Progress Daily

As “Hollywood economist” Edward Jay Epstein has written, only about 10 percent of the U.S. population goes to movies on a weekly basis these days. That’s down from 65 percent half a century ago. The share of studio receipts coming from theater box office has declined from 100 percent in 1948 to a mere 18 percent in 2003. It’s been replaced over the years by what Epstein dubs “the rise of the home entertainment economy,” which consists of VHS and DVD rentals and sales, and pay and free TV fees. He also points out that this has hardly been a disaster for the six major studios — Paramount, Warner Bros., 20th Century Fox, Disney, Universal, and Sony — which are in fact doing as well as or better than ever.

Government figures on media usage of people 18 years and older estimate that the typical American consumed 3,444 hours of books, music, video, Internet, and the like in 1999. That figure was 3,599 hours in 2002 and is projected to rise to 3,874 hours by 2007.

In 2004, 19 million people could get video on demand, up 50 percent from 2003.

As Wired’s Chris Anderson detailed in his article ”The Long Tail” (also see his blog), the real action is offering everything for sale.

The average Barnes & Noble carries 130,000 titles. Yet more than half of Amazon’s book sales come from outside its top 130,000 titles.

“Hooray for Hollywood’s Slumping Sales,” by Nick Gillespie, Reason

A new study based on a survey of 5,000 couples across the country has determined that women whose husbands bring home more than 68 percent of the bacon are the most content.

“Regardless of what married women say they believe about gender, they tend to have happier marriages when their husband is a good provider — provided that he is also emotionally engaged,” said W. Bradford Wilcox, a University of Virginia sociologist. “I was very surprised to find that even egalitarian-minded women are happier when their marriages are organized along more gendered lines.”

Women who perceive that housework is shared in a fair manner consider themselves happier partners. Fair in this case does not necessarily mean splitting housework evenly — most of the women in this happier category perform the majority of household chores themselves. But because they believe that their husbands are playing an important role as providers, they view the unequal work split as fair.

The findings are detailed in the journal Social Forces.

“How to Make Your Wife Happy,” by Sara Goudarzi

While watching the same emotionally arousing event, different parts of women’s and men’s brains light up.

Larry Cahill has scanned the brains of men and women while they watched emotionally arousing events. The results show that typically for men only the right amygdala is activated, whereas in women, the left amygdala is activated. Previous research suggests that the right brain processes the general gist of events while the left side focuses on the details. This split could account for discrepancies between the way men and women recall emotional fights or events.

Imaging studies published in Nature indicate that in women, neurons on both sides of the brain are activated when they are listening, while in men, neurons on only one side of the brain are activated. When negotiating a virtual reality maze, men use both the left and right hippocampus for the task. To accomplish the same task, women use the right hippocampus and the right prefrontal cortex.

Rutgers University’s Helen Fisher conducts research on what men’s and women’s brains look like when they fall in love. For men, the most active regions of the brain are related to visual stimuli and penile erection. Whereas with women, several regions affiliated with emotions and memory recall become active.

According to Deborah Blum, author of the book, Sex on the Brain: The Biological Differences Between Men & Women, behavioral gender differences can be traced back to the different demands of being a sperm producer versus being an egg maker. Fisher’s theory is that in order to determine who will be a good mate, females must remember details of personality and behavior to determine what kind of provider their partners will be. The romantic love experienced by women is intended to start a mating process and ensure the female is not abandoned in the early years of raising children.

It has been suggested that testosterone, which runs high in men and tends to spike in times of challenge, propels a quick aggressive response. In women, on the other hand, oxytocin provides for lactation and it has been associated with bonding and nurturing behavior. These hormones act upon the brain in distinctive ways and suggest why men and women develop different parts of their brains, at different rates and at different times. This field of research is complicated because the brain is plastic and easily influenced by environment and circumstance.

Men and women also may respond to illness in dissimilar ways. Research shows that men and women require different dosages and kinds of drugs to treat schizophrenia, Alzheimer’s disease and depression.

