Monkeys demand equal pay for their labors

Monkeys seem to have the ability to share the sentiment of the #OccupyWallStreet when it comes to equal pay. Grapes and cucumbers are not equal and these monkeys seem to know it.
It’s part of an experiment type that has been duplicated numerous times. Animals that are rewarded for performing a task are okay when they each receive the same compensation for performing the same work regardless of how good or bad the reward is, but once one animal seems to be getting more reward than the other, they take offense to it.
In the case of the angry monkey in the TED video below, one monkey takes great offense.