Friends' influence on changes in externalizing behavior during middle childhood: A longitudinal study of relational and physical aggression

Numerous longitudinal studies have shown that childhood physical aggression is the strongest risk-factor for future delinquency, crime, and substance abuse. Recently, it has been suggested that relationally aggressive children may be similarly at-risk for the development of antisocial behavior. This hypothesis is based on studies showing that relational aggression is associated with a range of antisocial behaviors across the lifespan, and on the results of one longitudinal study in which relationally aggressive children became increasingly delinquent between the 3rd and 4th grades (see Crick et al., 1999, for a review). According to peer influence theories (e.g., Dishion, Patterson, & Griesler, 1994), involvement with deviant peers may account for linkages between childhood relational aggression and future antisocial behavior. The present study was designed to test this hypothesis by examining relations between relational aggression and physical aggression, friends' aggressiveness, and changes in antisocial behavior over the course of one year. In addition, it was hypothesized that the quality of the friendship between children and their best friend would moderate the relations between friends' aggression and changes in children's externalizing behaviors.;Two overlapping samples of children were participants in this study: a large, representative group of children, and a subgroup of highly aggressive and nonaggressive children. Information about children's and friends' aggression (relational and physical forms) and other externalizing behaviors were assessed in the 3rd grade, and once again in the 4th grade. Friendships were identified by having children nominate their 3 best friends in their classroom, and children provided information about the quality of their best friendship.;Results showed that girls who befriended relationally aggressive peers became increasingly relationally aggressive themselves between the 3 rd and 4th grades, whereas boys and girls who befriended physically aggressive peers showed increases in physical aggression over this time period. Association with aggressive friends was also found to predict changes in children's delinquency and aggressive-disruptive behavior, however, two factors moderated this relation---children's own level of aggressiveness, and the quality of the friendship. The significance of these results for the application of peer influence theories to relational aggression, and to females, is discussed.