Evolutionarily Stable Strategy, ESS
Updated 2026-08-05
INTRODUCTION
English translation pending.
CORE DEFINITION
Introduced by John Maynard Smith, a strategy is evolutionarily stable if, in a population where nearly everyone plays it, any mutant minority playing a different strategy cannot gain a selective advantage and therefore cannot spread. The concept refines the Nash equilibrium by adding an evolutionary dynamic, and it explains why social customs and moral norms persist even when better alternatives are conceivable, because stability against invasion, not optimality, is what selects them.
SCAFFOLDING EFFECT
Reduce cognitive load
- Find the stable state: look for the behavior no newcomer can displace by better payoffs. - Design for invasion: check whether your proposed reform survives contact with mutant strategies. - Respect norms: treat persistent customs as equilibrium, not as mere ignorance of something better.
Anchor fast decisions
A strategy's payoff depends on what the rest of the population plays, so a mutant arriving in a population nearly all playing the incumbent strategy faces opponents almost entirely of that type. If the incumbent does better against itself than the mutant does against the incumbent, the mutant cannot grow, and the incumbent resists invasion. Stability therefore comes from the payoff structure against the incumbent itself, not from any global optimum.
MINIMUM ACTION
In progress 0/1Practice this model in one real situation:
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Source support: Explicit
- zh.wikipedia.orghttps://zh.wikipedia.org/wiki/%E8%BF%9B%E5%8C%96%E7%A8%B3%E5%AE%9A%E5%AF%B9%E7%AD%96verified
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