Monkeys Avoid 'Jerks': Research Reveals Capuchins Shun Selfish Humans

Even monkeys can tell when someone is being a jerk. New research reveals that capuchins who observed humans acting badly were less likely to interact with them.

The new pair of studies, one of which was published in the journal Nature Communications, used actors in order to act out several scenarios in front of capuchin monkeys. In one experiment, the capuchins watched as one actor handed over several balls to the other. The other actor then either reciprocated the action, or selfishly kept all of the balls. In another scenario, one actor struggled to open a container and the other actor either helped or refused to help. These particular displays are often used to test how children develop a sense of fairness.

So what did the monkeys think? After each scenario, the capuchin monkeys got to choose a treat from one of the actors. Researchers found that they consistently avoided treats from the actors who acted like "jerks."

In 2009, a similar study was conducted that revealed that capuchins prefer humans who imitate their actions. Yet this latest research shows an even deeper level of judgment at work among these monkeys.

In the wild, capuchins are highly social. This new study reveals that they may observe group members closely in order to learn which ones to avoid interacting with on a specific day. It could allow these monkeys a better chance at survival.

"The research implies capuchin monkeys are judging other individuals even when they aren't involved in the action, something that humans do all the time," said Sarah Brosnan, an ethnologist at Georgia State University, who wasn't involved with the research, in an interview with LiveScience. "It suggests the behavior may be deeply rooted in the primate family tree."

In fact, the behavior could have helped encourage helpfulness. Being social creatures, primates and monkeys need to work together in order to succeed as a group. The disdain that the monkeys showed the unhelpful actor would possibly encourage the actor to be more helpful in the future--if she were a monkey.