Aggression between peers in early childhood: individual continuity and developmental change.

43 children were observed in play with "best available friends" at 2 and again at 5 years of age. An arousing stimulus, an angry interaction between adults, was introduced during play sessions to increase the likelihood of elicitation of aggressive patterns. Dimensions of physical aggression at age 2 (e.g., object-related aggression, bodily aggression) predicted dimensions of children's physical aggression at age 5. However, substantial sex differences in the stability of aggression were found. Among boys, the disposition to engage in physical aggression was highly stable, with correlations ranging as high as r = .76. Certain dimensions of physical aggression at age 2 were also positively associated with verbal aggression at age 5. Fewer and more modest correlations were found among girls. The frequency of aggression, particularly bodily aggression (e.g., hitting, pushing), initiations of aggression, and the average length of aggression episodes, decreased between 2 and 5 years of age. These results indicate that relative aggressiveness tends to remain stable despite declines in the frequency of aggressive behavior between 2 and 5 years of age.