Handedness distribution in a nonspeaking population with mental retardation.

Fifty nonspeaking or minimally speaking subjects with moderate, severe, or profound mental retardation underwent evaluation of handedness. Results confirmed previously reported increased prevalence of non-right handedness and the occurrence of a large subtype of ambiguous handedness. Results suggest that incidence of atypical hand preference is not closely linked to level of cognitive impairment, especially as represented by significant speech-language impairment in this population, as has been previously hypothesized. Atypical handedness of persons with mental retardation probably depends on language organization, and there is little support for the view that such subtypes represent bilateral hemispheric damage.