This post is the first in a four-part series of essays for Scientific American by primatologist Frans de Waal on human nature, based on his ongoing research. De Waal and other researchers appear in a series of Department of Expansion videos focusing on the same topic. [See below for parts 2, 3, and 4.]
Frans de Waal in Scientific American:
Fairness is viewed differently by the haves and have-nots. The underlying emotions and desires aren't half as lofty as the ideal itself. The most recognizable emotion is resentment. Look at how children react to the slightest discrepancy in the size of their pizza slice compared with their siblings'. They shout, “That's not fair!” but never in a way transcending their own desires.
An experiment with capuchin monkeys by Sarah Brosnan, of Georgia State University's CEBUS Lab, and myself illuminated this emotional basis. These monkeys will happily perform a task for cucumber slices until they see others getting grapes, which taste so much better. They become agitated, throw down their measly cucumbers, and go on strike. A perfectly fine vegetable has become unpalatable! Not all economists, philosophers and anthropologists were happy with our interpretation, because they traditionally consider the “sense of fairness” uniquely human. But by now there are many other experiments, even on dogs, that confirm our initial findings.
More here. And here are parts two, three, and four.