1 Toward a more psychometrically sound brief measure of schizotypal traits:... Brief Revised

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Toward a more psychometrically sound brief measure of schizotypal traits: Introducing the SPQBrief Revised
Running head: The SPQ-Brief Revised
Address correspondence to:
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Abstract
Psychometric case identification of individuals at risk for developing schizophrenia-spectrum
disorders is an important enterprise. Unfortunately, current instruments for this purpose are
limited. The present studies sought to improve the Schizotypal Personality Questionnaire-Brief
(SPQ-Brief), a measure of schizotypal traits that has come under recent criticism. In the first
study, we conducted exploratory factor analysis on the SPQ-Brief using a Likert-style scoring
format in a large sample of nonclinical adults. Although acceptable internal consistency was
found, the original factor structure was not supported. In the second study, we administered the
full version of the SPQ to a separate large nonclinical adult sample and employed exploratory and
confirmatory factor analysis to identify critical items that could be used to revise the SPQ-Brief.
The end product of these studies is the SPQ-Brief Revised, which offers a subordinate sevenfactor and super-ordinate three or four factor solution, employs a Likert-scale format to improve
sensitivity, and is brief (34 items).
Keywords: schizotypy, brief, schizophrenia, psychometric, positive, negative, disorganized,
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INTRODUCTION
Psychometric detection of individuals at risk for developing schizophrenia-spectrum
disorders is a critical enterprise for understanding the schizophrenia prodrome and for clarifying
potentiators that influence illness trajectory. A number of measures have been advanced for this
purpose based on self-report assessment of subclinical schizophrenia symptomatology. This
“psychometric-identification” method is advantageous over other risk-identification procedures
(e.g., Genetic identification; Addington, 2004; Tsuang, Stone, Tarbox, & Faraone, 2002) in that it
can be applied to large samples in a cost-effective manner. There is considerable variability
across measures in length (e.g., Chapman Schizotypy Scales, N of items = 166; Chapman,
Chapman, & Kwapil, 1995; Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE), N
of items = 159, Mason, Claridge, & Jackson, 1995; Schizotypal Personality Questionnaire (SPQ),
N of items = 74 items, Raine, 1991) and trait coverage (e.g., Chapman Schizotypy scales cover
four domains, O-life covers four-five domains, SPQ covers nine domains). A researcher must
balance brevity with breadth when selecting a screening measure. An abbreviated version of a
popular instrument, the Schizotypal Personality Questionnaire (SPQ-Brief), was developed that
covers three important schizotypal trait domains (Raine & Benishay, 1995). Although a solid
literature employing this instrument has been established (e.g., Bedwell, Kamath & Baksh, 2006;
Jahshan & Sergi, 2007; Koo, Dickey, Park, Kubicki, Ji, Bouix, et al., 2006), its psychometric
adequacy has come into question (Axelrod, Grilo, Sanislow, & McGlashan, 2001; Aycicegi, Dinn,
& Harris, 2005; Compton, Chien, & Bollini, 2007; Mata, Mataix-Cols, & Peralta, 2005). The
present project reports data from two studies of the SPQ. In the first study, we examine the
psychometric properties of the SPQ-Brief in a large sample of nonclinical young adults using a
more sensitive response (i.e., Likert) format. In the second study, we develop an improved
version of this brief measure, the SPQ-Brief Revised (SPQ-BR) based on full SPQ data
administered to a separate sample of nonclinical adults.
The SPQ (Raine, 1991) is an important instrument for schizotypy research. The full
version is comprised of 74 true-false items and covers nine distinct domains which closely mirror
the diagnostic criteria for Schizotypal Personality Disorder included in the Diagnostic and
Statistical Manual of Mental Disorders (DSM-IV; American Psychiatric Association, 1994). The full
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SPQ captures a broader range of schizotypal traits than other instruments and has shown
adequate reliability and convergent validity (Raine, 1991; Reynolds, Raine, Mellingen, Venables,
& Mednick, 2000). Factor analysis of the full SPQ supports the breadth of coverage, although
there is disagreement over whether a three-factor structure (covering “Cognitive-Perceptual”,
“Disorganized” and “Interpersonal” factors; Reynolds et al., 2000; Wuthrich & Bates, 2006), a four
factor model (covering “Cognitive-Perceptual,” “Paranoid,” “Disorganized,” and “Interpersonal”
factors, Compton, Goulding, Bakeman, & McClure-Tone, in press) or even larger factor structures
(e.g., covering “social anhedonia”, “social anxiety”, “eccentric/odd behavior”, “mistrust” and
“unusual beliefs and experiences”; Chmielewski & Watson, 2008) are most appropriate. The
factor structure seems to depend, in large part, on whether the analysis is conducted at the
subscale level or the item level (Chmielewski & Watson, 2008). However, as noted by Raine &
Benishay (1995), the length of the SPQ has made it less than ideal for some screening situations.
The SPQ-Brief (Raine & Benishay, 1995), developed as a more concise measure of
schizotypy, comprises 22 true-false items from the full SPQ covering three domains--“CognitivePerceptual”, “Disorganized” and “Interpersonal.” The selection strategy for this measure was
based on identifying full SPQ items that were most highly correlated with their respective factors.
This approach is consistent with one of the most common methodologies for item selection in
scale reduction - selecting items that maximize internal consistency (i.e., selecting items with high
inter-item correlations (Clark & Watson, 1995; Stanton, Sinar, Balzer, & Smith, 2002)). However,
as discussed by these and other authors (Boyle, 1991; Kline, 1986) using an internal consistency
maximizing approach can have some drawbacks. First, this approach can lead to item
redundancy (Stanton et al., 2002). After all, the most internally consistent measure would likely
occur when items are simply paraphrases of each other. Second, this approach can lead to
factor structure limitations, such that, for example, only positively worded items are retained in the
abbreviated measure (Miller & Cleary, 1993). Finally, focusing on maximizing internal consistency
can lead to reduced validity (Kline, 1986). Reductions in validity can occur because when
trimming items to increase internal consistency, the researcher may inadvertently trim items that
serve to represent an increased portion of the theoretical construct space (Smith & Stanton,
1998). Thus, the scale may have less construct validity.
