Personality resemblances in adoptive families when the children are late-adolescent or adult.

Members of 220 families who had adopted one or more children from a Texas home for unwed mothers at least 14 years ago completed the California Psychological Inventory and the Thurstone Temperament Schedule. Consistent with other recent adoption studies in Minnesota and Texas, there was very little resemblance between parents and adopted children or between adoptive siblings (average correlations about .05). The presence of a biological relationship raised correlations a little, but only a little, to about .15, suggesting that much of the explanation for personality variation must lie in within-family environmental variation or nonadditive genetic effects. In an earlier study, young adopted children appeared to be better adjusted, on the average, than biological children in the same families. This was no longer true for the late-adolescents and young adults of the present study.