Messer, David; Dockrell, Julie; Parmigiani, Charlotte and Karmiloff-Smith, Annette
Speeded naming, frequency and the development of the lexicon in Williams syndrome.
Language and Cognitive Processes, 21
Atypical vocabulary has been reported as one of the most notable features of the language of adolescents and adults with Williams syndrome (WS), including use of unusual or low frequency words. Two hypotheses were identified regarding the developmental origins of this phenomenon. The intra-lexicon hypothesis views the cause in terms of domain-specific anomalies of structure or activation dynamics in the WS lexicon. The extra-lexicon hypothesis views the cause in terms of pragmatic influences, whereby individuals with WS use social engagement devices in their language in service of their “hyper-social” profile (Jones et al., 2000), and domain-general deficits to lexical-semantic representations in line with the level of learning disability present in WS. The hypotheses were evaluated using a speeded picture-naming task, in which frequency and semantic category were manipulated as implicit variables. The performance of 16 adolescents and adults with WS was compared with two individually matched control groups, one matched on chronological age (CA) and the other on receptive vocabulary age (RVA). Developmental trajectories were also constructed to assess the relationship between performance and age. Results indicated slower and less accurate naming in the WS group compared with both CA and RVA groups, but frequency and semantic category effects in line with the RVA group. Trajectories were delayed but not atypical. The data support a normal encoding of word frequency (rarity) in the WS lexicon, with rare-word usage explained as a pragmatic aspect of the WS social profile. The finding sets bounds on the domain-specificity of the complex developmental pathway between atypical genotype and atypical phenotype in WS. [ABSTRACT FROM AUTHOR]
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