“He Said, She Said,” by Polly Hanson and Maggie Villiger, Scientific American

Evidence has been accumulating since the 1930s that calorie restriction — reducing an animal’s energy intake below its energy expenditure — extends lifespan and delays the onset of age-related diseases in rats, dogs, fish and monkeys. Such results have inspired thousands of people to put up with constant hunger in the hope of living longer, healthier lives.

A study, known as CALERIE (Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy), sponsored by America’s National Institutes of Health, took 48 men and women aged between 25 and 50 and assigned them randomly to either a control group or a calorie-restriction regime. Those in the second group were required to cut their calorie intake for six months to 75% of that needed to maintain their weight.

Those on restricted diets had lower insulin resistance (high resistance is a risk factor for type 2 diabetes) and lower levels of low-density lipoprotein cholesterol (high levels are a risk factor for heart disease). They showed drops in body temperature and blood-insulin levels — both phenomena that have been seen in long-lived, calorie-restricted animals. They also suffered less oxidative damage to their DNA.

A family of enzymes called sirtuins act both as sensors of nutrient availability and as regulators of metabolic rate. Boosting the activity of sirtuins in yeast, nematode worms and fruitflies (three rapidly reproducing stalwarts of biological laboratories) results in longer lifespans. In 2003 a team led by David Sinclair of Harvard Medical School described 19 plant-derived molecules that activate sirtuins in yeast. One of these molecules, resveratrol, is found in red wine — which created excitement among those who think that a wine-rich diet is part of the explanation for the healthy old age apparently enjoyed by many who live in southern Europe.

In February, a group led by Dario Valenzano of the Scuola Normale Superiore in Pisa, Italy, showed that the effect applies in vertebrates, too. Dr Valenzano’s experiments with resveratrol increased the maximum lifespan of a small fish, called Nothobranchius furzeri, by 60%. (Nothobranchius furzeri was chosen because it is the shortest-lived vertebrate known, with a normal maximum lifespan of 12 weeks.)

Sirtris Pharmaceuticals, a firm based in Cambridge, Massachusetts, has identified a number of synthetic molecules whose effect on yeast is many times more potent than resveratrol’s.

Resveratrol is produced when a vine is under stress—for example, due to dehydration or over-exposure to sunshine. According to Dr Sinclair’s theory, which he calls xenohormesis, animals rely on such botanical stress signals to give them extra information about their own environments, in the same way that the alarm calls of one species warn others of danger. If bad things are happening to plants, he surmises, that is a reason for pre-emptive animal action. Animal bodies thus react to molecules such as resveratrol by activating their own defence mechanisms. These, in turn, protect their cells from stress-related damage.

Xenohormesis is a variation of a more general theory, hormesis. A good example of hormesis is exercise. In theory, this should damage cells because it increases oxygen uptake, and oxidative stress is bad for things like DNA. Of course, exercise is not actually bad for cells — and the reason is that the body activates defence mechanisms which overcompensate for the stress the exercise creates, producing beneficial effects. So, while chronic stress is always bad for you, a short period of mild stress followed by a period of recovery can be good.

Many of the health benefits of exercise are thought to be due to the synthesis of damage-controlling molecules called heat-shock proteins. A group led by Dr Suresh Rattan of Aarhus University in Denmark has been experimenting with other ways of triggering these proteins. He has found that taken in combination with exercise, a spice called curcumin boosts the production of heat-shock proteins several-fold.

According to Dr Rattan, such interventions improve the function of a cell over time, and in doing so, may produce clinical benefits such as protection against neurodegenerative diseases.

“Eat less, live more,” The Economist

One of the largest studies of the possible link between human traits and astrology has found little, if any, connection between the traditional Sun signs of the zodiac and people’s characteristics.

The study adds to the growing body of evidence that there is no scientific basis for star signs, like Aries and Taurus, signs that are based on the place of the Sun in relation to someone’s date of birth.

