Altered social decision making in borderline personality disorder: an Ultimatum Game study

The authors examined social decision-making strategies in borderline personality disorder (BPD) using the Ultimatum Game (UG). They sought to extend previous findings by investigating altruistic punishment, a behavior that increases group cooperation in the long term. They tested the effect of the proposer's facial expression on responses. BPD patients (n = 47) and healthy controls (n = 43) played the responder's role in a series of computerized UG interactions, with proposers expressing positive or negative emotions. BPD patients accepted unfair offers at a higher rate compared to controls. The effect of facial expression differed in the two groups, as positive expressions increased the acceptance likelihood in the control group at stakes from 20:80 to 50:50. In the BPD group, this effect was observed only at higher stakes (40:60 and 50:50). These results suggest that BPD patients exhibit altruistic punishment to a lesser extent and are less influenced by their partners' emotional expression in the UG.