"Human beings, as it turns out, have too much faith in themselves. The detection of falsehood is scarcely the only domain where they overestimate their abilities. A survey of British motorists not long ago revealed that 95 percent thought they were better-than-average drivers. Similarly, most people think they are likely to live longer than the mean. In a classic 1977 paper in the Journal of Experimental Psychology, Baruch Fischhoff, Paul Slovic, and Sarah Lichtenstein reported that people often pronounce themselves absolutely certain of beliefs that are untrue. Subjects would declare themselves 100 percent sure that, say, the potato originated in Ireland, when it actually came from Peru.

Overconfidence is nearly universal. In fact, a study some years ago found that the only group of people free from it--the only group with a realistic view of their own capacities--were the clinically depressed. But is overconfidence distributed equally? Not according to a widely publicized paper in last December's issue of the Journal of Personality and Social Psychology. The authors, David A. Dunning of Cornell and his graduate student Justin Kruger, drew a poignant conclusion from their research: The most incompetent people have the most inflated notion of their abilities. "Not only do they reach erroneous conclusions and make unfortunate choices," the two psychologists wrote, "but their incompetence robs them of the ability to realize it.""