We first estimated the fit of a full model (including genetic factors A1 through A7 and full Cholesky decompositions for shared and individual-specific environment—that is C and E, respectively). This model included both MM and FF pairs and constrained the parameter values (not including means) to be equal across the two sexes. We then allowed the parameters to differ in males and females and obtained a substantial improvement in fit (ΔAIC = −151.8). Therefore, for the remainder of these analyses, we estimated the models separately in the two sexes.
