Modeling strategies as generous and greedy in prisoner’s dilemma like games

Abstract

Four different prisoner’s dilemma and associated games were studied by running a round robin as well as a population tournament, using 15 different strategies. The results were analyzed in terms of definitions of generous, even-matched, and greedy strategies. In the round robin, prisoner’s dilemma favored greedy strategies. Chicken game and coordinate game were favoring generous strategies, and compromise dilemma the even-matched strategy Anti Tit-for-Tat. These results were not surprising because all strategies used were fully dependent on the mutual encounters, not the actual payoff values of the game. A population tournament is a zero-sum game balancing generous and greedy strategies. When strategies disappear, the population will form a new balance between the remaining strategies. A winning strategy in a population tournament has to do well against itself because there will be numerous copies of that strategy. A winning strategy must also be good at resisting invasion from other competing strategies. These restrictions make it natural to look for winning strategies among originally generous or even-matched strategies. For three of the games, this was found true, with original generous strategies being most successful. The most diverging result was that compromise dilemma, despite its close relationship to prisoner’s dilemma, had two greedy strategies almost entirely dominating the population tournament.