Heritability of Personality

5s were 68 pairs of adolescent twins from the public schools of an urban area. They comprised 60% of the same-sexed twin population. Zygosity diagtlosis was detennined by blood grouping for 9 groups; half of the sample was identical (MZ) and half was fraternal (DZ). Personality was assessed by the MMPI and Cattell's HSPQ. 24 standard scaies were analyzed by intraclass correlations (R) and heritability indexes (H). Hoiistic analyses of MMPI profile similarity were done clinically and statistically. 6 personality scales had significant genetic components as revealed by higher MZ R~. 11 scales had appreciable hereditary variance. Pooled accuracy of profile similarity judgments matching zygosity was 68% (p =:: .005). The general idea that psychopathology in man has a substantial genetic component, especially the psychoses, was supported. A dimension of introversion was the most heavily influenced by genetic factors.