Income Inequality in Action, Monkey-Style

Legendary primatologist Frans de Waal presents a video in which two capuchin monkeys are given unequal pay for equal work. One of them gets paid in cucumbers, the other in grapes. Can you guess which one is happier?

It is amazing to see how the principles of behavioral economics spill so easily into the animal kingdom. (You may also wish to consider Keith Chen‘s economic research with capuchins.)

So the next time you feel you’re being unfairly compensated, or feel the broader sting of income inequality, you can say to your friends, “I feel just like a monkey who’s been given a cucumber while the monkey next door got a grape,” and thanks to Frans de Waal they will know what you are talking about.

(HT: V. Brenner)


more evidence that we are hardwired to instantiate social justice- this empirical fact trumps the propaganda that stratification is a result of just rewards (carnegie gets the grapes while the rest can eat cake)


I dunno, the monkey on the right doesn't seem all that interested in instantiating social justice.


There you have it... What better way to explain society and revolution than this.


Doesn't explain why grapes should be considered to be worth more than cucumbers.

Due to the vagaries of weather, I happen to have a surplus of grapes in my garden at the moment, but no cucumbers at all. I would gladly trade...


Grapes have more sugar. Seems pretty obvious.


It would be also fascinating to have the monkeys do unequal tasks then see if they still want an equal treat. Who wants to bet they do?

Since we are using this one example to make points about income inequality, maybe we could make some points about people who believe redistribution of wealth.


That was my thought too. To make relevant to today's discussion of income inequality, we would have to first give the monkeys unequal rewards for unequal tasks to identify which tasks get done only when the reward is a grape ("grape-only" tasks), not a cucumber. Then, we would give the monkeys grapes for all tasks and observe whether the monkeys would still perform the grape-only tasks or whether they would instead substitute the previous cucumber-tasks to get grapes. Finally, to make really relevant to current discussions, we should observe what happens if we give a grape to the *other* monkey every time the first monkey performs a grape-only task. That would be the Occupy Wall Street test.


You have to wonder sometimes…

I think we’ve all been there…

Sitting in your cubicle, watching the denizen of another nearby cubicle garner the sweet admiration and esteem of the overseers for seemingly arbitrary reasons while your contributions garner stony anonymity…

You have to wonder…

Am I one of the lab monkeys of some grand sociology experiment?

You really have to wonder…


Dr. Constantinos Charalambous

here is my input on this article. I wrote a post using the dictator and the ultimatum game to describe the concept of fairness.


Certainly it sometimes happens that people get different rewards for the same work but much, much more often the work is only similar and the degree of similarity and the appropriateness of reward is subjective. This is the fundamental problem with all kinds of justice. How and by whom what is just is determined is the question and at one time or another everything humankind could think of has been tried and each time someone felt they weren't getting a fair deal.

What i find most amusing is the same people who cry out for justice when they feel they got the cucumber aren't over eager to share the grapes that come their way. When I see an American crying out for justice who lives with the material goods and income of the average person on the planet I'll listen, until then they are just people who want to level those above them down without leveling those below them up.

Daniel Chamudot

This test doesn't conclusively show that the capuchins are bothered by inequality per se.

One could argue that the first capuchin is just irritated because as much as he tries, he can't seem to get a grape. Before the grape was offered to the second monkey, he didn't know the grape option was even available.

It's NOT like the wall street protests because the first capuchin is not taking out his frustration on the second one (i.e the 99% blaming the 1%), but rather on the tester (aka the "financial system").


I agree that this is not a test of preferences for fairness. I would like to see a reaction in this case: the two individuals BOTH get cucumber after they have been given grapes at last once. That would show if they react because they just like grapes better than cucumber, rather than because the other one got grapes.

Nate Mathan

I loved the video and sent it to friends.

A minor correction - your introduction states: "It is amazing to see how the principles of behavioral economics spill so easily into the animal kingdom."
er... humans ARE part of the animal kingdom.


Notice that the monkey getting the greater reward isn't offering to share. It seems that envy and selfishness are both endemic to primate nature.

Daniel Chamudot

Not necessarily. De Waal repeated the experiment in chimpanzees and found that the second chimpanzee refused the grape reward after seeing the unfair treatment towards the first chimpanzee.


"It is amazing to see how the principles of behavioral economics spill so easily into the animal kingdom"

I guess this depends which side you're coming from (human or animal). It's not the least bit surprising to animal behaviorists to see how easily the two worlds overlap.

Humans are, after all, members of the animal kingdom.

Animal behavior is full of topics where an economist would feel right at home. Start with something like food sharing in Vampire Bats.

It's interesting - I promise. You'll also find yourself understanding more about why your crazy Aunt Helga behaves the way she does.

Julien Couvreur

This is funny and cute.

But if? humans were caged and enslaved to their "employers" then I could understand the parallel. The closest example is that of kids (since they are not in a voluntary relationship with their parents).

In contrast, most adults know what salary they will receive *before* they do the job.

Ian M

The monkey on the right had 4 years of formal training as a rock giver at a very prestigious school. He studied rock giving theory. He completed a thesis on rock giving. He even took a course in rock giving ethics and another course in philosophy so he was a more well rounded monkey.
The monkey on the left has far more experience as a rock giver as he has been a 40hr/wk rock giver for the last 10 years. No matter though as he has never been to rock giving school. He doesn't have much chance at a life of grapes. His Dad was a happy cucumber eater who married a zucchini eater and raised 4 monkeys. Maybe he should ignore the grape eaters and just try to be happy.


A better test would be to give one monkey 3 grapes and the other monkey 5 grapes. You're supposed to be testing an inequal amount of rewards . . . not totally different rewards. That's like paying one employee with dollars and the other employee with an equal dollar amount of discount coupons.