Handedness and language among the mentally retarded: implications for the model of pathological left-handedness and gender differences in hemispheric specialization.

The relationship between handedness and language was examined among 238 mentally retarded subjects representing the four DSM III classification ranges of mental retardation. Language ability was found to be significantly related to handedness, with an increased prevalence of left-handedness among those individuals with language deficits. In addition, both expressive and receptive language ability interacted with gender, with the main effects of each language variable being stronger for females than males. Although no main effects were found for severity of retardation, a significant interaction was found between severity and gender. Results support the model of pathological left-handedness and are discussed within the context of this theory, as well as with regard to gender differences in cerebral lateralization of language and cognitive functioning.