GENETIC AND ENVIRONMENTAL-INFLUENCES ON MMPI FACTOR SCALES - JOINT MODEL-FITTING TO TWIN AND ADOPTION DATA

In general, the shared family environment appears to play a negligible role in determining individual differences in personality and interes ts. Nevertheless, scattered reports of significant shared environmenta l influence on such variables appear in the literature. Using data fro m the Texas Adoption Project (TAP), the current study attempted to rep licate twin study findings of significant shared environmental varianc e on four of nine Minnesota Multiphasic Personality Inventory (MMPI) f actor scales (Rose, 1988). Conventional behavioral genetic analyses of the adoption data agreed in affirming a significant shared environmen tal influence on individual differences in Religious Orthodoxy only. S ubsequent simultaneous modeling of Rose's ruin data and TAP adoption d ata resulted in three scales (Extraversion, Inadequacy, and Religious Orthodoxy) showing significant shared environmental influence. Again. effects were most substantial for Religious Orthodoxy, where the share d environment accounted for nearly 50% of the variance. It is argued t hat assortative mating cannot explain this finding.