Handing Over a Cube

Even though joint action is highly developed in humans, not much is known about motor control in physical joint‐action tasks. Here we investigated a physical handover task: one subject sequentially passed wooden cubes to another without communicating verbally. Temporal parameters such as reaction time decreased on a trial‐to‐trial basis, showing that the efficiency of the task is optimized on‐line by implicit negotiation between the partners. In contrast, the spatial position of the handover was found to be invariant and trial‐independent. Thus, our results suggest that physical joint‐action is guided by on‐line adaptation and a priori assumptions.