Scientists have confirmed what pet owners have always suspected: our pooches may pout when they sense another pup is getting favorable treatment.

Researchers at the University of Vienna in Austria report today in the Proceedings of the National Academy of Sciences USA that dogs may be like our human best buds: they get jealous if they feel we're treating another dog better.

Fredericke Range and her colleagues did a series of experiments with dogs that indicated they were happy to "shake hands" whether or not they were rewarded –at least for a while. But that changed if one pup got a treat and the other got nada.

For a long time, scientists believed a sense of equity was a purely human trait. Then in 2003 researchers discovered that capuchin monkeys  complied with requests in return for cucumber slices, but got their backs up when they saw another monkey getting grapes, which they perceived as sweeter, better treats.

The dogs apparently weren't quite as picky. They were eager to please their human experimenters as long as they got something – be it a piece of bread or sausage -- acknowledging their effort. But they became visibly stressed and stopped playing along if they shook hands and got nothing, especially if another dog was rewarded for doing the same thing. They cooperated longer if their canine compeers also were stiffed or if they were being tested alone.

FYI: All of the owners reported their dogs preferred the sausage to the bread, but they didn't act up if their neighbors got the primo prize and they got grain as long as they got a tidbit, too.

The scientists worked with 14 well-trained dogs that either lived together or knew one another. A familiar human companion remained on the scene while researchers did their thing. Range and her colleagues put the dogs through a series of experiments to determine how long each one would follow commands in different circumstances: when rewarded or not, solo or with another pooch on hand.

Beware oh pet owners: the next thing you know your pups and their pals may begin organizing a la George Orwell's Animal Farm.

Photo of Emma by Lisa Stein.