Brain laterality: differences in cognitive style or motor function?

Two studies were completed to evaluate the role of motor function in the observable brain laterality of normal, familial, dextral males. A right-brain advantage was demonstrated on a figure-matching task and on a sequential-spatial task when subjects responded with a manual key press. A left-brain advantage for the same two tasks was demonstrated when subjects responded by compressing a microswitch embedded in a mouthpiece. The data suggest that both hemispheres of the brain may be capable of processing visuospatial stimuli but do not share the same facility for effecting appropriate motor responses. The results were discussed in terms of lateralized cognitive styles in brain and lateralized control of effector systems.