Failure to confirm a spatial ability impairment in persons with evidence of right hemisphere speech capability.

Levy hypothesized that persons lacking strict left hemispheric dominance for language processing should be impaired in spatial processing ability. This leads to the expectation that left-handers, because they are more often not strictly left hemisphere dominant for language, would, as a group, be impaired in spatial ability relative to right-handers. Evidence regarding this hypothesis has been inconsistent. The present study systematically examined the effects of handedness, sex, and hemispheric language dominance on verbal and spatial ability in 80 right-handed and 71 left-handed university students. Males were found to be superior to females in all handedness-hemispheric language dominance groups on the spatial ability measure. No effects of handedness or hemispheric lanaguage dominance nor interactions of these factors obtained for either verbal or spatial ability measures. It was concluded that the hypothesis of verbal-spatial processing incompatibility within the same hemisphere was not supported.