Hand movement asymmetry during speech: no effect of speaking topic.

Right-handed subjects were videotaped as they spoke on verbal, spatial and neutral topics and the frequencies of their spontaneous hand movements were analyzed. Although subjects made more free movement gestures during the spatial topics than during the other topics, there was a consistent level of right hand preference for free movements across topics. Self-touching movements showed no hand preference in any topic. The results suggest that free movements are generated by a left-hemisphere motor control system which exerts consistently greater influence over the right than the left hand regardless of the source of processing preceding activation of this system.