Ambiguity refers to a decision situation under uncertainty when there is incomplete information about the likelihood of … ambiguity and ambiguity aversion. …

differences lies in the dichotomy between first-order and second-order ambiguity aversion which I define here. My definition and …-order ambiguity aversion a positive exposure to ambiguity is optimal if and only if there is a subjective belief such that the actś … expected outcome is positive. With first-order ambiguity aversion, zero exposure to ambiguity can be optimal. Examples in …

information structures; complete separations of attitudes toward risk and ambiguity; and new classes of preferences that allow … decreasing relative ambiguity aversion and thereby rationalize recent challenges to many of the extant multiple prior models of … ambiguity aversion. We also characterize a property of sets of priors, descriptive completeness, that resolves several open …