Predictive representation of other people's actions in joint action planning: an EEG study.

It has been postulated that when people engage in joint actions they form internal representations not only of their part of the joint task but of their co-actors' parts of the task as well. However, empirical evidence for this claim is scarce. By means of high-density electroencephalography, this study investigated whether one represents and simulates the action of an interaction partner when planning to perform a joint action. The results showed that joint action planning compared with individual action planning resulted in amplitude modulations of the frontal P3a and parietal P3b event-related potentials, which are associated with stimulus classification, updating of representations, and decision-making. Moreover, there was evidence for anticipatory motor simulation of the partner's action in the amplitude and peak latency of the late, motor part of the Contingent Negative Variation, which was correlated with joint action performance. Our results provide evidence that when people engage in joint tasks, they represent in advance each other's actions in order to facilitate coordination.