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Explanation:
The Prisoner’s Dilemma is a logical exercise where two players are given the choice to cooperate with or defect against one another. The highest score a player can receive is 5 points, which he earns when he defects while his opponent cooperates. In this scenario, his opponent receives no points. If both players defect, then each receives 1 point, and if both cooperate, they receive 3 points. The Iterated Prisoner’s Dilemma (IPD) repeats this exercise many times over, giving each player a chance to react to the choices of his opponent. This sets up the dilemma: in each isolated round, it’s in the best interest of the player to defect. But if this leads both players to repeatedly defect against each other, then they will both score fewer points than if they repeatedly cooperated with each other.

In this demonstration, you can pit different strategies of play against one another in a tournament. By setting the numbers next to the names of the different agent types, you control the composition of your IPD tournament. When you hit the Play button, every agent you chose plays the same number of rounds of the Prisoner’s Dilemma against every other agent. The table displays the total results from all of these matchups.

This demonstration is based on Robert Axelrod’s original IPD tournaments as well as Chris Cook’s own demo of the IPD. On Wikipedia, you can read more about the Prisoner’s Dilemma and the Evolution of Cooperation. You can also download Chris Cook’s IPD demo. It has several features that this demo doesn’t.

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