Evolution of Cooperation Without Awareness in Minimal Social Situations

A surprising prediction from a simple evolutionary game-theoretic model, based on meagre assumptions, is that a form of cooperation can evolve among agents acting without any deliberate intention to cooperate. There are circumstances in which agents can learn to behave cooperatively without even becoming aware of their strategic interdependence. This phenomenon occurs in what are called minimal social situations, through an unconscious mechanism of adaptive learning in pairs or groups of agents lacking any deliberate intention to cooperate.1 Whether or not it is reasonable to interpret this as a form of teamwork is debatable. The argument pivots on what are considered to be the essential or prototypic features of teamwork, and other contributors to this volume are better qualified than I to analyze this conceptual issue. But what seems uncontroversial is that minimal social situations represent special or limiting cases that should interest people who study teamwork and may help to throw light on more complex forms of teamwork. Minimal social situations are curiosities, outside the mainstream of evolutionary game theory, but the underlying theory is intrinsically interesting and may turn out to have some utility in explaining the evolution of social behaviour in conditions of incomplete information. The increasing popularity of evolutionary games, from the closing decades of the second millennium onwards, has been fuelled by a growing suspicion that orthodox game theory, based on ideally rational players, may be irredeemably indeterminate. Orthodox game theory seeks to specify the strategies that would be chosen by rational players – rational in the sense of invariably acting to maximize their expected utilities relative to their knowledge and beliefs. It is easy to prove, via the celebrated Indirect Argument2 of von Neumann and Morgenstern (1944, pp. 146–148), that if a game has a uniquely rational solution, then that solution necessarily comprises a profile of strategies that we now call a Nash equilibrium in which each strategy is a utility-maximizing best reply to the combined strategies of the remaining players. But most interesting games, apart from those that