Robert Axelrod sought the optimal strategy to an iterated Prisoner’s Dilemma scenario. He convened a diverse group to develop solutions to the problem, and of the varying submissions, ranging from complex to simple, it was simplicity that won the day.
‘Tit for Tat’, formally known as equivalent retaliation, begins by cooperating and will then mimic the other player’s move.
Tit for Tat succeeds because it is nice, retaliatory, forgiving, and clear.
Nice because it begins with cooperation.
Retaliatory because it reacts with defection to any defection of the other player.
Forgiving because it only remembers the other player’s latest move.
Clear because its behaviour is deterministic.