Motor simulation of multiple observed actions

Research has shown that observed actions are represented in the motor system, leading to automatic imitative responses. However, in social life, we often see multiple persons acting together. Here, we use an automatic imitation paradigm with four stimulus hands to investigate the hypothesis that multiple observed actions can be represented at the same time in the motor system. Experiments 1 and 2 revealed weaker automatic imitation when one hand performed a different action than the other three hands, compared with when three or four hands all performed the same action. Experiment 3 replicated this effect with mutually exclusive actions. These results show that multiple observed actions can be represented simultaneously in the motor system, even when they cannot be executed together. This has important implications for theories of interaction representation.