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Although the SPQ-Brief has been employed in a number of recent studies (e.g., Bedwell,
Kamath & Baksh, 2006; Jahshan & Sergi, 2007; Koo, Dickey, Park, Kubicki, Ji, Bouix, et al.,
2006), enthusiasm for this instrument is tempered for several reasons. First, multiple studies have
reported a high level of intercorrelation between items from different subscales (Axelrod et al.,
2001; Aycicegi et al., 2005; Compton et al., 2007; Mata et al., 2005), and less than ideal internal
consistency (<.70) for the Cognitive-Perceptual and Disorganized subscales in three studies
(Aycicegi et al., 2005; Compton et al., 2007; Mata et al., 2005). Second, factor analyses of the
SPQ-Brief have provided only limited support for a three-factor solution. For example, Compton et
al. (2007) reported that a three-factor solution offered little improvement over a single-factor
model while Aycicegi et al. (2005) found that a two-factor solution best fit the data. Similarly,
considerable item cross loading between the Interpersonal and Cognitive-Perceptual factors has
been reported (Axelrod et al., 2001; Mata et al., 2005). Third, the brief SPQ offers limited
coverage compared to the full SPQ because it covers only Cognitive-Perceptual, Disorganization
and Interpersonal domains, and not individual subscales. This is important as one considers
recent evidence suggesting that the Interpersonal subscale reflects two distinct constructs –
social anxiety and social anhedonia. These domains appear to reflect very different underlying
pathological processes in individuals with schizophrenia and schizotypy (Brown, Silvia, MyinGermeys, Lewandowski, & Kwapil, 2008; Chmielewski & Watson, 2008; Kirkpatrick, Buchanan,
Ross, & Carpenter, 2001; Lewandowski et al., 2006).
A final consideration with the full SPQ involves the scoring format which employs a
forced-choice true-false decision. Forcing participants to make an “all or none” evaluation
prevents participants from taking into account degrees of trait severity, which is an issue because
it means the SPQ may be insensitive to subtle trait manifestations (Peltier & Walsh, 1990;
Wuthrich & Bates, 2005). Moreover, some have suggested that individuals may be reluctant to
endorse seemingly severe symptoms of mental illness (Peltier & Walsh, 1990). To address these
concerns, Wuthrich and Bates (2005) adapted the response format to include a five-point Likert
scale and found improved reliability/sensitivity for the Likert format over the traditional format.
This format has not been applied to the SPQ-Brief to our knowledge, but is particularly promising
for offering expanded scoring range and improved sensitivity for its limited number of items.
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The present study employed exploratory and confirmatory factor analytic procedures to
examine and create the SPQ-BR. In the first study, the psychometric properties of a Likert-type
SPQ-Brief were examined in a large nonclinical adult sample. Given that the psychometrics from
this first study were less than ideal, we sought to develop a more valid and conceptually
consistent version of the SPQ-Brief by identifying critical items from the full SPQ, using a Likerttype response format administered to a separate large nonclinical adult sample. A primary
difference between this study and the original SPQ-Brief development study is that our
procedures are based on factor analytic procedures that control for inter-item correlation. Finally,
we examined the convergence between SPQ-BR scores and quality of life with the expectation
that increasing trait severity would be associated with poorer quality of life (as seen in Cohen &
Davis, in press). In sum, we aimed to develop a revised SPQ-Brief that would (1) employ a more
sensitive response format than the original SPQ-brief while providing adequate internal
consistency, (2) offer expanded trait coverage beyond the three broad Interpersonal, CognitivePerceptual and Disorganization factor domains while minimizing factor cross-loading, (3) yield a
higher order four-factor solution, characterized by Social Anxiety, Social Anhedonia,
Disorganization, and Cognitive-Perceptual dimensions, and (4) convergent validity with a
measure of subjective and objective quality of life.
STUDY 1 METHODS: PSYCHOMETRICS OF THE BRIEF SPQ
Participants. Participants were undergraduate students enrolled at Louisiana State
University. Freshmen and sophomore students (N = 8,591) were approached by email to
participate in an on-line survey, and offered a chance to win monetary compensation as part of a
lottery (10 prizes of $25us). Embedded within this survey were a consent form, basic
demographic questions, Infrequency Scale items (Chapman & Chapman, 1983) and a modified
SPQ. The response rate was approximately 17% (n = 1507). Of these responses, 9% (n = 138) of
the questionnaires was discarded because of incomplete responses (n = 128) or questionable
validity (n = 10, as detailed below). The final dataset included 1,356 participants. Demographic
and descriptive variables are included in Table 1. This study was approved by the LSU Human
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Subject Review Board and all participants offered informed consent prior to completing the
surveys.
[Insert Table 1 about here]
Schizotypal Traits. Schizoptyal traits were assessed using the SPQ-Brief (Raine & Benishay,
1995), a 22-item measure. We adopted a five-point Likert scale system that has been employed
in recent research using the full SPQ (Wuthrich & Bates, 2005). Participants’ response options
ranged from “strongly disagree” to “neutral” to “strongly agree”. The Likert scale version of the full
SPQ has shown high convergence and improved internal reliability (α = .95) when administered in
either computer or standard paper and pencil versions, compared to the original version. For
each of the SPQ measures included in this study, increasing scores reflect more severe traits.
Infrequency Scale. To screen out responders who provided random or grossly invalid responses,
we included three questions from the Infrequency Scale (Chapman & Chapman, 1983). This
abbreviated version, used in our prior research (e.g., Cohen & Davis, in press), was employed to
reduce the overall burden of test administration. This includes items such as ‘I find that I often
walk with a limp, which is the result of a skydiving accident. Individuals who endorsed two or
more infrequency items were excluded from this study (66% of total items), a more stringent
threshold than the traditional three of 13 items used in prior research (e.g., Gooding, Tallent &
Matts, 2005).”
