For centuries, people have wondered if animals feel jealousy like humans do.
When we see someone else get something we want, like a reward or attention, it can trigger strong feelings. But do animals share this sense of unfairness?
Recent research from the University of California, Berkeley, suggests that while animals react to certain situations, their behavior may not stem from jealousy or fairness in the way humans experience it.
UC Berkeley researchers examined data from 23 studies involving more than 60,000 observations of 18 different animal species, including monkeys, birds, and dogs.
This meta-analysis is the largest investigation into what scientists call “inequity aversion”—the dislike of unfair treatment—ever conducted.
The study found that animals do react when they don’t get what they expect, but this doesn’t seem to be driven by jealousy or a sense of fairness. Instead, their reactions may be tied to unmet expectations or disappointment, rather than feeling upset that another animal got something better.
One famous experiment led by primatologist Frans de Waal showed a capuchin monkey reacting strongly to perceived unfair treatment.
In the study, two monkeys were rewarded for completing the same task, but one received a cucumber while the other got a more desirable grape. The cucumber-eating monkey grew angry, throwing the cucumber and rattling its cage. This behavior was interpreted as jealousy.
However, the new research suggests there might be another explanation.
When the data was analyzed differently, researchers found that monkeys displayed similar reactions when grapes were placed in an empty cage, with no other monkey present.
This suggests their reaction wasn’t about unfairness or jealousy but about unmet expectations.
Humans have a strong sense of fairness that goes beyond unmet expectations. This sense of fairness, called inequity aversion, helps humans share resources, cooperate, and build complex societies.
For example, if one child receives a better toy than another, the second child often reacts not just because they want the toy, but because it feels unfair.
In contrast, animals may be more focused on whether their own needs or expectations are met. Oded Ritov, the study’s lead researcher, explained that animals’ reactions might be more about protesting poor treatment from humans rather than feeling upset about what others receive.
This research sheds light on how animals and humans differ in their social behaviors. While animals clearly respond to certain situations, their reactions are likely tied to their immediate environment and past experiences rather than a deeper sense of fairness.
By better understanding these differences, scientists can learn more about the evolution of human behavior and what makes us unique. It also provides insight into how animals interact with humans, helping improve our relationships with them.
Ultimately, the study suggests that while animals may not experience jealousy or fairness the way humans do, they are still capable of complex emotions and responses. And that’s something both humans and animals can relate to.
Source: UC Berkeley.
