Reiterated Prisoner's Dilemma simulation based on Axelrod's book "Evolution of Cooperation"
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Stability Example
Strategy Set Example


A computer simulation of the evolution of cooperation, based on the book of R.Axelrod: "The Evolution of Cooperation"

Version: 0.9.9 beta 6 (September 6th, 2015)

(c) 2015 by Eckhart Arnold, MIT Open Source License

Author: Eckhart Arnold web: email:


CoopSim is a computer program for simulating a game theoretic model of cooperative behavior that can be used in biology as well as social sciences. The model is the reiterated pairwise prisoners dilemma that has been made popular by Robert Axelrod and his book "The Evolution of Cooperation". The reiterated pairwise prisoners dilemma can be regarded as a formal description of some (but certainly not all!) cooperation dilemmas.

CoopSim follows the description in Axelrod's book. Different strategies can be put against each other in a computer tournament. The user can select the strategies, adjust game parameters and inspect the outcome of single matches, the whole tournament and the ecological development over a sequence of tournaments.

CoopSim is open source software under the MIT License (

Most of the development of CoopSim took place 10 years ago. While I still add changes so that it can run on current machines, I do not think it is really worth while to develop it further. Due to the use of the wxPython widgets toolkit it cannot even be ported to Python3.

There exists another project by Vincent Knight, Own Campbell and Marc Harper with the same goal, however, that is being actively developed, and which I'd like to recommend to anyone interested in this kind of computer simulations:


The CoopSim-Manual can be read online:

Some Remarks on Game Theoretical Simulation Models

While I enjoyed programming CoopSim and doing Prisoner's Dilemma simulations, I have become more and more skeptical about game theory as a scientific method. In my opinion game theory becomes the most valuable if it is combined with empirical research - both field research and laboratory research! Good examples of the combination of empirical and theoretical research methods can be found in the research on public goods. The challenges of such research are well described in the book: Working Together: Collective Action, the Commons, and Multiple Methods in Practice by Amy R. Poteete, Marco A. Janssen & Elinor Ostrom, Princeton University Press2010.

Unfortunately, though, the research on the Reiterated Prisoner's Dilemma (RPD) in the Axelrod tradition has for its greater part remained thoroughly theoretical and the myriads of RPD-simulations that have been conducted have in fact contributed only very little to our understanding of the evolution of cooperation as a natural and social phenomenon. I have expressed my worries about this in a few scientific papers and I very much hope that they might convince some simulation scientists that it is important to be concerned about how their simulations can be validated empirically and how their theoretical findings can be integrated with empirical research:

How Models Fail. A Critical Look at the History of Computer Simulations of the Evolution of Cooperation, in: Catrin Misselhorn (Ed.): Collective Agency and Cooperation in Natural and Artificial Systems. Explanation, Implementation and Simulation, Philosophical Studies Series, Springer 2015, DOI 10.1007/978-3-319-15515-9, pp. 261-279.

What's wrong with social simulations? in: The Monist 2014 (97,3), 361-379, DOI: 10.5840/monist201497323

Simulation Models of the Evolution of Cooperation as Proofs of Logical Possibilities. How Useful Are They? in: Etica & Politica / Ethics & Politics, XV, 2013, 2, pp. 101-138,