Analyses. Analyses were conducted in three steps. First, we examined descriptive statistics and
ranges of SPQ scores. Second, we examined the internal consistency in SPQ factors scores
using the factor structure reported in Raine and Benishay (Raine & Benishay, 1995). Third,
principal components factoring analysis with varimax rotation was conducted to examine the
structure of the SPQ-Brief using the 22 items from the original measure, with Likert-type response
options. It is important to note that prior studies have reported differences between males and
females in SPQ scores (Raine, 1992).
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STUDY 1 RESULTS
Descriptive statistics and ranges for the SPQ are provided in Table 1. There was a
notable range of responses suggesting that participants, by and large, made use of the full
spectrum of options. Interestingly, only a minority (approximately 5%) of responses reflected
strong endorsement of schizotypal traits (i.e., “strongly agree”). However, a large number of
responses (approximately 20%) reflected more modest endorsement (i.e., “agree). Internal
consistency was good for each of the subscales (i.e., Chronbach’s α for the Cognitive-Perceptual
factor = .79, for the Interpersonal factor = .86, and for the Disorganization factor = .83), although
internal consistency was highest for the total score (Chronbach’s α = .90). Females reported
significantly less severe traits within each of the factors (all t’s[1354] > 3.41, p’s < .001), although
the effect sizes for each of these differences were generally small (< .32; using Cohen’s 1988
criteria). Scores from the individual subscales were each significantly positively correlated with
each other (range of r[1354] values = .21 - .64).
[Insert Table 1 about here]
Given both three and four factor models have been argued in the literature, using
Kaiser’s criterion, all factors with eigenvalue over one were retained; in our initial examination we
did not constrain our exploratory factor analysis in terms of factors retained. A four-factor solution
was extracted with a cumulative variance of 56.21% explained. However, review of the scree plot
did not suggest that a scree started at the fourth or fifth factor raising questions about the stability
of the four-factor solution. Factor loadings and explained variances for each factor in the fourfactor solution are reported in Table 2. Currently there does not exist a commonly agreed upon
standard for interpreting factor loadings. As noted by Stevens (2002), in samples over 1000 factor
loadings greater than .16 are statistically meaningful. Furthermore, Comrey and Lee (1992) note
that although factor loadings at or above .32 are “poor” in terms of overlapping variance with the
factor, they are still potentially meaningful depending on the research question. For the purpose
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of this study, factor loadings greater than .40 are considered strong, and we consider items with
loadings of .30 or more on two or more factors as cross-loading items.
In sum, only limited support for Raine and Benishay’s (1995) SPQ-brief measure or for
Axelrod et al.’s (2001) empirically derived version of the SPQ-Brief measure was found. Of note,
the Interpersonal dimension appears to split into two sub-factors. Additionally, eight of the 22
items (36%) demonstrate cross-loadings, which calls into question whether these items tap into
unique underlying constructs, or some other higher order construct.
As a follow-up analysis, given that Axelrod et al. (2001) in their analysis forced a three
factor solution, we re-ran our exploratory factor analysis, constraining the model to three factors.
In this model, the cumulative variance explained was 51.36%. Again though, review of the scree
plot did not support this model, and interpretation of the factor loadings was even more
complicated, with 12 of the 22 items (54%) demonstrating cross-loadings (the full results of these
analysis, including factor loadings, can be obtained from the first author).
[Insert Table 2 about here]
STUDY 1 DISCUSSION
In contrast to prior studies (Aycicegi et al., 2005; Compton et al., 2007; Mata et al., 2005),
adequate internal consistency of the traditional three-factor solution was found. However, the
factor structure identified by Raine and Benishay (1995) or Axelrod et al. (2001) was not
maintained. Rather, a four-factor solution marked by two separate Interpersonal factors was
observed. It is interesting to interpret this factor structure in light of recent evidence (from the full
SPQ) that the Interpersonal factor defined in Raine and Benishay (1995) actually reflects distinct
social anxiety and social anhedonia (e.g., Constricted Affect, No Close Friends) constructs.
Evidence from studies employing instruments other than the SPQ provide further evidence that
social anhedonia and social anxiety are separable constructs (Brown et al., 2008; Chmielewski &
Watson, 2008; Lewandowski et al., 2006). However, the Interpersonal factors identified in this first
study were not neatly comprised of Social Anxiety versus Constricted Affect/No Close Friends
factors, as there was considerable cross-contamination from suspiciousness, ideas of reference,
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and odd speech items. Thus, it seems the original SPQ-Brief Interpersonal factor reflects a
heterogeneous mix of traits. Although this lack of replication could reflect our use of a modified
response format, the fact that the factor structure has not been found in most prior studies argues
against this concern.
Regarding the expanded format, there were several interesting findings. Although
approximately a quarter of items were endorsed at the “agree” level or above, only a small subset
of these were in the “strongly agree” range. This supports the notion that the dichotomous
response format offers insufficient sensitivity, whereas the expanded Likert format offers greater
ability to discriminate. In the next study, we employed factor analysis procedures from the full
SPQ, modified using the Likert-like response format, to derive the SPQ-BR.
STUDY 2 METHODS
Participants. Participants were undergraduate students enrolled at Louisiana State University.
Freshmen and sophomore students (N = 8,993) were approached via email to participate in an
on-line survey, and offered a chance to win monetary compensation (10 prizes of $25us) as part
of a lottery. Embedded within this survey were a consent form, basic demographic questions,
Infrequency Scale Items (Chapman & Chapman, 1983), and the full SPQ. The response rate was
approximately 20% (n = 1,775). Of these responses, 21% (n = 380) of the questionnaires was
discarded due to elevated infrequency scores (n = 5, using the 2-item criterion detailed above) or
incomplete responses (n = 375). It is noteworthy that there were over twice as many invalid
questionnaires in this study employing the full SPQ version compared to the first study which
used the SPQ-Brief, used in the first study. This underscores the importance of a
psychometrically sound brief schizotypy measure to diminish effects of participant fatigue or
boredom. The final dataset included 1,395 participants. Demographic and descriptive variables
are included in Table 1. This study was approved by the LSU Human Subject Review Board and
all participants provided informed consent prior to completing the surveys.
