| Abstract: | Appraised cognitive patterning and development for 142 pairs of twins at 4, 5, and 6 yrs of age, based on their test scores on the Wechsler Preschool and Primary Scale of Intelligence. Compared with the singleton norms, the twins showed an initial lag at age 4, with Verbal IQ being somewhat more depressed than Performance IQ. By age 6, however, the twins had fully recovered their deficit on both scales and reached parity with singletons. Monozygotic twins displayed relatively high within-pair correlations for Verbal IQ and Performance IQ, and even higher correlations for Full Scale IQ. Dizygotic twins displayed moderate within-pair correlations for the IQ scores, and most were significantly lower than the monozygotic correlations. Further analysis showed that monozygotic twins were also significantly more concordant for the differences between Verbal IQ and Performance IQ, and for the patterning of the subtest scores. Measures of family socioeconomic status and parental education correlated .28-.32 with the twins' IQ at age 6. Results suggest that within a broad range of home environments, the genetic blueprint made a substantial contribution to cognitive patterning and development. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) |
