摘要: SUMMARY In the last decade, numerous collaborations between developmentalists and behavior geneticists have extended developmental theories to genetically informative samples. This study integrates approaches used by environmental researchers further our understanding of etiology children's externalizing behavior. First, genetic influences on are reviewed studies using data from parent reports, self-reports, teacher public records, observation described. Second, observational a middle-childhood twin sample presented. Results suggest significant dominant effects observed negative during friend interaction (N= 148 pairs). addition, nonshared were substantial; when controlling for coparticipant's behavior, environment was sole source variation. Context method discussed.