List asked how long the break would last.

"Well, we don't know," the man said, "so why don't you just start unloading yourself."

It was customary for warehouse workers to unload a trucker's truck, or at least help. Plainly that wasn't going to happen.

"Well, if you guys don't want to help, that's fine," List said. "Just give me the keys to the forklift."

They laughed and told him the keys were lost.

So List, along with Jennifer, began unloading the truck, box by box. Drenched in sweat and thoroughly miserable, they labored under the mocking eyes of the four workmen. Finally only a few boxes were left. One of the workmen suddenly found the keys to the forklift and drove it over to List's truck.

Encounters like this had made John List seriously question whether altruism truly runs wild through the veins of humankind, as Dictator and other lab experiments argued.

Yes, that research had won much acclaim, including a n.o.bel Prize. But the more List thought about it, the more he wondered if perhaps those findings were simply-well, wrong.

In 2005, thanks largely to his field experiments, List was offered a tenured professor position at the University of Chicago, perhaps the most storied economics program in the world. This wasn't supposed to happen. It is a nearly inexorable law of academia that when a professor lands a tenured job, he does so at an inst.i.tution less prestigious than the one where he began teaching, and also less prestigious than where he received his Ph.D. John List, meanwhile, was like a salmon who swam downstream to sp.a.w.n, into the open water. Back in Wisconsin, his family was unimpressed. "They wonder why I've failed so miserably," he says, "why I'm not still in Orlando, where the weather is really great, instead of Chicago, where the crime is really high."

By now he knew the literature on altruism experiments as well as anyone. And he knew the real world a bit better. "What is puzzling," he wrote, "is that neither I nor any of my family or friends (or their families or friends) have ever received an anonymous envelope stuffed with cash. How can this be, given that scores of students around the world have outwardly exhibited their preferences for giving in laboratory experiments by sending anonymous cash gifts to anonymous souls?"

So List set out to definitively determine if people are altruistic by nature. His weapon of choice was Dictator, the same tool that created the conventional wisdom. But List had a few modifications up his sleeve. This meant recruiting a whole bunch of student volunteers and running a few different versions of the experiment.

He began with cla.s.sic Dictator. The first player (whom we'll call Annika once again) was given some cash and had to decide whether to give none, some, or even all of it to some anonymous Zelda. List found that 70 percent of the Annikas gave some money to Zelda, and the average "donation" was about 25 percent of the total. This result was perfectly in line with the typical Dictator findings, and perfectly consistent with altruism.

In the second version, List gave Annika another option: she could still give Zelda any amount of her money but, if she preferred, she could instead take $1 from Zelda. If the dictators were altruistic, this tweak to the game shouldn't matter at all; it should only affect the people who otherwise would have given nothing. All List did was expand the dictator's "choice set" in a way that was irrelevant for all but the stingiest of players.

But only 35 percent of the Annikas in this modified, steal-a-dollar-if-you-want version gave any money to Zelda. That was just half the number who gave in the original Dictator. Nearly 45 percent, meanwhile, didn't give a penny, while the remaining 20 percent took a dollar from Zelda.

Hey, what happened to all the altruism?

But List didn't stop there. In the third version, Annika was told that Zelda had been given the same amount of money that she, Annika, was given. And Annika could steal Zelda's entire payment-or, if she preferred, she could give Zelda any portion of her own money.

What happened? Now only 10 percent of the Annikas gave Zelda any money, while more than 60 percent of the Annikas took from Zelda. More than 40 percent of the Annikas took all of Zelda's money. Under List's guidance, a band of altruists had suddenly-and quite easily-been turned into a gang of thieves.

The fourth and final version of List's experiment was identical to the third-the dictator could steal the other player's entire pile of money-but with one simple twist. Instead of being handed some money to play the game, as is standard in such lab experiments, Annika and Zelda first had to work for it. (List needed some envelopes stuffed for another experiment, and with limited research funds he was killing two birds with one stone.)

After they worked, it was time to play. Annika still had the option of taking all of Zelda's money, as more than 60 percent of the Annikas did in the previous version. But now, with both players having earned their money, only 28 percent of the Annikas took from Zelda. Fully two-thirds of the Annikas neither gave nor took a penny.

