Model” (Neale et al., 2003), that assumes that there are no sex-specific additive genetic factors but that the relative contribution of genetic and environmental factors differs between men and women (Model II). Finally, we tested a model that posits that there are no sex-specific additive genetic factors, and that the magnitude of genetic and environmental effects are the same across sexes (Model III; otherwise known as a “Scalar Effects Sex-Limitation Model” (Neale et al., 2003). All three models were fitted to the data to test for both qualitative and quantitative gender differences. After establishing the best-fitting sex-limitation model, we then proceeded to test specific parameters.
