Factorial structure of the Waterloo Handedness Questionnaire for control and learning-disabled adults.

This study examined the factorial structure of the 32-item version of the Waterloo Handedness Questionnaire (Steenhuis & Bryden, 1989) with a sample of control (n = 325) and learning-disabled (LD) (n = 147) subjects. On the basis of Principal Components Analyses, we have replicated the work of Steenhuis and Bryden (1989) who suggested that hand preference factors for control subjects are multifactorial in nature and are related more to "skilled" and "less skilled" activities rather than on distal/proximal musculature. Further, we have found that the factor structure for hand preference in LD adults is somewhat different than of normally achieving adults. The primary difference occurred within Factor 2. Unlike control subjects, whose Factor 2 items were classified as "less skilled" and preference was less lateralized, items loading on this factor for LD subjects were classified as "skilled" and showed strongly lateralized responses for both left and right handers. Presumably, LD adults show a less marked distinction between "skilled" and "less skilled" unimanual motor activities than control subjects suggesting different degrees of manual laterality between the groups.