A unifying mechanism governing inter-brain neural relationship during social interactions

A key goal of social neuroscience is to understand the relationship between the neural activity of socially interacting individuals. Decades of research have focused on a single aspect of that relationship: the similarity in neural activity across brains. Here we instead asked how neural activity differs between brains, and how that difference evolves alongside activity patterns shared between brains. Applying this framework to pairs of bats engaged in spontaneous social interactions revealed two complementary phenomena characterizing the inter-brain neural relationship: fast "inter-brain catch-up" unfolding in parallel with slow activity covariation across brains. A model reproduced these observations, generated multiple predictions that we confirmed using experimental data, and provided testable hypotheses for studying the inter-brain relationship in larger social groups. Together, the data and model suggest a parsimonious computational mechanism--opposite feedback to neural activity components reflecting inter-brain difference and similarity--that unifies diverse aspects of the inter-brain neural relationship.