We perform two types of lab experiments to assess the normative and positive appeal of preference models exhibiting ambiguity aversion. Our first experiment is a simple extension of the Ellsberg [1961] two-color urn experiment in which there is an option that hedges ambiguity away completely and that dominates the options that correspond to Ellsberg behavior. 63% of subjects choose the dominated Ellsberg options, which compares similarly to the proportion of subjects choosing the risky urn in the standard two-color experiment. While subjective expected utility cannot explain this choice, also none of the classical models of ambiguity aversion can explain this choice. Our second experiment is also based on the Ellsberg two-color urn experiment. In this experiment, in various treatments, we provide advice in the form of short video clips in favor of, as well as against, the Ellsberg choice. We find suggestive, but not conclusive, evidence that subjects' choices are influenced by advice and, in these cases, mostly in the direction of abandoning the Ellsberg option.

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We design and implement lab experiments to evaluate the normative appeal of behavior arising from models of ambiguity-averse preferences. We report two main empirical findings. First, we demonstrate that behavior reflects an incomplete understanding of the problem, providing evidence that subjects do not act on the basis of preferences alone. Second, additional clarification of the decision making environment pushes subjects' choices in the direction of ambiguity aversion models, regardless of whether or not the choices are also consistent with subjective expected utility, supporting the position that subjects find such behavior normatively appealing.

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