AGGRESSIVE BEHAVIOUR
Sex Differences
More males than females commit crimes
Developmental Evidence
Kochanska, Coy & Murray (2001);
- Looked at compliance with prohibition from parent in preschoolers (e.g. don’t do this, do
that)
- Girls were more likely to comply in both conditions and with commitment
- Because of - more impulse control (have to inhibit action when told not to do something -
inhibit aggressive response), or increased fear response (linked to BIS)
Romano, Trembley, Boulerice & Swisher (2005)
- National longitudinal survey of children and youth (0-11 years)
- 59,000 households in Canada - large sample, good selection details
- Males exhibited more aggression and less pro-social aggression (even after controlling for
parental style, family variables and neighbourhood variables)
- Maternal hostility, maternal depression, punitive parenting, greater perceived
neighbourhood problems and poverty all associated with higher levels of psychical
aggression
- Neighbourhood variables play a small role
- Longitudinal
- But only correlational
- Only looked at physical aggression
Girls highly aggressive in preschool IF relational aggression is considered (Bonica et al., 2003)
Middle childhood - 4.2% physically aggressive, 21.6% relational/physically aggressive
Aggression effects established into adulthood (Tremblay, 2000)
Males and females feel equally angry - but express it in different ways
Differences in gender lies in how we define aggression
Neuropharmacological evidence
Testosterone = biological difference between boys and girls
Six hypotheses (Archer, 2006) - sexual selection and dominance linked to aggression - evolutionary
model
Hypothesis 1
No rise in aggression with testosterone rise in adolescence (following bird not mouse model)
Evidence:
, Halpern (1994):
- 3 year longitudinal study 100 adolescent boys
- Testosterone increased at puberty
- Self reported aggression did not
- No correlation between testosterone and aggression
Archer (2004):
- Magnitude of sex differences in aggression did not increase at puberty
Hypothesis 2a
• Testosterone levels should increase in presence of sexually desirable females
Evidence:
Helhammer et al. (1985):
- Males salivary T increase 15 mins after the start of erotic / sexual films
- No change for neutral or humorous film (arousal control)
Roney (2003):
- Males exposed to brief conversation with attractive young female or young male.
- Significant increase in testosterone in female encounter condition
Hypothesis 2b
• Testosterone levels should increase in presence of challenge to status
Evidence:
Cohen et al (1996):
- North America/Southern US males testosterone levels
- Southerners testosterone levels increased more after insult
- These testosterone mirrored increases in observed anger, and self-reported willingness to
challenge a larger person
- Explained by culture of honor, so insult serves to act as challenge to status
Hypothesis 3
• Testosterone increases to challenge increases aggression
Evidence:
Berman et al. (1993):
- Males involved in competitive reaction time task
- Shocks delivered to confederate
- Correlation between testosterone level and aggression
Sex Differences
More males than females commit crimes
Developmental Evidence
Kochanska, Coy & Murray (2001);
- Looked at compliance with prohibition from parent in preschoolers (e.g. don’t do this, do
that)
- Girls were more likely to comply in both conditions and with commitment
- Because of - more impulse control (have to inhibit action when told not to do something -
inhibit aggressive response), or increased fear response (linked to BIS)
Romano, Trembley, Boulerice & Swisher (2005)
- National longitudinal survey of children and youth (0-11 years)
- 59,000 households in Canada - large sample, good selection details
- Males exhibited more aggression and less pro-social aggression (even after controlling for
parental style, family variables and neighbourhood variables)
- Maternal hostility, maternal depression, punitive parenting, greater perceived
neighbourhood problems and poverty all associated with higher levels of psychical
aggression
- Neighbourhood variables play a small role
- Longitudinal
- But only correlational
- Only looked at physical aggression
Girls highly aggressive in preschool IF relational aggression is considered (Bonica et al., 2003)
Middle childhood - 4.2% physically aggressive, 21.6% relational/physically aggressive
Aggression effects established into adulthood (Tremblay, 2000)
Males and females feel equally angry - but express it in different ways
Differences in gender lies in how we define aggression
Neuropharmacological evidence
Testosterone = biological difference between boys and girls
Six hypotheses (Archer, 2006) - sexual selection and dominance linked to aggression - evolutionary
model
Hypothesis 1
No rise in aggression with testosterone rise in adolescence (following bird not mouse model)
Evidence:
, Halpern (1994):
- 3 year longitudinal study 100 adolescent boys
- Testosterone increased at puberty
- Self reported aggression did not
- No correlation between testosterone and aggression
Archer (2004):
- Magnitude of sex differences in aggression did not increase at puberty
Hypothesis 2a
• Testosterone levels should increase in presence of sexually desirable females
Evidence:
Helhammer et al. (1985):
- Males salivary T increase 15 mins after the start of erotic / sexual films
- No change for neutral or humorous film (arousal control)
Roney (2003):
- Males exposed to brief conversation with attractive young female or young male.
- Significant increase in testosterone in female encounter condition
Hypothesis 2b
• Testosterone levels should increase in presence of challenge to status
Evidence:
Cohen et al (1996):
- North America/Southern US males testosterone levels
- Southerners testosterone levels increased more after insult
- These testosterone mirrored increases in observed anger, and self-reported willingness to
challenge a larger person
- Explained by culture of honor, so insult serves to act as challenge to status
Hypothesis 3
• Testosterone increases to challenge increases aggression
Evidence:
Berman et al. (1993):
- Males involved in competitive reaction time task
- Shocks delivered to confederate
- Correlation between testosterone level and aggression
