What Happens When Two Monkeys Are Paid Unequally

Frans de Waal, a Professor of Primate Behavior at Emory University, displays what happens when two capuchin monkeys are paid unequally. After receiving a rock as a payment the monkey on the left is given a cucumber, but when he sees the monkey on the right being paid in grapes, he becomes irate and rejects the pay.
[TEDBlogVideo]