Inhibition in individuals with Williams syndrome and neurotypical children

Individuals with Williams syndrome may experience challenges in executive function relative to neurotypical individuals, including inhibition. However, previous studies have reported conflicting findings on the extent of these differences. This may partially reflect a failure to account for the effects of working memory on inhibition task performance. This study, therefore, examined the extent of any differences in inhibition between individuals with Williams syndrome and neurotypical children, while investigating whether such differences are moderated by concurrent working memory load and individuals’ general mental ability level. Performance was examined on novel Go/No-go and colour-word Stroop tasks that varied in inhibition and memory loads in individuals with Williams syndrome (N = 24) and a comparison sample of neurotypical children (N = 82) of broadly equivalent verbal ability. Bayesian analysis revealed a meaningful difference between the participant groups on Go/No-go sensitivity scores (d′), with participants with Williams syndrome showing generally poorer sensitivity. 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, many of these previously meaningful group differences in task performance were removed after accounting for sample differences in non-verbal ability or word reading speed. These findings indicate that inhibition is not entirely preserved in Williams syndrome. However, performance was broadly consistent with individuals’ measured intellectual capabilities. It would therefore be premature to conclude that inhibition is a fundamental weakness within executive function for individuals with Williams syndrome, and, of course, individual differences occur.