Correlated Equilibria, Good and Bad: An Experimental Study

We report results from an experiment that explores the empirical validity of correlated equilibrium, an important generalization of the Nash equilibrium concept. Specifically, we seek to understand the conditions under which subjects will condition their behavior on private, third-party recommendations drawn from known distributions in playing the game of Chicken. In a `good-recommendations` treatment, the distribution is such that following recommendations comprises a correlated equilibrium with payoffs better than any symmetric payoff in the convex hull of Nash equilibrium payoff vectors. In a `bad-recommendations` treatment, the distribution is such that following recommendations comprises a correlated equilibrium with payoffs worse than any Nash equilibrium payoff vector. In a `Nash-recommendations` treatment, the distribution is a convex combination of Nash equilibrium outcomes (which is also a correlated equilibrium), and in a fourth `very-good-recommendations` treatment, the distribution yields high payoffs, but following recommendations does not comprise a correlated equilibrium. We compare behavior in all of these treatments to the case where subjects do not receive recommendations. We find that when recommendations are not given to subjects, behavior is very close to mixed-strategy Nash equilibrium play. When recommendations are given, behavior does differ from mixed-strategy Nash equilibrium, with the nature of the differences varying according to the treatment. Our main finding is that subjects will follow third-party recommendations only if those recommendations derive from a correlated equilibrium, and further, if that correlated equilibrium is payoff-enhancing relative to the available Nash equilibria.