STABILITY AND CHANGE IN ADULT PERSONALITY - GENETIC AND ENVIRONMENTALCOMPONENTS

The enduring nature of personality, particularly in adulthood, has bee n demonstrated in numerous cross-sectional and longitudinal studies wh ere high stability has been observed even with decades between testing intervals. Biometrical studies, reporting genetic effects as the prim ary cause of familial resemblance, have been interpreted as lending fu rther support to theories concerning an inherent stability of personal ity. Heterogeneity in heritability estimates across age cohorts may, h owever, alter this notion. Furthermore, recent phenotypic studies repo rt some evidence for change over the life course for characteristics s uch as 'outgoingness'. The purpose of the present analysis was to exam ine longitudinal stability and change in the sources of variation in p ersonality in the latter half of the life-span using a twin/adoption d esign with up to four times of measurement. Data from the Swedish Adop tion/Twin Study of Aging (SATSA) are used both to demonstrate how gene tic and environmental effects can contribute to phenotypic stability, and to estimate the extent to which these influences are, themselves, stable. Particularly intriguing are findings of increasing variability in rate of change despite relative mean level stability as well as ge netic stability. (C) 1998 John Wiley & Sons, Ltd.