“When considering the current scientific standing with respect to Sun signs, it becomes clear that there is little or no truth in [them],” says Dr Peter Hartmann, who led the study in the May issue of the journal Personality and Individual Differences.

“As for the weekly horoscope based on mere Sun signs, then according to the current scientific standing, there is probably more truth in the comic strips.”

Hartmann and his colleagues used computer analysis and statistical methods to study possible astrological connections between over 15,000 individuals. Their test subjects came from two sources.

The first was the Vietnam Experience Study, which gathered information about intelligence, personality and date of birth for male military veterans.

The second was the 1979 National Longitudinal Study of Youth, which included intelligence and date of birth information for males and females aged between 15 and 24 years.

If connections existed over a rate of 5%, they were considered valid and not the result of random links.

The scientists could find no relationship between the time and date of a person’s birth and their personality traits, which the Vietnam study categorised using terms such as psychoticism, extraversion, neuroticism and social desirability.

Geoffrey Dean, a former astrologist based in Australia who researches the possible scientific validity of astrology, tracked over 2000 people who were born within minutes of each other.

The study, which spanned several decades, covered over 100 different characteristics, like marital status, IQ, anxiety and temperament was published in 2003 in the Journal of Consciousness Studies.

Dean came to a similar conclusion as Hartmann and his team, that date of birth does not affect an individual’s personality.

“Scientists dump cold water on astrology,” by Jennifer Viegas, News in Science

Men are more aware of potential love rivals when their partners are at their most fertile, a study suggests. A Liverpool University study of 64 men suggested those with ovulating partners were more wary of the dominant-looking men who attract women at this time.

Those with partners not at risk of conception are less aware, the Evolution and Human Behaviour study suggested.

Earlier research shows ovulating women are more attracted to dominant men.

Researchers in the university’s School of Biological Sciences showed their subjects, all of whom were in long-term relationships, a series of 66 pictures of two facial types — dominant and submissive.

They were then asked to rate the pictures for dominance, with a dominant person being defined as someone who “appeared as if they could get what they wanted.”

Those with partners in the most fertile stage of their menstrual cycle were more able to spot classic masculine face types — ie men with strong jaw lines, thinner lips and smaller eyes.

But those with partners who were not at risk of getting pregnant at that particular time were not.

Researcher Rob Burriss said many previous studies show that women’s preferences for male physical appearance change according to their fertility status.

He said during the fertile stage of their menstrual cycle they are more likely to be attracted to, and have an affair with, a masculine-looking man.

“Earlier research has shown that women are more interested in men who have a high testosterone face type — a jaw line like Arnold Schwarzenegger for example — for a short term relationship. They have better genes and are more likely to have strong children. This is because high testosterone levels create stronger immune systems which make them more resistant to disease.”

“Groups of animals, such as chimpanzees, can live quite happily together, but when a female is ready to mate the two dominant males within the group become rivals and fight for her attention. Similarly in humans, rated dominance increases when the female is most fertile. Men become more wary of masculine-looking men only when the female’s facial preferences begin to shift prior to ovulation.”

Dr George Fieldman, principal lecturer in psychology at Buckinghamshire Chilterns University College said, “Whether they consciously know it or not, women do tend to have affairs with dominant males during their most fertile phase. That’s independent of whether they want to get pregnant or not.”

“Fertility sparks ‘male rivalry’,” BBC News

Cambridge Energy Research Associates (CERA), an energy consultancy, has scrutinised all of the oil projects now under way around the world. The firm concludes that the world’s oil-production capacity could increase by as much as 15m barrels per day (bpd) between 2005 and 2010 — equivalent to almost 18% of today’s output and the biggest surge in history. Since most of these projects are already budgeted and in development, there is no geological reason why this wave of supply will not become available (though politics or civil strife can always disrupt output).

