threshold identified and compared between boys and girls. 151 Agenda for future research Similar factors, similar mechanisms? Many risk factors appeared to be similar for boys and girls. An important next step is to examine whether the shared factors for boys and girls assert influence in the same manner for both sexes. We need to know whether the mechanisms behind the associations are similar between boys and girls. If so, than we can be certain that particular existing theories developed to explain boys’ delinquency can be applied to girls’ delinquency as well. For example, adolescents with delinquent friends are more likely to become delinquent themselves because they learn attitudes, techniques and motives from them (Sutherland, 1947). It is the question though whether girls – when they have delinquent friends – learn delinquent behaviour as well in this way. It may be that different processes underlie the influence of delinquent friends on adolescents’ delinquency for boys and girls. For theoretical advancement, it is essential to examine this. Besides, the sex of friends should also be taken into account as processes might dependent of the sex of delinquent friends too. It might very well be that a group of delinquent male friends has a different influence on a girl than a group of delinquent female friends for instance. Hence, future studies should investigate whether and how the mechanisms behind the association between factors and delinquency vary by sex. The unique role of mothers Research should also examine the unique factors of girl delinquency more closely. One interesting domain in which girls appeared to experience quite some unique influences is the mother domain. The relationship between daughters and mothers appeared to have an important and distinctive effect on girls’ delinquency. Mothers therefore seem to have a stronger inhibiting effect on delinquent behaviour of girls than on that of boys. This possibly not only because girls interact more with their mothers, but also because maternal knowledge (multivariately) and support (univariately) has a stronger restraining effect on girls. Girls are perhaps more afraid than boys to endanger the bond they have with their mother by committing crimes. The social control theory (Hirschi, 1969) postulates that people naturally have the tendency to commit crimes, but that good relationships with other people can inhibit this propensity. Future research should examine whether this indeed is particularly so for girls with respect to their mothers, and why. On the other hand, it was found that high levels of maternal control had a risk effect on girls’ delinquency, whereas maternal control was a promotive factor for boys. It should be noted that cross-sectional data were used for these results, but it might be that different processes are involved here. Prospective studies should examine the nature of this sex difference. Furthermore, since quite some differences were found between mothers and fathers, future research should always distinguish between mothers and 152 fathers. It should also be investigated why it is that mothers have a differential effect on boys and girls, whereas fathers do not. It might be that because girls are more relationship-focused than boys, the relationships with both parents (and even the teacher) affect their delinquent behaviour whereas for boys this only holds for the relationship with the parent of the same sex. This is, however, only speculation; again, future research should examine this. The finding that mothers have such an important influence on girls makes it even more relevant to study girl delinquency. This is because many delinquent girls will, most likely, eventually become mothers as well. The question is what will happen with the children of these mothers if their delinquent behaviour is not intervened on during adolescence. Previous research has shown that seriously delinquent girls are at increased likelihood to suffer problems in adulthood, such as various psychological or psychiatric problems, substance abuse, being in a dysfunctional or violent relationships, poor educational achievement and unstable employment (Fontaine et al., 2008; Giordano, 2010; Pajer, 1998). These features likely interfere with adequate parenting (Cummings, Davies, & Campbell, 2000). The pathology of the delinquent girl Next to mothers, girls also appeared to be uniquely affected by mental health disorders. Previous studies that examined characteristics of arrested or detained boys and girls also found that a larger number of delinquent girls than boys had mental health problems, such as depression, anxiety and anger (Alemagno et al., 2006; Cauffman, Lexcen, Goldweber, Shulman, & Grisso, 2007; Gavazzi et al., 2006; Johansson & Kempf-Leonard, 2009; Kataoka et al., 2001). However, these results concern incarcerated youth and, again, it might be that girls are at relatively higher risk than boys to become arrested when they have mental health problems. Furthermore, girls in general suffer more from mental health problems than boys (Gray, 2002) and since no control group was included in these studies, it could not be tested whether delinquent girls indeed had more mental health problems than the average girl. More research should thus be carried out in better suited designs to investigate why delinquent girls and not delinquent boys are affected by mental health problems. It is important for future research not to study this in a setting were selection effects can play a role, but instead to use randomly selected populations-based samples. In addition, it is essential to take a nondelinquent comparison group into account. The sex difference in delinquency The studies in this dissertation have shown that the sex difference in delinquency might be explained by differential exposure between boys and girls. Sex differences in vulnerability appeared to be less important for the explanation and sex differences in thresholds for delinquency were found to 153 be (almost) non-existent and therefore not related to the sex difference in the delinquency prevalence. Hence, future research should focus mostly on sex differences in exposure to account for the sex difference in delinquency. In specific, it was found that sex differences in exposure to parental solicitation of mothers, to adolescent disclosure toward mothers and to the number of delinquent friends were related to the difference in delinquency prevalence between boys and girls. These results imply that if girls had a similar number of delinquent friends as boys and similar levels of interaction with their mothers, their delinquency prevalence might be as high as that of boys. However, this is probably not true. Although the association between sex and delinquency in our analysis became insignificant when differential exposure to the previous mentioned factors was included, this might not be the entire explanation of the sex difference. It should not be ignored, for instance, that boys and girls are biologically seen different types of beings. Sex differences in biological factors therefore most probably also play a role in explaining in prevalence differences. It is even possible that biological sex differences are the reason of the differences found in exposure. Future research should pay more attention to including and combining biological and environmental factors that might influence (the sex difference in) delinquency. In