Many humans have highly developed senses of fairness and morality. Some monkeys may not be far behind. Watch as one gets cucumbers and the other gets delicious, delicious grapes.
Recent research shows that although economic gains make us happier over the short term, money still can't buy happiness in the long run. What may be more important is how deep your neighbor's pockets are: Income inequality tends to make us more unhappy and less trustful, and in the short term can lead to explosions of anger and resentment.
Many humans have highly developed senses of fairness and morality, and it seems monkeys aren't far behind. Alex Tabarrok highlights research by Emory University psychologist Dr. Frans B.M. de Waal, who studied how monkeys and other mammals share many of our social mores. The reaction to unequal pay is (ahem) priceless.