The Experimenting Society

Abstract

We present empirical tests of the stability of individual differences over the lifespan using a novel methodological technique to combine behavior-genetic data from twin dyads with longitudinal measures of life history-related traits (including health and personality) from non-twin samples. Using data from The Midlife in the United States (MIDUS) Longitudinal Survey, we constructed a series of "hybrid" models that permitted the estimation of both temporal stability parameters and behavior-genetic variance components to determine the contributions of genetic and environmental influences on individual differences. Our results indicate that changes in a higher-order factor of life history strategy (Super-K, composed of the K-Factor, Covitality, and Personality) over the study period were very small in magnitude and that this temporal stability is under a considerable degree of shared genetic influence and a substantial degree of non-shared environmental influence, but a statistically non-significant degree of shared environmental influence. Implications and future directions are discussed.