Abstract

Game theory has progressed from analysis of one-move games between two rational agents, to iterated n-person games in which strategies evolve, and actors use prior experience to coordinate their moves. The next step in this direction is to analyse commitment strategies. An individual can influence others by announcing his or her commitment to a future act that would not be in his or her best interests. Spiteful threats can coerce others. Promises to aid someone when nothing can be reciprocated can create deep relationships. Such strategies are inherently paradoxical because the maximum payoff comes from not having to follow through on the commitment, and this is made more likely by expensive signalling of commitments to outlandish threats and promises whose plausibility declines with their magnitude. Nonetheless, the fitness benefits of subjective commitment are substantial and may well have shaped human capacities for revenge and spite, as well as deep attachment and genuine morality