When the United States Geological Survey (USGS) studied the matter closely, it concluded that the world had around 3 trillion barrels of recoverable conventional oil in the ground. Of that, only one-third has been produced. That, argued the USGS, puts the global peak beyond 2025. And if “unconventional” hydrocarbons such as tar sands and shale oil (which can be converted with greater effort to petrol) are included, the resource base grows dramatically — and the peak recedes much further into the future.

Technological breakthroughs such as multi-lateral drilling helped defy predictions of decline in Britain’s North Sea that have been made since the 1980s: the region is only now peaking.

Globally, the oil industry recovers only about one-third of the oil that is known to exist in any given reservoir. New technologies like 4-D seismic analysis and electromagnetic “direct detection” of hydrocarbons are lifting that “recovery rate,” and even a rise of a few percentage points would provide more oil to the market than another discovery on the scale of those in the Caspian or North Sea.

Using ever fancier technologies, the oil business is drilling in deeper waters, more difficult terrain and even in the Arctic (which, as global warming melts the polar ice cap, will perversely become the next great prize in oil). Large parts of Siberia, Iraq and Saudi Arabia have not even been explored with modern kit.

There are good reasons to think that a global peak, whenever it comes, need not lead to a collapse in output. Saudi Arabia’s oil minister, Ali Naimi, points to an unexplored area on the Iraqi-Saudi border the size of California, and argues that such untapped resources could add 200 billion barrels to his country’s tally.

CERA’s Peter Jackson points out that the price signals that would surely foreshadow any “peak” would encourage efficiency, promote new oil discoveries and speed investments in alternatives to oil. That, he reckons, means the metaphor of a peak is misleading: “The right picture is of an undulating plateau.”

Kenneth Rogoff, a Harvard professor and the former chief economist of the IMF: “The oil market is highly developed, with worldwide trading and long-dated futures going out five to seven years. As oil production slows, prices will rise up and down the futures curve, stimulating new technology and conservation. We might be running low on $20 oil, but for $60 we have adequate oil supplies for decades to come.”

If the peak were to come after 2020 or 2030, as the International Energy Agency and other mainstream forecasters predict, then the rising tide of alternative fuels will help transform it into a plateau and ease the transition to life after oil.

In March, at the Sebring test track in Florida, a sleek Audi prototype R-10 became the first diesel-powered car to win an endurance race, pipping a field of petrol-powered rivals to the post. What makes this tale extraordinary is that the diesel used by the Audi was not made in the normal way, exclusively from petroleum. Instead, Shell blended conventional diesel with a super-clean and super-powerful new form of diesel made from natural gas (with the clunky name of gas-to-liquids, or GTL).

Several big GTL projects are under way in Qatar, where the North gas field is perhaps twice the size of even Ghawar when measured in terms of the energy it contains. Nigeria and others are also pursuing GTL. Since the world has far more natural gas left than oil — much of it outside the Middle East — making fuel in this way would greatly increase the world’s remaining supplies of oil.

So, too, would blending petrol or diesel with ethanol and biodiesel made from agricultural crops, or with fuel made from Canada’s “tar sands” or America’s shale oil. Companies are now also investing furiously to convert not only natural gas but also coal into a liquid fuel. Daniel Yergin of CERA says “the very definition of oil is changing, since non-conventional oil becomes conventional over time.”

The Kern River oil field near Bakersfield, California is a super-giant field that is part of a cluster that has been pumping out oil for more than 100 years. It has already produced 2 billion barrels of oil, but has perhaps as much again left. The trouble is that it contains extremely heavy oil, which is very difficult and costly to extract. After other companies despaired of the field, Chevron brought Kern back from the brink. Applying a sophisticated steam-injection process, the firm has increased its output beyond the anticipated peak.

China also has deposits of heavy oil that would benefit from such an advanced approach. America, Canada and Venezuela have deposits of heavy hydrocarbons that surpass even the Saudi oil reserves in size. The Saudis have invited Chevron to apply its steam-injection techniques to recover heavy oil in the neutral zone that the country shares with Kuwait. Mr Naimi, the oil minister, recently estimated that this new technology would lift the share of the reserve that could be recovered as useful oil from a pitiful 6% to above 40%.

