Two experiments show that violations of expected utility due to ambiguity, found in general decision experiments, also affect belief aggregation. Hence we use modern ambiguity theories to analyze belief aggregation, thus obtaining more refined and empirically more valid results than traditional...

This article develops a new approach to study the impact on beliefs and decisions of uncertain probability forecasts by advisors. The core concept of that approach, which builds on the revealed-preference approach favored by economists, is the one of revealed beliefs - the precise probability...

Testing whether risk professionals (here insurers) behave differently under risk and ambiguity when they cover catastrophic risks (floods and earthquakes) and non-catastrophic risks (fires), this paper reports the results of the first field experiment in the United States designed to distinguish...

In this paper, we build on the emerging literature on group decision-making to study the so-called ‘group shift’ effect, i.e., groups are less risk-averse than individuals. Our study complements past research in two ways. First, we study the group shift effect under two sources of...

We demonstrate how the standard usage of the random incentive system in ambiguity experiments is not incentive compatible if the decision maker is ambiguity averse. We propose a slight modification of the procedure in which the randomization takes place before decisions are made and the state is...

We often deal with uncertain events for which no probabilities are known. Several normative models have been proposed. Descriptive studies have usually been qualitative, or they estimated ambiguity aversion through one single number. This paper introduces the source method, a tractable method...

Machina (2009) introduced two examples that falsify Choquet expected utility, presently one of the most popular models of ambiguity. This article shows that Machina's examples falsify not only the model mentioned, but also four other popular models for ambiguity of the literature, namely maxmin...

In an experimental setting, we applied a dual strategy to better understand the effect of pictures of eyes on human behavior. First, we investigated whether the effect of eyes was limited to interaction tasks in which the subjects' decisions influenced the outcomes of other subjects. We expanded...

Many important decisions are made without precise information about the probabilities of the outcomes. In such situations, individual ambiguity attitudes influence decision making. The present study identifies affective states as a transient cause of ambiguity attitudes. We conducted two...

We propose simple behavioral definitions of comparative uncertainty aversion for a single agent towards different sources of uncertainty. Our definitions allow for the comparison of utility curvature towards different sources if the agent's choices satisfy subjective expected utility towards...