model was compared with the full model. If the difference in χ2 values between the nested model and the full model (Neale & Cardon, 1992), where degrees of freedom (df) is equal to the difference between the df of the nested model and the full model, was not significant, indicating no decrement in fit, the nested model was retained because it was the more parsimonious model. The model with the lowest Akaike’s Information Criteria [AIC; (Akaike, 1987)], the best-fitting model with regard to precision and complexity, was then selected as the overall best-fitting model. Results from the full and best-fitting models are presented.