“Why the world is not about to run out of oil,” The Economist

If you’ve ever lived in a big city, chances are you know the feeling: You’re walking around downtown with a few hours to spare at the end of the day, and you know that somewhere nearby — perhaps only a few blocks away — there’s a great bar or café that’s packed with interesting people. If it’s your hometown, you might even suspect that a few of your friends, or friends of your friends, are hanging out there. But there’s no easy way to find it, other than by roaming the streets and peering into windows.

This is what economists would call an inefficient market. You have, on the one hand, a service that the city provides: bars and cafés filled with cool people. And you have a buyer willing to pay for that service. Yet most of the time, the buyer ends up schlepping home unsatisfied because there’s no way to connect with the service he seeks.

A pair of tech-savvy twentysomethings named Dennis Crowley and Alex Rainert created a solution to this problem. They call it Dodgeball. The service is a mix of social network tools (à la Friendster), simple cell phone messaging, and mapping software.

You sign up for the service and identify other members who are your “friends.” The next time you find yourself with a few hours to spare, you send a text message to Dodgeball specifying your location, and the service sends back a reply notifying you if any friends, or friends of friends, are within 10 blocks of you. Or you can “announce” your own plans. Dodgeball even lets you define “crushes” that have a special weight on the system.

Dodgeball only knows where you are when you choose to announce your presence. You can’t be “seen” by other members until you’ve sent a text message alerting your friends and crushes that you’re at a specific location. So far, the service has been rolled out in 22 cities, including New York, San Francisco, Los Angeles, Chicago, Washington, Boston, and Seattle. Earlier this year, Crowley and Rainert announced that they had sold their two-person company to Google — so integration with the popular GoogleMaps feature can’t be far behind.

The ideal environment for Dodgeball is one where there are dozens of potential hangout spots within a few blocks of where you are and thousands of potential people to hang with. It’s easy to imagine the model extended beyond your immediate social network into more narrow needs: Find all the Civil War buffs within 10 blocks of me, or Jungian psychoanalysts, or native Portuguese speakers. Or find me the nearest bowl of vichyssoise, or an available masseuse, or an empty taxi.

Urban theorist Jane Jacobs observed many years ago that, paradoxically, huge cities create environments where small niches can flourish. A store selling nothing but buttons most likely won’t be able to find a market in a town of 50,000 people, but in New York City, there’s an entire button-store district. If you have idiosyncratic tastes, you’re much more likely to find someone who shares those tastes in a city of 9 million people.

The small greatly outnumber the large on the Internet as well. Amazon can maintain vast inventories of lesser-known titles because they don’t have the real estate constraints of traditional bookstores and because the Internet makes it so much easier to find the niche readers who will buy those books. The hot buzzword for this trend is “long tail” economics; instead of concentrating exclusively on big mass hits, online businesses can target the long tail of quirkier fare. In the old model, the economics dictated that it was always better to sell a million copies of one album. But in the digital age, it can be just as profitable to sell a hundred copies each of a thousand different albums.

As the technology increasingly allows us to satisfy more eclectic needs, any time those needs require a physical presence — whether it’s sipping your cold soup or meeting your crush in a bar — the logic of the long tail will favor urban environments over less densely populated ones.

“Friends 2005: Hooking Up,” by Steven Johnson

“The U.S. used to import coffee from around 25 countries,” says David E. Weinstein, an economist at Columbia University. “Now we import it from 52 countries. Beer we import from three times more countries than we used to.”

Starbucks’ Web site lists coffee varieties from Brazil, Colombia, Costa Rica, Ethiopia, Guatemala, Indonesia, Mexico, New Guinea, Panama, Yemen and Zimbabwe. “When you compare two types of coffee, you may not think one is necessarily better,” Professor Weinstein says. “But sometimes you’d like to drink a certain type of coffee, and other times you’d like to drink another type of coffee.” In most economic statistics, coffee is coffee, beer is beer and shoes are shoes.

