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 …

consistent with two prominent models of decision making under uncertainty: variational preferences and smooth ambiguity. The … characterised as special cases. We implement our tests on data from a portfolio choice experiment. …

expected utility should decrease if errors are excluded. The present paper presents an experiment which investigates this … ambiguity the exclusion of errors in contrast increases the violation rate significantly. In this sense the Ellsberg paradox can …