Sex, brains, hands, and spatial cognition

The literature that investigates the joint effects of sex, handedness, familial handedness, and spatial experience on the performance of spatial tasks shows numerous significant interactions, but the results are difficult to interpret. Casey has proposed a model that incorporates the biological notion of a ''genetic right-shift factor'' and participation in visual-spatial activities to produce systematic differences in spatial performance. This model has many strengths including the specific nature of its predictions that have been supported empirically across several different studies and the melding of biological propensities and experience. However, many of the basic assumptions rest on shaky ground, and there is a body of contradictory evidence that still remains to be explained. (C) 1996 Academic Press, Inc.