The AWA and Human Anger Aaron Sell - HBES `03

An evolutionary perspective on
inter-personal violence
VRPP 2015
Aaron Sell
School of Criminology
Griffith University
Manuel Eisner
Institute of Criminology
University of Cambridge
Denis Ribeaud
Chair of Sociology
ETH Zurich, CH-8092
Aggression is an evolved tool
 What

is aggression?
Disorganization of
complex design
 Function:

Prevent another
organism from
harming your
reproductive success
Conflicts of interest lead to
aggressive design
 Designed
for
“breaking your
opponent”



Weaponry
Aggressive “modes”
Timed to situations of
conflict
 see
Huntingford &
Turner 1987
Varying levels of aggressive
design lead to assessment
 Assessment

mechanisms
Arnott & Elwood 2009; Maynard Smith & Parker 1976
 Visual

Arnott & Elwood 2010; Beeching 1992
 Auditory

Clutton-Brock & Albon 1979; Mager et al. 2007
 Chemical

Breithaupt & Eger 2002
Assessments lead to
dominance hierarchies
 i.e.
a social system whereby
formidability sets internal thresholds of
acceptable divisions of resources
 In
short, the ability to injure another
animal allows an animal to bargain for
better treatment
Human conflict systems
 Bargaining


the ability to impose costs
the ability to deny benefits
 BP

power comes from:
should calibrate:
An individual’s sense of entitlement
• (Lukaszewski 2013; Sell, Tooby & Cosmides 2009)

An individual’s threshold for anger
• (Sell 2011)
 In
short, bargaining power should
predict aggressive bargaining
Prediction: bargaining power
predicts aggression

Two bargaining can come from:
1.
2.
Cooperative value
Formidability
Prediction: bargaining power
predicts aggression

Two bargaining can come from:
1.
2.
Cooperative value
Formidability
Prediction: bargaining power
predicts aggression
 One
component of formidability is personal
fighting ability.
 How
does one measure “fighting ability?”
Operationalizing fighting ability
 Upper

body strength
Relevant to ancestral
forms of aggression
• (Brues 1959; Walker 1997)

Highly sexually dimorphic
• (Lassek & Gaulin 2009)

Objectively and ethically
measureable
 Should
be most predictive
in males.
Why males?
 Males
commit most acts of physical
aggression
• (Wilson & Daly 1985; Wilson, Daly & Pound 2002)


Women can co-opt male fighting ability
Physical aggression more costly for females
• Campbell (2002)
Strength and violence
Swiss
adolescents
US college
students
Tsimane hunter
horticulturalists
of Bolivia
Aka huntergatherers
of the CAR
Data from US college students
 Study 1: 62 men at gym
 Strength measured on four
weight-lifting machines
 Study
2: 125 male and 156
female students

Strength measured by best proxies:
• Flexed bicep circumference: r = .74
• Photo ratings (full person): r = .71
• Self-report r = .66
Measures

Anger (11 items, .85 reliability)
 Ex: I get very angry when someone makes fun of me

History of Personal Violence (5 items, .82 reliability)
 Ex: I have physically intimidated someone who had it
coming.
1
2
Strongly disagree
3
4
5
6
7
Strongly agree
Sell, Tooby & Cosmides (2009) PNAS
Strength and anger
Anger
Gym
men
?
Male
students
?
Female
students
History of
Violence
Sell, Tooby & Cosmides (2009) PNAS
Strength and anger
Anger
Gym
men
.38***
Male
students
.32****
Female
students
History of
Violence
Sell, Tooby & Cosmides (2009) PNAS
Strength and violence
Anger
History of
Violence
Gym
men
.38***
?
Male
students
.32****
Female
students
?
Sell, Tooby & Cosmides (2009) PNAS
Strength and violence
Anger
History of
Violence
Gym
men
.38***
Male
students
.32****
.47****
.37*****
Female
students
Sell, Tooby & Cosmides (2009) PNAS
Women’s strength
Anger
History of
Violence
Gym
men
.38***
Male
students
.32****
Female
students
.07
.47****
.37*****
.07
Sell, Tooby & Cosmides (2009) PNAS
Women and strength
 Determining
factor:
bargaining power
 Among the Aka,
men and women
have highly
overlapping
measures of
physical strength
Strength and anger among the Aka
 Aka women
Anger: r = .37*
Aggression r = .28

