The results of the homogeneity model for physical maltreatment suggest that approximately one quarter of the variance is due to nonpassive gene-environment correlation, about one fifth is due to the shared and twin environmental influences, and the remainder is due to the nonshared environment. In contrast, the heterogeneity model suggests that genetically mediated child effects on physical maltreatment are small for both males and females. Shared environmental influences accounted for approximately one quarter of the variance for both genders, whereas twin environmental factors appear to not influence males but accounted for another quarter of females’ variance.
