Abstract ↔ claims

¹This study investigated the neural mechanisms involved in feelings of interpersonal guilt and responsibility evoked by social decisions in humans. ²In two studies (one during fMRI), participants repeatedly chose between safe and risky monetary outcomes in social contexts. ³Across conditions, each participant chose for both themselves and a partner ( Social condition), or the partner chose for both themselves and the participant ( Partner condition), or the participant chose just for themselves ( Solo condition, control). ⁴If the risky option was chosen in the Social or Partner condition, participant and partner could each receive either the high or the low outcome of a lottery with 50% probability, independently of each other. ⁵Participants were shown the outcomes for themselves and for their partner on each trial and reported their momentary happiness every few trials. ⁶As expected, participant happiness decreased following both low lottery outcomes for themselves and for the partner. ⁷Crucially, happiness decreases following low outcomes for the partner were larger when the participant rather than their partner had made the choice, which fits an operational definition of guilt. ⁸This guilt effect was associated with BOLD signal increase in the left anterior insula. ⁹Connectivity between this region and the right inferior frontal gyrus varied depending on choice and experimental condition, suggesting that this part of prefrontal cortex is sensitive to guilt-related information during social choices. ¹⁰Variations in happiness were well explained by computational models based on participants’ and partners’ rewards and reward prediction errors. ¹¹A model-based analysis revealed a left superior temporal sulcus cluster that tracked partner reward prediction errors that followed participant choices. ¹²Our findings identify neural mechanisms of guilt and social responsibility during social decisions under risk.