By Dr. Becker
Fascinating new research suggests both dogs and wolves react to inequity in ways similar to humans and primates. The ability to recognize unfairness is a key social skill that plays a significant role in helping humans successfully cooperate with one another. Simply put, we like to work with people who treat us fairly, and tend to avoid those who treat us badly.
Certain primates show the ability to sense injustice, and past studies have demonstrated that dogs also seem to possess some form of "inequity aversion" that has been attributed to human influence during domestication.
But now comparative psychologists at the Messerli Research Institute and the Wolf Science Center of the University of Veterinary Medicine in Vienna have discovered that wolves also exhibit a deeply ingrained recognition and dislike of unfair treatment. This finding suggests that dogs possessed a sense of fair play before they became domesticated.
Both Dogs and Wolves Stop Cooperating If Treated Unfairly
The study was performed with dogs and wolves raised in packs under similar circumstances and with similar life experiences.1 Pairs of dogs or wolves were placed in side-by-side cages equipped with buzzers. When they pressed the buzzer with their paw on command, both got a reward some of the time. Other times, in the "no-reward test," the dog or wolf who pressed the buzzer got nothing, while the animal in the other enclosure got a reward.
In the "quality test," a lower value reward was given to the animal who pressed the buzzer, while the animal in the other cage received a higher quality reward.
The result? The dogs and especially the wolves who pressed the buzzer on command and received either nothing or a lower quality reward than their partners in the other enclosure (who had performed exactly the same behavior), simply stopped participating in the tests! In an interview with BBC News, study-coauthor Jennifer Essler of the University of Veterinary Medicine in Vienna observed:
"For some of them it was a really really quick and strong response. One of the wolves stopped working after the third trial of not receiving anything while his partner received something. I think he was so frustrated he even broke the apparatus."2
(You can see him doing exactly that in the video above.) Interestingly, both the dogs and wolves continued participating when there was no partner in the adjacent cage. "This showed that the fact that they themselves had not received a reward was not the only reason why they stopped cooperating with the trainer," says study co-author Friederike Range, Ph.D. "They refused to cooperate because the other one got something, but they themselves did not."3
Since both the dogs and wolves who were treated unfairly behaved more or less the same, it indicates inequity aversion in canines is a skill inherited from a common ancestor, which means domestication isn't the only contributing factor to the behavior.
Pack Ranking Also Influences How Quickly Dogs and Wolves Respond to Inequitable Treatment
Another interesting observation from the study was that a dog's or wolf's social status within the pack influenced when they stopped cooperating with the tests.
"High-ranking animals become frustrated more quickly by inequity because they are not used to this situation: not receiving something at all or only of lower quality," explained Range. "Thus, the hierarchy in their pack is directly linked to their reaction to inequity."
After the tests concluded, the researchers brought the dogs and wolves to a neutral location to evaluate how they interacted with both their test partners and the experimenters. The wolves who had been unfairly treated kept their distance from the humans, however, the dogs didn't. This finding led the study authors to conclude that dogs, even those who don't live directly with humans, are more responsive to us, which would seem to be an outcome of domestication.
"I think it's clear that this is affected by both domestication as well as their life experience with humans because you do see a difference between pet dogs and pack-living dogs," Essler told BBC News. "It seems that having a life experience living with humans makes them more tolerant to inequity that comes from humans."
Horses Also Demonstrate Inequity Aversion
For the experiment, the horses were trained to touch a target when given a visual and verbal command. For the unfair phase of the experiment, the researchers used a high-value food reward (a piece of carrot) and a low-value food (a single pellet). Upon successfully touching the target, one horse was given the piece of carrot and the other horse was given the pellet. The horse who received the pellet took significantly longer to react than he did when he was treated fairly. According to the research team:
"These results suggest that horses were slower to perform the task and adopted a more indirect strategy when unfairly rewarded compared to the fair and control conditions."