Bishop, E.G., Cherny, S.S., Corley, R., Plomin, R., DeFries, J.C., & Hewitt, J.K. (2003). Developmental genetic analysis of general cognitive ability from 1 to 12 years in a sample of adoptees, biological siblings, and twins. Intelligence, 31, 31-49.

Research in childhood suggests that heritability increases and shared environmental influence decreases, that genetic factors contribute to change as well as continuity, and that nonshared environmental influence contributes entirely to change. Longitudinal model fitting using data from the CAP and LTS supported these hypotheses with two exceptions. Nonshared environmental influences contribute to continuity as well as change in middle childhood. The most striking exception is that during the transition to adolescence, genetic factors no longer contribute to change, just to continuity.