Interhemispheric processing in left- and right-handers

Inter- and intrahemispheric processing for left- and right-handers were compared in two experiments. In one, subjects performed a digit-matching task and in the other they decided if two letters were part of a previously presented word. On some trials the matching items were presented initially only to one hemisphere (within-hemisphere trials), and hence the match decision could be reached by a hemisphere in isolation. On other trials, one item of the match pair was presented to each hemisphere (across-hemisphere trials), requiring interhemispheric interaction for the match decision. Patterns of performance on within-as compared to across-hemisphere trials were identical for the two handedness groups in both experiments. Furthermore, individual characteristics of subjects such as their hand posture, sex and family history of left-handedness did not affect the pattern of performance. These results suggest that interhemispheric processing may not differ between right- and left-handers.