So what had John List done, and what does it mean?

He upended the conventional wisdom on altruism by introducing new elements to a clever lab experiment to make it look a bit more like the real world. If your only option in the lab is to give away some money, you probably will. But in the real world, that is rarely your only option. The final version of his experiment, with the envelope-stuffing, was perhaps most compelling. It suggests that when a person comes into some money honestly and believes that another person has done the same, she neither gives away what she earned nor takes what doesn't belong to her.

But what about all the prizewinning behavioral economists who had identified altruism in the wild?

"I think it's pretty clear that most people are misinterpreting their data," List says. "To me, these experiments put the knife in it. It's certainly not altruism we've been seeing."

List had painstakingly worked his way up from truck driver's son to the center of an elite group of scholars who were rewriting the rules of economic behavior. Now, in order to stay true to his scientific principles, he had to betray them. As word of his findings began to trickle out, he suddenly became, as he puts it, "clearly the most hated guy in the field."

List can at least be consoled by knowing that he is almost certainly correct. Let's consider some of the forces that make such lab stories unbelievable.

The first is selection bias. Think back to the tricky nature of doctor report cards. The best cardiologist in town probably attracts the sickest and most desperate patients. So if you're keeping score solely by death rate, that doctor may get a failing grade even though he is excellent.

Similarly, are the people who volunteer to play Dictator more cooperative than average? Quite likely yes. Scholars long before John List pointed out that behavioral experiments in a college lab are "the science of just those soph.o.m.ores who volunteer to partic.i.p.ate in research and who also keep their appointment with the investigator." Moreover, such volunteers tend to be "scientific do-gooders" who "typically have...[a] higher need for approval and lower authoritarianism than non-volunteers."

Or maybe, if you're not a do-gooder, you simply don't partic.i.p.ate in this kind of experiment. That's what List observed during his baseball-card study. When he was recruiting volunteers for the first round, which he clearly identified as an economics experiment, he made note of which dealers declined to partic.i.p.ate. In the second round, when List dispatched customers to see if unwitting dealers would rip them off, he found that the dealers who declined to partic.i.p.ate in the first round were, on average, the biggest cheaters.

Another factor that pollutes laboratory experiments is scrutiny. When a scientist brings a lump of uranium into a lab, or a mealworm or a colony of bacteria, that object isn't likely to change its behavior just because it's being watched by someone in a white lab coat.

For human beings, however, scrutiny has a powerful effect. Do you run a red light when there's a police car-or, increasingly these days, a mounted camera-at the intersection? Thought not. Are you more likely to wash your hands in the office restroom if your boss is already washing hers? Thought so.

Our behavior can be changed by even subtler levels of scrutiny. At the University of Newcastle upon Tyne in England, a psychology professor named Melissa Bateson surrept.i.tiously ran an experiment in her own department's break room. Customarily, faculty members paid for coffee and other drinks by dropping money into an "honesty box." Each week, Bateson posted a new price list. The prices never changed, but the small photograph atop the list did. On odd weeks, there was a picture of flowers; on even weeks, a pair of human eyes. When the eyes were watching, Bateson's colleagues left nearly three times as much money in the honesty box. So the next time you laugh when a bird is frightened off by a silly scarecrow, remember that scarecrows work on human beings too.

How does scrutiny affect the Dictator game? Imagine you're a student-a soph.o.m.ore, probably-who volunteered to play. The professor running the experiment may stay in the background, but he's plainly there to record which choices the partic.i.p.ants are making. Keep in mind that the stakes are relatively low, just $20. Keep in mind also that you got the $20 just for showing up, so you didn't work for the money.

Now you are asked if you'd like to give some of your money to an anonymous student who didn't get $20 for free. You didn't really want to keep all that money, did you? You may not like this particular professor; you might even actively dislike him-but no one wants to look cheap in front of somebody else. What the heck, you decide, I'll give away a few of my dollars. But even a c.o.c.keyed optimist wouldn't call that altruism.

