Sex differences in aggression: a rejoinder and reprise

Area of Science:

• Developmental Psychology
• Comparative Psychology
• Behavioral Biology

Background:

• Peer-directed aggression in young children (aged 6 and under) is a significant area of developmental research.
• Existing literature suggests potential sex differences in aggressive behaviors, but comprehensive analysis is needed.

Purpose of the Study:

• To conduct a meta-analysis of observational studies to determine the existence and nature of sex differences in peer-directed aggression in young children.
• To explore potential explanations for observed sex differences, including activity levels, socialization, and cross-species comparisons.

Main Methods:

• Meta-analysis of 32 observational studies on peer-directed aggression in children aged 6 and younger.
• Analysis of sex differences in aggression rates and contexts (e.g., partner sex).
• Review of cross-cultural data, primate studies, and evidence on socialization and hormonal contributions.

Main Results:

• A highly significant sex difference favoring higher male aggression was found (24/32 studies).
• No studies indicated higher female aggression; 8 showed no difference.
• Boys' aggression was more often observed with male peers; findings were consistent across cultures and with primate data.

Conclusions:

• The observed sex difference in aggression in young children is robust and unlikely to be an artifact of activity levels or differential socialization.
• While hormonal influences are clear in animals, evidence in humans is inconclusive but consistent with a contribution.
• Self-socialization and cognitive development related to sex identity may play a role, but the timing suggests they may not fully explain the early onset of this sex difference.