Covariation of mathematics achievement and general cognitive ability in twins

Although the phenotypic relationship between mathematics performance and ge neral cognitive ability has been well established, relatively few studies h ave attempted to examine the nature of this observed relationship. The purp ose of the present report was to assess the etiology of the covariation bet ween mathematics performance and general cognitive ability in data from a s ample of 555 twins selected for learning deficits (310 monozygotic [MZ] and 245 same-sex dizygotic [DZ] twin pairs) and from a sample of 570 control t win pairs (319 MZ and 251 same-sex DZ twins). Subtests of the Wide Range Ac hievement Test and the Peabody Individual Achievement Test were used as mea sures of mathematics performance, whereas the verbal IQ and performance IQ scores from the Wechsler Intelligence Scale for Children-Revised or Wechsle r Adult Intelligence Scale-Revised were used as measures of general cogniti ve ability. In both samples, results of fitting bivariate genetic structura l equation models to the data indicated that approximately 90% of the varia bility in a latent factor for math performance and 80% of that from general cognitive ability were due to genetic effects. In addition, almost 90% of the phenotypic correlation between math performance and general cognitive a bility was due to heritable influences in both samples. Thus, the phenotypi c relationship between mathematics performance and general cognitive abilit y latent factors is due primarily to genetic influences. (C) 2000 Society f or the Study of School Psychology. Published by Elsevier Science Ltd.