In addition to scrutiny and selection bias, there's one more factor to consider. Human behavior is influenced by a dazzlingly complex set of incentives, social norms, framing references, and the lessons gleaned from past experience-in a word, context. We act as we do because, given the choices and incentives at play in a particular circ.u.mstance, it seems most productive to act that way. This is also known as rational behavior, which is what economics is all about.

It isn't that the Dictator partic.i.p.ants didn't behave in context. They did. But the lab context is unavoidably artificial. As one academic researcher wrote more than a century ago, lab experiments have the power to turn a person into "a stupid automaton" who may exhibit a "cheerful willingness to a.s.sist the investigator in every possible way by reporting to him those very things which he is most eager to find." The psychiatrist Martin Orne warned that the lab encouraged what might best be called forced cooperation. "Just about any request which could conceivably be asked of the subject by a reputable investigator," he wrote, "is legitimized by the quasi-magical phrase "This is an experiment.'"

Orne's point was borne out rather spectacularly by at least two infamous lab experiments. In a 196162 study designed to understand why n.a.z.i officers obeyed their superiors' brutal orders, the Yale psychologist Stanley Milgram got volunteers to follow his instructions and administer a series of increasingly painful electric shocks-at least they thought the shocks were painful; the whole thing was a setup-to unseen lab partners. In 1971, the Stanford psychologist Philip Zimbardo conducted a prison experiment, with some volunteers playing guards and others playing inmates. The guards started behaving so s.a.d.i.s.tically that Zimbardo had to shut down the experiment.

When you consider what Zimbardo and Milgram got their lab volunteers to do, it is no wonder that the esteemed researchers who ran the Dictator game, with its innocuous goal of transferring a few dollars from one undergrad to another, could, as List puts it, "induce almost any level of giving they desire."

When you look at the world through the eyes of an economist like John List, you realize that many seemingly altruistic acts no longer seem so altruistic.

It may appear altruistic when you donate $100 to your local public-radio station, but in exchange you get a year of guilt-free listening (and, if you're lucky, a canvas tote bag). U.S. citizens are easily the world's leaders in per-capita charitable contributions, but the U.S. tax code is among the most generous in allowing deductions for those contributions.

Most giving is, as economists call it, impure altruism or warm-glow altruism. You give not only because you want to help but because it makes you look good, or feel good, or perhaps feel less bad.

Consider the panhandler. Gary Becker once wrote that most people who give money to panhandlers do so only because "the unpleasant appearance or persuasive appeal of beggars makes them feel uncomfortable or guilty." That's why people often cross the street to avoid a panhandler but rarely cross over to visit one.

And what about U.S. organ-donation policy, based on its unyielding belief that altruism will satisfy the demand for organs-how has that worked out?

Not so well. There are currently 80,000 people in the United States on a waiting list for a new kidney, but only some 16,000 transplants will be performed this year. This gap grows larger every year. More than 50,000 people on the list have died over the past twenty years, with at least 13,000 more falling off the list as they became too ill to have the operation.

If altruism were the answer, this demand for kidneys would have been met by a ready supply of donors. But it hasn't been. This has led some people-including, not surprisingly, Gary Becker-to call for a well-regulated market in human organs, whereby a person who surrenders an organ would be compensated in cash, a college scholarship, a tax break, or some other form. This proposal has so far been greeted with widespread repugnance and seems for now politically untenable.

Recall, meanwhile, that Iran established a similar market nearly thirty years ago. Although this market has its flaws, anyone in Iran needing a kidney transplant does not have to go on a waiting list. The demand for transplantable kidneys is being fully met. The average American may not consider Iran the most forward-thinking nation in the world, but surely some credit should go to the only country that has recognized altruism for what it is-and, importantly, what it's not.

If John List's research proves anything, it's that a question like "Are people innately altruistic?" is the wrong kind of question to ask. People aren't "good" or "bad." People are people, and they respond to incentives. They can nearly always be manipulated-for good or ill-if only you find the right levers.

So are human beings capable of generous, selfless, even heroic behavior? Absolutely. Are they also capable of heartless acts of apathy? Absolutely.