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Schizotypal Traits. The full SPQ (Raine, 1991) was used, which includes 74 statements
measuring Ideas of Reference, Excessive Social Anxiety, Odd Beliefs or Magical Thinking,
Unusual Perceptual Experiences, Odd Or Eccentric Behavior, No Close Friends, Odd Speech,
Constricted Affect, and Suspiciousness. We adopted the same five-point Likert scale system
used in the first study, ranging from “strongly disagree” to “neutral” to “strongly agree” (Wuthrich &
Bates, 2005).
Quality of life. A modified version of Lehman’s Quality of Life Brief Interview (Lehman, 1995),
covering the prior month, was employed here. Presented in this study is a summary score
reflecting 23 objective quality of life items covering seven domains (home, daily activities, family,
social, financial, health and legal concerns). These items cover objectively anchored
assessments of behavior (e.g., “How often do you make plans ahead of time to do something with
a friend?”) and access to resources (e.g., “In the past month, did you have enough money for fun
activities?”). A separate summary score reflecting nine items assessing subjective satisfaction
across these seven domains (using a standardized 7 point Likert scale) is also derived from the
measure. Although these measures are typically used in patient studies (e.g., Bellack, Bennett,
Gearon, Brown, & Yang, 2006), prior lab research supports convergence with the SPQ-Brief in
university samples (Cohen et al., In press). Increasing scores reflect higher functioning.
Analyses.
A multi-step approach was taken to create the SPQ-BR. First, the sample was randomly
split into three equal sub-samples. These sub-samples were mutually exclusive and exhaustive,
and each sub-sample was used for one of the three analysis steps. In Step 1, a principal
components factoring analysis with varimax rotation was conducted to examine the structure of
the SPQ using the full 74 items from the original measure, with Likert-type response options.
Based on the results of these analyses, poorly functioning items [(a) low factor loadings (loadings
less than .40), (b) split factor loadings (loadings greater than .35 on two or more factors), (c)
factors consisting of only one item, or (d) poor conceptual fit with other items loading on the
factor] were excluded. In relation to this fourth criterion Likert-type response options , if, for
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example, for a particular factor four items demonstrated a clear conceptual relationship (e.g., all
were related to magical thinking) and a fifth, unrelated item (e.g., an item about constricted affect)
also loaded on that factor, the unrelated item was removed
.
In Step 2, the factor structure for the resulting subset of items was cross-validated with
the second sub-sample using a principal components factoring analysis with varimax rotation. In
Step 3, confirmatory factor analysis was used to further cross-validate the SPQ-BR using the third
sub-sample of respondents. As part of Step 3 we sought to confirm four models including (1) a
uni-dimensional solution, (2) an uncorrelated factor structure, (3) Raine and Benishay’s (1995)
conceptual three-factor model, and (4) a four-factor solution similar to Raine and Benishay’s
(1995) model but with Constricted Affect/No Close Friends and Social Anxiety as distinct factors.
In Step 4, we examined the convergent validity of the SPQ-BR by computing correlations with
QOL scores, with the expectation that they would be inversely and significantly correlated.
STUDY 2 RESULTS
Descriptive statistics and ranges for the SPQ are provided in Table 1. Internal
consistency was good for each the full SPQ subscales: Ideas of Reference (α = .82), Social
Anxiety (α = .87), Magical Thinking (α = .80), Unusual Perceptions (α = .81), Eccentric Behavior
(α = .90), No Close Friends (α = .85), Odd Speech (α = .86), Constricted Affect (α = .81) and
Suspiciousness (α = .86). The distribution of responses was almost identical to that seen in Study
1. As in the prior study, females reported significantly less severe traits for most of the subscales
(all t’s[1354] > 2.16, p’s < .05) except for Ideas of Reference, Magical Thinking and
Suspiciousness subscales, which were statistical trends (all t’s[1354] > 1.79, p’s < .07). The effect
sizes for each were small (Cohen’s d’s < .33). Scores from the individual subscales were each
significantly positively correlated with each other (range of r[1354] values = .19 - .80).
Step 1: Initial Exploratory Factor Analysis
Using the first subsample of respondents (n = 465) an initial fourteen-factor solution was
extracted using the full 74 items. The cumulative variance explained with this fourteen-factor
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model was 63.34%. Review of the scree plot suggested that a more parsimonious solution might
be found. All items were reviewed for low factor loadings (loadings less than .40), split factor
loadings (loadings greater than .35 on two or more factors), factors consisting of only one item, or
poor conceptual fit with other items loading on the factor. Based on these criteria, 42 items were
excluded (approximately 65% of these excluded items were excluded for demonstrating split
loadings).
Step 2: Exploratory Factor Analysis Cross-Validation
Using the second subsample of respondents (n = 465) a second exploratory factor
analysis was conducted on the remaining 32 items. A seven factor solution was extracted using
the 32 items retained after Step 1. The cumulative variance explained with this seven-factor
model was 61.65%. Review of the scree plot suggested a scree started at the eighth factor,
providing additional support for the seven-factor solution. Factor loadings and explained
variances for each factor in the seven-factor solution are reported in Table 3.
[Insert Table 3 about here]
In the factor analysis, five of the observed factors map directly to subscales suggested by
Raine (1991)--Eccentric Behavior, Social Anxiety, Magical Thinking, Odd Speech, And Unusual
Perceptions. Raine’s other four subscales are represented in the two remaining factors. Within
each of these two remaining factors, two subscales are collapsed--Ideas of Reference and
Suspiciousness are collapsed in the first factor, and No Close Friends and Constricted Affect are
collapsed in the second factor. Based on the results of this factor analysis, average scale scores
were computed for each factor. Means, standard deviations, internal consistency reliability
estimates, and bivariate correlations for the seven subscales are reported in Table 4. There are
several notables. First, internal consistency was adequate for each subscale. Second, each of the
subscales was modestly correlated with each other subscale. With only two exceptions, the
magnitudes of the correlations were between .29 and .53, roughly equating to a medium effect
size level. Magical Thinking showed smaller correlations with two measures: No Close
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Friends/Constricted Affect and Social Anxiety, suggesting that these dimensions may be relatively
independent. Finally, it is worth noting that No Close Friends/Constricted Affect and Social
Anxiety measures showed only modest correlation with each other, suggesting they are by no
means redundant with each other.
