(NaturalNews) Humans aren't the only animals that understand the concept of fairness, according to research presented recently at the 122nd Annual Convention of the American Psychological Association.
Fairness is a topic of particular interest to researchers who study the evolution of social behavior and the extent to which cooperation is built into the genes of various animals, including humans. While selfishness might often appear to grant an individual the best chance of propagating its genes more widely in the next generation compared with other individuals, researchers have shown that, in many cases, cooperation increases an organism's evolutionary fitness more than selfishness does. Understanding the idea of fairness may be a necessary prerequisite for developing complex cooperative relationships.
Dogs recognize fairness, but don't care
In a presentation titled "Fair is Fine, but More is Better: Limits to Inequity Aversion in the Domestic Dog," Alexandra Horowitz of Barnard College discussed her research into fairness-related behavior in dogs.
Horowitz and colleagues performed the study on 38 dogs, one at a time. Each dog interacted with several trainers at the same time as a control dog. The trainers either under-rewarded or over-rewarded the control dogs, or rewarded both dogs fairly.
Once the dogs had gotten to know the trainers, they were allowed to choose which trainer to approach, in the absence of any other dogs. The dogs showed a clear preference for trainers that had over-rewarded the control dog but had no preference between the under-rewarding trainers and fair ones.
Previous studies, which looked only at under-rewarding, showed that dogs avoided trainers whom they perceived as unfair. The newer study suggests that, while dogs are able to recognize unfairness, they have no qualms about exploiting it in the hopes of getting a greater reward.
Notably, older dogs were significantly more likely to prefer the fair trainer than younger dogs. This suggests that dogs may develop a preference for fairness over time as a consequence of long-term relationships with humans.
The researchers noted that, in addition to being descended from highly social wild animals, dogs have been actively bred to work cooperatively with humans.
Primates refuse to play unfair games
In another presentation, "Responses to Inequity in Non-human Primates," Dr. Sarah Brosnan of Georgia State University discussed several different studies conducted on our closest nonhuman relatives. Several of these studies indicated that many species of primates will refuse to participate in activities that they perceive as unfairly favoring another animal.
For example, in a 2003 study published in the journal Nature, Dr. Brosnan and colleagues taught female capuchin monkeys to hand pebbles over to human trainers in exchange for food. The monkeys were always caged in pairs, so they could see what sort of treatment another monkey was receiving.
When one monkey was rewarded with a grape (more desirable) but another monkey was only offered a piece of cucumber (less desirable) for the same task, the monkey offered the cucumber would often refuse to participate in the trial further. For example, the monkey might refuse to hand over the pebble, refuse to accept the cucumber or even throw the pebble or cucumber onto the floor in obvious exasperation. These behaviors are not typically seen in monkeys who are not comparing their treatment to that of another animal.
The monkeys' negative reactions were twice as common in cases where they saw the other monkey receive a grape without handing over a pebble at all.
Similar studies have shown comparable reactions in chimpanzees.
A keen sense of fairness probably served our ancestors well throughout evolutionary history, Dr. Brosnan said.
"The fact that we find the sense of fairness in a nonhuman primate implies it is an evolved behavior and has a good benefit," she said.