A study was conducted to compare relationships with control subjects to individuals with borderline personality disorder (BPD).

55 participants with BPD and 38 healthy controls were told to interact between computers with investors and trustees. Investors started every 10-round game with $20 and could invest anywhere in between 0-20. If investors clicked a button it would send the investment offer and would automatically triple the amount, at which point the trustee decided how much to return. If the amount returned was less than the amount invested, the investor was likely to offer smaller amounts in future rounds, which signaled a breakdown in trust and cooperation in the relationship. Trustees could try to “coax” their investor partner by returning a large portion of the tripled investment, even when the offer was low.
Results found that trust and cooperation faltered over time in pairs that included a person with borderline personality disorder. Subjects with BPD behaved in ways that caused a breakdown in cooperation with their healthy partners. Were half as likely as healthy trustees to try to repair the relationship through coaxing. Findings suggest that people with borderline personality disorder are not persuaded by rewards of money in the same ways as healthy people, or that they do not regard low investment offers as a violation of social norms. Also, people with BPD reported lower levels of trust in general, compared with healthy participants. This study offers a new way of studying and understanding interpersonal relationships and mental illnesses that impair social interactions.

Source: http://psychcentral.com/news/2008/08/19/borderline-personality-disorder-challenges-relationships/2779.html