DOGS might be man鈥檚 best friend, but only if they are being treated fairly. When a dog thinks it鈥檚 getting a raw deal in comparison with other dogs, it quickly expresses its displeasure.
Until now, such overt dislike of unfairness had only been shown in primates, but some scientists had suspected that other species that live cooperatively could also be sensitive to foul play.
To test this theory, Friederike Range鈥檚 team at the University of Vienna, Austria, asked 43 trained dogs to extend their paw to a human in various situations.
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The animals performed the trick at almost every request, regardless of whether they were given a reward or not, or whether alone or alongside another dog.
However, the dogs鈥� enthusiasm quickly waned when they saw another dog getting a food reward but received nothing themselves.
Dogs that got this raw deal extended their paws on average a third less often than in all other circumstances.
The dogs also showed far more symptoms of stress, such as licking or scratching themselves (Proceedings of the National Academies of Science, ).
鈥淭hey are clearly unhappy with the unfair situation,鈥� says Range. She also suspects that this sensitivity might go beyond food: 鈥淚t might explain why some dogs react with 鈥榥ew-baby envy鈥� when their owners have a child.鈥�
Marc Bekoff at the University of Colorado, Boulder, who studies social carnivores, says,鈥漈he fate of a wolf or coyote pack can really hang on whether an individual pulls its weight. These animals learn not to tolerate unfairness.鈥�
Range agrees that dogs鈥� sense of fairness probably evolved long before domestication. 鈥淲e are now testing for envy in wolves, and I would be surprised if we didn鈥檛 find it,鈥� she says.