Aka men
Anger r = .38*
Aggression r = .43*
Hess, Helfrect, Sell, Hagen & Hewlett (2010) Human Nature
Prediction: bargaining power
predicts aggression
 Fighting
ability is one component of
formidability.
 Another
is “coalitional strength.”
Coalitional strength
 Humans
magnify fighting
ability with coalitions


(Fessler & Holbrook 2013; Wrangham 1999;
Wrangham & Glowacki 2012)
Humans also use coalitional
strength to deliver benefits

(Ostrom 2000; Tooby, Cosmides & Price
2006)
Coalitional strength should
predict aggressive bargaining
Swiss
adolescents
Tsimane hunter
horticulturalists
of Bolivia
The Tsimane men of Bolivia
 Small
scale society
with cohesive group
structure, allows for:


peer rating of number
of allies
peer ratings of anger
with Chris von Rueden and Mike Gurven
The Tsimane men of Bolivia
 Two
measures of
bargaining power:
1.
2.
Physical strength
Coalitional strength
with Chris von Rueden and Mike Gurven
Physical strength measure
 Three
upper body
strength tests
 Proxy
body
measures
Peer Ratings of:

Number of allies: “When he has a
conflict he will have a lot of people
who will defend or help him.”

Anger: “Does he get angry when
things don’t go his way?”
with Chris von Rueden and Mike Gurven
r = .56***
r = .46***
These are independent effects
 Regression


Strength:
Allies:
predicting anger (std. β)
.27*
.41**
Prediction: bargaining power
predicts aggression

Two bargaining can come from:
1.
2.
Cooperative value
Formidability
Prediction: bargaining power
predicts aggression

Two bargaining can come from:
1.
2.
Cooperative value
Formidability
Cooperative value
 Non-human
examples
include:



Food provisioning
Offspring care
Mating
Cooperative value
 Non-human
examples
include:



Food provisioning
Offspring care
Mating
Mate value
 Individuals
differ in
“mate value” in ways
that enable men and
women to bargain with
the opposite sex for
better treatment
Mate value
 Furthermore,
mate
value is based on
elements of bargaining
power:





Health
Longevity
Competence
Strength
Skills
Mate value
 Prediction:
Mate Value
should predict
aggressiveness
among young males
and females
Mate value and violence
Swiss
adolescents
US college
students
Z-proso longitudinal study
 Zurich
Project on the Social
Development of Children and
Youths


N ~1500
Started at age 9, now 16
 Contains
Prof. Manuel Eisner
multiple measures of
aggressive behaviour, sociality.
 Contains self and teacher report
Measures of fighting ability
 Measures:



Flexed bicep circumference
Self-reported strength (1-100)
Self-reported fighting ability (1-100)
Measures of coalitional strength
Measure
Valid N, m/f
Details of measure
749/696
“Youths often have a group of friends
they regularly hang around with. Are you
in such a group?”
CS1
Measures of coalitional strength
Measure
Valid N, m/f
CS1
749/696
a) Group size
378/431
Details of measure
“Youths often have a group of friends
they regularly hang around with. Are you
in such a group?”
“How many people (including you) are in
that group?”
b) Age of group
members
378/430
“How old are they on average?”
c) Longevity of
group
378/428
“How long has your group existed?”
Measures of coalitional strength
Measure
Valid N, m/f
CS1
749/696
a) Group size
378/431
Details of measure
“Youths often have a group of friends
they regularly hang around with. Are you
in such a group?”
“How many people (including you) are in
that group?”
b) Age of group
members
378/430
“How old are they on average?”
c) Longevity of
group
378/428
“How long has your group existed?”
CS2
379/432
Composite of measures a-c
Measures of coalitional strength
Measure
Valid N, m/f
CS1
749/696
a) Group size
378/431
Details of measure
“Youths often have a group of friends
they regularly hang around with. Are you
in such a group?”
“How many people (including you) are in
that group?”
b) Age of group
members
378/430
“How old are they on average?”
c) Longevity of
group
378/428
“How long has your group existed?”
CS2
379/432
Composite of measures a-c
CS3
749/696
Composite of CS1, a, b, c
Measures of mate value
 Questionnaire
based:

