Existing models of regret aversion assume that individuals can make an ex-post comparison between their choice and a foregone alternative. Yet in many situations such a comparison can be made only if someone else chose the alternative option. We develop a model where regret-averse agents must...

We provide an evolutionary foundation to evidence that in some situations humans maintain either optimistic or pessimistic attitudes towards uncertainty and are ignorant to relevant aspects of the environment. Players in strategic games face Knightian uncertainty about opponents' actions and...

I investigate the decision problem of a player in a game of incomplete information who faces uncertainty about the other players' strategies. I propose a new decision criterion which works in two steps. First, I assume common knowledge of rationality and eliminate all strategies which are not...

This paper proposes that the ambiguity reflected by a set of priors remains unchanged when the set is translated within the probability simplex, i.e. ambiguity is location invariant. This unifies and generalises numerous influential definitions of ambiguity in the literature. Location invariance...

Ellsberg (1961) introduced the Ellsberg urns experiments as evidence against Savage's theory of subjective expected utility. The restrictive Bayes/Hurwicz criterion (Ellsberg, 2001) is proposed to explain the phenomena of subjects shunning the ambiguous urns. Modeling the interaction between the...

Goeree and Holt (2001) experimentally study a number of games. In each case they initially find strong support for Nash equilibrium, however by changing an apparently irrelevant parameter they find results which contradict Nash equilibrium. In this paper, we study the five normal form games from...

In the standard formulation of game theory, agents use mixed strategies in the form of objective and probabilistically precise devices to conceal their actions. We introduce the larger set of probabilistically imprecise devices and study the consequences for the basic results on normal form...

Riedel and Sass (2013) propose a framework for normal form games where players can use imprecise probabilistic devices. We extend this strategic use of objective ambiguity to extensive form games. We show that with rectangularity of Ellsberg strategies we have dynamic consistency in the sense of...

Riedel and Sass (2013) propose a framework for normal form games where players can use imprecise probabilistic devices. We extend this strategic use of objective ambiguity to extensive form games. We show that with rectangularity of Ellsberg strategies we have dynamic consistency in the sense of...

This text reviews a recent approach to modeling "radically uncertain" behavior in strategic interactions. By rigorously rooting the approach in decision theory, we provide a foundation for applications of Knightian uncertainty in mechanism design, principal agent and moral hazard models. We...