A model of complex contracts†

I study a mechanism design problem involving a principal and a single, boundedly rational agent. The agent transitions among belief states by combining current beliefs with up to K pieces of information at a time. By expressing a mechanism as a complex contract—a collection of clauses, each providing limited information about the mechanism—the principal manipulates the agent into believing truthful reporting is optimal. I show that such bounded rationality expands the set of implementable functions and that optimal contracts are robust not only to variation in K, but to several plausible variations on the agent’s cognitive procedure.