the current dissertation this was not possible, since data on biological factors were not available. Besides, more research is needed that attempts to explain why it is so that differential exposure to adolescent disclosure to mothers, to maternal solicitation and to peer delinquency are associated with the lower prevalence of delinquency among girls. Put differently, it should be investigated how these factors influence delinquency in boys and girls. Furthermore, research should try to explain the differences between boys and girls in exposure to these factors. Why is it that girls tell their mothers more than boys? And why do mothers put more effort in talking to their daughters than to their sons? And are girls less exposed to delinquent peers simply because they have less friends of the opposite sex who are thus less often delinquent, or is there another explanation? Sex differences in exposure should also be examined in future research for different age periods, since different factors may be important during different ages. In this dissertation it was only possible to examine the hypotheses in early adolescence (when the adolescents were aged 12 to 13). Another important issue for prospective exposure (and vulnerability) studies is that risk and promotive effects should be disentangled. In order to know what the consequence is of differential exposure, it should be known how the factors affect delinquency to which boys and girls are differently exposed to. Besides, the results of this dissertation suggested that differential vulnerability for risk factors cannot account for the sex difference in delinquency, but that differential vulnerability for promotive factors maybe can. 154 Higher arrest threshold The studies in this dissertation have shown that there is no higher threshold for delinquency for girls than for boys. Previous studies did however suggest a higher threshold for girls than for boys, because they found that girls in juvenile justice institutions had more problematic characteristics than their male counterparts (Belknap & Holsinger, 2006; Emeka & Sorensen, 2009; Gavazzi, Yarcheck, & Chesney-Lind, 2006; Gover, 2004; Johansson & Kempf-Leonard, 2009) or because they found that delinquent girls had a higher number of risk factors than delinquent boys (Alemagno et al., 2006; Van der Laan & Van der Schans, 2010). It should be noted that all of these studies based their results on selective samples of arrested or incarcerated youth. However, different studies have shown that girls are less often arrested and incarcerated than boys (Jeffries, Fletcher, & Newbold, 2003; Sealock & Simpson, 1998; Spohn & Beichner, 2000; Williams, 1999) which implies that it is a selected group of girls that ends up in juvenile justice institutions. This suggests that there is no higher threshold for girls than for boys to become delinquent – as is shown by the self-reported data used in this dissertation – but that there is a higher threshold for girls to become arrested. It might thus be that girls should have many problems and risk factors before the police notice a girl or maybe the police is more lenient towards girls. Whether and why this occurs should be examined in future research. It might be that it is a deliberate choice of the police only to take in problematic girls. However, this would imply that no juvenile justice interventions are offered to delinquent girls that are less problematic and therefore no attempt is made to diminish their delinquent behaviour. To adequately examine a higher threshold for girls to become arrested, it is essential to include two comparison groups for both boys and girls: a non-delinquent group and a delinquent-but-not-arrested group. With the nondelinquent group typical characteristics of boys and girls can be distinguished from characteristics of delinquent boys and girls (i.e. risk factors). Subsequently, with the delinquent-but-not-arrested group, it can be investigated whether there is indeed a higher threshold for girls to become arrested. Next to including these comparison groups, it should be noted again that including promotive factors is of great importance in examining the threshold. Furthermore, future research should consider that different factors can have different weights of influence on delinquency. Otherwise, factors that only affect delinquency to a small extent are regarded as important as factors that have a large influence on delinquency. All in all, this dissertation has shown that the relationship with mothers and the number of delinquent friends come across as important ingredients of the sex difference in the prevalence of delinquency. In addition, maternal factors and mental health problems appeared to be uniquely related to delinquency of girls. Moreover, no sex differences in thresholds for delinquency appeared 155 to exist. This dissertation therefore provided a next stepping stone for the development of theories about girl delinquency and about sex differences in delinquency. 156 References 157 Agnew, R. (2009). The contribution of ‘mainstream’ theories to the explanation of female delinquency. In M. A. Zahn (Ed.), The delinquent girl (pp. 147-163). Philadelphia: Temple University Press. Alemagno, S. A., Shaffer-King, E., & Hammel, R. (2006). Juveniles in detention: How do girls differ from boys? Journal of Correctional Health Care, 12, 45-53. Alesina, A. & Glaeser, E. L. (2004). Fighting poverty in the US and Europe: A world of difference. Oxford: University Press. Baker, L. A., Mack, W., Moffitt, T. E., & Mednick, S. (1989). Sex differences in property crime in a Danish adoption cohort. Behavior Genetics, 19, 355-370. Belknap, J., & Holsinger, K. (2006). The gendered nature of risk factors for delinquency. Feminist Criminology, 1, 48-71. Bentler, P. M. (1990). Comparative fit indexes in structural models. Psychological Bulletin, 107, 238-246. Bijleveld, C. C. J. H. & Wijkman, M. (2009). Intergenerational continuity in convictions: A five-generation study. Criminal Behaviour and Mental Health, 19, 142-155. Blitstein, J. L., Murray, D. M., Lytle, L. A., Birnbaum, A. S., & Perry, C. L. (2005). Predictors of violent behavior in an early adolescent cohort: Similarities and differences across genders. Health Education & Behavior, 32, 175-194. Blom, M., Van der Laan, A. M., & Huijbregts, G. L. A. M. (2005). Monitor Jeugd terecht 2005. Den Haag: WODC Cahier 2005-17. Blum, J. B. A., Ireland, M., & Blum, R. W. M. D. (2003). Gender differences in juvenile violence: A report from add health. Journal of Adolescent Health, 32, 234-240. Bontekoe, E. H. M. (1984). Criminaliteit en geslacht. [Criminal behaviour and sex] Tijdschrift voor Criminologie, 26, 18-31. Browne, M. W., & Cudeck, R. (1993). Alternative ways of assessing model fit. In K. A. Bollen & J. S. Long (Eds.), Testing structural equation models (pp. 136-162). Newbury Park, CA: Sage Bruinsma, G. & Lissenberg, E. (1987). Vrouwen in de theoretische en empirische criminologie. [Women in the theoretical and empirical criminology] Tijdschrift voor Criminologie, 29, 111-114. Campbell, A. (1987). Self-reported delinquency and home life: Evidence from a sample of British females. Journal of Youth and Adolescence, 16, 167-177. Cauffman, E., Lexcen, F. J., Goldweber, A., Shulman, E. P., & Grisso, T. (2007). Gender differences in mental health symptoms among delinquent and community youth. Youth Violence and Juvenile Justice, 5, 287-307. 