the cooperation game
200 rounds of betrayal. the nicest strategy wins.
the prisoner's dilemma: both cooperate and you each get 3. both defect, you each get 1. betray a cooperator for 5, but they get 0.
| they cooperate | they defect | |
|---|---|---|
| you cooperate | 3, 3 | 0, 5 |
| you defect | 5, 0 | 1, 1 |
pick an opponent. play 20 rounds.
select strategies for a round-robin tournament. each pair plays 200 rounds.
why nice strategies win
in 1980, robert axelrod invited game theorists to submit strategies for an iterated prisoner's dilemma tournament. tit for tat, the simplest entry, won.
it won because of four properties:
nice
never defects first. starts every relationship with trust.
retaliatory
punishes defection immediately. you cannot exploit it for free.
forgiving
goes back to cooperating after one round of punishment. grudges are expensive.
clear
simple enough that opponents figure it out fast and start cooperating.
the lesson: in repeated interactions, being nice pays off. but only if you also retaliate.