Covariation among measures of cognitive ability and academic achievement in the Colorado Adoption Project: Sibling analysis

Although correlations among measures of cognitive ability and academic achievement are substantial, relatively little is known about the etiology of their interrelationships. The purpose of the current study was to assess the etiology of these relationships by applying the methods of multivariate be...

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Bibliographic Details
Published in:Personality and individual differences 1995, Vol.18 (1), p.63-73
Main Authors: Wadsworth, S.J., DeFries, J.C., Fulker, D.W., Plomin, R.
Format: Article
Language:English
Subjects:
Achievement
Cognitive abilities
Covariance analysis
Siblings
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Summary:Although correlations among measures of cognitive ability and academic achievement are substantial, relatively little is known about the etiology of their interrelationships. The purpose of the current study was to assess the etiology of these relationships by applying the methods of multivariate behavioral genetic analysis to sibling data from the Colorado Adoption Project. The current study analyzed data from 100 pairs of related siblings and 90 pairs of unrelated siblings tested at age 7 on two measures of cognitive ability (verbal comprehension and perceptual organization) and two measures of academic achievement (reading recognition and mathematics achievement). Phenotypic correlations among the cognitive and achievement measures averaged about 0.30. Although a substantial proportion of the covariation among the measures was due to influences shared with verbal ability, results of fitting a Cholesky factor model to the data provided evidence for significant covariation between the achievement measures that was independent of cognitive ability. Results of the genetic analysis confirmed previous findings of substantial genetic influence, with heritabilities ranging from 0.21 for mathematics achievement to 0.60 for perceptual organization. The environmental variance was primarily due to nonshared influences specific to each of the measures, with shared environmental influences being nonsignificant. In addition, genetic influences accounted for most of the phenotypic covariance among the variables, with much of the genetic covariation being due to influences shared with verbal ability.
ISSN:0191-8869
1873-3549
DOI:10.1016/0191-8869(94)00112-6