Fairness Study with Capuchin Monkeys

Background

• A well-known study conducted about 10 years ago.
• Originally done with capuchin monkeys, now replicated with dogs, birds, and chimpanzees.
• The study investigates behavioral responses to fairness and inequity.

Experiment Setup

• Two capuchin monkeys are placed side by side in a test chamber.
• Monkeys come from the same group and are familiar with each other.
• Simple task: Monkeys exchange a rock with researchers for food.

Experiment Details

• Task Consistency:

  • Both monkeys receive cucumber in exchange for the rock.
  • Cucumber is considered satisfactory by the monkeys.
  • Monkeys perform the task willingly 25 times in a row when both receive cucumbers.

• Introducing Inequity:

  • One monkey is given cucumber, the other grape.
  • Grapes are a preferred food, causing inequity.
  • Food preferences of capuchin monkeys mirror supermarket prices.

Observations

• Initial Reaction:

  • Monkey receiving cucumber accepts it initially.
  • After observing the peer receiving a grape instead, the reaction changes.

• Behavioral Response:

  • Cucumber-receiving monkey shows agitation.
  • Starts testing the rock against the wall, indicating frustration.
  • Comparisons to human social protests ("Wall Street protest") made due to the reaction against perceived unfairness.

Conclusion

• The experiment highlights the intrinsic sense of fairness in capuchin monkeys.
• Demonstrates the impact of inequity not just in humans but in primates as well, sparking further research studies across different species.