The evolution of overconfidence

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Confidence is an essential ingredient of success in a wide range of domains ranging from job performance and mental health to sports, business and combat1,2,3,4. Some authors have suggested that not just confidence but overconfidence—believing you are better than you are in reality—is advantageous because it serves to increase ambition, morale, resolve, persistence or the credibility of bluffing, generating a self-fulfilling prophecy in which exaggerated confidence actually increases the probability of success3,4,5,6,7,8. However, overconfidence also leads to faulty assessments, unrealistic expectations and hazardous decisions, so it remains a puzzle how such a false belief could evolve or remain stable in a population of competing strategies that include accurate, unbiased beliefs. Here we present an evolutionary model showing that, counterintuitively, overconfidence maximizes individual fitness and populations tend to become overconfident, as long as benefits from contested resources are sufficiently large compared with the cost of competition. In contrast, unbiased strategies are only stable under limited conditions. The fact that overconfident populations are evolutionarily stable in a wide range of environments may help to explain why overconfidence remains prevalent today, even if it contributes to hubris, market bubbles, financial collapses, policy failures, disasters and costly wars9,10,11,12,13.

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  1. 1.

    Confidence: How Winning Streaks and Losing Streaks Begin and End (Crown Business, 2004)

  2. 2.

    & Positive illusions and well-being revisited: separating fact from fiction. Psychol. Bull. 116, 21–27 (1994)

  3. 3.

    Positive Illusions: Creative Self-Deception and the Healthy Mind (Basic Books, 1989)

  4. 4.

    A Primer in Positive Psychology (Oxford Univ. Press, 2006)

  5. 5.

    Is military incompetence adaptive? Evol. Hum. Behav. 20, 3–17 (1999)

  6. 6.

    The elements of a scientific theory of self-deception. Ann. NY Acad. Sci. 907, 114–131 (2000)

  7. 7.

    Deceit and Self-Deception: Fooling Yourself the Better to Fool Others (Allen Lane, 2011)

  8. 8.

    & The evolution of misbelief. Behav. Brain Sci. 32, 493–510 (2009)

  9. 9.

    The March of Folly: From Troy to Vietnam (Alfred A. Knopf, 1984)

  10. 10.

    & Overconfidence and excess entry: an experimental approach. Am. Econ. Rev. 89, 306–318 (1999)

  11. 11.

    & CEO overconfidence and corporate investment. J. Finance 60, 2661–2700 (2005)

  12. 12.

    Overconfidence and War: The Havoc and Glory of Positive Illusions (Harvard University Press, 2004)

  13. 13.

    & The Rubicon theory of war: how the path to conflict reaches the point of no return. Int. Secur. 36, 7–40 (2011)

  14. 14.

    The Optimism Bias: A Tour of The Irrationally Positive Brain (Pantheon, 2011)

  15. 15.

    & The tragedy of cognition: psychological biases and environmental inaction. Curr. Sci. 97, 1593–1603 (2009)

  16. 16.

    & Animal Spirits: How Human Psychology Drives the Economy, and Why it Matters for Global Capitalism (Princeton Univ. Press, 2009)

  17. 17.

    & Perfect Bayesian equilibrium and sequential equilibrium. J. Econ. Theory 53, 236–260 (1991)

  18. 18.

    Adaptive Thinking: Rationality in the Real World (Oxford Univ. Press, 2002)

  19. 19.

    in Emotion, Evolution and Rationality (eds Evans, D. & Cruse, P.) 193–208 (Oxford Univ. Press, 2004)

  20. 20.

    & The paranoid optimist: an integrative evolutionary model of cognitive biases. Pers. Soc. Psychol. Rev. 10, 47–66 (2006)

  21. 21.

    & Better than rational: evolutionary psychology and the invisible hand. Am. Econ. Rev. 84, 327–332 (1994)

  22. 22.

    & Some properties of symmetric stable distributions. J. Am. Stat. Assoc. 63, 817–836 (1968)

  23. 23.

    Rationalist explanations for war. Int. Organ. 49, 379–414 (1995)

  24. 24.

    & The logic of asymmetric contests. Anim. Behav. 24, 159–175 (1976)

  25. 25.

    Assessment strategy and the evolution of fighting behaviour. J. Theor. Biol. 47, 223–243 (1974)

  26. 26.

    & Evolution of fighting behaviour: decision rules and assessment of relative strength. J. Theor. Biol. 102, 387–410 (1983)

  27. 27.

    Evolutionary Dynamics: Exploring the Equations of Life (Belknap Press, 2006)

  28. 28.

    & The evolution of fatal fighting. Anim. Behav. 39, 1–9 (1990)

  29. 29.

    , & Fortune favours the bold: an agent-based model reveals adaptive advantages of overconfidence in war. PLoS ONE 6, e20851 (2011)

  30. 30.

    , & On the evolutionary origin of prospect theory preferences. J. Polit. 70, 335–350 (2008)

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We thank C. Barrett, D. Blumstein, L.-E. Cederman, D. Fessler, P. Gocˇev, M. Haselton, D. Nettle, J. Orbell, K. Panchanathan, M. Price, D. Tierney, R. Trivers, N. Weidmann and R. Wrangham for discussions and help leading to this paper.

Author information


  1. Politics and International Relations, University of Edinburgh, Edinburgh EH8 9LD, UK

    • Dominic D. P. Johnson
  2. Division of Medical Genetics and Department of Political Science, University of California, San Diego, California 92093, USA

    • James H. Fowler


  1. Search for Dominic D. P. Johnson in:

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D.J. and J.F. conceived the study. J.F. performed the modelling. D.J. and J.F. analysed the results, revised the models and wrote the paper.

Competing interests

The authors declare no competing financial interests.

Supplementary information

PDF files

  1. 1.

    Supplementary Information

    This file contains Supplementary Text and Data 1-7, (see Contents for details), which includes Supplementary Figures 1-4 with legends and Supplementary Table 1.


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