Variability and standardized test profiles in typically developing children and children with Williams Syndrome.

Williams Syndrome (WS) is a developmental disorder, which due to its specific cognitive profile, has been of interest to multidisciplinary research in order to study the pathways between cognition, brain, and genes. Previous studies investigating individual performance on cognitive tasks have reported large variability within the WS cognitive profile, which has encouraged the investigation of WS subgroups. The current study compared the variability in performance scores on five verbal and non-verbal standardized tests in 33 children with WS and in 33 typically developing (TD) children of a similar chronological age (CA). In contrast to previous studies, the current study did not find significant differences in variability in performance on British Picture Vocabulary scale, Test Reception of Grammar and Digit span Forward between WS and TD groups when CA was controlled for. However, there was significantly less variability in younger WS participants for performance scores on Pattern Construction compared to the TD group. In light of these results, methodological issues and the importance of taking CA into account in analyses will be discussed. ©2010 The British Psychological Society.