In two experiments, decision makers chose between risky and ambiguous gambles under conditions of both single (unrepeated) and multiply repeated choices. The gambles were presented either as modified Ellsberg urn choices or as marketing strategy decisions. In both experiments, decision makers...

The phenomena of ambiguity and ambiguity aversion , introduced in Daniel Ellsberg’s seminal 1961 article, are ubiquitous in the real world and violate both the key rationality axioms and classic models of choice under uncertainty. In particular, they violate the hypothesis that individuals’...

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...

When confronted with uncertain prospects, people often exhibit both choice deferral and Ellsberg-type ambiguity aversion. This paper obtains a joint representation for these behavioral phenomena. The decision maker as portrayed by my model is willing to choose an uncertain prospect f over g...