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 taugh