ON SEX, HANDS, HANDEDNESS, HANDWRITING POSITION, FAMILIAL HANDEDNESS, AND THE CEREBRAL LATERALIZATION OF LANGUAGE IN MONOLINGUALS AND BILINGUALS

The cerebral lateralization of language was investigated in a group of two hundred sixty monolinguals and ninety-four bilinguals by means of a concurrent-tasks, verbal-manual interference paradigm. The results show that left-handed and right-handed monolinguals have very different lateralization profiles. As a group, right-handed males and females were left hemisphere dominant for speech, but left-handed males were right hemisphere dominant, and left-handed females showed no hemispheric dominance. A relationship was also observed between the speed of finger tapping without concurrent speech (control tapping) and language lateralization. Fast tappers were left hemisphere language dominant, but slow tappers displayed a trend toward right hemisphere language dominance. Furthermore, whether an individual tapped much faster with one hand than the other during control tapping was related to language lateralization. Left handers with highly asymmetrical control tapping were right hemisphere language dominant, and right handers with highly asymetrical control tapping were left hemisphere dominant.However, left handers and right handers with fairly symmetrical control tapping showed no hemispheric dominance for language. Familial handedness and handwriting position were found to be unrelated to cerebral language lateralization.;These results suggest that strong relationships exist between cerebral language lateralization and an individual's gender, handedness, and manual performance. These findings have important implications for theories of cerebral language development and organization.;As was the case with the right-handed monolinguals, right-handed bilingual males and females were left hemisphere dominant for their first language. However, unlike the left-handed monolinguals, the left-handed bilingual females were right hemisphere dominant in their first language, and the left-handed bilingual males showed only a trend toward right hemisphere lateralization. The most important finding among the bilinguals was the gender difference in the lateralization of the second language. Bilingual males revealed comparable first and second language lateralization patterns. However, both left-handed and right-handed bilingual females had asymmetrical first language lateralization, but symmetrical, bilateral second language lateralization.