Saturday, July 7, 2012

To Hell With Human Cooperation and Trust: There are Indeed Ultimatum Strategies to Win an Iterated Prisoners Dilemma

Listen up you sociopathic bastards, here's your excuse.

From Neuroanthropology:
Prisoner’s Dilemma and the Evolution of Inequality – Does Unfairness Triumph After All?
A new paper, Iterated Prisoner’s Dilemma contains strategies that dominate any evolutionary opponent (pdf), has just been published in the Proceedings of the National Academy of Sciences. Written by William Press and Freeman Dyson, it represents a substantial breakthrough in strategies that work in the Prisoner’s Dilemma game.

The key point? There does exist a strategy where a player can “enforce a unilateral claim to an unfair share of rewards.”

The implications of this paper are fascinating. For biological evolution, it opens up new thinking about reproductive strategies and life history theory, as well as the direct impact on ideas about the evolution of cooperation.

For cultural evolution, it seems to provide some powerful insights into the evolution of inequality in human society. As the agriculture revolution and population growth led to the ability to monopolize social resources and create differential wealth, what happened with social class? Did human cooperation turn from fairness to enforcing the sort of unfair game that Press and Dyson outline?

Zero Determinant Strategies and Beating Tit-for-Tat
Here is the paper’s abstract for Press and Dyson (2012):
The two-player Iterated Prisoner’s Dilemma game is a model for both sentient and evolutionary behaviors, especially including the emergence of cooperation. It is generally assumed that there exists no simple ultimatum strategy whereby one player can enforce a unilateral claim to an unfair share of rewards. Here, we show that such strategies unexpectedly do exist. In particular, a player X who is witting of these strategies can (i) deterministically set her opponent Y’s score, independently of his strategy or response, or (ii) enforce an extortionate linear relation between her and his scores. Against such a player, an evolutionary player’s best response is to accede to the extortion. Only a player with a theory of mind about his opponent can do better, in which case Iterated Prisoner’s Dilemma is an Ultimatum Game.
PNAS also gives an informative commentary by Alexander Stewart and Joshua Plotkin entitled “Extortion and cooperation in the Prisoner’s Dilemma (pdf).”...MORE
HT: Simoleon Sense