Sense of agency and intentional binding in joint action.

Understanding the sense of agency is a key challenge for the psychological and brain sciences. When an individual makes an action that is followed by an effect such as an auditory tone, there is a perceived compression in time of the interval between the action and the effect. Since this only occurs for intentional actions, this compression is termed 'intentional binding' and has been suggested as an implicit measure of agency. Very little is known about how the sense of agency and indeed intentional binding may be altered in joint action contexts in which two individuals act and an effect occurs. Here, we assessed the subjective sense of agency via self-report and implicit agency via intentional binding in a joint action task in which one person initiated a movement which another person joined in with. We further manipulated whether both individuals knew who the initiator would be ahead of time (by assigning one person as the initiator at the start of a block of trials) or whether this became apparent in a dynamic fashion based on who acted first. In both settings, only the initiator reported reliable subjective feelings of agency, whereas both the initiator and the responder demonstrated significant and indistinguishable intentional binding. We suggest that, when two individuals are involved in a joint action context, there is an automatic formation of a new agentic identity (a 'we' identity). In such contexts, both partners register agency at the pre-reflective level, despite the fact that their subjective experience of agency differs, and indeed, their role in producing the outcome differs. Hence, the subjective sense of agency and intentional binding are dissociable, and it remains for future work to understand how pre-reflective agency 'registration' and the reflective 'experience' of agency are, if at all, related.