HERITABILITY OF FACET-LEVEL TRAITS IN A CROSS-CULTURAL TWIN SAMPLE - SUPPORT FOR A HIERARCHICAL MODEL OF PERSONALITY

The common variance among personality traits can be summarized in the factors of the five-factor model, which are known to be heritable. Thi s study examined heritability of the residual specific variance in fac et-level traits from the Revised NEO Personality Inventory. Analyses o f raw and residual facet scales across Canadian (183 monozygotic [MZ] and 175 dizogotic [DZ] pairs) and German (435 MZ and 205 DZ pairs) twi n samples showed genetic and environmental influences of the same type and magnitude across the 2 samples for most facets. Additive genetic effects accounted for 25% to 65% of the reliable specific variance. Re sults provide strong support for hierarchical models of personality th at posit a large number of narrow traits in addition to a few broader trait factors or domains. Facet-level traits are not simply exemplars of the broad factors they define; they are discrete constructs with th eir own heritable and thus biological basis.