Abstract
Interpersonal formulations are used to define, understand, and diagnose personality disorders. The accuracy of these formulations rests on a clear understanding of how those with personality pathology behave in interpersonal situations. To test these formulations, we conducted 4 experiments across 2 studies examining how participants with trait dependence and narcissism respond to predetermined strategies in an iterated prisoner's dilemma. These predetermined strategies were: always cooperate, cheat once then always cooperate (Study 1), always cheat, and cooperate once then always cheat (Study 2). Results indicated that trait dependency promoted cooperation, particularly against the cheat-once-then-always-cooperate strategy and in early interactions with the cooperate-once-then-always-cheat strategy. However, there was no evidence that trait narcissism reduces cooperation. Our results suggest a nuanced association between trait personality pathology and cooperation, which is influenced by others’ behavior over repeated interactions.