Dogs will go on strike over unfair treats

First nonprimates tested for a sense of fair pay, which is key to cooperation

If Congress literally went to the dogs, there could still be growling over corporate bailout requests from highly compensated executives.

UNFAIR SHAKES A dog refuses to shake hands with a kneeling researcher in a test for sensitivity to unfair rewards. Dogs that didn’t get snacks for their handshakes soon stopped cooperating if a neighbor repeatedly scored sausages after offering a paw. Friederike Range

Dogs are the first animals outside primates that have passed an experimental test for an aversion to inequity. In other words, dogs have a sense of whether payment for work is fair, says Friederike Range, of the University of Vienna in Austria.

Dogs got increasingly fidgety and finally stopped shaking hands when a researcher repeatedly failed to supply rewards for a trick but gave another handshaking dog bread bits, Range says. The dogs cooperated longer, though, if their neighbors didn’t get a snack either, Range and her colleagues report online December 8 in Proceedings of the National Academy of Sciences.

Biologists interested in the evolution and maintenance of cooperative behavior have theorized that a critical factor for cooperative behavior is this aversion to inequity, Range says. It keeps slackers from eventually overwhelming the system.

Anthropologists and economists studying cooperation in people “have had a tendency to declare inequity aversion, and the associated sense of fairness, to be uniquely human,” says Frans de Waal of Emory University’s Yerkes National Primate Research Center in Atlanta. “So it is important to show that it is a profound reaction, of which we also find signs in other animals.”

Some form of this aversion could show up in all animals that show strong cooperative behavior, de Waal predicts. “You’d expect it in canines, but perhaps not in domestic cats, which are solitary hunters.”

Figuring out clear-cut tests for determining this quality in animals has stirred up a lot of debate. De Waal, among other researchers, has worked with pairs of primates. So far, those studies have proposed evidence of inequity aversion in chimps, capuchin monkeys and cottontop tamarins.

To test dogs, Range recruited 21 pairs of well-trained dogs that either lived together or knew each other well. A familiar human companion stood with a lone dog or a pair as a researcher asked for a paw to shake. Range and her colleagues ran the dogs through a series of tests, establishing such things as how long each dog on its own kept shaking hands without rewards. Dogs cooperated longer without a reward when working solo than when they could see a rewarded partner, Range says.

This experiment tested the dogs’ sense of payment for work, she emphasizes. It’s different from a dog’s objection to attention lavished on other dogs. Also, Range says, the experiment tests only the selfish version of fair pay. What she looked for was whether a dog objected to its own lack of compensation. A full sense of fairness as people use the word implies objecting also to unfair compensation for others.

Quality of compensation didn’t seem to matter to the dogs, Range says. All the dog owners told her that their animals preferred sausage to the test’s alternative reward of bread. Yet dogs rewarded with bread bits didn’t rebel when a neighbor scored sausage.

“I wonder what would have happened if dogs had been tested who didn’t know each other,” de Waal says. Monkeys and apes react more strongly to a stranger’s unfair bonus than to a pal’s.

Range, herself the human companion of a border collie, predicts her results won’t surprise some people. Many dog owners will think, ‘well, yes,’” Range says. Just having a sense that pets behave in complex ways isn’t enough for science, though, she says. Researchers have to devise objective tests.

A sequence showing the experiment in progress. Panels 1-3 show the reaction/reward experience between two dogs from the study.
A sequence showing the experiment in progress. Panels 1-3 show the reaction/reward experience between two dogs from the study.
FAIR TEST To see if dogs have a sense when pay for work is fair, a kneeling researcher asks for a paw to shake (left – 1st panel). If that dog doesn’t get treats for repeated handshakes, but sees one of its pals rewarded with a bit of bread or sausage (middle – 2nd panel), the unrewarded animal eventually goes on strike, refusing to shake hands any more (right – 3rd panel). Yet dogs cooperated longer when the neighbor wasn’t getting a reward either. Friederike Range
Susan Milius

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.

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