Dogs Feel Envy -- or at Least Grasp Inequity When It Comes to Treats
Monday, December 15, 2008
Do dogs feel envy? A provocative new study indicates that they do, making man's best friend the first species after humans and primates to appear to chafe at being treated unfairly.
Aside from offering the first scientific evidence supporting what many dog lovers take for granted, the finding adds to the growing body of literature suggesting that animals, including dogs, have much richer emotional lives and more sophisticated behavior than humans have traditionally believed.
"The more we study animals and the more we learn about them, the more we are realizing that maybe humans are somewhat different but not really all that different," said Friederike Range of the University of Vienna in Austria, who led the team that published the findings last week in the Proceedings of the National Academy of Sciences. "They have these kinds of feelings, or at least the precursors of these feelings, that we thought were uniquely human."
Before the new study, the only creatures other than humans for which there was evidence of anything similar to envy were monkeys and chimpanzees. When asked to return rocks to their keepers in exchange for a treat, for example, monkeys that got cucumbers essentially went on strike and started throwing the rocks and cucumbers at researchers if they saw other animals getting grapes instead.
To see whether dogs would respond with similar indignation, Range and her colleagues conducted a series of experiments involving 43 border collies, shepherds, retrievers, mutts, Rottweilers, terriers and other breeds. The researchers sat pairs of dogs next to each other with their owners standing behind them. The researchers then:
Asked each dog repeatedly to give them a paw.
Rewarded each dog with either a piece of bread or sausage.
Showed that the pooches would eventually get upset if their partner was getting rewarded while they got nothing.
"The dogs that were not getting the reward started to hesitate. You had to prompt them more often to give the paw," said Range, noting that some of the deprived dogs would start acting frustrated, scratching themselves, licking their mouths and yawning. "They would refuse to look at you, start looking at their owners or at the other dog chewing, and eventually refuse to cooperate. They would look away or lay down and not give the paw anymore if they were not getting rewarded."
To rule out alternative explanations, the researchers conducted several variations of the test. For example, to see if the dogs were refusing to give their paw more out of frustration than from a sense of inequity, they repeated the experiment with dogs by themselves sometimes rewarding them and sometimes not. In that situation, the dogs continued to cooperate for much longer even when they were not getting a treat. The same thing happened when neither dog in a pair got rewarded.
"It's not just 'Oh, shoot. I'm not getting rewarded, so I stop working,' " Range said. "If both are not rewarded, that is not a big problem. But if you rewarded one and not the other, that's where you saw a problem."
Range hesitated to conclude with certainty that dogs feel what humans call envy. Instead, she used a more technical term: inequity aversion.