Memories of hand movements are tied to speech through learning

Hand movements frequently occur with speech. The extent to which the memories that guide co-speech hand movements are tied to the speech they occur with is unclear. Here, we paired the acquisition of a new hand movement with speech. Thirty participants adapted a ballistic hand movement of a joystick to a visuomotor rotation either in isolation or while producing a word in time with their movements. Within participants, the after-effect of adaptation (i.e., the motor memory) was examined with or without co-incident speech. After-effects were greater for hand movements produced in the context in which adaptation occurred - i.e., with or without speech. In a second experiment, 30 new participants adapted a hand movement while saying the words "tap" or "hit". After-effects were greater when hand movements occurred with the specific word produced during adaptation. The results demonstrate that memories of co-speech hand movements are partially tied to the speech they are learned with. The findings have implications for theories of sensorimotor control and our understanding of the relationship between gestures, speech and meaning.