By Steve Gillman - August 1, 2011
It isn't a topic that I ever anticipated writing about, but
monkey prostitution is not just a joke. It has actually been
observed, as I discovered when I was recently was reading Super
Freakonomics, by Steven D. Levitt and Stephen J. Dubner. It all
started with some economics research using... monkeys, of course.
Economist Keith Chen wondered what would happen if he taught
monkeys to use money, so he designed an experiment to do just
that. Using Capuchin monkeys, he kept them in a large enclosure
with a small chamber they could enter at one end. In that chamber
one monkey at a time could interact with the handlers. For money
he use small shiny discs.
When the monkeys were given the coins they usually threw them
aside after inspecting them. If they couldn't eat it or have
sex with it, they weren't interested in much. But when they gave
it back to the handlers, they were given something good to eat.
Thus, with time and difficulty they learned that the coins had
value: they could buy tasty treats with them.
Once they knew that the coins had value, Chen and colleagues
experimented with prices. A monkey might be given a dozen coins,
for example, and normally could trade one for three sweet gelatin
cubes or an three apple slices (and they each had their preferences).
But when they started getting just one or two gelatin cubes for
a coin, the monkeys did as humans do: they bought less of the
snacks. This is considered rational behavior by economists.
Then irrational behavior was tested with gambling games. Two
scenarios were created. First, a monkey was shown a grape and
a coin was tossed. If it landed showing heads, another grape
was added. Another researcher presented them with a different
game in which two grapes were shown to the monkey, but if the
coin flip was lost one was removed and the monkey just got the
remaining one. (Don't worry, we'll get the monkey prostitution
The games were the same statistically speaking, but the monkeys
eventually strongly preferred the first game. Getting a bonus
versus suffering a loss was more palatable, even if the net outcome
was the same. This is referred to as "loss aversion"
in behavioral economics, and has been noted in humans in many
experiments. We are as irrational as the monkeys, in other words.
The most interesting discovery was made by accident. One day
a monkey threw all of his dozen coins into the large enclosure
instead of spending them. Chaos erupted as the other monkeys
grabbed them. As the researchers bribed the monkeys with treats
to get the coins back, they saw one of the male monkeys approaching
a female. He gave a coin to her and soon they were having sex.
This is believed to be the first recorded instance of monkey
prostitution. As soon as they were done (about eight seconds
for capuchins), the female brought the coin to a researcher to
buy some grapes.
And some people think economics is a boring subject.