 Bicchieri, Duffy and Tolle (2004) present an alternative model of norm emergence to explain how a norm of impersonal trust/reciprocity can emerge and survive in a heterogeneous population. This model does not rely on a meta-norm of punishment; instead, it is purely driven by repeated interactions of conditional strategies. In their model, agents play anywhere from 1 to 30 rounds of a trust game for 1,000 iterations, relying on the 4 unconditional strategies, and the 16 conditional strategies that are standard for the trust game. After each round, agents update their strategies based on the replicator dynamic. As the number of rounds grows, a norm of impersonal trust/reciprocity emerges in the population. Most interestingly, however, the norm is not associated with a single strategy, but it is supported by several strategies behaving in similar ways. This model suggests that Trivers’ basic model works well in normal social contexts, but we can further enrich the story by allowing a social norm to supervene on several behavioral strategies.