The genetic structure of personality-II. Genetic item analysis of the EPQ

Most studies of the inheritance of personality have performed genetic analysis of scale scores, which will sometimes give a misleading impression of what is inherited. Item genetic analysis, where this is focused on differences in genetic architecture rather than merely differences in item heritability, should guide the development of genetically homogeneous scales. Item genetic analyses of the EPQ were performed, using data from 3810 pairs from the Australian Twin Register. All but three items exhibited significant genetic variance. Genetic dominance was found for a majority of items from the Extraversion and Neuroticism scales, although the dominance effects were weak for N items, particularly in females. Shared environmental effects were found for items from the Lie and Psychoticism scales; for P items they were strong in males but weak in females. These differences in genetic architecture and genotype x sex interaction should permit use of multivariate item genetic analysis to identify the underlying genetic structure of the personality dimensions assessed by the EPQ.