Connection between movements of mouth and hand: Perspectives on development and evolution of speech.
Mounting evidence shows interaction between manipulative hand movements and movements of tongue, lips and mouth in a vocal and non-vocal context. The current article reviews this evidence and discusses its contribution to perspectives of development and evolution of speech. In particular, the article aims to present novel insight on how processes controlling the two primary grasp components of manipulative hand movements, the precision and power grip, might be systematically connected to motor processes involved in producing certain articulatory gestures. This view assumes that due to these motor overlaps between grasping and articulation, development of these grip types in infancy can facilitate development of specific articulatory gestures. In addition, the hand-mouth connections might have even boosted the evolution of some articulatory gestures. This account also proposes that some semantic sound-symbolic pairings between a speech sound and a referent concept might be partially based on these hand-mouth interactions.