36. Waldman, I. D., DeFries, J. C., & Fulker, D. W. (1992) Quantitative genetic analysis of IQ development in young children: Multivariate multiple regression with orthogonal polynomials. Behavior Genetics, 22, 229-238.

The study of psychological development has recently benefited from innovative methods for estimating and examining individual growth curves. These methods are consistent with conceptualizing development as an ongoing process rather than as discrete changes. Recent developmental behavior genetic models have focused on continuity and change in the genetic and environmental influences underlying phenotypes. In contrast, presented is a model for phenotypic development per se. The results suggested familial environmental influences on children's mean IQ for ages 1-4 but environmental influences specific to fathers' cognitive ability on children's IQ development.