Observation of Externalizing Behavior During a Twin-Friend Discussion Task

SUMMARY

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

Key Words:

• Genetics
• peers
• externalizing
• observational methods