This article compared the language profiles of adolescents with Down syndrome (DS) and children with specific language impairment matched for nonverbal cognitive ability, and investigated whether similar relationships could be established between language measures and other capacities in both groups. Language profiles were very similar: Expressive language was more affected than language comprehension, and grammar was more affected than vocabulary in both domains. Both groups were impaired on tests of grammatical morphology and phonological memory. There were some differences between the groups, but these could be attributed to other features of development of people with DS.

Despite earlier reports that emphasize a strong social interest and empathy, this study suggests that individuals with Williams syndrome have pragmatic language impairments, poor social relationships and restricted interests. Far from representing the polar opposite of autism, as suggested by some researchers, Williams syndrome would seem to share many of the characteristics of autistic disorder.

Relationships among the processes involved in language and memory development in Down syndrome may be similar to those established for typical development.

Their focal colour memory was significantly related to digit span, but only Corsi span was related to focal colour memory in the group with Down syndrome.

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