Did you ever complain to your parents about a sibling getting better treatment than you? Well, then you know how this monkey feels.

In the following excerpt from primatologist Frans de Waal’s popular TEDTalk, we see how monkeys are susceptible to anger from perceived unfairness. In a now-famous experiment, researchers taught two monkeys to hand them a rock in exchange for a reward. In this case, each monkey received a cucumber.

However, after several exchanges, the researchers began rewarding one of the monkeys with a grape. The other monkey still received a cucumber. (Like any normal person, the monkeys prefer grapes to cucumbers.) In the video, we see that one of the monkeys does not like the situation at all. The once-cucumber-loving monkey now wants nothing more than to receive a grape!

De Waal’s full talk features other examples of animals demonstrating traits we think of as very human: empathy, cooperation, reciprocity. He titles it “Moral Behavior in Animals.” For as he puts it, as the cucumber-receiving monkey protests not getting a grape, “So this is basically the [Occupy] Wall Street protest that you see here.”

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