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Tit-for-Tat

Tit-for-tat is a strategy for the iterated prisoner's dilemma in which a prisoner cooperates on the first move, and thereafter copies the previous move of the other prisoner. It was submitted by A. Rapoport to Axelrod's computer tournaments, where it performed notably well despite its simplicity (Axelrod 1980ab, Axelrod and Hamilton 1981).

Tit-for-tat is neither uniformly optimal nor uniquely successful among simple strategies. For example, Nowak and Sigmund (1993) described a win-stay, lose-shift strategy that can outperform tit-for-tat.

Wolfram (2026) found that, among deterministic 2-state-machine strategies for the iterated prisoner's dilemma, tit-for-tat ranks below the top performer for long-run average payoff.

See also

Iterated Prisoner's Dilemma, Prisoner's Dilemma

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References

Axelrod, R. "Effective Choice in the Prisoner's Dilemma." J. Conflict Resolution 24, 3-25, 1980a. https://doi.org/10.1177/002200278002400101.Axelrod, R. "More Effective Choice in the Prisoner's Dilemma." J. Conflict Resolution 24, 379-403, 1980b. https://doi.org/10.1177/002200278002400301.Axelrod, R. and Hamilton, W. D. "The Evolution of Cooperation." Science 211, 1390-1396, 1981. https://doi.org/10.1126/science.7466396.Goetz, P. "Phil Goetz's Complexity Dictionary." https://web.archive.org/web/20001209121200/http://www.cs.buffalo.edu/~goetz/DICT/dict2.html#T.Nowak, M. and Sigmund, K. "A strategy of win-stay, lose-shift that outperforms tit-for-tat in the Prisoner's Dilemma game." Nature 364, 56-58, 1993. https://doi.org/10.1038/364056a0.Veritasium. "This Game Theory Problem Will Change the Way You See the World." Dec. 23, 2023. https://www.youtube.com/watch?v=mScpHTIi-kM.Wolfram, S. "Games between Programs: The Ruliology of Competition." Jun. 4, 2026. https://writings.stephenwolfram.com/2026/06/games-between-programs-the-ruliology-of-competition/.

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Tit-for-Tat

Cite this as:

Weisstein, Eric W. "Tit-for-Tat." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/Tit-for-Tat.html

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