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Related Experiment Video

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Combining Behavioral Endocrinology and Experimental Economics: Testosterone and Social Decision Making

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Published on: March 2, 2011

From extortion to generosity, evolution in the Iterated Prisoner's Dilemma.

Alexander J Stewart¹, Joshua B Plotkin

¹Department of Biology, University of Pennsylvania, Philadelphia, PA 19104.

Proceedings of the National Academy of Sciences of the United States of America

|September 5, 2013

Summary

Generous zero-determinant (ZD) strategies, a new class of game theory tactics, surprisingly dominate in evolving populations of the Iterated Prisoner's Dilemma (IPD). These forgiving strategies outperform even established tactics like win-stay-lose-shift.

Keywords:

altruism evolution of cooperation evolutionary stability nash

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Area of Science:

Evolutionary game theory
Computational game theory
Behavioral economics

Background:

Zero-determinant (ZD) strategies offer players unilateral control over payoffs in iterated games.
Previous research on ZD strategies in evolving populations, particularly "extortion strategies," showed limited success.
The Iterated Prisoner's Dilemma (IPD) is a key model for studying cooperation and competition.

Purpose of the Study:

To investigate the evolutionary viability of ZD strategies within the Iterated Prisoner's Dilemma (IPD).
To identify specific types of ZD strategies that can thrive in evolving populations.
To compare the performance of novel ZD strategies against established IPD strategies.

Main Methods:

Simulations of evolving populations playing the Iterated Prisoner's Dilemma.
Analysis of "generous ZD strategies" characterized by forgiveness of defecting opponents.
Comparative performance assessment against noncooperative ZD strategies and other known IPD strategies.

Main Results:

Generous ZD strategies demonstrate robustness and dominance in evolving IPD populations, outcompeting noncooperative ZD strategies.
These strategies are resilient to invasion and can replace other strategies, especially in larger populations.
Generous strategies, when generalized, outperform even well-known IPD strategies like win-stay-lose-shift in certain scenarios.

Conclusions:

Generous ZD strategies represent a significant advancement in evolutionary game theory, offering novel insights into cooperation.
These forgiving strategies exhibit superior evolutionary success in the IPD compared to previously studied ZD variants.
The findings suggest that forgiveness and generosity can be evolutionarily advantageous in competitive environments.