In this famous experiment on fairness, two capuchin monkeys are given different rewards for the same task; one gets grapes, the other cucumbers. At first, the cucumber is accepted... until the monkey notices the unfairness. Its reaction: angry, defiant, and hilariously human. This offers a powerful glimpse into how deeply rooted our sense of justice really is. Even monkeys know when they’re being ripped off. Credit: @ted | History In Pictures