Despite the fact that conceptual models of individual decision making under risk are deterministic, attempts to econometrically estimate risk preferences require some assumption about the stochastic nature of choice. Unfortunately, the consequences of making different assumptions are, at present, unclear. In this paper, we compare two popular error specifications (Luce vs. Fechner), with and wi...

A biological model is developed here to determine the fittest attitude to risk. With a fixed environment, the type maximizing expected offspring is selected. This yields the expected utility theorem when translated into a criterion for evaluating gambles over commodities. With a random environment, however, the type selected is strictly less averse to idiosyncratic risk than to risk which is co...

We focus on a class of Multiple Prior Models. Those characterized by nonatomic countably additive priors. Preferences generating such representations have been recently axiomatized in [17]. We argue that this is the proper setting for comparing the notions of unambiguous event given by Epstein and Zhang in [7] and by Ghirardato, Maccheroni and Marinacci in [10]. The two definitions are known to...

This paper studies learning under multiple priors by characterizing the decision maker’s attitude toward information. She is incredulous if she integrates new information with respect to only those measures that minimizes the likelihood of the new information and credulous if she uses the maximum likelihood procedure to update her priors. Both updating rules expose her to dynamic inconsistency....

A subjective expected utility agent is given information about the state of the world in the form of a set of possible priors. She is allowed to condition her prior on this information. A set of priors may be updated according to Bayes’ rule, prior-by-prior, upon learning that some state of the world has not obtained. We show that there exists no decision maker who obeys Bayes’ rule, conditions...

The objective of this paper is to show how ambiguity, and a decision maker (DM)’s response to it, can be modelled formally in the context of a general decision model. We introduce a relation derived from the DM’s preferences, called ‘‘unambiguous preference’’, and show that it can be represented by a set of probabilities. We provide such set with a simple differential characterization, and argu...

The standard expected utility (EUT) model of tax evasion predicts that evasion is decreasing in the marginal tax rate (the Yitzhaki puzzle). Recent literature shows cases in which incorporating prospect theory (PT) does and does not overturn the Puzzle. In a general environment that nests both PT and EUT preferences, we provide a detailed study of how the elements of PT affect the Puzzle. PT do...

In many important economic decisions under uncertainty, the expected-utility maximizing choice is ex post optimal only if certain later states are reached. We investigate whether, outside of discounting, subjects are biased towards options faring well in early-period comparisons. We conduct neutral-context laboratory experiments to systematically investigate this bias and its interaction with a...

The Savagian choice-theoretic construction of subjective probability does not apply to preferences, like those in the Ellsberg Paradox, that reflect a distinction between risk and ambiguity.We formulate two representation results—one for expected utility, the other for probabilistic sophistication—that derive subjective probabilities but only on a “small” domain of risky events. Risky events ca...

This article introduces the symposium on model uncertainty and robustness. © 2006 Elsevier Inc. All rights reserved. JEL classification: D81; D91