http://edge.org/conversation/on-iterated-prisoner-dilemma "Robert Axelrod's 1980 tournaments of iterated prisoner's dilemma strategies have been condensed into the slogan, Don't be too clever, don't be unfair. Press and Dyson have shown that cleverness and unfairness triumph after all." ­ William Poundstone, from his Commentary Introduction In January I had the occasion to spend sometime in Munich with Freeman Dyson who informed me about a paper on "The Prisoner's Dilemma" he had co-authored with William H. Press, and he then briefly sketched out some of its ramifications. He indicated that they had come up with something new, a way to win the game. It's simple, he said. The winning strategy: go to lunch. And, he added, the only way to trump this strategy is to come up with a new theory of mind. I tried to go deeper but, he said, "I don't really understand game theory, I just did the math. This is really Bill Press's work." The highly technical paper, <http://www.pnas.org/content/early/2012/05/16/1206569109.abstract>"<http://www.pnas.org/content/early/2012/05/16/1206569109.abstract>Iterated Prisoner’s Dilemma contains strategies that dominate any evolutionary opponent" by William H. Press and Freeman J. Dyson has now been published in PNAS (May 22, 2012), which was followed by a PNAS Commentary by Alexander Stewart and Joshua Plotkin of the Department of Biology, University of Pennsylvania, entitled <http://www.pnas.org/content/early/2012/XXX>"<http://nr.com/whp/StewartPlotkinExtortion2012.pdf>Extortion and cooperation in the Prisoner’s Dilemma"<http://nr.com/whp/StewartPlotkinExtortion2012.pdf> (June 18, 2012). Here's the Abstract of the paper: "The two-player Iterated Prisoner’s Dilemma game is a model for both sentient and evolutionary behaviors, especially including the emergence of cooperation. It is generally assumed that there exists no simple ultimatum strategy whereby one player can enforce a unilateral claim to an unfair share of rewards. Here, we show that such strategies unexpectedly do exist. In particular, a player X who is witting of these strategies can (i) deterministically set her opponent Y’s score, independently of his strategy or response, or (ii) enforce an extortionate linear relation between her and his scores. Against such a player, an evolutionary player’s best response is to accede to the extortion. Only a player with a theory of mind about his opponent can do better, in which case Iterated Prisoner’s Dilemma is an Ultimatum Game." Edge asked William Poundstone, author of the book The Prisoner's Dilemma, to explain the paper in non-technical terms. In his Commentary below, he writes: "Robert Axelrod's 1980 tournaments of iterated prisoner's dilemma strategies have been condensed into the slogan, Don't be too clever, don't be unfair. Press and Dyson have shown that cleverness and unfairness triumph after all." Also below are responses by William Press to Poundstone and by Freeman Dyson to Stewart and Plotkin. To kick off a Reality Club conversation, mathematician Karl Sigmund at University of Vienna, and biological mathematician Martin Nowak of Harvard, two pioneers of evolutionary game theory, comment below. --- co-chair http://ocjug.org/