Payoff levels, loss avoidance, and equilibrium selection in the Stag Hunt: an experimental study

Game theorists typically assume that changing a game’s payoff levels—by adding the same constant to, or subtracting it from, all payoffs—should not affect behavior. While this invariance is an implication of the theory when payoffs mirror expected utilities, it is an empirical question when the “payoffs” are actually money amounts. In particular, if individuals treat monetary gains and losses differently, then payoff–level changes may matter when they result in positive payoffs becoming negative, or vice versa. We report the results of a human–subjects experiment designed to test for two types of loss avoidance: certain–loss avoidance (avoiding a strategy leading to a sure loss, in favor of an alternative that might lead to a gain) and possible–loss avoidance (avoiding a strategy leading to a possible loss, in favor of an alternative that leads to a sure gain). Subjects in the experiment play three versions of Stag Hunt, which are identical up to the level of payoffs, under a variety of treatments. We find differences in behavior across the three versions of Stag Hunt; these differences are hard to detect in the first round of play, but grow over time. When significant, the differences we find are in the direction predicted by certain– and possible–loss avoidance. Our results carry implications for games with multiple equilibria, and for theories that attempt to select among equilibria in such games

Negatively Correlated Bandits

We analyze a two-player game of strategic experimentation with two-armed bandits. Each player has to decide in continuous time whether to use a safe arm with a known payoff or a risky arm whose likelihood of delivering payoffs is initially unknown. The quality of the risky arms is perfectly negatively correlated between players. In marked contrast to the case where both risky arms are of the same type, we find that learning will be complete in any Markov perfect equilibrium if the stakes exceed a certain threshold, and that all equilibria are in cutoff strategies. For low stakes, the equilibrium is unique, symmetric, and coincides with the planner's solution. For high stakes, the equilibrium is unique, symmetric, and tantamount to myopic behavior. For intermediate stakes, there is a continuum of equilibria

Peer effects in risk taking: Envy or conformity?

We examine two explanations for peer effects in risk taking: relative payoff concerns and preferences that depend on peer choices. We vary experimentally whether individuals can condition a simple lottery choice on the lottery choice or the lottery allocation of a peer. We find that peer effects increase significantly, almost double, when peers make choices, relative to when they are allocated a lottery. In both situations, imitation is the most frequent form of peer effect. Hence, peer effects in our environment are explained by a combination of relative payoff concerns and preferences that depend on peer choices. Comparative statics analyses and structural estimation results suggest that a norm to conform to the peer may explain why peer choices matter. Our results suggest that peer choices are important in generating peer effects and hence have important implications for modeling as well as for policy

A Model of Noisy Introspection

This paper presents a theoretical model of noisy introspection designed to explain behavior in games played only once. The equilibrium determines layers of beliefs about others' beliefs about ..., etc., but allows for surprises by relaxing the equilibrium requirement that belief distributions coincide with decision distributions. The paper contains a convergence proof and reports estimated introspection and error parameters for data from 37 one-shot matrix games. The accuracy of the model is compared with that of two alternative approaches: the Nash equilibrium and the logit quantal response equilibrium.game theory, introspection, Nash equilibrium, experiments.

Risk Dominance Selects the Leader: An Experimental Analysis

We perform an experimental analysis to test whether the risk dominance prediction is supported by the behavior of laboratory agents, in a 2X 2 coordination game whose equilibria are not Pareto ranked. This type of game arises very often in studies of industrial organization and international trade, and we extract the parameters for the experiment from a vertical product differentiation model with two asymmetric players choosing first qualities and then prices.We show that the higher the degree of asymmetry of the game, the higher the predictive power of the risk dominance criterion.Publicad

The Logit Equilibrium: A Perspective on Intuitive Behavioral Anomalies

This paper considers a class of models in which rank-based payoffs are sensitive to small amounts of noise in decision making. Examples include auction, price-competition, coordination, and location games. Observed laboratory behavior in these games is often responsive to asymmetric costs associated with deviations from the Nash equilibrium. These payoff asymmetry effects are incorporated in an approach that introduces noisy behavior via probabilistic choice. In equilibrium, behavior is characterized by a probability distribution that satisfies a "rational expectations" consistency condition: the beliefs that determine player's expected payoffs match the decision distributions that arise from applying a logit probabilistic choice function to those expected payoffs. We prove existence of a unique, symmetric logit (quantal response) equilibrium and derive comparative statics results. The paper provides a unified perspective on many recent laboratory studies of games in which Nash equilibrium predictions are inconsistent with both intuition and experimental evidence.logit equilibrium, quantal response equilibrium, probabilistic choice, auctions.

Playing strategically against nature? – Decisions viewed from a game-theoretic frame

Common research on decision-making investigates non-interdependent situations, i.e., “games against nature”. However, humans are social beings and many decisions are made in social settings, where they mutually influence each other, i.e., “strategic games”. Mathematical game theory gives a benchmark for rational decisions in such situations. The strategic character makes psychological decision-making more complex by introducing the outcomes for others as an additional attribute of that situation; it also broadens the field for potential coordination and cooperation problems. From an evolutionary point of view, behavior in strategic situations was at a competitive edge. This paper demonstrates that even in games against nature, people sometimes decide as if they were in a strategic game; it outlines theoretical and empirical consequences of such a shift of the frame. It examines whether some irrationalities of human decision-making might be explained by such a shift in grasping the situation. It concludes that the mixed strategies in games against nature demand a high expertise and can only be found in situations where these strategies improve the effects of minimax-strategies that are used in cases of risk-aversion.

Learning and payoff externalities in an investment game

This paper examines the interplay of informational and payoff externalities in a two-player irreversible investment game. Each player learns about the quality of his project by observing a private signal and the action of his opponent. I characterize the unique symmetric equilibrium in a timing game that features a second-mover advantage, allowing for arbitrary correlation in project qualities. Despite private learning, the game reduces to a stochastic war of attrition. In contrast to the case of purely informational externalities, all investments happen at the same real time instant—irrespective of the sign of the correlation—and beliefs never get trapped in a no-learning region, provided that the second-mover advantage is sufficiently high.Accepted manuscrip