[Insert Table 4 about here]
Step 3: Confirmatory Factor Analysis (CFA) of the SPQ-BR
To confirm the factor structure of the SPQ-BR, the third subsample of respondents (n =
465) was analyzed using the structural equation modeling software package AMOS 7 (Arbuckle,
2006). Item level listwise deletion resulted in a working sample of 441 participants. We
conducted our analyses across four nested models. In Model 1 we sought to examine whether
our 32 items loaded on one uni-dimensional latent factor (we expected this model to have poor
fit). In Model 2 we tested a model of 7 under-related latent factors, with each latent factor
representing one of the factors extracted in our exploratory factor analysis (we expected this
model to have poor fit). For each latent factor, the items for each of the subscales were included
as indicators for that latent factor. In Model 3, based on work by Raine and Benishay (1995) we
predicted that three higher order constructs would exist--Interpersonal, Cognitive-Perceptual, and
Disorganized. We predicted that the Interpersonal second order construct would be a function of
two subscales: No Close Friends/Constricted Affect and Social Anxiety. We predicted that the
Cognitive-Perceptual second order construct would be a function of three subscale: Ideas of
Reference/Suspiciousness, Magical Thinking, and Unusual Perceptions. We predicted that the
Disorganized second order construct would be a function of two subscales: Eccentric Behavior
and Odd Speech. We predicted that Model 3 would demonstrate acceptable fit. In Model 4 we
sought to examine the possibility that the SPQ is better conceptualized as having 4 factors. As
such, in Model 4, we predicted a similar factor structure to Model 3 but with the No Close
Friends/Constricted Affect and Social Anxiety factors reflecting distinct factors (Brown et al.,
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2008; Chmielewski & Watson, 2008; Lewandowski et al., 2006). We predicted that Model 4 would
demonstrate acceptable fit.
For each model four measures of model fit were calculated: χ2, comparative fit index
(CFI), root mean square error of approximation (RMSEA), and standard root mean residual
(SRMR). A non-significant χ2 indicates good model fit; however, χ2 is sensitive to sample size.
The CFI and RMSEA are less sensitive to sampling characteristics and take degrees of freedom
into account. A CFI value of .90 or higher (Medsker, Williams, & Holahan, 1994), a RMSEA value
of .06 or lower, and an SRMR value of .08 or lower are also indicative of good model fit (Hu &
Bentler, 1999). Results for the four models are reported in Table 5. Also reported in Table 5 are
χ2-differences tests to test for significant improvement in model fit based on the successive
models tested. The 3-factor and 4-factor models were both found to be invariant across gender in
terms of structural weights and covariances
[Insert Table 5 about here]
As expected, neither the Model 1 or Model 2 demonstrated acceptable fit. Model 3 and
Model 4 both demonstrated acceptable fit. However, based on the χ2-differences tests, neither
model significantly explained the data better compared to the other model; both the three-factor
and four-factor model adequately explain the data. Results for the three-factor model are reported
in Figure 1 and the results for the four-factor model are reported in Figure 2.
[Insert Figure 1 about here]
[Insert Figure 2 about here]
Convergent Validity. The correlations between the SPQ-BR and the QOL scores are presented in
Table 6. Each of these correlations was statistically significant such that increasing schizotypal
traits were associated with poorer quality of life.
[Insert Table 6 about here]
DISCUSSION
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In study 2, the SPQ-BR was constructed, using a Likert-style response format, and
featuring seven trait subscales. Although these subscales are by no means redundant with each
other, confirmatory factor analysis suggests that they have a three or four factor higher-order
structure that is generally consistent with prior research (see below for elaboration). The
psychometric properties of this instrument are promising. Moreover, the brevity of the SPQ-Brief
was maintained, such that the final questionnaire comprised only 32 items. Finally, convergent
validity was demonstrated in that increase severity of schizotypal traits, measuring by the SPQBR, was associated with notable declinations in quality of life.
GENERAL DISCUSSION
The chief advance of the present studies is the realization of a psychometrically sound
brief measure of schizotypal traits. The practical benefits of using a brief over the full instrument
were demonstrated in the dramatically increased incomplete response rate for the longer SPQ (>
20%) compared to the briefer measure (< 10%). The SPQ-BR is an improvement over the SPQBrief in that it covers a broader set of pathological traits - seven as opposed to three domains.
Moreover, it offers a coherent factor structure manifesting in a three or four-part (see below)
super-ordinate factor structure. These factor structures have not been supported in studies of the
original SPQ-Brief (Compton et al., 2007, Aycicegi et al., 2005). Our use of an expanded
response format greatly improves the potential range of responses. Given that the SPQ is
typically employed as a screening tool to identify extreme scorers for laboratory studies, improved
resolution of SPQ traits vis a vis expanded score ranges should improve accuracy in identifying
schizotypic individuals. Implications of these findings, with regard to assessment and theoretical
understanding of schizotypy are expounded below.
The SPQ-BR covers a broader range of schizotypal traits than any of the other commonly
used measures (save the traditional full SPQ). This is particularly important given that schizotypy
is considered a heterogeneous construct comprised of three-factors that are closely tied to the
positive, negative and disorganized symptom structure observed in schizophrenia more generally
(Liddle, Barnes, Morris, & Haque, 1989). However, recent research employing the full SPQ has
raised questions about whether schizotypy reflects more than three factors (Chmielewski &
17
Watson, 2008; Compton, Goulding, Bakeman, & McClure-Tone, in press). Our data suggest that
schizotypy is best explained by seven subordinate factors subsumed under three or four superordinate factors. This is an issue of importance as changes to the operational definition of
schizotypal personality disorder are consideredfor the fifth version of the DSM. Our data suggest
that a more refined definition of seven traits, as opposed to nine, reflecting three or four broad
clusters is worth considering..
