Paired Prisoners' Dilemma

Students can be paired off and instructed to play several ver-sions of a particular game with a prisoners' dilemma structure.Provide each pair with a sheet describing the payoff tablefor the game and with space available to indicate the choicesmade by each player in each round and in each version ofthe game.

First, tell students that the game will end after a knownnumber of rounds, say 10. Have them play through 10 rounds,keeping track of their choices. Then have them play another10-round game, and a third if there is time. As with the dimegames, you should see convergence to the rollback equilibrium of always cheating within a few plays of the finite game;students who try to cooperate originally will lose out to cheat-ing rivals at the end of the game and will cheat earlier andearlier in each successive play of the game.

Second, try a version in which the students play a roundat a time without knowing when the game will end; you callout an end to the game after some number of minutes. Thisversion is similar to the Serendip version available on theweb (see URL above) except that the rival's strategy is not as predictable. In addition, there is uncertainty about howlong the game will last since it could be very short (unlikethe web version) or relatively long. You can do this severaltimes and ask the students to describe how their behaviorchanges in future plays of the game.

Each of these games gives the students the opportunity toexperience the actual play of a prisoners' dilemma. The dis-cussion that follows can be used to consider discrepanciesbetween predicted and actual behavior, changes in behaviorin later plays of the same game, how players update infor-mation about a rival's play, and other issues related to players'willingness to cooperate (including cultural norms, friendships,rivalries, etc.)