158 Calhoun, G. B. (2001). Differences between male and female juvenile offenders as measured by the BASC. Journal of Offenders Rehabilitation, 33, 87-96. Chamberlain, P. & Moore, K. (2002). Chaos and trauma in the lives of adolescent females with antisocial behavior and delinquency. Journal of Aggression, Maltreatment & Trauma, 6, 79-108. Chapple, C. L., McQuillan, J. A., & Berdahl, T. A. (2005). Gender, social bonds, and delinquency: a comparison of boys' and girls' models. Social Science Research, 34, 357-383. Chesney-Lind, M. (1989). Girl's crime and woman's place: Toward a feminist model of female delinquency. Crime and Delinquency, 35, 529. Chesney-Lind, M. (1999). Challenging females’ invisibility in Juvenile Court. The ANNALS of the American Academy of Political and Social Science, 564, 185-202. Cloninger, C. R. & Gottesman, I. I. (1987). Genetic and environmental factors in antisocial behavior disorders. In S. A. Mednick, T. E. Moffitt, & S. A. Stack (Eds.), The causes of crime: New biological approaches (pp. 92-109). Cambridge: Cambridge University Press. Cummings, E. M., Davies, P. T., & CAmpbell, S. B. (2000). Developmental psychopathology and family process: Theory, research, and clinical implications. New York: The Guilford Press. Daigle, L. E., Cullen, F. T., & Wright, J. P. (2007). Gender differences in the predictors of juvenile delinquency: Assessing the generality-specificity debate. Youth Violence and Juvenile Justice, 5, 254-286. Daly, K. (1994). Gender, crime, and punishment. New Haven : Yale University Press. Davis, M. 1983. Measuring individual differences in empathy: Evidence for a multidimensional approach. Journal of Personality and Social Psychology, 44, 113–126. Dijksterhuis, F. P. H. & Nijboer, J. A. (1987). Meisjes- en jongensdelinquentie: Dezelfde etiologische processen. [Girl and boy delinquency. Similar etiological processes] Tijdschrift voor Criminologie, 29, 104-110. Dowden, C. & Andrews, D. A. (1999). What works for female offenders: A meta-analytic review. Crime and Delinquency, 45, 438-452. Eggen, A.Th.J. (2009). Geregistreerde criminaliteit. [Official crime]. In S. N. Kalidien & A. Th. J. Eggen (red.), Criminaliteit en rechtshandhaving 2008. Den Haag: Boom Juridische uitgevers. Eichelsheim, V., Buist, K., Deković, M., Wissink, I., Frijns, T., van Lier, P., Koot, H., & Meeus, W. (2010). Associations among the parentadolescent relationship, aggression and delinquency in different ethnic groups: A replication across two Dutch samples. Social Psychiatry and Psychiatric Epidemiology, 45, 293-300. 159 Eichelsheim, V. I., Buist, K., Deković, M., Cook, W. L., Manders, W., Branje, S., Frijns, T., Van Lier, P. A. C., Koot, H. M., & Meeus, W. (in press). Negativity in problematic and non-problematic families: A multigroup Social Relations Model analysis with structured means. Journal of Family Psychology. Elliott, D. S., Huizinga, D., & Ageton, S. S. (1985). Explaining delinquency and drug use. Beverly Hills, CA: Sage. Eme, R. F. (1992). Selective females affliction in the developmental disorders of childhood: A literature review. Journal of Clinical Child Psychology, 21, 354. Emeka, T. Q. & Sorensen, J. R. (2009). Female juvenile risk: Is there a need for gendered assessment instruments? Youth Violence and Juvenile Justice, 7, 313-330. Fagan, A. A., Van Horn, M. L., Hawkins, J. D., & Arthur, M. W. (2007). Gender similarities and differences in the association between risk and protective factors and self-reported serious delinquency. Prevention Science, 8, 115-124. Farrington, D. P. (1973). Self-reports of deviant behavior: Predictive and stable ? Journal of Criminal Law and Criminology, 64, 99-110. Farrington, D. P. (1986). Age and crime. Crime and justice: An annual review of research (Vol. 7, pp. 189-250). Chicago: University of Chicago Press. Farrington, D. P., Jolliffe, D., Hawkins, J. D., Catalano, R. F., Hill, K. G., & Kosterman, R. (2003). Comparing delinquency careers in court records and self-reports. Criminology, 41, 933-958. Farrington, D. P. & Painter, K. A. (2004). Gender differences in risk factors for offending: Implications for risk-focused prevention: Home Office. Fontaine, N., Carbonneau, R., Barker, E. D., Vitaro, F., Hébert, M., Côté, S., et al. (2008). Girls’ hyperactivity and physical aggression during childhood and adjustment problems in early adulthood. Archives of General Psychiatry, 65, 320-328. Furman, W. & Buhrmester, D. (1985). Children’s perceptions of the personal relationship in their social networks. Developmental Psychology, 21, 1016-1024. Gaarder, E. & Belknap, J. (2002). Tenuous borders: Girls transferred to adult court. Criminology, 40, 481-517. Gavazzi, S. M., Yarcheck, C. M., & Chesney-Lind, M. (2006). Global risk indicators and the role of gender in a juvenile detention sample. Criminal Justice Behavior, 33, 597-612. Gecas, V. & Seff, M. A. (1990). Families and adolescents: A review of the 1980s. Journal of Marriage and the Family, 52, 941–958. Gilligan, C. (1982). In a different voice. Cambridge, MA: Harvard University Press. 160 Giordano, P. C. (2010). Legacies of crime. A follow-up of the children of highly delinquent girls and boys. New York: Cambridge University Press. Giordano, P. C., Cernkovich, S. A., & Pugh, M. D. (1986). Friendships and delinquency. American Journal of Sociology, 91, 1170-1202. Glasner, T. & van der Vaart, W. (2009) Applications of calender instruments in social surveys: A review. Quality and Quantity, 43, 333-349 Gover, A. R. (2004). Childhood sexual abuse, gender, and depression among incarcerated youth. International Journal of Offender Therapy and Comparative Criminology, 48, 683-696. Graham, J. & Bowling, B. (1996). Young people and crime (Research study no. 145). London: Home Office. Gratz, K. L. & Roemer, L. (2004). Multidimensional assessment of emotion regulation and dysregulation: Development, factor structure, and initial validation of the Difficulties in Emotion Regulation Scale. Journal of Psychopathology and Behavioral Assessment, 26, 41-54. Gray, P. (2002). Psychology, 4th edition. New York: Worth Publisher. Haen-Marshall, I. (1996). How exceptional is the United States? European Journal on Criminal Policy and Research, 4, 7-35. Hale, W., Keijsers, L., Klimstra, T., Raaijmakers, Q., Hawk, S., Branje, S., Frijns, T., Wijsbroek, S., Van Lier, P., & Meeus, W. (2011). How does longitudinally measured maternal Expressed Emotion affect adolescent antisocial and depressive symptoms? Journal of Child Psychology and Psychiatry, 52, 1174–1183. Hartjen, C. A. & Priyadarsini, S. (2003). Gender, peers, and delinquency: A study of males and females in rural France. Youth & Society, 34, 387414. Hauber, A., Toornvliet, L., & Willemse, H. (1987). Achtergronden van criminaliteit bij meisjes. [Backgrounds of criminality in girls]. In G. Bruisma (ed.), Vrouw en criminaliteit: Vrouwen als plegers en slachtoffers van criminaliteit (pp. 41-52). Meppel: Boom. Heimer, K., De Coster, S., & Unal, H. (2006). Opening the black box: Understanding the social psychology of the gender gap in delinquency. Sociology of Crime, Law, and Deviance, 7, 109-135. Hessing, D. J. & Elffers, H. (1995). De validiteit van de self-report methode in onderzoek naar regelovertredend gedrag. Tijdschrift voor Criminologie, 1, 55-70. Hill, K. G., Howell, J. C., Hawkins, J. D., & Battin-Pearson, S. R. (1999). Childhood risk factors for adolescent gang membership: Results from the Seattle Social Development Project. Journal of Research in Crime and Delinquency, 36, 300-322. Hirschi, T. (1969). Causes of Delinquency. Berkeley, CA: University of California Press. 