A study was carried out on the Capuchin Monkey to teach them the concept of money and a little bit about Economics. They were taught to buy fruit and Jell-O by means of silver discs used as currency. The monkeys understood and followed this. They were observed budgeting and following the same laws of economics that we follow.
During one chaotic incident, a researcher observed what appeared to be a monkey exchanging a disc for sex. The monkey that was paid for sex immediately traded the silver disc for a grape.
Stephen Dubner describes the research of Keith Chen and his experiments with the monkey economy. When monkeys were taught the concept of money, it resulted in the first recorded incident of monkey prostitution.