of the χ2 statistic by 2.74 for 2 degrees of freedom. Next, it was tested whether the non-additive genetic effects could be dropped from the model. The χ2 statistic increased to 170.39, which is highly significant. Thus, for Neuroticism, both additive and non-additive genetic effects seem to be operating, which seem to be the same in males and females, and of equal importance in males and females. Proportions of additive and non-additive genetic variance were estimated at 27 and 21 %, respectively.
