This article explores the sale of an object to an ambiguity averse buyer. We show that the seller can increase his profit by using an ambiguous mechanism. That is, the seller can benefit from hiding certain features of the mechanism that he has committed to from the agent. We then characterize the profit maximizing mechanisms for the seller and characterize the conditions under which the seller can gain by employing an ambiguous mechanism. Finally, we propose a class of ambiguous mechanisms that are easy to implement and perform better than the best non-ambiguous mechanism.

Previous research has established that the predictions of game theory are quite sensitive to the assumptions made about the players’ beliefs. We evaluate the severity of this robustness problem by characterizing conditions on the primitives of the model—the players’ beliefs and higher-order beliefs about the payoff-relevant parameters—for the behaviour of a given Harsanyi type to be approximated by the behaviour of (a sequence of) perturbed types. This amounts to providing belief-based characterizations of the strategic topologies of Dekel et al. (2006). We apply our characterizations to a variety of questions concerning robustness to perturbations of higher-order beliefs, including genericity of types that are consistent with a common prior, and we investigate the connections between our notions of robustness and the notion of common p-belief of Monderer and Samet (1989).