Associations between Cognitive Abilities and Scholastic Achievement: Genetic Overlap but Environmental Differences

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Abstract
Little is known about the genetic and environmental etiology of the association between specific cognitive abilities and scholastic achievement during the early school years. A multivariate genetic analysis of cognitive and achievement measures was conducted for 146 pairs of identical twins and 132 pairs of fraternal twins from 6 to 12 years of age. At the phenotypic level, measures of achievement were moderately correlated with specific cognitive abilities. A multivariate model including one general factor and specific factors in the genetic and environmental matrices indicated that the phenotypic relationship between achievement and cognition was mediated primarily by genetic influences. Genetic correlations among the cognitive and achievement tests ranged from .57 to .85, shared environment correlations were essentially zero, and specific environment correlations were low (.00 to .19). We conclude that there is substantial overlap between genetic effects on scholastic achievement and specific cognitive abilities. Performance on ability measures differs from that on achievement measures largely for environmental reasons.