Automatic Imitation of Multiple Agents: Simultaneous or Random Representation?
Research has shown that the observation of another’s movement activates the corresponding motor representation in the observer. However, it is largely unknown how activation of these shared representations is influenced by the number of observed agents. In recent work, we have studied automatic imitation while participants saw 2 hands of which either one hand or both hands made a movement. These studies found that 2 hands produced a stronger imitative response than a single hand when the hands made an identical movement but not when they made different movements. It was argued that identical movements were mapped onto the same motor representation and therefore produced a stronger motor response. Nevertheless, an alternative explanation is that participants randomly represented 1 hand on each trial. The goal of the current study was to disentangle these 2 hypotheses. In Experiments 1 and 2, we replicate our results using a stimulus setup that made random sampling unlikely. In Experiment 3, we show that an additive effect was still present when attention was directed to 1 hand that always made a movement. Finally, in Experiment 4, we show that intentional imitation of 1 hand did not preclude automatic imitation of a second hand. Together, these findings support the hypothesis that the actions of multiple persons can be represented together in the motor system.