Pure Pedantry

Monkey Economics

i-265c7f321525c72194ae093b7d4f1ea1-normal_ABM-capuchin monkey-monteverde.jpgThe Freakonomics guys have a simply hysterical article in the New York Times magazine about monkey economics. The article discusses how monkeys possess the mental apparatus for economic valuation including the use of money. They train the monkeys to use silver tokens as currency to trade for food, and then they show that the monkeys behave very similarly to humans in a variety of situations. Money quote:

The capuchin is a New World monkey, brown and cute, the size of a scrawny year-old human baby plus a long tail. ”The capuchin has a small brain, and it’s pretty much focused on food and sex,” says Keith Chen, a Yale economist who, along with Laurie Santos, a psychologist, is exploiting these natural desires — well, the desire for food at least — to teach the capuchins to buy grapes, apples and Jell-O. “You should really think of a capuchin as a bottomless stomach of want,” Chen says. ”You can feed them marshmallows all day, they’ll throw up and then come back for more.” When most people think of economics, they probably conjure images of inflation charts or currency rates rather than monkeys and marshmallows. But economics is increasingly being recognized as a science whose statistical tools can be put to work on nearly any aspect of modern life. That’s because economics is in essence the study of incentives, and how people — perhaps even monkeys — respond to those incentives. A quick scan of the current literature reveals that top economists are studying subjects like prostitution, rock ‘n’ roll, baseball cards and media bias.

But do the capuchins actually understand money? Or is Chen simply exploiting their endless appetites to make them perform neat tricks?

Several facts suggest the former. 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.

Then there is the stealing. Santos has observed that 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, a reinforcement that in effect encouraged more stealing.

Something else happened during that chaotic scene, something 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 something out of the corner of his eye that he would later try to play down but in his heart of hearts he knew to be true. What he witnessed was probably the first observed exchange of money for sex in the history of monkeykind. (Further proof that the monkeys truly understood money: the monkey who was paid for sex immediately traded the token in for a grape.) (Emphasis mine.)

Read the whole thing. It’s hysterical.

Two things about this:

1) I am super jealous of these guys because this kind of research is too cool for words.

2) The fact that monkeys can perform these operations should not be surprising.

First, S-S conditioning — where the response associated with stimulus 1 becomes associated with stimulus 2 because of the association of stimulus 1 and 2 — is not new, and basically that is all money is. (It’s been a while since I took a class in classical conditioning, but I think they would call stimulus 2 a secondary reinforcer.) Money is only valuable because of the positive associations attached to things that money can buy. It is essentially a secondary reinforcer. If S-S conditioning is present in even lower animals, than most of them should be able to associate value with money.

Second, I work with rats at the moment, and sometimes they amaze me with the subtle calculations about value even they can make. Let me give you an example. I was running this experiment where I would switch the rats between two different tasks in a maze repeatedly. Basically the rat had to keep switching strategies to achieve a maximum reward. (Sort of like a Wisconsin Card Sorting Task for rats.)

Anyway, I was running this experiment for days and days and days until one day the rat just stopped switching between strategies. Instead he adopted this sort of middle of the road strategy where he would get a moderate reward no matter which task I expected him to do at the time. Annoying as all hell, but tricky that he could even make that calculation. He essentially calculated the highest expected value over a long period that could be expected if he did not change what he was doing (I think he was getting annoyed with switching).

What I am saying is that the mental apparatus in animals for calculating rewards is easily applied to economic calculation. Thus, it should not be surprising that given sufficient training animals can adopt economic behaviors similar to humans. The machinery in humans is more complex and more precise, but it is essentially the same.


  1. #1 Rick Bogle
    May 2, 2007

    Is it the word “monkey” that you found “hysterical” or the vomiting or the notion that they have sex?

  2. #2 Drekab
    May 2, 2007

    I think its the word monkey that gets me mostly.

    Personally, I think that the fact the monkeys confused cucumbers with silver coins supports the later hypothesis, the monkeys were trained to trade discy thingies for food, but thats just me.
    I’m confused about the gambling bit though. The obvious goal is to end up with the most grapes. If you start with one, at best you can have a 50% chance of getting two grapes. If you start with two, you have at best a 100% chance if you play the game right. I think it just proves that the monkeys and the average stockbroker are a bit smarter than the economists, or maybe I just don’t understand loss-aversion. :)
    Great find though, I’ll be passing this along!!

  3. #3 Cat Faber
    May 2, 2007

    This was a great post–thanks for alerting me to this article.

  4. #4 Drugmonkey
    May 2, 2007

    of course, it would have been a better model if the paid sex worker monkey traded the token for some cocaine. hmm, i smell grant application…

  5. #5 Jongpil Yun
    May 2, 2007

    That monkey is a whore. She’s going to hell.

  6. #6 Chris Crawford
    May 3, 2007

    I think the experimenters should be indicted for contributing to the delinquency of a monkey.

