Studies investigating executive functioning (EF) - namely skills involving higher-order cognitive activity and/or the concurrent storage and processing of material – in individuals with Williams syndrome (WS) and Down syndrome (DS) – have not generally treated task modality (verbal vs. visuospatial) as a meaningful factor. This is surprising, given the respective ability profiles which with the two conditions have been associated. Individuals with WS display relative verbal strengths, along with visuospatial processing difficulties, while individuals with DS are often reported to display verbal difficulties more marked than their overall, or non-verbal, levels of cognitive functioning would suggest. Of the studies which have treated task modality as a meaningful factor, very few have examined skills in more than one EF domain, and none have compared individuals from either population with any other specific diagnostic group, rendering difficult considerations of whether performance patterns are syndrome-specific. The principal aim of this thesis was thus to specify the finer-grained nature of EF skills in both populations, across a wider range of EF domains than previously employed. Another aim was to better enable a consideration of the syndrome specifity of each group‟s performance, by including both populations. Four empirical research studies were undertaken. In each, children and adolescents with WS and DS were presented with an analogous verbal and visuospatial task pair, within a specific EF domain; executive-loaded working memory (ELWM), inhibition, fluency and switching respectively. The two groups were compared to typically-developing (TD) children using regression 2 techniques controlling for factors which may influence executive performance. The hypotheses were a) that individuals with WS would show relative verbal EF strengths, as indicated by comparison to the TD group, with weaker performance on the corresponding visuospatial measures, b) that individuals with DS would show relative visuospatial EF strengths, as indexed in the same way, and c) that syndrome specifity would be indicated by differences between the performance patterns of each group. Findings across the four studies were mixed. Individuals with WS showed expected relative verbal strengths with regard to both ELWM and fluency. However, verbal and visuospatial inhibitory difficulties, as well as a relative verbal switching weakness, were also observed. Individuals with DS displayed the expected relative visuospatial strength on the switching task. However, no effect of task modality was found for inhibition and fluency in this group, while difficulties were observed across both verbal and visuospatial ELWM tasks. A preliminary indication of syndrome specificity was offered by the differing patterns displayed by the two groups, across EF domains. These findings are discussed in terms of their implications for a more multi-faceted understanding of the respective EF profiles of individuals with WS and DS, which attempts to account for the effect of task modality across a number of EF domains
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:570869 |
| Date | January 2011 |
| Creators | Carney, Daniel P. J. |
| Publisher | London South Bank University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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