clip art image of prisoners dilemma

The Prisoner’s Dilemma (PD) and Iterated Prisoner’s Dilemma (IPD) have been a rich source of research material since the 1950s. However, the publication of Axelrod’s book in the 1980s was largely responsible for bring this research to the attention of other areas outside of game theory, including evolutionary computation, evolutionary biology, conflict resolution, networked computer systems and promoting cooperation between opposing countries. Despite the large literature base that now exists this is an ongoing area of research.

The Prisoner’s Dilemma: You and a friend have committed a crime and have been caught. You are being held in separate cells so that you cannot communicate with each other. You are both offered a deal by the police and you have to decide what to do independently. Essentially the deal is this.

  • If you confess and your partner denies taking part in the crime, you go free and your partner goes to prison for ten years.
  • If your partner confesses and you deny participating in the crime, you go to prison for ten years and your partner goes free.
  • If you both confess you will serve six years each.
  • If you both deny taking part in the crime, you both go to prison for six months.

What will you do?

Iterated Prisoner’s DilemmaIf two players play PD more than once in succession and they remember previous actions of their opponent and change their strategy accordingly, the game becomes an IPD. An IPD can be finite or infinite, definite or indefinite, and even noisy, spatial, evolutionary …