Cocksure: Banks, Battles, and the Psychology of Overconfidence (click here)

This is what social scientists mean when they say that human overconfidence can be an adaptive trait. “In conflicts involving mutual assessment, an exaggerated assessment of the probability of winning increases the probability of winning,” Richard Wrangham, a biological anthropologist at Harvard, writes. “Selection therefore favors this form of overconfidence.” Winners know how to bluff. And who bluffs the best? The person who, instead of pretending to be stronger than he is, actually believes himself to be stronger than he is. According to Wrangham, self-deception reduces the chances of “behavioral leakage”; that is, of “inadvertently revealing the truth through an inappropriate behavior.” This much is in keeping with what some psychologists have been telling us for years—that it can be useful to be especially optimistic about how attractive our spouse is, or how marketable our new idea is. In the words of the social psychologist Roy Baumeister, humans have an “optimal margin of illusion.”