Daniel Kahneman's ground-breaking research into decision making and judgment has challenged fundamental beliefs about human nature. In study after study,together with Amos Tversky, he showed that when it comes to making decisions, humans are predisposed to irrationality. Their surprising findings have had profound implications for everything from behavioral economics and politics, to advanced medicine and sports. Their work, and its impact, is hardly obscure. Mr. Kahneman won the 2002 Nobel Prize in Economics (Mr. Tversky died in 1996.)