Longitudinal stability of cognitive ability in the Colorado Adoption Project

Measures of general cognitive ability in 1- and 2-year-old adopted and nonadopted infants and their parents were subjected to path analysis to estimate the contribution of genetic and environmental factors to short-term stability. Although significant genetic influences were found at both 1 and 2 years of age, no significant environmental influences shared by parents and children were observed at these ages. Short-term stability of mental ability between the 2 ages was relatively independent of both between-family genetic and environmental influences. However, genetic factors may contribute importantly to long-term stability.