Personality resemblance in adoptive families.

Adoption studies provide an opportunity to check on twin-study inferences about genetic and environmental effects on personality. The Texas Adoption Project obtained personality tests and ratings from members of 300 adoptive families: MMPIs and 16PFs for adults, and Cattell scales and parents' ratings for children. Overall there was little personality resemblance among family members, either biologically or adoptively related. Median correlations were typically positive, but under 0.10. Elimination of a rating bias and the use of multiple correlations did not yield notably higher levels of prediction, but restriction to a subsample of well-measured children provided higher correlations and more evidence of heritability, particularly in the extraversion domain.