Abstract: A great deal of research documents the importance of relationships such as mutual friends for a child’s development and the importance of negative behaviors such as aggression for a child’s maladjustment. However, previous research on peer relations, especially in China, has been limited in two crucial ways: (1) most of the studies have employed cross-sectional designs, which precludes directly examining developmental changes; and (2) few studies have analyzed for influences between friendships and aggression. The present research investigated developmental trends and individual differences for children’s mutual friendship and explored the longitudinal effects of aggressive behavior on children’s mutual friendships.
Data were collected for 285 students from Grade 3 and Grade 4 in June of 2002, 2003 and 2004. Measures included (1) Friendship Nominations, from which we determined each child’s number of mutual friends with boys and with girls; and (2) peer nominations for overt aggression and relational aggression behaviors, using the Revised Class Play procedure.
The present study employed Hierarchical Linear Model to analyze the longitudinal data. In terms of friendships, results indicated that, as expected, the number of mutual friends increased over time and children had more same sex mutual friends than opposite sex mutual friends. This same sex preference increased more for girls than for boys. For girls, having more mutual friends at the first assessment predicted a faster rate of accumulating mutual friends during the three years. After controlling for the effect of relational aggression, overt aggression had a significantly negative effect on the number of children’s mutual friends at each time of testing for girls but not for boys. After controlling for the effect of overt aggression, relational aggression had a significantly positive effect on children’s number of mutual friends for girls at each time of testing, but not for boys
These findings confirm an increase of mutual friends over time as well indicate a strong gender segregation in children’s friendships. Also, aggressive behaviors were not necessarily associated with maladjustment, in that friendships were not negatively affected for children who exhibited gender normative aggressive behaviors

Key words: mutual friendship, overt aggression, relational aggression, Hierarchical Linear Model