Nash equilibrium – definition

Nash equilibrium, named after American Economist John Nash (1928-2015) is a solution to a non-cooperative game where players, knowing the playing strategies of their opponents, have no incentive to change their strategy.

Having reached Nash equilibrium a player will be worse off by changing their strategy. In the Prisoner’s Dilemma game, when both players adopt the confess strategy there will be no incentive for either player to switch to a ‘deny’ strategy, unless it can be guaranteed that the other player also denies.

The name ‘prisoner’s dilemma’ was first used in 1950 by Canadian mathematician, Albert W. Tucker.