Monkeys don't like mean people.
Monkeys are adverse to accepting food from people who are selfish, according to a new study.
Researchers from the University of Stirling in Scotland tested capuchin monkeys behavior by having them observe a pair of actors open a jar, and then offer the monkeys some food.
When the actors helped each other open the jar, the monkeys would accept food from either of them.
But when one of the actors refused to help the other open the jar, the monkeys turned down food that was offered to them by the selfish person.
Capuchin monkeys are very social and cooperative with each other.
Similar results have been shown in studies involving chimpanzees and human infants not accepting food from someone who came off as being selfish.
Another study that involved capuchins showed that they also have a sense of fairness.
Scientists gave the monkeys cucumbers in exchange for rocks they collected.
Then the scientists started giving some of the monkeys grapes, which are a more popular food.
The monkeys that kept getting cucumbers noticed that other monkeys were getting grapes for the stones and either threw the cucumbers at the scientists, or just stopped collecting stones.