Unitary personality source traits analyzed for heritability.

1,768 12- to 18-year-old boys, in pairs from five constellations (identical and fraternal twins, brothers, unrelated boys raised together and a random general population sample) were measured by the O-A (performance) personality battery on source traits UI 16, 17 and 19. Corrections were made for ages and test validities in computing observed variances. Nine equations were set up in the multiple abstract variance (MAVA) model giving expectancies from seven unknown abstract variances (genetic, threptic, and genothreptic covariances) with respect to observed variances. Maximum likelihood analysis showed that genetic or threptic contribution alone was unable to fit the data, and the best fit was given by a parsimonious form of MAVA dropping genothreptic correlations. Population heritabilities calculated on this basis were 0.46 for UI 16 (ego assertion), 0.21 for UI 17 (control, upbringing), and 0.50 for UI 19 (independence). When compared with an earlier study by the O-A, but by a different analysis, and with the same data analyzed by tho other methods, a reasonably consistent conclusion emerges that UI 17 is little inherited, while UI 16 and UI 19 are rather strongly inherited. The contribution of the behavior-genetic evidence to the theories about these source traits is discussed. It is concluded that UI 16 is initially in development a temperament factor, probably with physiological associations in metabolic rate, etc.; that UI 19 is a strong and sex-related temperament factor, and that UI 17 is a sentiment pattern of cultured inhibition almost wholly dependent on family and social upbringing.