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We describe language acquisition in two distinct genetically based syndromes. Parents of children with Williams syndrome (WMS) and Down syndrome (DNS) were given the MacArthur Communicative Development Inventory (CDI), a parental report measure of child language development. Although both groups of children were found to be equally delayed according to normative standards, differential patterns of language acquisition emerged. Early in language development, the groups were differentiated primarily by a proclivity for gesture production by the children with DNS. Later in language development, the groups were cleaved by grammatical development: Children with WMS displayed a significant advantage over children with DNS. These findings are striking given the marked differences observed between adolescents and adults with WMS and DNS: Individuals with WMS exhibit linguistic skills superior to those of matched DNS controls despite significant but comparable cognitive deficits.
Harris et al. (Wed,) studied this question.