Language and memory in Williams syndrome

Brock, J., (2002). Language and memory in Williams syndrome. Unpublished PhD thesis, University of Warwick. PDF

Thesis submitted for the degree of Doctor of Philosophy, Department of Psychology, University of Warwick, July 2002.

This thesis investigated the relationship between language, memory, and temporal processing abilities in Williams syndrome (WS). Despite mild to moderate mental retardation, there is evidence that individuals with WS have relatively spared language abilities and, in particular, that their receptive vocabulary increases at a rate faster than that predicted by overall abilities. However, it has also been suggested that semantic processing is impaired in WS and that individuals with WS have relative difficulty learning the meanings of words.

In Experiments 1 and 2, the performance of children with WS on temporal discrimination tasks was comparable with that of typically developing (TD) children and children with moderate learning disabilities (MLD) matched on vocabulary. However, there was little evidence to support the idea that temporal discrimination mechanisms contribute to language abilities.

Experiments 3, 4, 5, 6, and 7 investigated short-term memory abilities. Contrary to previous findings, there was no evidence for a reduced influence of lexical-semantic knowledge on STM in WS. Children with WS and TD and MLD controls matched on vocabulary showed equivalent effects of lexicality, word-frequency, concreteness, and wordlikeness, and similar tendencies to lexicalize nonwords. Overall performance in the WS group was generally worse than that of TD controls, but was comparable with that of MLD children matched on chronological age. This group difference was accounted for by differences in order memory, suggesting that serial order mechanisms may influence the rate of vocabulary acquisition.

Experiments 8 and 9 investigated free recall. Contrary to previous findings, children with WS and TD controls showed no evidence of a primacy effect in a standard free recall task, but both groups showed significant primacy effects when taught to rehearse.

Overall, therefore, children with WS showed a normal relationship between language and memory abilities. Implications for theoretical accounts of language in WS are discussed.