When Are Mixed Equilibria Relevant?

Mixed strategy equilibria — Nash (NE) and maximin (MM) — are cornerstones of game theory, but their empirical relevance has always been questionable. We study in the laboratory two games, each with a unique NE and a unique (and distinct) MM in completely mixed strategies. Treatments include the matching protocol (pairwise random vs population mean matching), whether time is discrete or continuous, and whether players can specify explicit mixtures or only pure strategy realizations. NE mixes predict observed behavior relatively well in population mean matching treatments, and predict better than MM in all treatments. However, in most random pairwise treatments, uniform mixes predict better than NE. Regret-based and sign preserving dynamics capture regularities across all treatments.

Keywords: Nash equilibrium, Maximin, Mixed strategy, Sign preserving dynamics, Laboratory experiment.

JEL Classification: C72, C73, C92