The problem of ambiguity in games is discussed, and a class of ambiguous games is identified. A total of 195 participants played strategic-form games of various sizes with unidentified co-players. In each case, they first chose between a known-risk game involving a co-player indifferent between strategies and an equivalent ambiguous game involving one of several co-player types, each with a dif...

This paper takes the Anscombe-Aumann framework with horse and roulette lotteries, and applies the Savage axioms to the horse lotteries and the von Neumann-Morgenstern independence axiom to the roulette lotteries. The resulting representation of preferences yields a subjective probability measure over states and two utility functions, one governing risk attitudes and one governing ambiguity atti...

People typically find bets less attractive when the probability of receiving a prize is more vague or ambiguous (Ellsberg, 1961). According to Fox & Tversky’s (1995) comparative ignorance hypothesis, ambiguity aversion is driven by the comparison with more familiar events or more knowledgeable individuals, and diminishes or disappears in the absence of such a comparison. In this paper we emphas...

We examine the problem of setting optimal incentives to a portfolio manager (to be employed by an investor through a contract) making an ambiguity-robust portfolio choice with respect to estimation errors in expected returns. We consider a one-period model with a set of risky assets (with multivariate normal returns) whose expected returns are estimated with uncertainty and a linear sharing rul...

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I introduce novel preference formulations which capture aversion to ambiguity about unknown and potentially time-varying volatility. compare these preferences with Gilboa Schmeidler's maxmin expected utility as well variational of aversion. The impact is illustrated in a simple static model portfolio choice, dynamic optimal contracting under repeated moral hazard. Implications for investor beli...