161 Hodgins, S., Kratzer, L., & McNeil, T. F. (2001). Obstetric complications, parenting, and risk of criminal behavior. Archives of General Psychiatry, 58, 746. Hoeve, M. (2008). Parenting and juvenile delinquency. (Doctoral dissertation, Radboud University, Nijmegen. Hoeve, M., Dubas, J. S., Eichelsheim, V. E., Van der Laan, P. H., Smeenk, W., & Gerris, J. R. M. (2009). The relationship between parenting and delinquency: A meta-analysis. Journal of Abnormal Child Psychology, 37, 749-775. Holsinger, K. (2000). Feminist perspectives on female offending: Examining real girls’ lives. Women and Criminal Justice, 12, 23-51. Honkatukia, P. (1998). Gender, social control and crime: The conforming behaviour of females. In: P. Honkatukia, Sopeutuvat tytöt? Sukupuoli, sosiaalinen kontrolli ja rikokset. Helsinki: Hakapaino OY. Hoyt, S. & Scherer, D. G. (1998). Female juvenile delinquency: Misunderstood by the juvenile justice system, neglected by social science. Law and Human Behavior, 22, 81-107. Hubbard, D. J. & Pratt, T. C. (2002). A meta-analysis of the predictors of delinquency among females. Journal of Offender Rehabilitation, 34, 113. Jeffries, S., Fletcher, G. J. O., & Newbold, G. (2003). Pathways to sex-based differentiation in criminal court sentencing. Criminology, 41, 329-354. Johansson, P. & Kempf-Leonard, K. (2009). A gender-specific pathway to serious, violent, and chronic offending? Exploring Howell's risk factors for serious delinquency. Crime & Delinquency, 55, 216-240. Jolliffe, D. & Farrington, D. P. (2007). Examining the relationship between low empathy and self-reported offending. Legal and Criminological Psychology, 12, 265-286. Junger-Tas, J. (1992). Criminaliteit en leeftijd. [Crime and age]. Justitiële Verkenningen, 18, 66-89 Junger-Tas, J., Haen-Marshall, I., & Ribeaud, D. (2003). Delinquency in an international perspective: The International Self-Reported Delinquency Study (ISRD). Amsterdam: Kugler. Junger-Tas, J., Ribeaud, D., & Cruyff, M. (2004). Juvenile delinquency and gender. European Journal of Criminology, 1, 333-375. Kataoka, S. H., Zima, B. T., Dupre, D. A., Moreno, K. A., Yang, X., & McCracken, J. T. (2001). Mental health problems and service use among female juvenile offenders: Their relationship to criminal history. Journal of the American Academy of Child and Adolescent Psychiatry, 40, 549-555. Keenan, K., Hipwell, A., Chung, T., Stepp, S., Stouthamer-Loeber, M., Loeber, R., & McTigue, K. (2010). The Pittsburgh Girls Study: Overview and initial findings. Journal of Clinical Child and Adolescent Psychology, 39, 506–521. 162 Keenan, K., Loeber, R., & Green, S. (1999). Conduct disorder in girls: A review of the literature. Clinical Child and Family Psychology Review, 2, 3-19. Kemppainen, L., Jokelainen, J., Isohanni, M., Järvelin, M.-J., & Räsänen, P. (2002). Predictors of female criminality: Findings from the northern Finland 1966 birth cohort. Journal of the American Academy of Child and Adolescent Psychiatry, 41, 854-859. Kerr, M. & Stattin, H. (2000). What parents know, how they know it, and several forms of adolescent adjustment: Further support for a reinterpretation of monitoring. Developmental Psychology, 36, 366-380. Kerr, M. & Stattin, H. (2003). Parenting of adolescents: Action or reaction?. In A.C. Crouter, & A. Booth (Eds.), Children’s influence on family dynamics: The neglected side of family relationships. Mahwah, NJ: Erlbaum. Klein, M. W., Kerner, H.-J., Maxson, C. L., & Weitekamp, E. G. M. (2001). The Eurogang paradox: Street gangs and youth groups in the US and Europe. Dordrecht: Kluwer Academic Pub. Klimstra, T. A., Luyckx, K., Hale, W. W., Frijns T., Van Lier, P., & Meeus, W. (2010). Short term fluctuations in identity: Introducing a micro-level approach to identity formation. Journal of Personality and Social Psychology, 99, 191-202. Kratzer, L. & Hodgins, S. (1999). A typology of offenders: A test of Moffitt’s theory among males and females from childhood to age 30. Criminal Behaviour and Mental Health, 9, 57-73. Lahey, B. B., Van Hulle, C. A., Waldman, I. D., Rodgers, J. L., D’Onofrio, B. M., Pedlow, S., et al. (2006). Testing descriptive hypotheses regarding sex differences in the development of conduct problems and delinquency. Journal of Abnormal Child Psychology, 34, 730-748. Landsheer, J. A. & Van Dijkum (2005). Male and female delinquency trajectories from pre through middle adolescence and their continuation in late adolescence. Adolescence, 40, 729-748. Laursen, B. (1993). The perceived impact of conflict on adolescent relationships. Merrill Palmer Quarterly, 39, 535-550. Leaper, C., Anderson, K. J., & Sanders, P. (1998). Moderators of gender effects on parents’ talk to their children: A meta-analysis. Developmental Psychology, 34, 3–27. Lederman, C. S., Dakof, G. A., Larrea, M. A., & Li, H. (2004). Characteristics of adolescent females in juvenile detention. International Journal of Law and Psychiatry, 27, 321-337. Lipsey, M. W. & Derzon, J. H. (1998). Predictors of violent or serious delinquency in adolescence and early adulthood: A synthesis of longitudinal research. In R. Loeber & D. P. Farrington (Eds.), Serious and violent juvenile offenders: Risk factors and successful interventions (pp. 86-105). Thousand Oaks, CA: Sage. 163 Liu, X. & Kaplan, H. B. (1999). Explaining the gender difference in adolescent delinquent behavior: A longitudinal test of mediating mechanisms. Criminology, 37, 195. Loeber, R. (1990). Development and risk factors of juvenile antisocial behavior and delinquency. Clinical Psychology Review, 10, 1-41. Loeber, R., Farrington, D. P., Stouthamer-Loeber, M., & Van Kammen, W. B. (1998). Antisocial behavior and mental health problems: Explanatory factors in childhood and adolescence. Mahwah, NJ: Erlbaum. Loeber, R., Farrington, D. P., Stouthamer-Loeber, M., & White, H. R. (2008). Violence and serious theft: Development and prediction from childhood to adulthood. New York: Routledge. Loeber, R. & Keenan, K. (1994). Interaction between conduct disorder and its comorbid conditions: Effects of age and gender. Clinical Psychology Review, 14, 497–523. Loeber, R., Slot, N. W., & Stouthamer-Loeber, M. (2008). A cumulative developmental model of risk and promotive factors. In R. Loeber, N. W. Slot, P. H. Van der Laan & M. Hoeve (Eds.), Tomorrow’s criminals. The development of child delinquency and effective interventions (pp. 133-161). Farnham: Ashgate Publishing. Luthar, S. S. (1993). Annotation: Methodological and conceptual issues in research on childhood resilience. Journal of Child Psychology and Psychiatry, 34, 441-453. Lytton, H. & Romney, D. M. (1991). Parents’ differential socialization of boys and girls: A meta-analysis. Psychological Bulletin, 109, 267-296. Maguin, E. & Loeber, R. (1996). Academic performance and delinquency. In M. Tonry (Ed.), Crime and Justice (pp. 259-281). Chicago, Ill: University of Chicago Press. Mansel, J. (2003). Die Selektivität strafrechtlicher Sozialkontrolle: Frauen und Delinquenz im Hell- und Dunkelfeld, als Opfer und Täter, als Anzeigende und Angezeigte. In S. Lamnek & M. Boatca (eds.), Geschlecht - Gewalt – Gesellschaft, 384-406. Opladen: Leske u. Martens, P. L. (1997). Parental monitoring and deviant behaviour among juveniles. Studies on Crime and Crime Prevention, 6, 224-240 