Maymunlar üzerinde ekonomi oyunları

Some of these microeconomists do not limit their research to the human race.

Keith Chen, the son of Chinese immigrants, is a hyper-verbal, sharp-dressing thirty-three-year-old with spiky hair. After an itinerant upbringing in the rural Midwest, Chen attended Stanford, where after a brief infatuation with Marxism, he made an about-face and took up economics. Now he is an associate professor of economics at Yale.

His research agenda was inspired by something written long ago by Adam Smith, the founder of classical economics: “Nobody ever saw a dog make a fair and deliberate exchange of one bone for another with another dog. Nobody ever saw one animal by its gestures and natural cries signify to another, this is mine, that yours; I am willing to give this for that.”

In other words, Smith was certain that humankind alone had a knack for monetary exchange.

But was he right?

In economics, as in life, you’ll never find the answer to a question unless you’re willing to ask it, as silly as it may seem. Chen’s question was simply this: What would happen if I could teach a bunch of monkeys to use money?

Chen’s monkey of choice was the capuchin, a cute, brown New World monkey about the size of a one-year-old child, or at least a scrawny one-year-old who has a very long tail. “The capuchin has a small brain,” Chen says, “and it’s pretty much focused on food and sex.” (This, we would argue, doesn’t make the capuchin so different from many people we know, but that’s another story.) “You should really think of a capuchin as a bottomless stomach of want. You can feed them marshmallows all day, they’ll throw up, and then come back for more.”

To an economist, this makes the capuchin an excellent research subject.

Chen, along with Venkat Lakshminarayanan, went to work with seven capuchins at a lab set up by the psychologist Laurie Santos at Yale–New Haven Hospital. In the tradition of monkey labs everywhere, the capuchins were given names—in this case, derived from characters in James Bond films. There were four females and three males. The alpha male was named Felix, after the CIA agent Felix Leiter. He was Chen’s favorite.

The monkeys lived together in a large, open cage. Down at one end was a much smaller cage, the testing chamber, where one monkey at a time could enter to take part in experiments. For currency, Chen settled on a one-inch silver disc with a hole in the middle—“kind of like Chinese money,” he says.

The first step was to teach the monkeys that the coins had value. This took some effort. If you give a capuchin a coin, he will sniff it and, after determining he can’t eat it (or have sex with it), he’ll toss it aside. If you repeat this several times, he may start tossing the coins at you, and hard.

So Chen and his colleagues gave the monkey a coin and then showed a treat. Whenever the monkey gave the coin back to the researcher, it got the treat. It took many months, but the monkeys eventually learned that the coins could buy the treats.

It turned out that individual monkeys had strong preferences for different treats. A capuchin would be presented with twelve coins on a tray—his budget constraint—and then be offered, say, Jell-O cubes by one researcher and apple slices by another. The monkey would hand his coins to whichever researcher held the food he preferred, and the researcher would fork over the goodies.

Chen now introduced price shocks and income shocks to the monkeys’ economy. Let’s say Felix’s favorite food was Jell-O, and he was accustomed to getting three cubes of it for one coin. How would he respond if one coin suddenly bought just two cubes? To Chen’s surprise, Felix and the others responded rationally. When the price of a given food rose, the monkeys bought less of it, and when the price fell, they bought more. The most basic law of economics—that the demand curve slopes downward—held for monkeys as well as humans.

Now that he had witnessed their rational behavior, Chen wanted to test the capuchins for irrational behavior. He set up two gambling games. In the first, a capuchin was shown one grape and, dependent on a coin flip, either got only that grape or won a bonus grape as well. In the second game, the capuchin started out seeing two grapes, but if the coin flip went against him, the researchers took away one grape and the monkey got only one.

In both cases, the monkey got the same number of grapes on average. But the first gamble was framed as a potential gain while the second was framed as a potential loss.

How did the capuchins react?

