Social prediction errors and feedback shape momentary mood and anxiety: Moderation by social anxiety and depression symptoms.

Social interactions strongly influence mental wellbeing, yet 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), varying in social anxiety and depression symptoms, completed a 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, while social feedback predicted mood more strongly than social PEs. Critically, 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 potential risk markers and treatment targets.