A sulky dog
© stock.xchngA sulky dog might just feel unfairly.
A dog might be a man's best friend, but only if it is being treated fairly. When a dog thinks it's getting a raw deal in comparison to other dogs, it doesn't shy away from expressing its envy.

Until now, such overt dislike of unfairness had only been demonstrated in primates, but some scientists have suspected that other species that live cooperatively could also be sensitive to fair play - or a lack of one.

To test this theory, Friederike Range and her colleagues at the University of Vienna, Austria, asked 43 trained dogs to extend their paw to a human in various situations.

The animals performed the trick almost at every request, regardless of whether they were given a reward or not; as well as when working alone or alongside another dog.

The dogs' enthusiasm quickly waned, though, when they saw the other dog being rewarded but received nothing themselves.

'Baby envy'

The dogs that were ignored extended their paws significantly less often than in all other circumstances, doing so in only 13 out of 30 trials. They also showed significantly more symptoms of stress, such as licking or scratching themselves.

"They are clearly unhappy with the unfair situation", says Range. She also suspects that this sensitivity might stretch beyond food to things like praise and attention. "It might explain why some dogs react with 'new baby envy' when their owners have a child", she says.

To Marc Bekoff at the University of Colorado, Boulder, the study confirms an impression he has been forming in years of field studies on social carnivores (Virtuous Nature).

"The fate of a wolf or coyote pack can really hang on whether an individual pulls its weight," says Bekoff. "These animals learn not to tolerate unfairness."

Range agrees that the dogs' sense of fairness probably evolved long before domestication. "We are now testing for envy in wolves, and I would be surprised if we didn't find it", she says.

Journal reference: PNAS