Evolution of extortion in Iterated Prisoner's Dilemma games
Abstract
Iterated games are a fundamental component of economic and evolutionary game theory. They describe situations where two players interact repeatedly and have the ability to use conditional strategies that depend on the outcome of previous interactions, thus allowing for reciprocation. Recently, a new class of strategies has been proposed, socalled "zerodeterminant" strategies. These strategies enforce a fixed linear relationship between one's own payoff and that of the other player. A subset of those strategies allows "extortioners" to ensure that any increase in one player's own payoff exceeds that of the other player by a fixed percentage. Here, we analyze the evolutionary performance of this new class of strategies. We show that in reasonably large populations, they can act as catalysts for the evolution of cooperation, similar to titfortat, but that they are not the stable outcome of natural selection. In very small populations, however, extortioners hold their ground. Extortion strategies do particularly well in coevolutionary arms races between two distinct populations. Significantly, they benefit the population that evolves at the slower rate, an example of the socalled "Red King" effect. This may affect the evolution of interactions between host species and their endosymbionts.
 Publication:

Proceedings of the National Academy of Science
 Pub Date:
 April 2013
 DOI:
 10.1073/pnas.1214834110
 arXiv:
 arXiv:1212.1067
 Bibcode:
 2013PNAS..110.6913H
 Keywords:

 Quantitative Biology  Populations and Evolution;
 Mathematics  Dynamical Systems
 EPrint:
 contains 4 figures