ENVIRONMENTAL PREDICTORS OF PERSONALITY-DIFFERENCES - A TWIN AND SIBLING STUDY

Nonshared environmental influences have consistently been shown to acc ount for at least as much of the variance in personality as genetic fa ctors, but the nature of these nonshared influences has largely remain ed unidentified. To identify environmental predictors of differential personality development, the Personality Research Form and 4 measures of people's perceptions of their background environments were administ ered to 143 adult twin pairs (93 monozygotic [MZ] and 50 dizygotic [DZ ]) and 66 pairs of same-sex nontwin (NT) siblings. Differences between MZ twins, DZ twins, and NT siblings in a number of dimensions of pers onality were significantly related to differences on the environmental measures, and phenotypic correlations between the personality and env ironment measures were themselves entirely attributable to correlated nonshared environmental effects.