Assortative marriage for cognitive abilities.

One hundred and twenty-three spouse pairs gathered as part of a family study of the genetics of special abilities were examined on a battery of ability tests. Four principal components were interpreted after rotation: Spatial, Verbal, Perceptual Speed, and Memory. In addition, the first factor from a common factor analysis (unrotated) was taken as an estimate of g. Assortive marriage was measured by the spouse correlations on the test and factor scores. Three multiple regression models were designed to determine whether phenotypic convergence during marriage occurs and whether resemblance between spouses in cognitive ability is related to fertility. The following independent variables were partialed out in the models: (1) sex and age; (2) sex, age, and length of marriage; and (3) sex, age, and number of children. Model 1 (age and sex) accounted for part of the correlation between spouses on the spatial tests, the verbal tests and the spatial and general factors. The perceptual speed and memory tests and factors were largely unaffected by partialing out the independent variables. No evidence of phenotypic convergence over years of marriage or of a relationship between fertility and resemblance in abilities was found.