Cognitive abilities in the early school years: No effects of shared environment between parents and offspring

Abstract

From the little that is known about the genetic and environmental origins of individual differences in specific cognitive abilities in middle childhood, we predicted that verbal and spatial abilities but not perceptual speed and memory would show significant genetic influence at age 7. To test this hypothesis, specific cognitive abilities were compared for biological, adoptive, and nonadoptive parents and their 163 adopted and 142 nonadopted children tested at age 7 as part of the longitudinal Colorado Adoption Project. Model-fitting analyses support the hypothesis of significant genetic influence on verbal and spatial abilities but not on perceptual speed and memory. These results imply the existence of some genetic continuity from the early school years to adulthood for verbal and spatial abilities. In addition, genetic influence of parents on their children appears to increase from early childhood to middle childhood, accounting for about 25% of the variance of verbal and spatial abilities at age 7. In contrast, environmental resemblance between parents and offspring is nonsignificant for all four specific cognitive abilities as well as for a composite score representing general cognitive ability. Such shared environmental influence between parent and child accounts for less than 1% of the variance at age 7.