Monkeys show sense of justice

economics > primate
"Monkeys have a sense of justice. They will protest if they see another monkey get paid more for the same task.
Researchers taught brown capuchin monkeys to swap tokens for food. Usually they were happy to exchange this "money" for cucumber.
But if they saw another monkey getting a grape - a more-liked food - they took offence. Some refused to work, others took the food and refused to eat it.
Scientists say this work suggests that human's sense of justice is inherited and not a social construct..."
Fascinating research: This is the Brosnan and de Waal paper from "Letters to Nature" [pdf format].
Politically and philosophically, research in primate ethology can hardly become more relevant than this. (and a rather direct blow to the hard versions of social constructivism I'd say...)