Given that the monkeys aren’t very smart in the first place, you might assume that any gambling strategy was well beyond their capabilities. In that case, you’d expect them to prefer it when a researcher initially offered them two grapes instead of one. But precisely the opposite happened! Once the monkeys figured out that the two-grape researcher sometimes withheld the second grape and that the one-grape researcher sometimes added a bonus grape, the monkeys strongly preferred the one-grape researcher. A rational monkey wouldn’t have cared, but these irrational monkeys suffered from what psychologists call “loss aversion.” They behaved as if the pain from losing a grape was greater than the pleasure from gaining one.

Up to now, the monkeys appeared to be as rational as humans in their use of money. But surely this last experiment showed the vast gulf that lay between monkey and man.

Or did it?

The fact is that similar experiments with human beings—day traders, for instance—had found that people make the same kind of irrational decisions at a nearly identical rate. The data generated by the capuchin monkeys, Chen says, “make them statistically indistinguishable from most stock-market investors.”

So the parallels between human beings and these tiny-brained, food-and-sex monkeys remained intact. And then, as if Chen needed any further evidence of these parallels, the strangest thing happened in the lab.

Felix scurried into the testing chamber, just as he’d done countless times before, but on this day, for reasons Chen could never understand, Felix did not gather up the twelve coins on the tray and use them to buy food. Instead, he flung the entire tray’s worth of coins back into the communal cage and, fleeing the testing chamber, dashed in after them—a bank heist followed by a jailbreak.

There was chaos in the big cage, with twelve coins on the floor and seven monkeys going after them. When Chen and the other researchers went inside to get the coins, the monkeys wouldn’t give them up. After all, they had learned that the coins had value. So the humans resorted to bribing the capuchins with treats. This taught the monkeys another valuable lesson: crime pays.

Then, out of the corner of his eye, Chen saw something remarkable. One monkey, rather than handing his coin over to the humans for a grape or a slice of apple, instead approached a second monkey and gave it to her. Chen had done earlier research in which monkeys were found to be altruistic. Had he just witnessed an unprompted act of monkey altruism?

After a few seconds of grooming—bam!—the two capuchins were having sex. What Chen had seen wasn’t altruism at all, but rather the first instance of monkey prostitution in the recorded history of science.

And then, just to prove how thoroughly the monkeys had assimilated the concept of money, as soon as the sex was over—it lasted about eight seconds; they’re monkeys, after all—the capuchin who’d received the coin promptly brought it over to Chen to purchase some grapes.

Superfreakonomics,

The fight against cancer and effectiveness of chemotherapy

Most people want to fend off death no matter the cost. More than $40 billion is spent worldwide each year on cancer drugs. In the United States, they constitute the second-largest category of pharmaceutical sales, after heart drugs, and are growing twice as fast as the rest of the market. The bulk of this spending goes to chemotherapy, which is used in a variety of ways and has proven effective on some cancers, including leukemia, lymphoma, Hodgkin’s disease, and testicular cancer, especially if these cancers are detected early. 

But in most other cases, chemotherapy is remarkably ineffective. An exhaustive analysis of cancer treatment in the United States and Australia showed that the five-year survival rate for all patients was about 63 percent but that chemotherapy contributed barely 2 percent to this result. There is a long list of cancers for which chemotherapy had zero discernible effect, including multiple myeloma, soft-tissue sarcoma, melanoma of the skin, and cancers of the pancreas, uterus, prostate, bladder, and kidney. Consider lung cancer, by far the most prevalent fatal cancer, killing more than 150,000 people a year in the United States. 

A typical chemotherapy regime for non-small-cell lung cancer costs more than $40,000 but helps extend a patient’s life by an average of just two months. Thomas J. Smith, a highly regarded oncology researcher and clinician at Virginia Commonwealth University, examined a promising new chemotherapy treatment for metastasized breast cancer and found that each additional year of healthy life gained from it costs $360,000—if such a gain could actually be had. Unfortunately, it couldn’t: the new treatment typically extended a patient’s life by less than two months. Costs like these put a tremendous strain on the entire health-care system. 

