This is the unspecified version of the paper.This version of the publication may differ from the final published version. Few investigations into the executive function (EF) skills of these groups have examined the effect of verbal/visuospatial task type on performance. Analogous verbal and visuospatial measures were administered to these populations within four EF domains: executive-loaded working memory (ELWM), inhibition, fluency and set-shifting. Performance in both groups was compared to that of typically-developing (TD) children using regression techniques controlling for potentially influential cognitive/developmental factors. Individuals with WS showed the expected relative visuospatial difficulties, as indicated by poorer performance than TD individuals, on tests of ELWM and fluency. Individuals with DS displayed the expected relative verbal difficulty in the domain of set-shifting. In addition, each population showed pervasive deficits across modality in one domain; ELWM for individuals with DS, and inhibition for individuals with WS. Individuals with WS and DS showed EF difficulties in comparison to a TD group, but, their executive performance was affected by EF task type (verbal/visuospatial) and EF domain in different ways. While the findings indicated that EF in these populations is characterised by a range of specific strengths and weaknesses, it was also suggested that the relative verbal/visuospatial strengths associated with each population do not consistently manifest across EF domains. Lastly, syndrome specificity was indicated by the differences in groups' performance patterns.
Permanent repository linkKeywords: Williams syndrome, Down syndrome, executive function.
INTRODUCTION
Cognitive profiles associated with Williams and Down syndromesThe genetic conditions Williams syndrome (WS) and Down syndrome (DS) are characterised by roughly opposing ability profiles. Individuals with WS display relative verbal strengths alongside impairments on visuospatial tasks (Bellugi, Korenberg, & Klima, 2001;Pani, Mervis, & Robinson, 1999), particularly those involving a constructive element (Hoffman, Landau, & Pagani, 2003). Saccadic abnormalities (Brown et al., 2003;van der Geest, et al., 2004), and problems with location encoding (Farran & Jarrold, 2005), as well as the perceptual grouping of elements (Farran, 2005), have all been suggested as contributory factors with regard to these spatial difficulties, while vulnerability of the dorsal stream -a brain region thought to mediate the processing of spatial location and movement (Milner & Goodale, 1995) -has been implicated at the neurological level (e.g. Atkinson et al., 2003;Galaburda & Bellugi, 2000 Alberti, & Vianello, 2010;Porter, Coltheart, & Langdon, 2007;Rhodes, Riby, Park, Fraser, & Campbell, 2010). However, studies have not generally acknowledged verbal/visuospatial task modality as a potential contributing influence. This is surprising when the ability profiles associated with each population are considered. Furthermore, EF performance has been...