Psychoticism as a dimension of personality: a multivariate genetic test of Eysenck and Eysenck's psychoticism construct.

In this study, we applied multivariate genetic analysis, a generalization of factor analysis and behavior genetic analysis, to responses to items of the Psychoticism scale of the Eysenck Personality Questionnaire by 2,903 adult same-sex Australian twin pairs. Item loadings on genetic, shared environmental, and nonshared environmental common and specific factors were estimated. The genetic factor structure differed considerably from the environmental structures, particularly in men. The genetic correlation between suspiciousness items and items reflecting unconventional or tough-minded attitudes or hostility to others was negative, but the environmental correlation was positive. Thus, conventional behavior genetic studies that have reported significant heritability of psychoticism, on the basis of analyses of scale scores, are misleading as to what trait is being inherited.