Cited by 381Evolutionary Game Theory and CooperationEvolution and Genetic DynamicsGame Theory and Applications

Evolutionary cycles of cooperation and defection

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Imhof, Lorens A., Fudenberg, Drew, Nowak, Martin A.·2005·Proceedings of the National Academy of Sciences

Abstract

The main obstacle for the evolution of cooperation is that natural selection favors defection in most settings. In the repeated prisoner's dilemma, two individuals interact several times, and, in each round, they have a choice between cooperation and defection. We analyze the evolutionary dynamics of three simple strategies for the repeated prisoner's dilemma: always defect (ALLD), always cooperate (ALLC), and tit-for-tat (TFT). We study mutation-selection dynamics in finite populations. Despite ALLD being the only strict Nash equilibrium, we observe evolutionary oscillations among all three strategies. The population cycles from ALLD to TFT to ALLC and back to ALLD. Most surprisingly, the time average of these oscillations can be entirely concentrated on TFT. In contrast to the classical expectation, which is informed by deterministic evolutionary game theory of infinitely large populations, stochastic evolution of finite populations need not choose the strict Nash equilibrium and can therefore favor cooperation over defection.

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Crossref · 10.1073/pnas.0502589102

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    “In real experiments, many donors transfer substantial amounts, and some obtain large returns, so that both players win.”

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Authors
Imhof, L. A., Fudenberg, D., & Nowak, M. A.
Affiliations
University of Bonn (DE)
Venue
Proceedings of the National Academy of Sciences
Published
2005-07-25
Volume
102
Issue
31
Pages
10797-10800
ISSN
  • 0027-8424 (ISSN-L)
  • 1091-6490
OpenAlex
W2122801036
Cited by
381
References
1
Citations by year
2026: 19 · 2025: 15 · 2024: 16 · 2023: 17 · 2022: 18 · 2021: 26 · 2020: 17 · 2019: 13 · 2018: 16 · 2017: 16 · 2016: 21 · 2015: 17 · 2014: 23 · 2013: 21 · 2012: 25
FWCI
46.17
Type
journal article
Language
en
Open access
Locations
  • Proceedings of the National Academy of Sciences (publishedVersion)
  • Europe PMC (PubMed Central) (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
  • Digital Access to Scholarship at Harvard (DASH) (Harvard University) (submittedVersion, cc-by)
Topics
  • Social Sciences › Sociology and Political Science › Evolutionary Game Theory and Cooperation
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Evolution and Genetic Dynamics
  • Social Sciences › Decision Sciences › Management Science and Operations Research › Game Theory and Applications
Keywords
evolution of cooperation, iterated prisoner's dilemma, tit-for-tat, finite population, stochastic evolutionary dynamics, strict Nash equilibrium, time averages

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