Superior 'theory of mind' in borderline personality disorder: an analysis of interaction behavior in a virtual trust game.

To gain further insight into interpersonal dysfunction in Borderline Personality Disorder (BPD) we investigated the effects of emotional cues and the fairness of a social partner on the ability to infer other peoples' intentions in a virtual social exchange. 30 BPD patients and 30 nonpatients were asked to play a multiround trust game with four virtual trustees. The trustees varied in regard to fairness and presence of emotional facial cues which were both linked to repayment ratio. BPD patients adjusted their investment to the fairness of their partner. In contrast, nonpatients disregarded the trustees' fairness in the presence of emotional facial expressions. Both groups performed equally in an emotion recognition task and assessed the trustees' fairness comparably. When the unfair trustee provided emotional cues, BPD patients assessed their own behavior as more fair, while the lack of cues led patients to assess their own behavior as unfair. BPD patients are superior in the attribution of mental states to interaction partners when emotional cues are present. While the emotional expressions of a partner dominated the exchange behavior in nonpatients, BPD patients used the objective fairness of their social counterparts to guide their own behavior despite the existence of emotional cues.