As economic inequality increased in many wealthy nations in recent years, a debate has developed around the question of whether inequality is bad for national economies and bad for their citizens. A captivating video clip of monkey behavior (see below), taken from a 2011 TED talk by primatologist Frans de Waal, has become a surprising piece of ammunition in this discussion.
The video illustrates a famous 2003 experiment by de Waal and his colleague Sarah Brosnan. It begins with a capuchin monkey being rewarded with a cucumber slice for handing a rock to the experimenter. The monkey happily performs this task and collects her payment until the monkey next to her is given a more desirable reward, a grape, for the same job. The first monkey then flings the unappetizing cucumber from her cage. In the study, the monkeys often refused to hand over a rock if they saw the other monkey get grapes while they themselves continued to get cucumbers.