Genotype-environment interaction in personality development: identical twins reared apart

The focus of this study is to identify specific genotype-environment (GE) interactions as they contribute to individual differences in personality in later life. In behavioral genetics, GE interaction refers to the possibility that individuals of different genotypes may respond differently to specific environments. A sample of 99 pairs of identical twins reared apart, whose average age is 59 years, has been studied as part of the Swedish Adoption/Twin Study of Aging (SATSA). Hierarchical multiple regression was used to detect interactions between personality and environmental measures after the main effects of genotype and environment were removed. Analyses yield evidence for 11 significant interactions that provide the first evidence for GE interaction in human development using specific environmental measures. Thus, in addition to the main-effect contributions of heredity and environment, GE interactions contribute to individual differences in personality as measured in the second half of the life course.