By Helen Pow
Even monkeys think unequal pay is the pits.
A fascinating experiment has revealed that primates go berserk when they don't get the same reward as their pals when they do the same job.
The hilarious 'Fairness Study' was uploaded to YouTube in May and has since gone viral, garnering more than 1.3 million views.
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Frans de Waal, a primatologist and Emory University professor, first conducted the experiment with Capuchin monkeys close to a decade ago but performed it again recently and taped the results.
In the study, two monkeys are asked to do a job - handing a lab worker a small rock - for which one was given a piece of cucumber and the other was given a grape.
The first time a monkey completes the required task he is recompensed with a small chunk of cucumber and eats it without a kerfuffle.
But when he notices his pal getting a grape - obviously valuable currency among primates - for doing exactly the same task he goes mad.
He ditches his second chunk of cucumber at the scientist then pounds the table and rattles the walls of his cage in protest of the pay disparity.
Mr de Waal said if both monkeys get cucumber as a reward they are happy to repeat the task up to 25 times.
'But if you give one grapes, which is a far better food, then you create inequity between them,' Mr de Waal said.
'So, this is basically the Wall Street protest that you see here,' he added, referring to the Occupy Wall Street movement.
Mr de Waal and his colleague, Sarah Brosnan, published their findings in the journal Nature in 2003. He said the study has now been repeated with dogs, birds and chimpanzees.
VIDEO: TED's clever experiment shows a monkey's reaction to unequal pay