McAra, L. (2005). Negotiated order: Gender, youth transitions and crime. British Society of Criminology, e-journal 6. McFall, R. M. & Treat, T. A. (1999). Quantifying the information value of clinical assessments with signal detection theory. Annual Review Psychology, 50, 215-241. Mears, D. P., Ploeger, M., & Warr, M. (1998). Explaining the gender gap in delinquency: Peer influence and moral evaluations of behavior. Journal of Research in Crime and Delinquency, 35, 251. Megens, K. & Day, S. (2007). Delinquentie van meisjes: Over de relatie tussen risicofactoren en delinquent gedrag na behandeling in een JJI. 164 [Delinquency of girls. On the relationship between risk factors and delinquent behavior after treatment in a Juvenile Justice Institution] Tijdschrift voor Criminologie, 49, 370-385. Mertens, N. M., Grapendaal, M., & Docter-Schamhardt, B. J. W. (1998). Meisjescriminaliteit in Nederland. [Girl delinquency in the Netherlands] Den Haag: WODC Messer, J., Goodman, R., Rowe, R., Meltzer, H., & Maughan, B. (2006). Preadolescent conduct problems in girls and boys. Journal of the American Academy of Child and Adolescent Psychiatry, 45, 184. Miller, J. & Mullins, C. W. (2009). Feminist theories of girls’ delinquency. In M.A. Zahn (Ed.), The delinquent girl (pp. 50-83). Philadelphia: Temple University Press. Ministry of Juctice (2002). Privé geweld, publieke zaak. Een nota over de gezamenlijke aanpak van huiselijk geweld. [Private violence, public case. An annotation about the collective approach of domestic violence]. Den Haag: Hega Offset. Moffitt, T. (1993). Adolescence-limited and life-course-persistent antisocial behavior: a developmental taxonomy. Psychological Review, 100, 674701. Moffitt, T. E., Caspi, A., Rutter, M., & Silva, P. A. (2001). Sex differences in antisocial behaviour: Conduct disorder, delinquency, and violence in the Dunedin longitudinal study. Cambridge: Cambridge University Press. Mounts, N. S. (2002). Parental management of adolescent peer relations in context: The role of parenting style. Journal of Family Psychology, 16, 58-69. Murray, J. (2002). Explaining sex differences in offending behaviour. Thesis, University of Cambridge. Muthén, L. K. & Muthén, B. O. (1998-2010). Mplus user’s guide. Sixth edition. Los Angeles, CA: Muthén and Muthén. Neumann, A., Barker, E. D., Koot, H. M., & Maughan, B. (2010). The role of contextual risk, impulsivity, and parental knowledge in the development of adolescent antisocial behavior. Journal of Abnormal Psychology, 119, 534-545. Nijboer, J. A. (1995). Het meten van delinquentie door middel van ‘selfreport’. [Measuring delinquency through self reports]. Tijdschrift voor Criminologie, 3, 273-280. Oberwittler, D. (2003). Geschlecht, Ethnizität und sozialräumliche Benachteiligung. Überraschende Interaktionen bei sozialen Bedingungsfaktoren von Gewalt und schwerer Eigentumsdelinquenz von Jugendlichen. In S. Lamnek & M. Boatca (eds.), Geschlecht Gewalt – Gesellschaft, 269-294. Opladen: Leske u. 165 Pajer, K. A. (1998). What happens to" bad" girls? A review of the adult outcomes of antisocial adolescent girls. American Journal of Psychiatry, 155, 862-870. Pedersen, W. (1994). Parental relations, mental health, and delinquency in adolescents. Adolescence, 29, 975-990. Piko, B. F., Fitzpatrick, K. M., & Wright, D. R. (2005). A risk and protective framework for understanding youths’ externalizing problem behaviour in two different cultural settings. European Child & Adolescent Psychiatry, 14, 95-103. Piquero, A. R., Macintosh, R., & Hickman, M. (2002). The validity of a selfreported delinquency scale: Comparisons across gender, age, race, and place of residence. Sociological Methods and Research, 30, 492–529. Pratt, T. C. & Cullen, F. T. (2005). Assessing macro-level predictors and theories of crime: A meta-analysis. Crime and Justice, 32, 373- 450. Putallaz, M. & Bierman, K. (2004). Aggression, antisocial behavior, and violence among girls: A developmental perspective. New York: Guilford. Rantakallia, P., Myhrman, A., & Koiranen, M. (1995). Juvenile offenders, with special reference to sex differences. Social Psychiatry and Psychiatric Epidemiology, 30, 113-120. Riley, D. & Shaw, M. (1985). Parental supervision and Juvenile delinquency. Home Office Research Study 83, HMSO. Ritakallio, M., Kaltiala-Heino, R., Kivivuori, J., & Rimpelä, M. (2005). Brief report: Delinquent behaviour and depression in middle adolescence: A Finish community sample. Journal of Adolescence, 28, 155-159. Robins, L. N. (1966). Deviant children grown up. Baltimore, MD: Williams and Wilkins. Rolf, J. & Johnson, J. (1990). Protected or vulnerable: The challenges of AIDS to developmental psychopathology. In J. E. Rolf, A. S. Masten, D. Cicchetti, K. H. Nuechterlein, and S. Weintraub (Eds.), Risk and protective factors in the development of psychopathology. New York: Cambridge University Press. Rose, A. J. & Rudolph, K. D. (2006). A review of sex differences in peer relationship processes: Potential trade-offs for the emotional and behavioral development of girls and boys. Psychological Bulletin, 132, 98–131. Rosenbaum, J. L. & Chesney-Lind, M. (1994). Appearance and delinquency: A research note. Crime and Delinquency, 40, 250-261. Rouwette, E., van Hooff, P., Vennix, J., & Jongebreur, W. (2007). Modeling crime control in the Netherlands: insights on process. Paper presented at the 25th International Conference of the System Dynamics Society. 166 Rowe, D. C., Vazsonyi, A. T., & Flannery, D. J. (1995). Sex differences in crime: Do means and within-sex variation have similar causes? Journal of Research in Crime and Delinquency, 32, 84. Rutenfrans, C. J. C. (1989). Criminaliteit en sexe.[Criminal behaviour and sex] (Doctoral dissertation, University of Nijmegen). Rutter, M. (1979). Protective factors in children’s responses to stress and disadvantage. In M. W. Kent & J. E. Rolf (Eds.), Primary prevention of psychopathology, Vol. 3: Social competence in children (pp. 49-74). Hanover, NH: University Press of New England. Sameroff, A. J., Bartko, W. T., Baldwin, A., Baldwin, C., & Seifer, R.(1998). Family and social influences on the development of child competence. In M. Wei & C. Fairing (Eds.), Families, risk, and competence. Mahwah, NJ: Erlbau Sameroff, A. J., Seifer, R., Barocas, R., Zax, M., & Greenspan, S. (1987). Intelligence quotient scores of 4-yearold children: Social-environmental risk factors. Pediatrics, 79, 343-350. Scholte, R. H. J., Engels, R. C. M., De Kemp, R. A. T., Harakeh, Z., & Overbeek, G. (2007). Differential parental treatment, sibling relationships and delinquency in adolescence. Journal of Youth and Adolescence, 36, 661–671. Schwartz, S., Klimstra, T., Luyckx, K., Hale, W., Frijns, T., Oosterwegel, A., van Lier, P., Koot, J., & Meeus, W. (in press). Daily dynamics of personal identity and self-concept clarity. European Journal of Personality. Sealock, M. D. & Simpson, S. S. (1998). Unraveling bias in arrest decisions: The role of juvenile offender type-scripts. Justice Quarterly, 15, 427. Simourd, L. & Andrews, D. A. (1994). Correlates of delinquency: A look at gender differences. Forum on Corrections Research, 6, 26-31. Singer, J. D. & Willett, J. B. (2003). Applied longitudinal data analysis. Modeling change and event occurrence. Oxford: University Press. Slotboom, A., Weerman, F. M., & Bijleveld, C. C. J. H. (2005). Misconduct and delinquency of schoolfemales. Presentation on ESC, August 2005. Slotboom, A., Wong, T. M. L., Swier, C., & Van der Broek, T. C. (2011). Delinquente meisjes: Achtergronden, risicofactoren en interventies. [Delinquent girls: Background characteristics, risk factors and interventions]. Den Haag: Boom Juridische uitgevers. Smith, D. J. & McAra, L. (2004). Gender and youth offending. The Edinburgh Study of Youth Transitions and Crime, number 2, Centre for Law and Society, The University of Edinburgh. Spohn, C. & Beichner, D. (2000). Is preferential treatment of female offenders a thing of the past? A multisite study of gender, race, and imprisonment. Criminal Justice Policy Review, 11, 149. Stattin, H. & Kerr, M. (2000). Parental monitoring: A reinterpretation. Child Development, 71, 1072-1085. 