In a recent working paper for the National Bureau of Economic Research, Professor Weinstein and Christian Broda, an economist with the Federal Reserve Bank of New York, estimate how much international trade has benefited consumers simply by increasing variety. Consumers, they estimate, would be willing to pay $280 billion a year, or about 3 percent of gross domestic product, to have access to the variety of goods that were available in 2001, rather than what they could have bought in 1972, which suggests that measurements of real price increases, like the Consumer Price Index, are overstated.

The economists looked at the number of goods, like red wine, and varieties, which they defined as goods from a certain country, like red wine from France. For thousands of goods, they calculated how much an increase in variety mattered to consumers — how “substitutable” the varieties were.

Consumers do not generally care what country a commodity like crude oil comes from, for example. They care much more about varieties of wine, automobiles or cheese, and they value some varieties more than others. Access to French wine is more important to most people than access to Japanese or Australian wine.

“The nasty mathematics,” Professor Weinstein says about the paper, “is all about trying to make adjustments for the fact that qualities of varieties may vary across countries.”

Economists generally use the term “variety” to mean the least aggregated version of a good in their data, but not necessarily a specific brand, much less an individual item. To a consumer, of course, variety has increased even more than the economists’ data indicate — not all red wine from France is the same. As a result, the paper’s calculations probably understate the gains from increasing variety.

The calculations took about four days, using four computers. Ten years ago, the economists estimate, the same calculations, also using four computers, would have taken more than four months.

Once the economists determined how much variety mattered for each good, they looked at how much variety had increased. From 1972 to 2001, the number of varieties increased from 74,667 (7,731 goods, from an average of 9.7 countries) to 259,215 (16,390 goods, from an average of 15.8 countries).

Using this information, they calculated a price index that measured how much each variety increase was worth to consumers.

The greatest gains took place from 1972 to 1988, a period when conventional measures show a relatively stagnant standard of living. During this period, major exporters, notably South Korea and China, liberalized their economies.

In an article published in The American Economic Review in May, the economists use less detailed data to estimate the worldwide benefits of variety growth. “Countries like China, Mexico, the former U.S.S.R., and Singapore have welfare gains that are double digits — three to five times larger than those for the U.S.,” Dr. Broda says.

The benefits of variety also help explain why many people are willing to pay more to live in big cities. Professor Weinstein, who used to teach at the University of Michigan, explains it this way: “In Ann Arbor, you have maybe a dozen good restaurants to choose from, and in New York you probably have several thousand good restaurants to choose from. Yet when you compute the price of a meal, you don’t take that at all into account.”

“Variety, the spice of life, has measurable value. But it’s not easy to determine,” by Virginia Postrel

In a laboratory at Yale-New Haven Hospital, seven capuchin monkeys have been taught to use money. They respond quite rationally to simple incentives; respond irrationally to risky gambles; fail to save; steal when they can; and use money for food and, on occasion, sex.

Keith Chen, a Yale economist who, along with Laurie Santos, a psychologist, is exploiting these natural the desire for food to teach the capuchins to buy grapes, apples and Jell-O.

Chen began his monkey work as a Harvard graduate student, in concert with Marc Hauser, a psychologist. The Harvard monkeys were cotton-top tamarins, and the experiments with them concerned altruism. Two monkeys faced each other in adjoining cages, each equipped with a lever that would release a marshmallow into the other monkey’s cage. The only way for one monkey to get a marshmallow was for the other monkey to pull its lever.

The tamarins were fairly cooperative but still showed a healthy amount of self-interest: over repeated encounters with fellow monkeys, the typical tamarin pulled the lever about 40 percent of the time. Then Hauser and Chen conditioned one tamarin to always pull the lever (thus creating an altruistic stooge) and another to never pull the lever (thus creating a selfish jerk). The stooge and the jerk were then sent to play the game with the other tamarins. The stooge blithely pulled her lever over and over, never failing to dump a marshmallow into the other monkey’s cage.

