ABSTRACT
A key fact about human society is the ubiquity of material incentives to cheat on implicit or explicit cooperative agreements. In any kind of social or economic exchange situation between two or more individuals in which not all aspects of the exchange are determined by enforceable contracts, there are material incentives to cheat the exchange partners. Even in modern human societies with a large cooperative infrastructure in the form of laws, courts and the police, the material incentive to cheat on cooperative agreements is probably the rule rather than the exception. This is so because, in general, not all obligations that arise in various contingencies of exchange situations can be unambiguously formulated and subjected to a binding contract.2 Therefore, by reneging on implicit or unenforceable obligations a party can always improve their material payoff relative to a situation where they meet its obligations. Of course, in premodern societies which lack a cooperative infrastructure, cheating incentives are even more prevalent.
