The next time you’re juggling options — which friend to see, whichhouse to buy, which career to pursue — try asking yourself thisquestion: What would Xiang Yu do?

Xiang Yu was a Chinese general in the third century B.C. who tookhis troops across the Yangtze River into enemy territory and performedan experiment in decision making. He crushed his troops’ cooking potsand burned their ships.

He explained this was to focus them onmoving forward – a motivational speech that was not appreciated by manyof the soldiers watching their retreat option go up in flames. But General Xiang Yu would be vindicated, both on the battlefield and inthe annals of social science research.

He is one of the rolemodels in Dan Ariely’s new book, “Predictably Irrational,” anentertaining look at human foibles like the penchant for keeping toomany options open. General Xiang Yu was a rare exception to the norm, awarrior who conquered by being unpredictably rational.

Most people can’t make such a painful choice, not even the students at a bastion of rationality like the Massachusetts Institute of Technology,where Dr. Ariely is a professor of behavioral economics. In a series ofexperiments, hundreds of students could not bear to let their optionsvanish, even though it was obviously a dumb strategy (and they weren’teven asked to burn anything).

The experiments involved a gamethat eliminated the excuses we usually have for refusing to let go. Inthe real world, we can always tell ourselves that it’s good to keepoptions open.

You don’t even know how a camera’s burst-modeflash works, but you persuade yourself to pay for the extra featurejust in case. You no longer have anything in common with someone whokeeps calling you, but you hate to just zap the relationship.

Yourchild is exhausted from after-school soccer, ballet and Chineselessons, but you won’t let her drop the piano lessons. They could comein handy! And who knows? Maybe they will.

In the M.I.T.experiments, the students should have known better. They played acomputer game that paid real cash to look for money behind three doorson the screen. (You can play it yourself, without pay, at tierneylab.blogs.nytimes.com.) After they opened a door by clicking on it, each subsequent click earned a little money, with the sum varying each time.

Aseach player went through the 100 allotted clicks, he could switch roomsto search for higher payoffs, but each switch used up a click to openthe new door. The best strategy was to quickly check out the threerooms and settle in the one with the highest rewards.

Evenafter students got the hang of the game by practicing it, they wereflummoxed when a new visual feature was introduced. If they stayed outof any room, its door would start shrinking and eventually disappear.

Theyshould have ignored those disappearing doors, but the studentscouldn’t. They wasted so many clicks rushing back to reopen doors thattheir earnings dropped 15 percent. Even when the penalties forswitching grew stiffer – besides losing a click, the players had to paya cash fee – the students kept losing money by frantically keeping alltheir doors open.

Why were they so attached to those doors? Theplayers, like the parents of that overscheduled piano student, wouldprobably say they were just trying to keep future options open. Butthat’s not the real reason, according to Dr. Ariely and hiscollaborator in the experiments, Jiwoong Shin, an economist who is nowat Yale.

They plumbed the players’ motivations by introducingyet another twist. This time, even if a door vanished from the screen,players could make it reappear whenever they wanted. But even when theyknew it would not cost anything to make the door reappear, they stillkept frantically trying to prevent doors from vanishing.

Apparentlythey did not care so much about maintaining flexibility in the future.What really motivated them was the desire to avoid the immediate painof watching a door close.”Closing a door on an option isexperienced as a loss, and people are willing to pay a price to avoidthe emotion of loss,” Dr. Ariely says. In the experiment, the price waseasy to measure in lost cash. In life, the costs are less obvious -wasted time, missed opportunities. If you are afraid to drop anyproject at the office, you pay for it at home.