or sibling pairs compared to same-sex pairs suggest that the genetic or shared environmental risk factors for antisocial behavior differ for males and females. If one focuses on effect sizes (that is, the actual estimates of rA and rC derived from comparisons of same-sex and opposite-sex twin correlations) rather than the results of null hypothesis significance tests, the results of the twin and sibling literature on qualitative sex differences are not as inconsistent as they may appear.
