Increased prevalences of left-handedness and left-eye sighting dominance in individuals with Williams-Beuren syndrome.

Handedness and eye sighting dominance were assessed in a sample of 50 individuals (25 male, 25 female; aged 5-38 years) with Williams-Beuren syndrome (WBS). The prevalences of left-handedness and left-eyedness were compared to the normative prevalences in the general population. We found significantly higher prevalences of left-handedness and left-eyedness in the WBS sample. The higher prevalences were more salient in younger than in older individuals and in male than in female individuals. We suggest that the increased prevalence of left-handedness in WBS is a consequence of a slower maturation rate, which allows deviation from a predetermined laterality pattern.