(Eaves et al., 1997; Jacobson et al., 2002; Saudino et al., 2005; Slutske et al., 1997; Tuvblad et al., 2005; Van Hulle et al., 2003), five reported twin/sibling correlations that were suggestive of sex-specific etiologic influences. In the present study, the correlation for CD was significantly smaller among opposite-sex twin pairs (.15) than among same-sex female (.28) and male (.33) DZ twin pairs, and the correlation for AAB was also smaller (but not significantly) among opposite-sex twin pairs (.08) than among same-sex female (.12) and male (.25) DZ twin pairs. In Eaves et al. (1997) the corresponding correlations obtained were .27, .43, and .35, in Saudino et al. (2005) they were .26, .48, and .43 for same-teacher-reported conduct problems, and in Jacobson et al (2002) they were .21, .34. and .35 for AAB. In addition, Van Hulle et al. (2003) reported that opposite-sex sibling correlations for self-reported aggressive delinquency were smaller than same-sex sibling correlations. Smaller correlations among opposite-sex twin 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
