Studies have already indicated that dogs have a sense of inequity – they know when another dog is receiving preferential treatment, and they consider that to be unfair. Many scientists have assumed that this is a result of domestication. A new study shows that wolves react in the same way, however, suggesting that the behavior originates with a common ancient ancestor.

Led by comparative psychologists Jennifer Essler, Friederike Range and Sarah Marshall-Pescini, the study was conducted at the Messerli Research Institute of the University of Veterinary Medicine, in Vienna. It included both wolves and domestic dogs, all of which were similarly raised in packs.

The animals were trained to press a button with their paw when told to do so by a trainer, in exchange for a treat. Sometimes, however, the canine being tested didn't get a treat, while a partner animal visible in an adjacent enclosure did. Other times, while the test subject did get a treat, it was clearly inferior to the one given to its partner.

In both cases, with both the dogs and the wolves, the unfairly-treated animals soon refused to continue pressing the button. They kept cooperating with the trainer when receiving the same treatment without a partner present, though, suggesting that what they really didn't like was the fact that another canine was getting rewards that they weren't.

Interestingly – and perhaps not surprisingly – the dogs and wolves that ranked highest within their packs stopped cooperating sooner. This was presumably because they were less used to getting the short end of the stick, so to speak.

Additionally, after the sessions were over, the unfairly-treated wolves were more aloof to both their partners and the trainers, than were the dogs. According to the researchers, this suggests that the domestication of dogs actually makes them less sensitive to feelings of inequity, instead of it being the cause of those feelings.

A paper on the research was recently published in the journal Current Biology.

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