Inhibition in individuals with Williams syndrome and neurotypical children

Individuals with Williams syndrome have been reported to experience challenges with executive functioning relative to neurotypical individuals, particularly in inhibition. However, previous studies have produced conflicting findings on the extent of differences between these two groups which might reflect a failure to deconfound inhibition and working memory effects on performance. This study assessed this issue by examining performance on novel Go/No-go and colour-word Stroop tasks that varied in inhibitory and memory loads in individuals with Williams syndrome (N = 24) and a large comparison sample of neurotypical children (N = 82). Bayesian analysis showed a meaningful difference between the participant groups on Go/No-go sensitivity scores (D’): participants with Williams syndrome showed poorer sensitivity on all conditions, with the exception of a high memory and high inhibition condition where they outperformed the comparison group. On the Stroop task, individuals with Williams syndrome were slower and less accurate than the comparison group, particularly on high memory and high inhibition conditions. However, accounting for sample differences in non-verbal ability, or word reading speed, removed many previously meaningful group differences in task performance. While inhibitory control is therefore not entirely ‘intact’ in Williams syndrome, individuals’ performance was broadly consistent with other abilities measured in this study. It would therefore be premature to conclude that inhibition is a fundamental area of weakness within executive control for individuals with Williams syndrome.