Initially, the other monkeys responded in kind, pulling their own levers 50 percent of the time. But once they figured out that their partner was a pushover (like a parent who buys her kid a toy on every outing whether the kid is a saint or a devil), their rate of reciprocation dropped to 30 percent — lower than the original average rate.

The selfish jerk, meanwhile, was punished even worse. Once her reputation was established, whenever she was led into the experimenting chamber, the other tamarins “would just go nuts,” Chen recalls. “They’d throw their feces at the wall, walk into the corner and sit on their hands, kind of sulk.”

When Chen began to teach the Yale capuchins to use money, the essential idea was to give a monkey a dollar and see what it did with it. The currency Chen settled on was a silver disc, one inch in diameter, with a hole in the middle. It took several months of rudimentary repetition to teach the monkeys that these tokens were valuable as a means of exchange for a treat and would be similarly valuable the next day. A capuchin would then be presented with 12 tokens on a tray and have to decide how many to surrender for, say, Jell-O cubes versus grapes. This first step allowed each capuchin to reveal its preferences and to grasp the concept of budgeting.

Then Chen introduced price shocks and wealth shocks. If, for instance, the price of Jell-O fell (two cubes instead of one per token), would the capuchin buy more Jell-O and fewer grapes? The capuchins responded rationally to tests like this. In economist-speak, the capuchins adhered to the rules of utility maximization and price theory: when the price of something falls, people tend to buy more of it.

Chen next introduced a pair of gambling games and set out to determine which one the monkeys preferred. In the first game, the capuchin was given one grape and, dependent on a coin flip, either retained the original grape or won a bonus grape. In the second game, the capuchin started out owning the bonus grape and, once again dependent on a coin flip, either kept the two grapes or lost one. These two games are in fact the same gamble, with identical odds, but one is framed as a potential win and the other as a potential loss.

The capuchins far preferred to take a gamble on the potential gain than the potential loss. This is not what an economics textbook would predict. The laws of economics state that these two gambles, because they represent such small stakes, should be treated equally. But in similar experiments, it turns out that humans tend to make the same type of irrational decision at a nearly identical rate. Documenting this phenomenon, known as loss aversion, is what helped the psychologist Daniel Kahneman win a Nobel Prize in economics. The data generated by the capuchin monkeys, Chen says, “make them statistically indistinguishable from most stock-market investors.”

During a recent capuchin experiment that used cucumbers as treats, a research assistant happened to slice the cucumber into discs instead of cubes, as was typical. One capuchin picked up a slice, started to eat it and then ran over to a researcher to see if he could “buy” something sweeter with it. To the capuchin, a round slice of cucumber bore enough resemblance to Chen’s silver tokens to seem like another piece of currency.

The monkeys never deliberately save any money, but they do sometimes purloin a token or two during an experiment. All seven monkeys live in a communal main chamber of about 750 cubic feet. For experiments, one capuchin at a time is let into a smaller testing chamber next door. Once, a capuchin in the testing chamber picked up an entire tray of tokens, flung them into the main chamber and then scurried in after them — a combination jailbreak and bank heist — which led to a chaotic scene in which the human researchers had to rush into the main chamber and offer food bribes for the tokens.

Something else happened during that chaotic scene that convinced Chen of the monkeys’ true grasp of money. Perhaps the most distinguishing characteristic of money, after all, is its fungibility, the fact that it can be used to buy not just food but anything. During the chaos in the monkey cage, Chen saw what was probably the first observed exchange of money for sex in the history of monkeykind. (The monkey who was paid for sex immediately traded the token in for a grape.)

“Monkey Business: Keith Chen’s Monkey Research” by Stephen J. Dubner and Steven D. Levitt