Self-other distinction modulates the sense of self-agency during joint actions

In daily life interactions, we achieve goals with partners through tight temporal coordination or sequential joint efforts. Is our individual sense of control over shared outcomes (sense of self-agency) the same as the one experienced when we act alone? Do we explicitly and implicitly feel like we are fully in control of the motor act even if the goal is finally achieved by our partner? To address these questions, we measured explicit and implicit sense of self-agency in individual and (coordinated or sequential) interactive contexts. We studied 42 healthy adult participants during active/passive button presses aimed at turning on a light bulb. This goal could be achieved individually (Solo condition) or by interacting with a partner (Joint condition) synchronously (joint Coordination task) or sequentially (joint Sequential task). We collected trial-by-trial explicit judgments of self-agency. To quantify the intentional binding phenomenon, an index of implicit sense of agency, we also measured the perceived compression of the time interval between the active or passive movements and their outcomes. Explicit sense of agency: we observed decreased judgments of self-agency in Joint trials compared with the Solo ones in both the Coordination and Sequential tasks. Implicit sense of agency: in the Coordination task, we found a significant intentional binding effect only in Solo trials but not in Joint ones. For the Sequential task, however, a significant intentional binding was also present in the Joint condition. Our results indicate that the individual sense of agency is reduced during joint actions, yet this can be restored at an implicit level when the format of the motor interaction makes the individual contribution to goal achievement more obvious. We discuss these results considering current cognitive theories on motor awareness and interactions.