This paper extends the subjective expected utility model of decision making under uncertainty to include incomplete beliefs and tastes. The main results are two axiomatizations of the multiprior expected multiutility representations of preference relations under uncertainty. The paper also introduces new axiomatizations of Knightian uncertainty and the expected multiutility model with complete beliefs.

Using a game-theoretic approach, we examine possible equilibrium explanations of the often-observed phenomenon that two neighboring restaurants offering similar menus nevertheless experience vastly different demands. The essential aspect of this analysis is the presence of a consumption externality that makes the popularity itself a factor in the determination of the relative attractiveness of the restaurants.

[This paper presents an expected utility theory for state-dependent preferences. It proposes axioms that permit the joint derivation of subjective probabilities and utilities when the decision maker's preferences are not independent of the prevailing state of nature. In addition to the usual von Neumann-Morgenstern axioms, these axioms also include the requirement that the decision-maker's actual preferences are consistent with his preferences contingent on an hypothetical probability distribution over the states of nature. Two versions of the consistency axiom are introduced and their significance in the context of Bayesian decision theory is discussed.]

Analyzing the optimal bidding behaviour in ascending-bid auctions and second-price sealed-bid auctions with independent private values, we show that expected utility maximizing behaviour is equivalent to: (a) dynamically consistent bidding in ascending-bid auctions; (b) the equivalence of the optimal bids in ascending-bid auctions and in second-price sealed-bid auctions; (c) bidding the value of the object in second-price sealed-bid auctions. In addition, the optimal bid in ascending-bid auctions equals the value of the object if and only if the bidder's preferences on lotteries are both quasi-concave and quasi-convex.