With regard to the super-ordinate factor solution of the SPQ-BR, our data can not speak
to whether this is best represented by the original three-factor solution recommended by Raine
and Benishay (1995) or by a modified four-factor solution, because the confirmatory fit statistics
for these models were nearly identical. At odds is the relationship between social anxiety and
more traditionally-defined negative traits (i.e., Constricted Affect, No Close Friends). There are
three possibilities worth entertaining regarding their relationship. First, it could be that Social
Anxiety and Constricted Affect/No Close Friends reflect a common construct. Parsimony would
argue for this insofar as the three-factor solution is less complicated than the four-factor solutions.
Second, it could be that social anxiety and negative schizotypy reflect distinct (yet modestly
correlated) dimensions that capture different aspects of schizotypal pathology. In support of this
notion, several recent schizotypy studies employing the Chapman scales (Chapman et al., 1995)
have found that social anxiety is actually more strongly related to magical ideation and perceptual
aberrations than social anhedonia (Brown et al., 2008; Lewandowski et al., 2006). Third, as noted
by Seiver, Bernstein, and Silverman (1991), it could be the case that social anxiety reflects a
nonspecific comorbid condition that is largely independent of schizotypal processes. This would
suggest that the Constricted Affect/No Close Friends factor is a “truer” indicator of negative
schizotypy, and that a three factor schizotypy model can be maintained by excluding Social
Anxiety. In evaluating these three possibilities, we favor the third because a) social anxiety is not
specific to schizotypy and is typical of a broad swath of mental illnesses, and b) original
conceptualizations of negative schizotypy were based on social apathy where an individual
neither enjoys nor is distressed by Interpersonal interactions (i.e., experiences low levels of social
anxiety; Kraepelin, 1971). As evidence of this, the Chapman’s Social Anhedonia Scale was
deliberately constructed to reflect social apathy as opposed to social anxiety (Eckblad, Chapman,
18
Chapman, & Mishlove, 1982) The present study provides limited insight into this issue, which thus
remains for future research.
Consistent with prior research using the full SPQ (Cohen & Davis, in press), SPQ-BR
scores were associated with poorer quality of life. Nearly all of these correlations were in the
small to medium effect size range, suggesting that the effects of schizotypy are by no means
trivial. Correlations were particularly pronounced between the “interpersonal” factors and reduced
self-reported prosocial behaviors (e.g., contacting friends and significant others) as well as
satisfaction with the amount of friendship in one’s life. These findings also document the
convergent validity of the SPQ-BR.
Use of instruments that capture a broad range of schizotypal traits may help lay the
foundation for improved insight into the neurodevelopmental trajectory of schizophrenia. There is
evidence to suggest that a sizable portion of schizotypic individuals show symptom exacerbation
and eventual onset of schizophrenia-spectrum disorder. Thus it could be the case that different
schizotypic manifestations may be associated with different psychosis-spectrum disorders or at
least different illness courses. Evidence from a 10-year longitudinal study supports this claim in
that positive schizotypy was predictive of psychosis spectrum disorders more generally, while
21% of individuals with “social anhedonia” met criteria for a schizophrenia-spectrum disorder by
study’s end (Kwapil, 1998). Longitudinal studies to date provide limited information to answer
these questions because they have not included the full spectrum of schizotypal traits (i.e.,
generally neglecting disorganized schizotypy). Furthermore, trait definitions used in these studies
are often not comprehensive. For example, negative schizotypal definitions often employ the
Chapman Social Anhedonia Scale, which measures social anhedonia without regard to
constricted affect (e.g., Gooding, Tallent & Matts, 2005; Kwapil, 1998; Kwapil, Barrantes-Vida, &
Silvia 2008). A psychometric identification tool with a broader scope, such as the SPQ-BR, would
help overcome these limitations.
The factor structure was invariant to gender suggesting that the SPQ-BR is appropriate
for use with both males and females. Consistent with Raine (1992), both studies presented here
found that males showed somewhat more severe schizotypal traits across each factor dimension.
Why males score higher is unclear from our data. Males typically show emergence of symptoms
19
earlier than females so it is possible that females would show similar levels of SPQ rated
pathology if assessed at an age reflecting peak window of risk (Goldstein, 1997). Thus, males
higher scores could reflect more an age (or more precisely, a stage of neurodevelopment) rather
than a gender issue. It is also worth noting that males with diagnosable schizophrenia-spectrum
pathology tend to show more negative/deficit symptoms (Kirkpatrick et al., 2001), so it stands to
reason that their scores on the Interpersonal dimension would exceed those of females.
Regardless of the underlying reason, the present data suggest that males and females should be
considered separately when employing the SPQ-BR.
Several limitations warrant mention here. Foremost, the schizotypal participants were
college students. Although student samples are typical of this line of research, they may not
represent the entire population. Second, assessment of schizotypal traits was dependent on selfreport measures, which are problematic in that they provide information on only subjectiveperceived attitudes. Clinical ratings, while costly for a sample size this large, would be an
important adjunct for use in further research. Third, our data were cross-sectional in nature, an
approach that limits understanding how symptoms manifest over time. Finally, our analyses were
underpowered to determine the influence of ethnicity on SPQ ratings. It would be important to
determine whether our factor structure is invariant across ethnicity
The present data provide important reliability and validity data supporting the use of the
SPQ-BR as an instrument for the psychometric assessment of schizotypy. Application of this
measure may provide important information regarding schizophrenia-spectrum disorders, and
may be helpful for understanding the neurodevelopmental progression of the disorder.
20
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24
Table 1. Means and standard deviations for the demographic and descriptive statistics.
