Preschooler Aggression During Free Play Shows Genetic Influences

Lisabeth F. DiLalla and Lorrie Nielson Gehlbach

Southern Illinois University School of Medicine

ABSTRACT

Genetic influences on aggressive behaviors in 5-year-old twins and sibling pairs were investigated. Aggression was measured by parent reports and by rating behaviors children engaged in during free play with a same-sex, same-age, unfamiliar peer. 65 pairs of twins and siblings were assessed. Results showed that identical twins were more alike than were fraternal twins or non-twin siblings on measures of aggression, suggesting that genetic influences are important for aggressive behaviors. This is one of the first studies to use behavioral ratings of children's play behaviors to assess genetic influences. These influences may be important indicators of the ways in which children interact with peers when entering new groups and may influence their attained peer status.