Cycles versus equilibrium in evolutionary games

摘要

Mixed-strategy equilibria are typically rather unstable in evolutionary game theory. "Monocyclic" games, such as Rock-Paper-Scissors, have only mixed equilibria, some of which are "stable" in the sense that sequential best replies lead to them; yet, even these games are prone to stable cycles under discrete-time simultaneous best replies, giving an unusual equilibrium-selection problem. This article analyzes such games in a random-utility setting where changing strategies is costly, and the speed of the dynamic is, thus, endogenous. The stochastically stable outcome is determined by the cost of switching strategies; when switching costs are high, mixed equilibria are selected, whereas when switching costs are low, cycles are selected.