We tested, in males only, whether an ACE, AE or CE model most parsimoniously explained the data: fitting an AE model resulted in an improvement in AIC (Δχ2 = 3.779, Δdf = 5, p = 0.582, AIC = −6.221), while a CE model fit substantially worse (Δχ2 = 106.859, Δdf = 5, p < 0.001, AIC = + 96.859). Thus, we tested subsequent models nested within an AE model. We were able to further improve AIC by removing the direct genetic correlation between MD and NDS (path a3,1) and the unique environmental correlation between MD and RUS (path e2,1) (Table 3).
