Examples

The single-trial Prisoner's Dilemma, discussed in Entry #5, is defined by the conflict between self-interest (“me”) and joint interest (“we”). An individual is always better off choosing a noncooperative option, irrespective of the partner's behavior, even though the cooperative choice is preferable from a dyadic standpoint. Choices in the “classic” case of the single-trial Prisoner's Dilemma, involving simultaneous and irrevocable choice (as in the story from which the situation takes its name), are unlikely to be influenced by past interactions or future goals. In contrast, in Iterated Prisoner's Dilemmas, behavior is likely to be affected by prior interactions and considerations regarding future interactions with the partner. This is true even when the choices at each point are simultaneous and irrevocable. The persons become able to react contingently to each other's prior behaviors and, therefore, to develop strategies for influencing each other's behavior. For example, a person is unlikely to prepare extensively for a joint working meeting if she knows that her colleague has repeatedly slacked off before in past meetings. On the other hand, a person may devote greater time and effort preparing for a joint task when anticipating future shared endeavors in order to motivate the other to enhance her performance in the future.

Iterated Prisoner's Dilemmas are common in everyday life (and are considerably more common than the single-trial Prisoner's Dilemma).