Letter

The evolution of overconfidence

  • Nature volume 477, pages 317320 (15 September 2011)
  • doi:10.1038/nature10384
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Abstract

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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Acknowledgements

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

Affiliations

  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

Authors

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

  2. Search for James H. Fowler in:

Contributions

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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