167 Steffensmeier, D. & Allan, E. (1996). Gender and crime: Toward a gendered theory of female offending. Annual Review of Sociology, 22, 459-487. Steffensmeier, D. & Haynie, D. (2000). Gender, structural disadvantage, and urban crime: Do macrosocial variables also explain female offending rates? Criminology, 38, 400-438. Steffensmeier, D., & Schwartz, J. (2009). Trends in girls‘ delinquency and the gender gap: Statistical assessment of diverse sources. In M. A. Zahn (Ed.), The delinquent girls (pp. 50-83). Philadelphia: Temple University Press. Stouthamer-Loeber, M., Loeber, R., Wei, E., Farrington, D., & Wikström, P. (2002). Risk and promotive effects in the explanation of persistent serious delinquency in boys. Journal of Consulting and Clinical Psychology, 70, 111-123. Stouthamer-Loeber, M., Loeber, R., Farrington, D. P., Zhang, Q., Van Kammen, W., & Maguin, E. (1993). The double edge of protective and risk factors for delinquency: Interrelations and developmental patterns. Development and Psychopathology, 5, 683-701. Sudman, S., Bradburn, N. M., & Schwarz, N. (1996) Thinking about questions: The application of cognitive processes to survey methodology. San Francisco: JosseyBass. Sutherland, E. H. (1947). Principles of Criminology: Fourth Edition. Philadelphia: Lippincott. Svensson, R. (2004). Shame as a consequence of the parent-child relationship: A study of gender differences in juvenile delinquency. European Journal of Criminology, 1, 477-504. Swets, J. A. (1964) Signal detection and recognition by human observers. Contemporary readings. Wiley, New York. Tankersley, V. L. & Rycraft, J. R. (2007). A qualitative examination of risk factors influencing female adolescent delinquency in Dallas county, Texas. University of Texas. Thornberry, T. P. & Krohn, M. D. (2000). The self-report method for measuring delinquency and crime. Measurement and Analysis of Crime and Justice, 4, 33-83. Thornberry, T. P. & Krohn, M. D. (2003). Taking stock of delinquency: An overview of findings from contemporary longitudinal studies. New York: Plenum Publishers. TK. (2002/2003b). Jeugd terecht; Actieprogramma Aanpak Jeugdcriminaliteit 2003-2006. 28 741, nr. 1 Tonry, M. (1999). Why are US incarceration rates so high? Crime and Delinquency, 45, 419-437. Torstensson, M. (1990). Female delinquents in a birth cohort: Tests of some aspects of control theory. Journal of Quantitative Criminology, 6, 101115. 168 Tourangeau, R., Rips, L. J., & Rasinski, K.A. (2000) The Psychology of Survey Response. Cambridge: Cambridge University Press Van der Geest, V., & Bijleveld, C. C. J. H. (2008). Personal, background and treatment characteristics associated with offending after residential treatment: A 13-year follow up in adolescent males. Psychology, Crime & Law, 14, 159-176. Van der Heijden, P. G. M., Sijtsma, K., & 't Hart, H. (1995). Self-report delinquentie-schalen zijn nog steeds betrouwbaar. Een reactie op de studies van Bruinsma. [Self reported delinquency scales are still reliable. A response to the studies of Bruinsma]. Tijdschrift voor Criminologie, 37, 71-77. Van der Laan, A. M. & Blom, M. (2006). Jeugddelinquentie: Risico’s en bescherming. Bevindingen uit de WODC Monitor Zelfgerapporteerde Jeugdcriminaliteit 2005. [Juvenile delinquency: Risks and protective factors. Findings of the WODC Youth Delinquency Survey, 2005]. Den Haag: Boom Juridische uitgevers. Van der Laan, A. M., & Van der Schans, C. (2010). Delinquente meisjes: Zijn ze anders dan jongens? Risico- en beschermende factoren bij jongeren die een basisraadsonderzoek ondergaan. [Delinquent girls: Do they differ from boys? Risk and promotive factors of juveniles getting a prescreen by the Child Protection Board]. Tijdschrift voor Orthopedagogiek, 49, 149-162. Van der Rakt, M., Weerman, F., & Need, A. (2005). Delinquent gedrag van jongens en meisjes: Het (anti)sociale kapitaal van vriendschapsrelaties. [Delinquent behaviour of boys and girls: The (anti)social value of peer relationships]. Mens en Maatschappij, 80, 329-354. Van de Schoot, R., & Wong, T. M. L. (in press). Do delinquent young adults have a high or a low level of self-concept? Self & Identity. Van Lier, P. A. C., Frijns, T., Neumann, A., Den Exter Blokland, E., Koot, J. M., & Meeus, W. (submitted). The RADAR study: Design, description of sample and validation of cohort assignment. Warr, M. (2002). Companions in crime: The social aspects of criminal conduct. Cambridge: Cambridge University Press. Weerman, F. (2007). Juvenile offending. In M. H. Tonry & C. C. J. H. Bijleveld (Eds.), Crime and Justice in the Netherlands, Vol. 35. Chicago: University of Chicago Press Journals. Williams, M. R. (1999). Gender and sentencing: An analysis of indicators. Criminal Justice Policy Review, 10, 471. Wong, T. M. L., Blom, M., & Van der Laan, A. (in press). De inhaalslag van vrouwen? Omvang, aard en trends in criminaliteit onder meisjes en vrouwen. In A. Slotboom, M. Hoeve, M. Ezinga, & P. van der Helm (Eds.), Criminele meisjes en vrouwen: Achtergronden en aanpak. Den Haag: Boom Juridische Uitgevers. 169 Wong, T. M. L., Loeber, R. Slotboom, A., & Bijleveld, C. C. J. H. (submitted). Identifying the threshold: The sex difference in the risk threshold for delinquency at different age periods. Wong, T. M. L., Slotboom, A., & Bijleveld, C. C. J. H. (2010). Risk factors for delinquency in adolescent and young adult females: A European review. European Journal of Criminology, 7, 266-284. Wong, T. M. L., Slotboom, A., Bijleveld, C. C. J. H., Van Lier, P. A. C., Meeus, W. H. J. & Koot, J. M. (submitted). The sex differences in delinquency: Do girls need a bigger push? Wong, T. M. L., Slotboom, A., Zahn, M. Bijleveld, C. C .J. H., Van Lier, P. A. C., Frijns, T., Meeus, W. H. J., & Koot, J.M. (submitted). The sex difference in delinquency explained? Differential exposure and vulnerability in the parent and peer domain. Youden, W. J. (1950). And index for rating diagnostic tests. Cancer, 3, 32, 35. Yu, R., Branje, S., Keijsers, L., & Meeus, W. (2011). Psychometric characteristics of Carver and White's BIS/BAS Scales in Dutch adolescents and their mothers. Journal of Personality Assessment, 93, 500-507. Zahn, M.A. (2009). The delinquent girl. Philedelphia: Temple University Press. Zahn-Waxler, C. & Polanichka, N. (2004). All things interpersonal. Socialization and female aggression. In: M. Putallaz & K. L. Bierman (Eds.), Aggression, antisocial behavior, and violence among girls: A developmental perspective (pp. 48-68). New York: The Guilford Press. 