Simple play in the Prisoner's Dilemma

Players do not have knowledge of the objective game. They know the availabl e strategies and have scalar valued non-probabilistic payoff assessments. T hey act myopically, always choosing the strategy they consider best. They u pdate these assessments in the direction of the received payoff. It is show n that such players converge to choose their maxmin strategies when facing a game against nature. In the Prisoner's Dilemma, however, the players need not converge to their maxmin strategy, and often end up cooperating. (C) 1 999 Elsevier Science B.V. All rights reserved. JEL classification: C72; D83 .