Social Surprises and Feedback Shape Momentary Mood and Anxiety in Humans

Social interactions strongly influence human affect, but the mechanisms linking them to momentary mood and anxiety remain unclear. Building on work showing that reward prediction errors (PEs) shape mood, we extend this framework to the social domain. In a preregistered study, 185 participants (ages 14–45) completed a novel task involving serial social interactions. We compared computational models to test how social feedback, expectations, and PEs related to momentary affect. Results showed that social feedback and PEs best explained affective fluctuations. Social PEs predicted anxiety more strongly than social feedback; the opposite pattern was observed for mood. Further analyses indicated that higher social anxiety symptoms heightened affective responses to social feedback, whereas depressive symptoms increased sensitivity to negative PEs for mood and to social feedback for anxiety. These findings provide a computational account of social affective dynamics across development and highlight novel opportunities for potential risk markers and treatment targets.