170 Publications Samenvatting (summary) Dankwoord (acknowledgement) Curriculum Vitae 171 172 PUBLICATIONS This dissertation Wong, T. M. L., Slotboom, A., & Bijleveld, C. C. J. H. (2010). Risk factors for delinquency in adolescent and youg adult females: A European review. European Journal of Criminology, 7,266-284. Wong, T. M. L., Blom, M., & Van der Laan, A. (in press). De inhaalslag van vrouwen? Omvang, aard en trends in criminaliteit onder meisjes en vrouwen. In A. Slotboom, M. Hoeve, M. Ezinga, & P. Van der Helm (Eds.), Criminele meisjes en vrouwen: Achtergronden en aanpak. Den Haag: Boom Juridische Uitgevers. Wong, T. M. L., Slotboom, A., Zahn, M., Bijleveld, C. C. J. H., Van Lier, P. A. C., Frijns, T., Meeus, W. H. J. & Koot, J. M. (submitted). The relationship between the sex difference in delinquency and differential exposure and vulnerability in the parent and peer domain. Wong, T. M. L., Slotboom, A., Bijleveld, C. C. J. H., Van Lier, P. A. C., Meeus, W. H. J. & Koot, J. M. (submitted). The sex difference in delinquency: Do girls need a bigger push? Wong, T. M. L., Loeber, R., Slotboom, A., Bijleveld, C. C. J. H., & Koot, J. M. (submitted). Sex and age differences in the risk threshold for delinquency. Other publications Wong, T. M. L., Branje, S. J. T., VanderValk, I. E., Hawk, S. T., & Meeus, W. H. J. (2010). The role of siblings in identity development in adolescence and emerging adulthood. Journal of Adolescence, 33, 673682. Wong, T. M. L., Bijleveld, C. C. J. H., & Slotboom, A. (2009). Van probleemmeisje naar delinquente vrouw? Criminele carrières van residentieel behandelde meisjes, van 12 tot 32 jaar. Tijdschrift voor Criminologie, 51, 246-261. Slotboom, A., Wong, T. M. L., Swier, C., & Van der Broek, T., (2011). Delinquente meisjes: Achtergronden, risicofactoren en interventies. Den Haag: Boom Juridische Uitgevers. Van de Schoot, R. & Wong, T. M. L. (in press). Do delinquent young adults have a high or a low level of self-concept? Self and Identity. Wong, T. M. L. & Van de Schoot, R. (in press). The Effect of Offenders' Sex on Reporting Crimes to the Police. Journal of Interpersonal Violence. Hoeve, M., Vogelvang, L., Wong, T. M. L. & Kruithof, B. (In press). Het mysterie van de criminele vrouw: Theorieën over criminaliteit door meisjes en vrouwen. In A. Slotboom, M. Hoeve, M. Ezinga, & P. Van der Helm (Eds.), Criminele meisjes en vrouwen: Achtergronden en aanpak. Den Haag: Boom Juridische Uitgevers. 173 Van de Schoot, R., Wong, T. M. L., Lugtig, P., Denissen, J. J. A., Oberski, D. L., Koot, J. M., Van Lier, P. A. C., & Meeus, W. (submitted). How to handle missing data in Mplus: A comparison of established and novel approaches. Van de Weijer, S., Wong, T., Verbruggen, J., Tolsma, J. & Bijleveld, C. (submitted). The criminal development of high-risk girls in the Netherlands. 174 SAMENVATTING (summary) Lange tijd is er weinig aandacht geweest voor meisjescriminaliteit in de wetenschap, zeker als we dat vergelijken met de aandacht die er voor criminele jongens was. Nu echter steeds meer meisjes in contact komen met de politie, neemt de noodzaak toe om meer te weten over hoe hiermee om te gaan. Het is van belang om te weten welke factoren meisjesdelinquentie beïnvloeden aangezien er geïntervenieerd zal moeten worden op risicofactoren voor meisjesdelinquentie om het delinquente gedrag terug te dringen. Daarom richt dit proefschrift zich in de eerste plaats op het vaststellen van welke factoren gerelateerd zijn aan meisjesdelinquentie. Hierbij wordt ook nagegaan of deze factoren gelijk zijn aan de factoren die zijn gerelateerd aan jongensdelinquentie. Een ander doel van dit proefschrift is verklaringen zoeken voor het structurele sekseverschil in de prevalentie van delinquentie, een verschil waarover nog weinig bekend is. Om eerst een compleet beeld te krijgen van de omvang, aard en trends van crimineel gedrag van meisjes en jongens, zijn zowel zelfrapportages als politieregistraties bekeken. Minder meisjes dan jongens blijken delicten te plegen, ongeacht de bron van gegevens en ongeacht het type delict. Desalniettemin blijken de sekseverschillen het grootst binnen de geregistreerde criminaliteit, wat deels lijkt te duiden op een verschil in behandeling door politie en justitie tussen meisjes en jongens en deels op selectieve zelfrapportage. Volgens beide bronnen piekt meisjescriminaliteit op 15-jarige leeftijd. Jongensdelinquentie piekt echter op 16-jarige leeftijd volgens zelfrapportages en op 19-jarige leeftijd volgens politiecijfers. Op grond van bestudering van zelfrapportage- en politiegegevens kan geconcludeerd worden dat meisjescriminaliteit de afgelopen jaren relatief harder is gestegen dan jongenscriminaliteit. Wat betreft het eerste doel van dit proefschrift, blijken meisjes en jongens veel gemeenschappelijke risicofactoren voor delinquentie te hebben. Vooral op het gebied van persoonlijkheid, bepaalde opvoedingskenmerken (meer specifiek: monitoring, harde disciplinering, het aantal regels thuis, de mate waarin ouders informeren naar hun kinderen en de mate waarin ouders zich bemoeien met school) en leeftijdsgenoten. Hiernaast zijn er een aantal unieke factoren voor meisjes- en jongensdelinquentie. In het individuele domein blijken vooral geboortecomplicaties uniek gerelateerd aan delinquentie van jongens, en mentale gezondheidsproblemen aan dat van meisjes. In het gezinsdomein zijn er vooral unieke factoren met betrekking tot moeder. Verschillende unieke moederfactoren zijn gevonden voor jongens en voor meisjes, terwijl factoren met betrekking tot vader niet seksespecifiek zijn. Hiernaast is het bijzonder dat factoren die uniek zijn voor meisjesdelinquentie vaak te maken hebben met de ernst van risico’s, zoals het aantal negatieve levensgebeurtenissen, de mate van delinquentie van vrienden en dat van de beste vriend. 175 Voor het tweede doel van dit proefschrift, zijn drie mogelijke verklaringen voor het sekseverschil in delinquentie onderzocht: de exposure hypothese, de vulnerability hypothese en de threshold hypothese. De exposure hypothese beweert dat meisjes minder worden blootgesteld (exposed) aan risicofactoren en meer aan beschermende factoren. Hierdoor lopen zij minder risico om delinquent te zijn. Deze hypothese is grotendeels bevestigd in dit proefschrift. In vergelijking met jongens, zijn meisjes meer open over zichzelf naar hun moeder (disclosure) en vergaren moeders meer informatie over hun dochter (solicitation). Beide factoren hebben een beschermend effect op delinquentie. Aan de andere kant worden jongens juist meer blootgesteld aan delinquente vrienden, een risicofactor voor delinquentie. Het verschil in blootstelling aan deze drie risicofactoren tussen jongens en meisjes blijkt gerelateerd aan het sekseverschil in delinquentie. De vulnerability-hypothese is niet bevestigd in dit proefschrift. Volgens deze hypothese zijn meisjes meer sensitief (vulnerable) voor beschermende factoren dan jongens en minder sensitief voor risicofactoren. In dit proefschrift worden wel sekseverschillen gevonden in sensitiviteit voor verschillende factoren, maar niet altijd in de richting die deze hypothese zou ondersteunen. Zo blijkt steun van moeder, naar verwachting, een sterker beschermend effect te hebben op meisjes dan op jongens, maar blijkt controle door moeder een beschermend effect te hebben op jongens en juist een risico-effect op meisjes. Daarnaast blijkt de mate van delinquentie van de beste vriend een risico voor delinquentie van meisjes, maar niet voor dat van jongens. Ook blijkt dat meisjes in algemene zin meer risicofactoren hebben dan jongens, wat men ook niet zou verwachten op basis van de hypothese. Meisjes hebben echter ook