Dogs Understand Fairness, Get Jealous, Study Finds A new study suggests that dogs can feel jealous and become resentful if they think another dog is getting a better deal. If canines spot unfair treatment, they're likely to become less cooperative, researchers found.

Dogs Understand Fairness, Get Jealous, Study Finds

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Scientists used to think a sense of fairness was uniquely human - used to because evidence is growing that some animals also care about fair play. NPR's Nell Greenfieldboyce reports.

NELL GREENFIELDBOYCE: Friederike Range has a dog, a black and white border collie.

GREENFIELDBOYCE: Her name is Guinness.

GREENFIELDBOYCE: And Guinness can have strong emotional reactions.

GREENFIELDBOYCE: She is very jealous of other dogs, and she doesn't like it if I pet another dog.

GREENFIELDBOYCE: The researchers then ran this experiment. They put the dogs in pairs and gave the command over and over again. One dog would always get rewarded with bread, but the other dog would get nothing. Range says it was interesting to watch the reactions of the unrewarded dogs.

GREENFIELDBOYCE: The first thing is that they look at the partner who received the food and really look, oh, he's eating. He's getting food.

GREENFIELDBOYCE: The next time the unlucky dogs held out the paw and didn't get rewarded, they started to realize that something was wrong, and they gave the researcher a long, hard look. As the experiment continued, some of the breadless dogs tried another trick, like rolling over, to see if that got the food. But eventually the dogs understood that they would never get anything, that the whole setup was just fundamentally unfair.

GREENFIELDBOYCE: They don't look at you anymore. So if you ask them for the paw, if you give the command paw to them, they just look away.

GREENFIELDBOYCE: Because the trained dogs knew that if they looked, they would feel a powerful urge to obey the command, until the injustice finally took them to the breaking point.

GREENFIELDBOYCE: They get so mad that they look at you and just don't give you the paw anymore.

GREENFIELDBOYCE: The study is reported in the "Proceedings of the National Academy of Sciences." Frans de Waal is impressed by the findings.

GREENFIELDBOYCE: Even if she found something that most dog owners will say, well, of course, it's still important to demonstrate it.

GREENFIELDBOYCE: De Waal is a scientist at Emory University. He says researchers have been looking for the evolutionary origins of fairness.

GREENFIELDBOYCE: Why are we humans interested in fairness? And why do we discuss it so much what is fair and unfair, and just and unjust, and so on?

GREENFIELDBOYCE: Five years ago, he published a key study showing that this wasn't just a human trait. Several monkeys were given the same little job to do. Some were paid with a boring bit of cucumber, but others got delicious grapes.

GREENFIELDBOYCE: Then the one who got cucumber became very agitated and at some point just stopped performing.

GREENFIELDBOYCE: That showed non-human primates cared about fairness. The new study in dogs suggests that other animals can have a similar sense, perhaps if they live in cooperative groups. The dogs weren't quite as sophisticated as the monkeys, though. The researchers looked to see what the dogs would do if they got rewarded with bread while their partners always got sausage. Unlike the monkeys, the dogs generally would keep working as long as they got some kind of food reward. A few dogs did seem to resent being denied sausage. One of them was Friederike Range's own dog, Guinness.

GREENFIELDBOYCE: She was not really happy about the whole thing and was hesitating to obey.

GREENFIELDBOYCE: She seemed to think that working for bread was totally unfair. Nell Greenfieldboyce, NPR News.

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