Demographic Variables
Study 1
(n = 1356)
Study 2
(n = 1395)
Age
% Female
Ethnicity
% Caucasian
% African American
% Asian-American
% Hispanic
% Other
19.32 ± 2.34
64%
19.18 ± 2.03
65%
83.9%
8.4%
2.9%
2.7%
2.0%
81.7%
8.4%
3.1%
3.2%
3.6%
-.22 ± 1.951
-.90 ± 2.171
-1.88 ± 1.671
-.85 ± 2.141
-1.77 ± 3.092
-1.22 ± 1.991
-1.99 ± 2.612
-.60 ± 1.971
-1.61 ± 3.633
-1.89 ± 6.324
-1.42 ± 6.795
-6.59 ± 5.096
-6.50 ± 6.334
-3.97 ± 6.036
-7.06 ± 6.704
-2.58 ± 6.704
-6.72 ± 5.375
-3.89 ± 6.125
24.12%
32.71%
17.48%
20.41%
5.27%
25.34%
33.77%
16.10%
20.15%
4.64%
Schizotypal Personality Trait Scores
Ideas of Reference
Social Anxiety
Magical Thinking
Unusual Perceptions
Eccentric Behavior
No Close Friends
Odd Speech
Constricted Affect
Suspiciousness
Response Frequency
Strongly Disagree
Disagree
Neutral
Agree
Strongly Agree
1
Scores range from -4 to 4, 2 Scores range from -6 to 6, 3 Scores range from -8 to 8, 4
Scores range from -18 to 18, 5 Scores range from -16 to 16, 6 Scores range from -14 to 14.
25
Table 2: Principal Component Analysis of SPQ-brief with Likert-type response options (n = 1356)
Factor
Raine &
Benishay
Factor
Axelrod et al.
Factor
I feel I have to be on my guard even with friends.
Interpersonal
Interpersonal
.78
Have you found that it is best not to let other people know too much about you?
Interpersonal
Interpersonal
.72
Do you feel that you are unable to get "close" to people?
Interpersonal
Interpersonal
.63
Do you often have to keep an eye out to stop people from taking advantage of you?
CognitivePerceptual
Interpersonal
Interpersonal
.58
Interpersonal
.52
I tend to keep my feelings to myself.
Do you often pick up hidden threats or put-downs from what people say or do?
1
2
3
4
.39
.41
.43
Interpersonal
.52
Some people find me a bit vague and elusive during a conversation.
CognitivePerceptual
Disorganized
Disorganized
.46
Some people think that I am a very bizarre person.
Disorganized
Disorganized
.82
I am an odd, unusual person.
Disorganized
Disorganized
.81
People sometimes comment on my unusual mannerisms and habits.
Disorganized
Disorganized
.72
I sometimes use words in unusual ways.
Disorganized
.60
People sometimes find me aloof and distant.
Interpersonal
CognitivePerceptual
Disorganized
I feel very uneasy talking to people I do not know well.
Interpersonal
Interpersonal
.85
I feel very uncomfortable in social situations involving unfamiliar people.
Interpersonal
Interpersonal
.83
I tend to keep in the background on social occasions.
Interpersonal
Interpersonal
.76
I find it hard to communicate clearly what I want to say to people.
Disorganized
Interpersonal
.52
CognitivePerceptual
CognitivePerceptual
CognitivePerceptual
.72
Have you ever had the sense that some person or force is around you, even though you
cannot see anyone?
CognitivePerceptual
CognitivePerceptual
CognitivePerceptual
Do you ever suddenly feel distracted by distant sounds that you are not normally aware
of?
When shopping do you get the feeling that other people are taking notice of you?
CognitivePerceptual
Cognitive-
CognitivePerceptual
Cognitive-
.57
Have you ever noticed a common event or object that seemed to be a special sign for
you?
Are you sometimes sure that other people can tell what you are thinking?
.35
.42
.39
.48
.37
.39
.61
.60
.35
.54
26
Have you had experiences with astrology, seeing the future, UFOs, ESP or a sixth
sense?
Eigen Value
Variance Explained
Perceptual
Perceptual
CognitivePerceptual
CognitivePerceptual
.40
3.21
3.16
14.57%
14.34%
3.14
2.86
14.26 13.0
%
1%
Note: The conceptual factor for each item as defined orginally by Raines & Benishay (1995) as well as by Axelrod et. al, are reported for
comparision purposes (results for Axelrod et al. (2001) are based on factor loadings reported in Tabel 2, p. 175). Factor loadings less than .35 are
not reported.
27
Table 3: Principal Component Analysis of revised SPQ-Brief Revised with Likert-type response options (n = 465)
Factor
Do you sometimes feel that people are talking about you? (IR4)
Do you sometimes feel that other people are watching you? (IR5)
When shopping do you get the feeling that other people are
taking notice of you? (IR6)
I often feel that others have it in for me. (S1)
Raine (1991)
Subscales
1
Ideas of
Reference
Ideas of
Reference
Ideas of
Reference
Suspiciousness
.78
Suspiciousness
.62
Suspiciousness
.55
2
3
4
.74
.68
.62
Do you sometimes get concerned that friends or co-workers are not
really loyal or trustworthy? (S2)
Do you often have to keep an eye out to stop people from
taking advantage of you? (S3)
Do you feel that you cannot get "close" to people. (CF1)
No Close Friends
.83
I find it hard to be emotionally close to other people (CF2)
No Close Friends
.77
Do you feel that there is no one you are really close to outside of
your immediate family, or people you can confide in or talk to about
personal problems? (CF3)
I tend to keep my feelings to myself. (CA1)
No Close Friends
.67
Constricted Affect
.66
I rarely laugh and smile. (CA2)
Constricted Affect
.57
I am not good at expressing my true feelings by the way I talk and
look. (CA3)
Other people see me as slightly eccentric (odd). (EB1)
Constricted Affect
.51
Eccentric Behavior
.81
I am an odd, unusual person. (EB2)
Eccentric Behavior
.76
I have some eccentric (odd) habits. (EB3)
Eccentric Behavior
.75
People sometimes comment on my unusual mannerisms and
habits. (EB4)
Do you often feel nervous when you are in a group of unfamiliar
people? (SA1)
I get anxious when meeting people for the first time. (SA2)
Eccentric Behavior
.70
Social Anxiety
.83
Social Anxiety
.82
5
6
7
28
I feel very uncomfortable in social situations involving
unfamiliar people. (SA3)
I sometimes avoid going to places where there will be many people
because I will get anxious. (SA4)
Do you believe in telepathy (mind-reading)? (MT1)
Do you believe in clairvoyance ( psychic forces, fortune telling)?