Self-reported attractiveness (1-100)

In a romantic relationship (y/n)

Have had sex with a romantic partner (y/n)
Aggressiveness measures
 Many
self and teacher report
 Problem
with “researcher degrees of
freedom”
 Solution:
kitchen sink approach
Measures of aggressiveness
Aggression Measure
Valid n Mean
(female) (SD)
Teacher-rating of
1287
1.35
aggression
(619)
(.52)
Self-rating of
1447
1.69
aggression
(697)
(.57)
Aggressive Conflict
1440
1.62
Coping Scale
(696)
(.61)
Violent Delinquency
1442
.21
(695)
(.52)
Norms of Masculinity
1436
2.47
(690)
(.74)
Moral Neutralization
1446
2.13
of Aggression
(697)
(.63)
Summation variable:
1447
0.00
Global Aggressiveness (697)
(.71)
Measure
Sex differences
Male bias, M = .157
t(1285) = 5.58***
Male bias, M = .270
t(1445) = 9.81***
Male bias, M = .254
t(1438) = 8.09***
Male bias, M = .209
t(1440) = 7.77***
Male bias, M = .344
t(1434) = 8.99***
Male bias, M = .510
t(1444) = 16.86***
Male bias, M = .49
t(1445) = 14.01***
α reliability
(# of items)
.93 (13)
.87 (11)
.67 (4)
.45 (3)
.73 (3)
.82 (7)
.83 (6)
#1: fighting ability in males
Aggress.
Global Teacher Self
Violent Norms
Moral
Conflict
Agg. Rating Rating
Delinq. of Masc. Neutral.
Coping
Male adolescents
Fighting ability
?
?
?
?
Coalitional
Strength (CS3)
Mate Value
Female adolescents
Fighting ability
Coalitional
Strength (CS3)
Mate Value
?
?
?
#1: fighting ability in males
Aggress.
Global Teacher Self
Violent Norms
Moral
Conflict
Agg. Rating Rating
Delinq. of Masc. Neutral.
Coping
Male adolescents
Fighting ability .26***
.13***
.17***
.20***
Coalitional
Strength (CS3)
Mate Value
Female adolescents
Fighting ability
Coalitional
Strength (CS3)
Mate Value
.15***
.25***
.23***
#2: fighting ability in females
Aggress.
Global Teacher Self
Violent Norms
Moral
Conflict
Agg. Rating Rating
Delinq. of Masc. Neutral.
Coping
Male adolescents
Fighting ability .26***
.13***
.17***
.20***
.15***
.25***
.23***
?
?
?
Coalitional
Strength (CS3)
Mate Value
Female adolescents
Fighting ability
Coalitional
Strength (CS3)
Mate Value
?
?
?
?
#2: fighting ability in females
Aggress.
Global Teacher Self
Violent Norms
Moral
Conflict
Agg. Rating Rating
Delinq. of Masc. Neutral.
Coping
Male adolescents
Fighting ability .26***
.13***
.17***
.20***
.15***
.25***
.23***
.08*
.08*
.13***
Coalitional
Strength (CS3)
Mate Value
Female adolescents
Fighting ability .17***
Coalitional
Strength (CS3)
Mate Value
.10*
.15***
.15***
#3: coalitional strength
Aggress.
Global Teacher Self
Violent Norms
Moral
Conflict
Agg. Rating Rating
Delinq. of Masc. Neutral.
Coping
Male adolescents
Fighting ability .26***
Coalitional
Strength (CS3)
?
.13***
.17***
.20***
.15***
.25***
.23***
?
?
?
?
?
?
Mate Value
Female adolescents
Fighting ability .17***
Coalitional
Strength (CS3)
Mate Value
?
.10*
.15***
.15***
.08*
.08*
.13***
?
?
?
?
?
?
#3: coalitional strength
Aggress.
Global Teacher Self
Violent Norms
Moral
Conflict
Agg. Rating Rating
Delinq. of Masc. Neutral.
Coping
Male adolescents
Fighting ability .26***
