Two monkeys were paid unequal wages...an old video from the TED series.

[pecosbob]

What happens when two monkeys are paid unequally? Fairness, reciprocity, empathy, cooperation -- caring about the well-being of others seems like a very human trait. But Frans de Waal shares some surprising videos of behavioral tests, on primates and other mammals, that show how many of these moral traits all of us share.

full video here...https://www.ted.com/talks/frans_de_waal_moral_behavior_in_animals