(MT2)
Have you had experiences with astrology, seeing the future, UFO's,
ESP, or a sixth sense? (MT3)
Have you ever felt that you are communicating with another person
telepathically (by mind-reading)? (MT4)
I sometimes jump quickly from one topic to another when speaking.
(OS1)
Do you tend to wander off the topic when having a conversation?
(OS2)
I often ramble on too much when speaking. (OS3)
I sometimes forget what I am trying to say. (OS4)
I often hear a voice speaking my thoughts aloud. (UP1)
When you look at a person or yourself in a mirror, have you ever
seen the face change right before your eyes? (UP2)
Are your thoughts sometimes so strong that you can almost hear
them? (UP3)
Do everyday things seem unusually large or small? (UP4)
Eigen Value
Variance Explained
Social Anxiety
.80
Social Anxiety
.63
Magical Thinking
.83
Magical Thinking
.82
Magical Thinking
.76
Magical Thinking
.63
Odd Speech
.77
Odd Speech
.76
Odd Speech
.70
Odd Speech
.64
Unusual
Perception
Unusual
Perception
Unusual
Perception
Unusual
Perception
.76
.63
.59
.47
3.36
3.32
2.87
2.79
2.69
2.66
2.04
10.49%
10.38%
8.96%
8.73%
8.41%
8.31%
6.34%
Note: The conceptual factor for each item as defined originally by Raine (1991) are reported for comparison purposes. Bolded items were included
in the original SPQ-Brief measure. Factor loadings less than .35 are not reported. Codes reported in parenthesis correspond with indicators
reported in Figures 3 and 4.
29
Table 4: Means, Standard Deviations, Internal Consistency Reliability Estimates, and Bivariate Correlations for the SPQ-Brief
Revised (n = 465)
1
.84
#
items
6
.78
.81
6
.46**
-.31
.96
.86
4
.47**
.34**
4. Social Anxiety
-.21
.97
.84
4
.43**
.47**
.37**
5. Magical Thinking
-1.06
.85
.82
4
.32**
.15**
.37**
.13**
.13
.92
.82
4
.53**
.30**
.50**
.33**
.33**
-1.00
.75
.70
4
.52**
.37**
.46**
.29**
.49**
Mean
SD
α
1. Ideas of Reference / Suspiciousness
-.41
.82
2. No Close Friends / Constricted Affect
-.79
3. Eccentric Behavior
6. Odd Speech
7. Unusual Perceptions
** p < .01.
2
3
4
5
6
.46**
30
Table 5: Model Fit Statistics Based on Four Nested Models Tested (n = 441)
χ2
df
CFI
RMSEA
SRMR
Δχ2 (df)
Uni-dimensional Model
2873.86
464
.56
.11
.10
--
Un-correlated model
1611.91
464
.79
.08
.21
1261.95 (0)a
3-Factor Model
820.49
454
.93
.04
.05
791.42 (10)**
4-Factor Model
817.37
453
.93
.04
.05
3.12 (1)
a: χ2-difference not tested given no change in degrees of freedom. ** p < .01. Note, the 3-factor
and 4-factor models were both found to be invariant across gender in terms of structural weights
and covariances
31
Table 6. Correlations between SPQ-BR total and subscale scores and subjective and objective Quality of Life
(QOL).
Total
Cognitive
Perceptual
Objective QOL
-.37
-.28
Subjective QOL
-.53
-.44
NOTE – all r values are statistically significant p < .001.
Disorganized
-.26
-.34
Constricted
Affect/No close
Friends
-.37
-.50
Interpersonal
-.37
-.52
32
Figure Captions
Figure 1. The three-factor super-ordinate structure of the revised SPQ-Brief Revised.
Item wordings for all indicators are reported Table 3.
Figure 2. The four-factor super-ordinate structure of the revised SPQ-Brief Revised. Item
wordings for all indicators are reported in Table 3.
33
CF1
CF2
CF3
.83
.83
CA4
CA6
CA5
.64 .66 .52
SA1
.60
.87
No Close Friends / Constricted Affect SA2
SA3
.83
.72
.72
SA4
.55
Ideas of Reference / Suspiciousness
Social Anxiety
.59
S2
.61
S3
.61
.71
.77
.73
Cognitive
Perceptual
.55
Magical Thinking
.64
Unusual Perceptions
Disorganized
EB1
.76
EB2
.65
EB3
.56
Odd Speech
.58
EB4
.81
OS1
.38
.76
.79
Eccentric Behavior
.69
.58
.76
.61
.77
.66
.92
.70
.84
OS2
.68
OS3
.74
OS4
IR5
IR6
.86
Interpersonal
IR4
.72
.71
.75
S1
MT1
MT2
MT3
MT4
UP1
UP2
UP3
UP4
34
CF1
CF2
CF3
.83
CA4
.64
.83
.66
.52
.60
Ideas of Reference / Suspiciousness
No Close Friends / Constricted Affect .54
.72
CA6
CA5
SA2
SA3
SA4
.61
S3
.61
.73
.72
Social Anxiety
Cognitive
Perceptual
.50
.55
Magical Thinking
.64
Unusual Perceptions
Disorganized
.61
EB1
.76
EB2
.65
EB3
.55
Odd Speech
.82
.59
EB4
OS1
.39
.76
.79
Eccentric Behavior
.69
.58
.76
.55
.77
.66
.92
.55
.84
OS2
.74
.68
OS3
OS4
IR4
.72
IR5
IR6
.86
.83
S2
.86
.53
SA1
.59
.71
.60
S1
MT1
MT2
MT3
MT4
UP1
UP2
UP3
UP4