Gesturing has a larger impact on problem-solving than action, even when action is accompanied by words.

The coordination of speech with gesture elicits changes in speakers' problem-solving behavior beyond the changes elicited by the coordination of speech with action. Participants solved the Tower of Hanoi puzzle (TOH1); explained their solution using speech coordinated with either Gestures (Gesture+Talk) or Actions (Action+Talk), or demonstrated their solution using Actions alone (Action); then solved the puzzle again (TOH2). For some participants (Switch group), disk weights during TOH2 were reversed (smallest = heaviest). Only in the Gesture+Talk Switch group did performance worsen from TOH1 to TOH2 - for all other groups, performance improved. In the Gesture+Talk Switch group, more one-handed gestures about the smallest disk during the explanation hurt subsequent performance, compared to all other groups. These findings contradict the hypothesis that gesture affects thought by promoting the coordination of task-relevant hand movements with task-relevant speech, and lend support to the hypothesis that gesture grounds thought in action via its representational properties.