Do Monkeys Understand Money?

Monkeys don't care about money, per se, but they do care about marshmallows. (This already is a difference of gigantic proportions in that monkeys must learn about resource-exchange using something that is already a primary reinforcer - food - whereas humans can extend the range of their motivations to secondary reinforcers.) A resource (marshmallows) exchange task was introduced whereby pressing a lever would give another monkey a marshmallow; hence this was a task that involved a bit of altruism. Not only were monkeys taught about the game. Two specific monkeys were conditioned (entrained), such that one always pulled the lever for his monkey partner (thus being a very generous partner) and the other never pulled the lever for his partner (stingy). Then they let these conditioned monkeys play the game with other monkeys. Monkeys that played with the highly generous monkey figured it out and quickly took advantage of him. Monkeys that played with the stingy monkey also figured it out quickly and subsequently shunned or were aggressive toward him.

http://blogs.psychologytoday.com/blog/cultural-animal/200807/the-evolution-economic-rationality-do-monkeys-understand-money