In 2005, Yale economist Keith Chen and psychologist Laurie Santos set out to answer a simple question: could monkeys understand money? They chose capuchin monkeys, gave them small silver tokens, and spent months teaching them that the tokens could be exchanged for food.
It worked. And then things got interesting.
Once the capuchins grasped the basic concept of currency, their behavior started looking uncomfortably familiar. They learned to budget, spending more tokens when prices dropped and holding back when things got expensive, exactly as economic theory predicts humans should behave. They figured out they could steal tokens from each other, and did so enthusiastically.
Then Chen tested their relationship with risk. He gave monkeys a choice between a guaranteed reward and a gamble with the same average payout. Like humans, they initially preferred the sure thing. But when he reframed the same choice so that the guaranteed option felt like a loss, the monkeys threw caution out and chased the gamble instead, even though the math hadn’t changed at all. It was the same irrational behavior seen in human gamblers doubling down when they’re losing.
The monkeys were doing it within weeks of learning what money was.
Then came the moment that made headlines. During a chaotic session in the enclosure, Chen noticed something happening in the corner of the cage. A male had paid a female a token. She accepted it. They spent some time together. Then she walked straight to a researcher and exchanged the token for a grape.
The researchers had set out to teach monkeys a simple economic concept. Within months, their subjects had independently discovered budgeting, theft, irrational gambling, and the oldest transaction in human history.
Scientists Taught Monkeys to Use Money — Then They Discovered Gambling, Theft, and Something Unexpected
