Handedness in mental retardation.

Mentally retarded and age-matched normal controls with no history of parental sinistrality were examined for their handedness with the Waterloo Handedness Questionnaire (Singh & Bryden, 1994). Normal controls showed a clear rightward bias, with the effect being significantly higher for skilled as compared to unskilled hand items. Mentally retarded subjects showed mixed handedness with a nonsignificant difference in performance between skilled and unskilled hand items.