Contrasting patterns of cognitive abilities of 9-and 10-year-olds with Williams syndrome or Down syndrome

Comparative cognitive strengths and weaknesses of 9- and 10-year-old children with Williams syndrome or Down syndrome were examined. From an original sample of 21 children with Williams syndrome and 25 children with Down syndrome, 13 pairs of children with Williams or Down syndrome were individually matched for chronological age and total points earned on the McCarthy Scales of Children's Abilities (MSCA). All of the unmatched children with Williams syndrome earned more total points than any of the unmatched children with Down syndrome, suggesting that the general cognitive ability distributions for Williams syndrome and Down syndrome are not equivalent. Performance of the matched pairs of participants on both the MSCA (domain and subtest) and the Peabody Picture Vocabulary Test-Revised (PPVT-R) was contrasted. Participants with Williams syndrome showed comparative strengths in the Verbal and Memory domains, whereas children with Down syndrome showed a comparative strength in the Perceptual-Performance domain. Children with Williams syndrome showed subtest strengths indicating comparatively stronger verbal memory abilities, but no significant differences in performance on subtests measuring semantic abilities or on the PPVT-R were observed. Children with Down syndrome showed subtest strengths indicating comparatively stronger visuospatial constructive skills. Findings are discussed in relation to results of previous studies contrasting adolescents and young adults with Williams syndrome or Down syndrome.