.13***
.17***
.20***
.15***
.25***
.23***
Coalitional
.23***
Strength (CS3)
.10**
.20***
.24***
.20***
.11**
.15***
Mate Value
Female adolescents
Fighting ability .17***
.10*
.15***
.15***
.08*
.08*
.13***
Coalitional
Strength (CS3)
.04
.06
.09*
.10**
.05
.03
Mate Value
.08*
#4: mate value
Aggress.
Global Teacher Self
Violent Norms
Moral
Conflict
Agg. Rating Rating
Delinq. of Masc. Neutral.
Coping
Male adolescents
Fighting ability .26***
.13***
.17***
.20***
.15***
.25***
.23***
Coalitional
.23***
Strength (CS3)
.10**
.20***
.24***
.20***
.11**
.15***
?
?
?
?
?
?
Mate Value
?
Female adolescents
Fighting ability .17***
.10*
.15***
.15***
.08*
.08*
.13***
Coalitional
Strength (CS3)
.08*
.04
.06
.09*
.10**
.05
.03
Mate Value
?
?
?
?
?
?
?
#4: mate value
Aggress.
Global Teacher Self
Violent Norms
Moral
Conflict
Agg. Rating Rating
Delinq. of Masc. Neutral.
Coping
Male adolescents
Fighting ability .26***
.13***
.17***
.20***
.15***
.25***
.23***
Coalitional
.23***
Strength (CS3)
.10**
.20***
.24***
.20***
.11**
.15***
.26***
.25***
.26***
.26***
.25***
.25***
Mate Value
.36***
Female adolescents
Fighting ability .17***
.10*
.15***
.15***
.08*
.08*
.13***
Coalitional
Strength (CS3)
.08*
.04
.06
.09*
.10**
.05
.03
Mate Value
.24***
.13***
.22***
.19***
.08*
.17***
.16***
#5: independence of predictors
 All
three components of bargaining
power are correlated for males:
Fighting Ability
CS3
 and
Coalitional Strength (CS3)
Mate Value
.15****
.31****
-
.17****
for females:
Coalitional Strength (CS3)
Fighting Ability
CS3
.08*
Mate Value
.17****
.13***
#5: independence of predictors
 Each
component of bargaining power
explained additional variance in
aggression
Simultaneous regression
predicting global aggression
Male
subjects
Female
subjects
Fighting Ability
.14***
.13***
Coalitional Strength (CS3)
.18***
n.s.
Mate Value
.28***
.22***
Additional analyses revealed:
 Results
were robust to the inclusion of
a litany of controls:








Age
Pubertal development
Body size
Optimism
Trust
Self-control
Competent conflict coping
…
Additional analyses revealed:
 Results
were not due to violent
subpopulations
 Results
use
not compromised by steroid
In conclusion…
1.
2.
Stronger men are more aggressive according to
themselves, their peers, and their teachers.
The effect of strength on aggressive bargaining is
robust across many cultures:
 US college students

(Sell, Tooby & Cosmides 2009, PNAS)
 Aka of the Central African Republic

(Hess, Helfrecht, Sell, Hewlett and Hagen, Human Nature, 2010)
 Tsimane of Bolivia

(Sell, von Rueden, Tooby, Cosmides & Gurven in prep.)
 Swiss adolescents

(Sell, Eisner and Ribeaud, under review)
In conclusion…
3.
4.
Men with more allies are more aggressive.
Young men and women with higher mate
value are also more aggressive.
General conclusion


Humans demonstrate a common mammalian
pattern of aggressive bargaining
Our understanding of human aggression will be
greatly advanced by understanding the process
whereby humans came to exist.
Thank You