Smith points out that cancer patients make up 20 percent of Medicare cases but consume 40 percent of the Medicare drug budget. Some oncologists argue that the benefits of chemotherapy aren’t necessarily captured in the mortality data, and that while chemotherapy may not help nine out of ten patients, it may do wonders for the tenth. Still, considering its expense, its frequent lack of efficacy, and its toxicity—nearly 30 percent of the lung-cancer patients on one protocol stopped treatment rather than live with its brutal side effects—why is chemotherapy so widely administered? The profit motive is certainly a factor. 

Doctors are, after all, human beings who respond to incentives. Oncologists are among the highest-paid doctors, their salaries increasing faster than any other specialists’, and they typically derive more than half of their income from selling and administering chemotherapy drugs. Chemotherapy can also help oncologists inflate their survival-rate data. It may not seem all that valuable to give a late-stage victim of lung cancer an extra two months to live, but perhaps the patient was only expected to live four months anyway. On paper, this will look like an impressive feat: the doctor extended the patient’s remaining life by 50 percent. Tom Smith doesn’t discount either of these reasons, but he provides two more. It is tempting, he says, for oncologists to overstate—or perhaps over-believe in—the efficacy of chemotherapy. “If your slogan is ‘We’re winning the war on cancer,’ that gets you press and charitable donations and money from Congress,” he says. “If your slogan is ‘We’re still getting our butts kicked by cancer but not as bad as we used to,’ that’s a different sell. 

The reality is that for most people with solid tumors—brain, breast, prostate, lung—we aren’t getting our butts kicked as badly, but we haven’t made much progress.” There’s also the fact that oncologists are, once again, human beings who have to tell other human beings they are dying and that, sadly, there isn’t much to be done about it. “Doctors like me find it incredibly hard to tell people the very bad news,” Smith says, “and how ineffective our medicines sometimes are.” If this task is so hard for doctors, surely it must also be hard for the politicians and insurance executives who subsidize the widespread use of chemotherapy. 

Despite the mountain of negative evidence, chemotherapy seems to afford cancer patients their last, best hope to nurse what Smith calls “the deep and abiding desire not to be dead.” Still, it is easy to envision a point in the future, perhaps fifty years from now, when we collectively look back at the early twenty-first century’s cutting-edge cancer treatments and say: We were giving our patients what? The age-adjusted mortality rate for cancer is essentially unchanged over the past half-century, at about 200 deaths per 100,000 people. 

This is despite President Nixon’s declaration of a “war on cancer” more than thirty years ago, which led to a dramatic increase in funding and public awareness. Believe it or not, this flat mortality rate actually hides some good news. Over the same period, age-adjusted mortality from cardiovascular disease has plummeted, from nearly 600 people per 100,000 to well beneath 300. What does this mean? Many people who in previous generations would have died from heart disease are now living long enough to die from cancer instead.

Indeed, nearly 90 percent of newly diagnosed lung-cancer victims are fifty-five or older; the median age is seventy-one. The flat cancer death rate obscures another hopeful trend. For people twenty and younger, mortality has fallen by more than 50 percent, while people aged twenty to forty have seen a decline of 20 percent. These gains are real and heartening—all the more so because the incidence of cancer among those age groups has been increasing. (The reasons for this increase aren’t yet clear, but among the suspects are diet, behaviors, and environmental factors.)

From Superfreakonomics

Ammonium nitrate

By 1850, worldwide population had grown to 1.3 billion; by 1900, 1.7 billion; by 1950, 2.6 billion. And then things really took off. Over the next fifty years, the population more than doubled, reaching well beyond 6 billion. If you had to pick a single silver bullet that allowed this surge, it would be ammonium nitrate, an astonishingly cheap and effective crop fertilizer. It wouldn’t be much of an overstatement to say that ammonium nitrate feeds the world. If it disappeared overnight, says the agricultural economist Will Masters, "most people’s diets would revert to heaps of cereal grains and root crops, with animal products and fruits only."

Food production per capita

In late eighteenth-century America, “it took 19 out of 20 workers to feed the country’s inhabitants and provide a surplus for export,” wrote the economist Milton Friedman. Two hundred years later, only 1 of 20 American workers was needed to feed a far larger population while also making the United States “the largest single exporter of food in the world.”