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Defection always results in a better payoff than cooperation, so it is a strictly dominant strategy for both players. Mutual defection is the only strong Nash equilibrium in the game. Since the collectively ideal result of mutual cooperation is irrational from a self-interested standpoint, this Nash equilibrium is not Pareto efficient.
In the context of this discussion, learning rules, specifically conformism and payoff-dependent imitation, are not arbitrarily predetermined but are biologically selected. Behavioral strategies, which include cooperation, defection, and cooperation coupled with punishment, are chosen in alignment with the agent's prevailing learning rule.
Direct reciprocity was proposed by Robert Trivers as a mechanism for the evolution of cooperation. [1] If there are repeated encounters between the same two players in an evolutionary game in which each of them can choose either to "cooperate" or "defect", then a strategy of mutual cooperation may be favoured even if it pays each player, in the short term, to defect when the other cooperates.
The characteristics of the multi-round game produce a danger of defection and the potentially lesser payoffs of cooperation in each round, but any such defection can lead to punishment in a following round – establishing the game as a repeated prisoner's dilemma. Therefore, the family of tit-for-tat strategies come to the fore. [34]
This strategy always reciprocates cooperation with cooperation, and usually replies to defection with defection. However, with some probability GTFT will forgive a defection by the other player and cooperate. In a world of errors in action and perception, such a strategy can be a Nash equilibrium and evolutionarily stable. The more beneficial ...
It assumes that cooperation is possible in the anarchic system of states, as regimes are, by definition, instances of international cooperation. Stephen D. Krasner was a key figure in establishing the theory as a prominent topic of study in IR, in part through the 1983 edited collection International Regimes . [ 2 ]
Since a single defect by the opponent triggers defection forever, grim trigger is the most strictly unforgiving of strategies in an iterated game. In Robert Axelrod 's book The Evolution of Cooperation , grim trigger is called "Friedman", [ 1 ] for a 1971 paper by James W. Friedman , which uses the concept.
The choice of a voluntary standard tends to be stable in situations in which all parties can realize mutual gains, but only by making mutually consistent decisions. In contrast, an obligation standard (enforced by law as " de jure standard") is a solution to the prisoner's problem .