Symmetric equilibrium

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	C	D
C	2, 2	0, 3
D	3, 0	1, 1

In game theory, a symmetric equilibrium is an equilibrium where both players use the same strategy (possibly mixed) in the equilibrium. In the Prisoner's Dilemma game pictured to the right, the only Nash equilibrium is (D, D). Since both players use the same strategy, the equilibrium is symmetric.

Symmetric equilibria have important properties. Only symmetric equilibria can be evolutionarily stable states in single population models.

[edit] See also

• Symmetric game

v·d·e Topics in game theory
Definitions	Normal-form game · Extensive-form game · Cooperative game · Information set · Preference
Equilibrium concepts	Nash equilibrium · Subgame perfection · Bayesian-Nash · Perfect Bayesian · Trembling hand · Proper equilibrium · Epsilon-equilibrium · Correlated equilibrium · Sequential equilibrium · Quasi-perfect equilibrium · Evolutionarily stable strategy · Risk dominance · Pareto efficiency
Strategies	Dominant strategies · Pure strategy · Mixed strategy · Tit for tat · Grim trigger · Collusion · Backward induction
Classes of games	Symmetric game · Perfect information · Dynamic game · Sequential game · Repeated game · Signaling game · Cheap talk · Zero-sum game · Mechanism design · Bargaining problem · Stochastic game · Nontransitive game · Global games
Games	Prisoner's dilemma · Traveler's dilemma · Coordination game · Chicken · Volunteer's dilemma · Dollar auction · Battle of the sexes · Stag hunt · Matching pennies · Ultimatum game · Minority game · Rock-paper-scissors · Pirate game · Dictator game · Public goods game · Blotto games  ·War of attrition  ·El Farol Bar problem  ·Cake cutting  ·Cournot game  ·Deadlock  ·Diner's dilemma  ·Guess 2/3 of the average  ·Kuhn poker  ·Nash bargaining game  ·Screening game  ·Signaling game  ·Trust game  ·Princess and monster game
Theorems	Minimax theorem · Purification theorem · Folk theorem · Revelation principle · Arrow's impossibility theorem

This page uses content from the English-language version of Wikipedia. The original article was at Symmetric equilibrium. The list of authors can be seen in the page history. As with Psychology Wiki, the text of Wikipedia is available under the GNU Free Documentation License.