There has been recent emphasis on the importance of investigating prosocial and antisocial behavior simultaneously owing to doubts about whether examining one automatically gives information about the other. However, there has been little empirical research into this question. The present study (based on a large population sample of…

Thirty-nine families were observed extensively at home when children were 2 1/2 and 4 1/2 years of age and again 2 years later. The Social Relations Model is used to investigate children's sex differences in aggression and parents' prohibiting aggression during sibling conflict. In the first observation period, boys engaged in more severe and mild…