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...

It is well known that the rock-paper-scissors game has no pure saddle point. Weshow that this holds more generally: A symmetric two-player zero-sum game hasa pure saddle point if and only if it is not a generalized rock-paper-scissors game.Moreover, we show that every finite symmetric...

We show that for many classes of symmetric two-player games, the simple decision rule \imitate-the-best" can hardly be beaten by any other decision rule. Weprovide necessary and sufficient conditions for imitation to be unbeatable and showthat it can only be beaten by much in games that are of...

Recently there has been much theoretical and experimental work on learning in games. However, learning usually means learning about the strategic behavior of opponents rather than learning about the game as such. In contrast, here we report on an experiment designed to test whether players learn...

We define a cautious version of extensive-form rationalizability for generalized extensive- form games with unawareness that we call prudent rationalizability. It is an extensive-form analogue of iterated admissibility. In each round of the procedure, for each tree and each information set of a...

It is known that there are uncoupled learning heuristics leading to Nash equilibrium in all finite games. Why should players use such learning heuristics and where could they come from? We show that there is no uncoupled learning heuristic leading to Nash equilibrium in all finite games that a...

It is known that there are uncoupled learning heuristics leading to Nash equilibrium in all finite games. Why should players use such learning heuristics and where could they come from? We show that there is no uncoupled learning heuristic leading to Nash equilibrium in all finite games that a...

We study the informational effectiveness of electoral campaigns. Voters may not think about all political issues and have incomplete information with regard to political positions of candidates. Nevertheless, we show that if candidates are allowed to microtarget voters with messages then...

We present a new solution concept for strategic games called comprehensive rationalizability that embodies "common cautious belief in rationality" based on a sound epistemic characterization in a universal type space. It refines rationalizability, but it neither refines nor is refined by...

We extend Kuhn's Theorem to extensive games with unawareness. This extension is not entirely obvious: First, extensive games with non-trivial unawareness involve a forest of partially ordered game trees rather than just one game tree. An information set at a history in one tree may consist of...