When Monkeys Learn Commerce

Keith Chen, associate professor of economics at Yale University, wanted to test Adam Smith’s confident and classical assertion that man is the only animal that engaged in commerce and monetary exchange.  “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,” Smith had written.

For his experiment, Chen chose a group of 7 capuchins.  The capuchin is a species of small monkeys with a very small brain.  They spend most of their active life engaged in two activities: food and sex.  Hence, thought Chen, they are quite similar to human beings.  In fact, the capuchins are so greedy for food that they can overeat, and then throw up what they had eaten in order to eat more.  What will happen if such creatures are taught to make use of money?

Chen and Venkat Lakshminarayanan worked with the 7 capuchins kept at a lab set up by Laurie Santos, a psychologist.  First of all, the capuchins were taught the value of money by giving them silver coins and teaching them to use the coins to procure choice food from the researchers.  The capuchins came to learn not only to use the money but also to choose the food they wanted to buy.

Then they were subjected to price shock.  They were given less of a particular food for the money they paid.  For example, if they were used to getting three slices of apple for one coin, now they got only two.  The capuchins bought less of that food now that its price had gone up.  When its price was reduced, the capuchins bought more of it.  In other words, they behaved exactly like rational human beings in this regard.

The researchers now brought in gambling.  There were two games.  In both a coin was tossed.  But in one game, the capuchins received either one grape or a bonus one, dependent on the coin flip.  In the other game, the capuchins received either two grapes or none, dependent again on the coin flip.  Though the number of grapes that the capuchins received would be the same on the average, the creatures showed a remarkable preference for the first game.  That is, they avoided “the potential loss.”  In other words, they revealed what economists refer to as ‘loss aversion’ in human beings.  

One day the researchers were shocked by an act of mischief (or crime?) perpetrated by one particular capuchin named Felix.  Felix collected his 12 coins and, instead of buying food for them as usual, flung the coins in the cage.  Then he made a dash for them.  But chaos ensued.  Not only Felix, but all other capuchins made a dash for the coins scattered in the cage.  Nothing would persuade the capuchins to part with the coins they got illegally.  Nothing, that is, but the bribe of food.  They exchanged their ill-gotten coins for the food provided by the researchers.  They learnt a new lesson: crime pays.

The researchers were in for more shock.  As they watched they saw one male capuchin approaching a female one with the coin he had captured.  The female one had not got anything in the scramble.  Ken and his companion initially thought that the capuchin was being altruistic.  They were fascinated – until they saw the two creatures engaged in sex a few seconds later.  They were watching “the first instance of monkey prostitution in the recorded history of science.”  [The quoted phrase is from Superfreakonomics by S D Levitt & S J Dubner.  I’ve adapted this whole article from the last chapter of this book.  I acknowledge my debt to the authors.]

Ken and his companion were not allowed to continue their experiments any further.  The psychologist who owned the capuchins thought that the two economists would cause irreparable damage to the social structure of the capuchins.  So much so that the offspring of the capuchins might want to ride BMWs or go to the outer space for honeymoon or...