By JOHN TIERNEYPublished: February 26, 2008The next time you’re juggling options — which friend to see, which house to buy, which career to pursue — try asking yourself this question: What would Xiang Yu do?Xiang Yu was a Chinese general in the third century B.C. who took his troops across the Yangtze River into enemy territory and performed an experiment in decision making. He crushed his troops’ cooking pots and burned their ships.He explained this was to focus them on moving forward — a motivational speech that was not appreciated by many of the soldiers watching their retreat option go up in flames. But General Xiang Yu would be vindicated, both on the battlefield and in the annals of social science research.He is one of the role models in Dan Ariely’s new book, “Predictably Irrational,”...