Relative to rational expectations models, learning models provide a theory of expectation formation where agents use observed data and a learning rule. Given the possibility of multiple equilibria under rational expectations, the learning literature often uses stability as a criterion to select...

What institutions can sustain cooperation in groups of strangers? Here we study the role of monetary systems. In an experiment, subjects sometimes needed help and sometimes could incur a cost to help an anonymous counterpart. In the absence of money, the intertemporal exchange of help, which...

We study the emergence of norms of cooperation in experimental economies populated by strangers interacting indefinitely and lacking formal enforcement institutions. In all treatments the efficient outcome is sustainable as an equilibrium. We address the following questions: can these economies...

Under what conditions can cooperation be sustained in a network of strangers? Here we study the role of institutions and uncover a new behavioral foundation for the use of monetary systems.In an experiment, anonymous subjects could cooperate or defect in bilateral random encounters. This...

We study an infinite-horizon economy with two basic frictions that are typical in monetary models. First, agents' trading paths cross at most once due to pairwise trade and other meeting obstacles. Second, actions must be compatible with individual incentives due to commitment and enforcement...

Monetary theorists have advanced an intriguing notion: we exchange money to make up for a lack of enforcement, when it is difficult to monitor and sanction opportunistic behaviors. We demonstrate that, in fact, monetary equilibrium cannot generally be sustained when monitoring and punishment...