At the crossroads of the biological sciences and computer science, the brain/ computer metaphor that has prevailed for more than fifty years in neuroscience has led to the consideration of isolated individuals without taking into account their social interactions. The neuro-imaging technique called hyperscanning now allows us to record the behaviour and brain activity of multiple participants simultaneously and thus, finally, study social interaction in a spontaneous, reciprocal context. Human interaction is then apprehended in a holistic way, by considering two individuals as a single system, and observing behaviour as well as brain activities. These methodological and theoretical developments have demonstrated that interacting with others is fundamentally different from passive social perception. These results therefore invite us to consider more broadly interactional dimensions in neuroscience work, as well as the complementarity between the dynamics of our social interactions and our biological grounding.