Quantal Response Equilibrium

A quantal response specifies choice probabilities that are smooth, increasing functions of expected payoffs. A quantal response equilibrium has the property that the choice distributions match the belief distributions used to calculate expected payoffs. This stochastic generalization of the Nash equilibrium provides strong empirical restrictions that are generally consistent with data from laboratory experiments with human subjects. We define the concept of regular quantal response equilibrium and discuss several applications from the recent literature.