meer beschermende factoren dan jongens. Verschillen in blootstelling en sensitiviteit blijken soms ook gelijktijdig plaats te kunnen vinden, en wel als het gaat om opvoedingsfactoren van moeder. Het samengaan van de verschillen in blootstelling en kwetsbaarheid zijn echter niet gerelateerd aan het sekseverschil in delinquentie. De threshold-hypothese, die ervan uit gaat dat meisjes een hoger aantal risico’s hebben dan jongens voordat zij delinquent worden, is ook niet bevestigd. Delinquente meisjes blijken geen hoger risiconiveau te hebben dan delinquente jongens. Ook het onderzoek naar de locatie van de threshold levert geen bewijs dat de threshold hoger ligt voor jongens dan voor meisjes, voor zowel delinquentie tijdens de late kindertijd (10 tot 12 jaar) als tijdens de adolescentie (13 tot 16 jaar). Wel blijkt de relatie tussen het aantal risico’s en de kans op delinquentie kwadratisch te zijn voor meisjes, in tegenstelling tot de lineaire relatie bij jongens. Dit wijst erop dat de kans op delinquent gedrag relatief steeds groter wordt bij meisjes, naarmate de risico’s toenemen. In het kort heeft dit proefschrift laten zien dat de relatie met moeder en het aantal delinquente vrienden belangrijke ingrediënten zijn voor het 176 sekseverschil in de prevalentie van delinquentie. Hiernaast zijn bepaalde moederfactoren en mentale gezondheidsproblemen unieke risicofactoren voor meisjes. Verschillen in sensitiviteit aan factoren kunnen geen verklaring bieden voor het sekseverschil in delinquentie. Bovendien blijken meisjes en jongens een gelijke threshold voor delinquentie te hebben. 177 178 DANKWOORD (acknowledgement) Na vele uren lezen en schrijven, plannen en bijstellen, denken en staren, en analyseren en structureren, is mijn proefschrift dan eindelijk af! Hoewel promoveren grotendeels solistisch werk is, heb ik in die vier jaar erg fijne mensen om mee heen gehad. Een aantal van hen wil ik in het bijzonder bedanken. Allereerst, mijn promotoren. Catrien, ik heb erg veel geleerd van jouw kijk op paper schrijven. Daarnaast heb ik grote bewondering voor het tempo waarin jij denkt en handelt (zie bijvoorbeeld jouw reactiesnelheid op mailtjes). Ik vond het altijd ongelooflijk dat wanneer ik het gevoel had vast te zitten, jij altijd met veel gemak een oplossing wist aan te dragen en me weer vertrouwen wist te geven. Bedankt voor je goede begeleiding, je positieve instelling, je bevlogenheid en scherpe pen. Anne-Marie, veel dank voor de prettige samenwerking. Zowel bij dit proefschrift als het WODC-rapport. Je wist me altijd enorm te motiveren, maar ook vragen bij me op te roepen waar ik nog niet aan had gedacht of waar ik (stiekem) niet aan wilde denken. Dank ook dat je me altijd betrok bij alles wat voorbijkwam rondom het thema criminele meisjes. En bovenal bedankt voor je betrokkenheid, gedrevenheid, toegankelijkheid en enthousiasme! Hans, het was erg waardevol om ook door iemand begeleid te worden die van ‘buitenaf’ kritisch naar mijn stukken keek. Dank hiervoor. Ik heb mogen werken op een prettige afdeling met zeer diverse mensen. Ik vond het dan ook erg fijn dat er altijd wel een expert te vinden was op welk criminologisch gebied dan ook. Hiernaast heb ik ook een hele leuke tijd gehad op de VU. Vooral de congresbezoekjes waren – naast het feit dat ze natúúrlijk erg nuttig waren – heel plezierig. Ik wil hiervoor mijn collega’s van Criminologie erg bedanken. Ik hoop dat ik nog vaak bij jullie mag komen borrelen. De afdeling was echter niet compleet zonder de mensen van Strafrecht, waar ik ook altijd leuk contact mee had. Mijn tijd op de VU was nog leuker doordat ik mocht zingen bij de Faculty All Stars. Geweldig om soms even mijn proefschrift te laten voor wat het was, om koortjes te oefenen in de kerkzaal of te repeteren met de hele band. You rock! De mensen van RADAR wil ik graag bedanken voor het opzetten van zo’n rijk onderzoek. Het was erg interessant om te mogen werken met zo’n veelzijdige dataset. Dank aan Endy voor de coördinatie van de dataverzameling; aan Pieter Bas voor het structureren en verspreiden van de data; en aan Wim, Pol en Tom voor jullie waardevolle commentaar op de studies die ik met de RADAR-data uitgevoerd heb. Hiernaast veel dank aan coauteurs van mijn proefschriftartikelen die ik nog niet genoemd heb. Margaret, I would like to thank you for the inspiring meetings we had. Your positive attitude is admirable and contagious. Rolf, hartelijk dank dat ik mocht werken met de mooie datasets uit Pittsburgh. Het 179 was niet alleen zeer uitdagend en interessant om hiermee aan de slag te gaan, maar ook erg leerzaam om mijn ideeën over de threshold met jou te kunnen delen. Dank voor je kritische blik. Daarnaast vind ik het ontzettend sympathiek hoe jij en Magda mij hebben ontvangen in Pittsburgh. Dan natuurlijk mijn paranimfen. Barbora, promoveren zonder jou was onmogelijk geweest. In elk geval zo veel minder leuk! Dat we al in het eerste jaar hadden besloten elkaars paranimfen te worden, zegt genoeg. Veel tegengestelde eigenschappen (en smaken!), maar toch zo’n goede match. In het Engels, but also in Dutch. Sharing frustrations, but also many delights. We were experts on anticipating on each other’s moods, but we especially had many many laughs. Thanks for being my roomy! Rens, dank dat ik je altijd kon bellen met mijn statistische vragen en frustraties. Fijn om soms ook met iemand van buiten de VU te kunnen sparren. Maar het was vooral leuk om samen onderzoek te doen en te publiceren. Goed, dan een ander onderdeel van dit boek. Floor, ontzettend bedankt dat je zulke mooie foto’s en zo’n sprekende omslag voor me hebt gemaakt! Je leek gelijk te snappen wat ik wilde, terwijl ik dat eigenlijk zelf nog niet eens zo goed wist. En Lotte, veel dank dat je het aandurfde om te schitteren op de voorkant van een proefschrift over criminele meisjes. Ik ben er van overtuigd dat dit jouw onderzoekscarrière alleen maar ten goede zal komen! Lieve vriendinnen, dankzij jullie had ik, naast promoveren, vooral gewoon een leven! Tegelijk kon ik wel altijd bij jullie proefschrift-spuien als dit nodig was. Humor en uitlaatklep. Lieve pap, mam, en ook Ilbert. Veel dank voor jullie onvoorwaardelijke vertrouwen in mij en jullie steun. Heerlijk om het gevoel te hebben dat jullie altijd achter me staan. Ook Peter, Bea en Ruben, bedankt voor jullie immer aanwezige betrokkenheid en interesse. Maar vooral veel dank aan Daan. Met jou erbij is alles zoveel makkelijker én leuker! Zo ook het schrijven van mijn proefschrift. Fijn dat jij goed aanvoelt wanneer je me met beide benen op de grond moet zetten of juist even moet laten ‘fladderen’. Dank je wel. 180 CURRICULUM VITAE Thessa Wong (16-01-1984) attended the Utrecht University from 2002 to 2007 where she earned a bachelor’s degree in pedagogics and graduated cum laude for the research master ‘Development and Socialization in Childhood and Adolescence’. In June 2007 she started a PhD-project at the Department of Criminal Law and Criminology at the VU University Amsterdam. During her PhD she also coordinated and co-authored a research project on behalf of the Research and Documentation Centre of the Ministry of Security and Justice, titled ‘Delinquent girls: Background characteristics, risk factors and interventions (orginal title: ‘Delinquente meisjes: Achtergronden, risicofactoren en interventies’). In November 2011 she started working in the police force Amsterdam-Amstelland as a criminal investigator in training. 181