Simple play in the Prisoner's Dilemma

Players do not have knowledge of the objective game. They know the available strategies and have scalar valued non-probabilistic payoff assessments. They act myopically, always choosing the strategy they consider best. They update these assessments in the direction of the received payoff. It is shown 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) 1999 Elsevier Science B.V. All rights reserved. JEL classification: C72; D83.