Abstract
Social life requires people to predict the future: people must anticipate others' thoughts, feelings, and actions to interact with them successfully. The theory of predictive coding suggests that the social brain may meet this need by automatically predicting others' social futures. If so, when representing others' current mental state, the brain should already start representing their future states. To test this hypothesis, we used fMRI to measure female and male human participants' neural representations of mental states. Representational similarity analysis revealed that neural patterns associated with mental states currently under consideration resembled patterns of likely future states more so than patterns of unlikely future states. This effect manifested in activity across the social brain network and in medial prefrontal cortex in particular. Repetition suppression analysis also supported the social predictive coding hypothesis: considering mental states presented in predictable sequences reduced activity in the precuneus relative to unpredictable sequences. In addition to demonstrating that the brain makes automatic predictions of others' social futures, the results also demonstrate that the brain leverages a 3D representational space to make these predictions. Proximity between mental states on the psychological dimensions of rationality, social impact, and valence explained much of the association between state-specific neural pattern similarity and state transition likelihood. Together, these findings suggest that the way the brain represents the social present gives people an automatic glimpse of the social future.SIGNIFICANCE STATEMENT When you see a ball in flight, your brain calculates, not just its static visual features such as size and shape, but also predicts its future trajectory. Here, we investigated whether the same might hold true in the social world: when we see someone flying into a rage, does our brain automatically predict their social trajectory? In this study, we scanned participants' brain activity while they judged others' mental states. We found that neural activity associated with a given state resembled activity associated with likely future states. Additionally, unpredictable sequences of states evoked more brain activity than predictable sequences, consistent with monitoring for, and updating from, prediction errors. These results suggest that the social brain automatically predicts others' future mental states.