Keith Chen, an economist at Yale who is researching whether monkeys can be trained to understand monetary transactions, never suspected that it would come to this:
Something else happened during that chaotic scene, something that convinced Chen of the monkeys’ true grasp of money. Perhaps the most distinguishing characteristic of money, after all, is its fungibility, the fact that it can be used to buy not just food but anything. During the chaos in the monkey cage, Chen saw something out of the corner of his eye that he would later try to play down but in his heart of hearts he knew to be true. What he witnessed was probably the first observed exchange of money for sex in the history of monkeykind. (Further proof that the monkeys truly understood money: the monkey who was paid for sex immediately traded the token in for a grape.)
This is a sensitive subject. The capuchin lab at Yale has been built and maintained to make the monkeys as comfortable as possible, and especially to allow them to carry on in a natural state. The introduction of money was tricky enough; it wouldn’t reflect well on anyone involved if the money turned the lab into a brothel. To this end, Chen has taken steps to ensure that future monkey sex at Yale occurs as nature intended it.
But these facts remain: When taught to use money, a group of capuchin monkeys responded quite rationally to simple incentives; responded irrationally to risky gambles; failed to save; stole when they could; used money for food and, on occasion, sex. In other words, they behaved a good bit like the creature that most of Chen’s more traditional colleagues study: Homo sapiens.
Now that I’ve gotten your attention, I do want to comment seriously on one aspect of this research, which is that money is a form of symbolic communication. As such, it meets several of Charles Hockett’s design features for comparing animal and human communication: interchangeability, arbitrariness, discreteness, displacement, and learnability. If, indeed, the monkeys do understand money (and I’m inclined to believe that they do), then they are displaying remarkable cognitive abilities. I have long believed that humans place too much stake on language in evaluating the cognitive abilities of our fellow creatures, and I hope that experiments like these serve to broaden our understanding of the multiple intelligences required for linguistic communication.
UPDATE: Mark Liberman thinks that “the silver disks” aren’t really relevant, and that its simply “a bit of a presentational trick.” Nonetheless, he concludes:
In my view, this is yet another interesting demonstration that non-human mammals have more of the basic abilities required for speech and language than one might have thought.
I thought that this is what I said. Maybe I’m lacking some of those basic abilities we supposedly share with non-human mammals.