What happens when two monkeys are paid unequally

LOS ANGELES. April 27. KAZINFORM 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 other monkey being paid in grapes he becomes irate and rejects the pay.