Hierarchies of conditional beliefs derived from commonly known priors

In this paper, we consider a finite set of agents with commonly known full-support priors on the fundamental space of uncertainty. Then, we show that if the hierarchies of conditional beliefs á la Battigalli and Siniscalchi (1999) are derived from these priors, then all types of the same agent yield the same hierarchy. We also show that the previous result does not necessarily hold when the priors are not full-support. Moreover, if the collections of conditioning events does not cover the underlying space of uncertainty, there are always commonly known (non-full-support) priors such that every agent''s conditional belief hierarchies are derived from these priors.mathematical economics;

A reasoning approach to introspection and unawareness

We introduce and study a unified reasoning process which allows to represent the beliefs of both a fully rational agent and of an unaware one. This reasoning process provides natural properties to introspection and unawareness. The corresponding model for the rational or boundedly rational agents is both easy to describe and to work with, and the agent’s full system of beliefs has natural descriptions using a reduced number of parameters.Economics (Jel: A)

The target projection dynamic

This paper studies the target projection dynamic, which is a model of myopic adjustment for population games. We put it into the standard microeconomic framework of utility maximization with control costs. We also show that it is well-behaved, since it satisfies the desirable properties: Nash stationarity, positive correlation, and existence, uniqueness, and continuity of solutions. We also show that, similarly to other well-behaved dynamics, a general result for elimination of strictly dominated strategies cannot be established. Instead we rule out survival of strictly dominated strategies in certain classes of games. We relate it to the projection dynamic, by showing that the two dynamics coincide in a subset of the strategy space. We show that strict equilibria, and evolutionarily stable strategies in $2\times2$ games are asymptotically stable under the target projection dynamic. Finally, we show that the stability results that hold under the projection dynamic for stable games, hold under the target projection dynamic too, for interior Nash equilibria.target projection dynamic; noncooperative games; adjustment

Pairwise interactive knowledge and Nash equilibrium

We provide epistemic conditions for Nash equilibrium, which are considerably weaker than thestandard ones by Aumann and Brandenburger (1995). Indeed, we simultaneously replace commonknowledge of conjectures and mutual knowledge of rationality with strictly weaker epistemicconditions of pairwise common knowledge of conjectures and pairwise mutual knowledge ofrationality respectively. It is also shown that, unlike the Aumann and Brandenburger''s conditions,ours do not imply common knowledge of rationality. Surprisingly, they actually do not even implymutual knowledge of rationality.microeconomics ;

Social capital, communication channels and opinion formation

We study how different forms of social capital lead to different distributions of multidimensional opinions by affecting the channels through which individuals communicate. We develop a model to compare and contrast the evolution of opinions between societies whose members communicate through bonding associations (i.e., which bond similar people together) and societies where communication is through bridging associations (i.e., which bridge the gap among different people). Both processes converge towards opinion distributions where there are groups within which there is consensus in all issues. Bridging processes are more likely to lead to society-wide consensus and converge to distributions that have, on average, fewer opinion groups. The latter result holds even when the confidence bound that allows successful communication in the bridging process is much smaller than the respective bound in the bonding process

Belief identification by proxy

It is well known that individual beliefs cannot be identified using traditional choice data, unless we exogenously assume state-independent utilities. In this paper, I propose a novel methodology that solves this long-standing identification problem in a simple way. This method relies on the extending the state space by introducing a proxy, for which the agent has no stakes conditional on the original state space. The latter allows us to identify the agent's conditional beliefs about the proxy given each state realization, which in turn suffices for indirectly identifying her beliefs about the original state space. This approach is analogous to the one of instrumental variables in econometrics. Similarly to instrumental variables, the appeal of this method comes from the flexibility in selecting a proxy.Comment: 22 page

Awareness in Repeated Games

In this paper we provide a framework to reason about limited awareness of the action space in finitely repeated games. Our framework is rich enough to capture the full strategic aspect of limited awareness in a dynamic setting, taking into account the possibility that agents might want to reveal or conceal actions to their opponent or that they might become "aware of unawareness" upon observing non rationalizable behavior. We show that one can think of these situations as a game with incomplete information, which is fundamentally different, though, from the standard treatment of repeated games with incomplete information. We establish conditions on the "level of mutual awareness" of the action space needed to recover Nash and subgame perfect Nash equilibria from the standard theory with common knowledge. We also show that the set of sustainable payoffs in games with folk theorems does not relate in a monotone way to the "level of mutual awareness".mathematical economics;

Decision Making with Imperfect Knowledge of the State Space

We conduct an experiment to study how imperfect knowledge of the state space affects subsequent choices under uncertainty with perfect knowledge of the state space. Participants in our experiment choose between a sure outcome and a lottery in 32 periods. All treatments are exactly identical in periods 17 to 32 but differ in periods 1 to 16. In the early periods of the “Risk Treatment” there is perfect information about the lottery; in the “Ambiguity Treatment” participants perfectly know the outcome space but not the associated probabilities; in the “Unawareness Treatment” participants have imperfect knowledge about both outcomes and probabilities. All three treatments induce strong behavioural differences in periods 17 to 32. In particular participants who have been exposed to an environment with very imperfect knowledge of the state space subsequently choose lotteries with high (low) variance less (more) often compared to other participants. Estimating individual risk attitudes from choices in periods 17 to 32 we find that the distribution of risk attitude parameters across our treatments can be ranked in terms of first order stochastic dominance. Our results show how exposure to different degrees of uncertainty can have long-lasting effects on individuals’ risk-taking behaviour.microeconomics ;