Sex differences in relational and overt aggression among 3rd (n=176), 4th (n=179), and 5th graders (n=145) from three public schools (n=500; 278 girls) were examined. Nominations of relational aggression increased over time among 4th and 5th grade girls, but not among boys or 3rd grade girls. Among 3rd graders, boys received more nominations for relational aggression than girls. By the end of the 5th grade, girls received more relational aggression nominations than boys. There was also a significant rise in nominations of overt aggression among 5th grade girls, but not among 5th grade boys or younger boys and girls. As expected, boys were more likely than girls to be nominated for overt aggression at all grade levels. The findings are helpful for explaining inconsistencies of earlier research pertaining to sex differences in relational aggression and for advancing our understanding of the causes of aggression.
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