  7. #7 Joseph T. Young
    May 3, 2007

    Economists are often mistaken for heartless automatons who care about numbers not people. This research shows they care about
    1] food
    2] cost of food
    3] monkeys
    4] explaining behavior
    5] sex
    That is very gratifying

  8. #8 Matthew
    May 6, 2007

    Actually, I bet there’s a lot of interesting psychological economics study that could be done on various animals—presumably animals will exhibit similar biases to humans, without the complications of complex extra value systems layered on top of the instincts (complex ethical systems, dimly remembered freshmen econ classes, etc.).

  9. #9 olivia
    November 7, 2007


  10. #10 Nunya
    December 2, 2007

    Wow. Capuchin monkeys are still cute ^-^

  11. #11 Deck
    January 21, 2008

    Can You buy these monkeys? To Train myself? I know someone who has got one but dont know where from?

  12. #12 Cristina
    February 21, 2008

    First of all, it is incorrect to say that Capuchin’s posses small brains, relative to humans, yes. However, for their size they have the largest brain of any monkey. This research is in fact quite interesting, but much more importantly it’s cruel. To keep these animals tucked away in a lab simply to perform tricks and solve puzzles for our own amusement, is terrible. While it’s interesting I’m still not sure after reading the article, exactly what benefit or point of these experiments is. To keep animals that will trek three miles just for two or three palm nuts in a cage of about 750 cubic meters is horrible! Capuchin’s are quite intelligent and there is no excuse for depriving our monkey cousins of everything that is natural to them. As for the postings by people wondering where they can acquire themselves a pet monkey, PLEASE don’t do it! You will be purchasing an animal that has been literally ripped from it’s mothers arms. Yes, it will be cute, and cuddly, and particularly clingy due to the pyschological trauma of being removed from his mother at only a few days old. The world is full of pet monkeys that have been tossed aside because once they reach maturity it’s just not possible for the average person to handle them anymore. Animals are not ours to experiment on or use for entertainment!

  13. #13 asdf
    March 8, 2008

    way to buzzkill Deck

  14. #14 kayla brown
    March 15, 2008

    where can I buy one and how much is it?

  15. #15 Kayla Brown
    March 15, 2008

    I would really like to know because I have wanted one for a long time, and I live in Georgia there is not one place to get one here!!!!! So any Help at all would be great!!!!!!!!! thanks

  16. #16 STEPHANIE
    April 6, 2008


  17. #17 Josh Salmea
    July 3, 2008

    How much dos a black and white capuchin monkey that is about 7 weeks old cost? are they hard to fiend? do you have one?
    I also have a pet that cums from south America also, it is a Green Winged Macaw, I bot her in Los Angeles. So do you think they can get along? Thank you fore reeding my E mail.


  18. #18 robert beckham
    July 5, 2008

    I would like to know if you can buy one in the US robert beckham july 5 1130

  19. #19 srd
    October 21, 2008

    My comment is to the person who wrote that the “monkey is a whore and she’s going to hell” all I wanted to say is that why you are intitled to your opinion NO ONE WANTS TO HERE IT!!! SO KEEP YOUR MOUTH OFF THE POOR LITTLE MONKEY THAT CAN’T CUT YOU DOWN AND JUDGE YOU. If she could I am sure she would have a more intellegent come back than you.
    I’m not trying to be rude, it is just that I love monkeys and instead of saying something smart or even funny you took your anger and left handed sence of humor out on a picture of a monkey. so what did the monkey ever do to you?

  20. #20 mju
    October 29, 2008

    So this guy walks into a bar and there’s a capuchin monkey grinding an organ. He stops playing his little instrument and gets the guy a beer. “Well trained monkey.” says guy. The monkey’s trainer responds, “You know it. He sucks excellent dick as well.” “Gross.” “No seriously. Try it.” So the guy takes the monkey to the bathroom, comes out a few minutes later and says, “I have to have it, now and immediately for any price.” “Six thousand dollars, and your shoes.” The guy takes his purchase and returns home. In the middle of the night, the guy’s wife wakes up to a terrible racket in the kitchen, pots banging, glass breaking. She runs downstairs to find her husband, standing in the kitchen buck nekkid with an enormous erection and a monkey throwing pots and pans around. “What the hell is going on?” she yells. The guy replies, “If I can teach this monkey to cook (and the value of money) you’re out of here, bitch.”

  21. #21 Brittany
    December 14, 2008

    how much do these monkey cost please let me know i am 12years old and realy want you to tell me how munch it cost please i’m lonly! please reply!!!!!!!!!!!!!!

  22. #22 Mike
    May 6, 2010

    dude to the person bitching about lab research on monkeys. 750cubic meters is like WAY more space then the monkeys would get in a zoo, go complain to the zoos you probably enjoy so much. and this study seems relatively harmless, its not like they are testing harmful chemicals or new styles of surgery, they are researching the cognitive capabilities of the monkeys, and noting how quickly the monkeys caught on to currencies and values. there are way better things to protest, how about teen suicide or child abuse? or government corruption maybe?

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