We investigate what it means for one act to be more ambiguous than another. The question is evidently analogous to asking what makes one prospect riskier than another, but beliefs are neither objective nor representable by a unique probability. Our starting point is an abstract class of...

Many decision situations involve two or more of the following divergences from subjective expected utility: imprecision of beliefs (or ambiguity), imprecision of tastes (or multi-utility), and state dependence of utility. Examples include multi-attribute decisions under uncertainty, such as some...

Different models of uncertainty aversion imply strikingly different economic behavior. The key to understanding these differences lies in the dichotomy between first-order and second-order ambiguity aversion which I define here. My definition and its characterization are independent of specific...

Although much of the theoretical literature on ambiguity works under the assumption of uncertainty aversion, experimental evidence suggests that it is not a universal behavioral trait. This paper introduces and axiomatises the family of α-UA (for α-Uncertainty Attitude) preferences: a simple...