Cerebral lateralization and handedness and their effects on verbal and spatial reasoning

Consistent and inconsistent left- and right-handed male subjects completed four tests each of verbal and spatial reasoning. They also participated in tachistoscopic measures of verbal and spatial lateralization--consonant-vowel-consonant recognition and dot enumeration, respectively. The consistent handedness groups displayed significantly more lateralized patterns of cerebral organization that the inconsistent handedness groups. Increased lateralization was associated with superior performance on measures of spatial reasoning, but not on measures of verbal reasoning. Results are interpreted in terms of a competition hypothesis. No differences were found between the handedness groups on either the verbal or spatial reasoning tests.