Genetic and environmental architecture of human aggression.

A meta-analysis was performed on data from 24 genetically informative studies by using various personality measures of aggression. There was a strong overall genetic effect that may account for up to 50% of the variance in aggression. This effect was not attributed to methodological inadequacies in the twin or adoption designs. Age differences were important. Self-report and parental ratings showed genes and the family environment to be important in youth; the influence of genes increased but that of family environment decreased at later ages. Observational ratings of laboratory behavior found no evidence for heritability and a very strong family environment effect. Given that almost all substantive conclusions about the genetics of personality have been drawn from self or parental reports, this last finding has obvious and important implications for both aggression research in particular and personality research.