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Zenda: a Prisoners' Dilemma Game for the NeXT Computer a. This application was written by Hal Varian, with some assistance from Joseph Klein. The address for Hal Varian is given at the end of the file. b. Economics c. Zenda is an implementation of a Prisoners' Dilemma game for a network of NeXT computers. d. Zenda has been used for research to illustrate a way that "contracts" can be used to induce cooperation in class Prisoners' Dilemma games. It may also be useful in the classroom. e. Zenda was developed under NeXTstep 2.1, but it should also run on 3.0. f. The file Referee.rtf tells how to install Zenda. The file Player.rtf should be given to the players as instructions. The first stage of Zenda is a classic Prisoners' Dilemma. Human subjects do pretty much as the theory predicts---after 6 or 7 rounds most people play the "defect" strategy. The twist on the classic Prisoners' Dilemma comes in the second stage of Zenda, where I offer the "pay for play" option. The subgame perfect equilibrium of this two-stage game is the efficient outcome. This has been confirmed in my experiments in the laboratory. The second stage of Zenda is a variation on the "compensation mechanism". This is a general mechanism to solve many kinds of externalities problems. It is described in my paper, "A Solution to the Problem of Externalities when Agents are Well-Informed." I found that if I run more than 8 subjects at a time, the network performance deteriorates significantly. I intend to rewrite the code when I move to distributed objects in NeXTstep 3.0 to see if this improves performance. The file DataAnalysis.ma uses some Mathematica routines to analyze the data generated by Zenda. If you use this code for something interesting, let me know about it. --- Hal.Varian@umich.edu Hal Varian voice: 313-764-2364 Dept of Economics fax: 313-764-2364 Univ of Michigan Ann Arbor, MI 48109-1220
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.