Project 3

Causes and Consequences of Overconfidence


Opponents rarely go to war without thinking they can win––and clearly, one side must be wrong. This conundrum lies at the heart of the so-called “war puzzle”: rational states should agree on their differences in power and thus not fight. But as Dominic Johnson argues in Overconfidence and War, states are no more rational than people, who are susceptible to exaggerated ideas of their own virtue, of their ability to control events, and of the future. By looking at this bias–called “positive illusions”–as it figures in evolutionary biology, psychology, and the politics of international conflict, this book offers compelling insights into why states wage war. Johnson traces the effects of positive illusions on four turning points in twentieth-century history: two that erupted into the war (World War I and Vietnam); and two that did not (the Munich crisis and the Cuban missile crisis). Examining the two wars, he shows how positive illusions have filtered into politics, causing leaders to overestimate themselves and underestimate their adversaries–and to resort to violence to settle a conflict against unreasonable odds. In the Munich and Cuban missile crises, he shows how lessening positive illusions may allow leaders to pursue peaceful solutions. The human tendency toward overconfidence may have been favored by natural selection throughout our evolutionary history because of the advantages it conferred–heightening combat performance or improving one’s ability to bluff an opponent. And yet, as this book suggests–and as the recent conflict in Iraq bears out–in the modern world the consequences of this evolutionary legacy are potentially deadly. Since writing the book, I have been conducting empirical tests of when and how overconfidence influences political decision–making, and whether overconfidence leads to success or failure. Recently, we demonstrated that in wargames played against other people, men (but not women) were overconfident about the probability of success, and greater levels of overconfidence increased the likelihood of attacking their opponent (“Overconfidence in Wargames”). In a new set of studies, we are examining whether there is a link between confidence and aggression in people’s solutions to actual international crisis scenarios.


Related Links


Johnson, D. D. P., McDermott, R., Barrett, E., Cowden, J., Wrangham, R., McIntyre, M. & Rosen, S. (2006). Overconfidence in wargames: experimental evidence on expectations, aggression, gender, and testosterone. Proceedings of the Royal Society of London, Series B 273, 2513–2520.

Johnson, D. D. P. (2004). Overconfidence and War: The Havoc and Glory of Positive Illusions. Cambridge, M.A.: Harvard University Press.

Wrangham, R. (1999). Is military incompetence adaptive? Evolution and Human Behaviour 20, 3–17.

Trivers, R. L. (2000). The elements of a scientific theory of self–deception. Annals of the New York Academy of Sciences 907, 114–131.

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