Your dog wants all of your attention, but can it feel jealousy? The answer appears to be yes, according to a study published in the online science journal PLOS ONE. The findings won't surprise dog owners, but they mark an important shift in the way scientists study jealousy -- which remains one of humanity's most baffling emotions.

Study author Christine Harris, a professor of psychology at the University of California, San Diego, was visiting her parents and their three border collies when the idea for the study came to her.

"I'd pet two of them at a time," she said, "and it wouldn't have been surprising if that had made the third want my attention, too."

But what intrigued her was that the two dogs being attended to would show aggression to one another. One dog would knock her hand away from the other, so it was the sole object of affection.

"To me," she said, "That really fit with the core motivation of jealousy."

Harris and researcher Caroline Prouvost took 36 dogs of various breeds and their owners and observed the dogs' behavior as their masters interacted with three nonliving objects. One object was a children's book, which they read aloud; another object was a plastic Jack-o'-lantern pail; and the third was a mechanical stuffed dog that emitted a bark when the owner pressed a button.

The authors based their experiment on several studies that examined whether human infants are capable of jealousy. The studies, which concluded that infants were probably capable of jealousy, involved experiments in which their mothers showed attention to a lifelike doll instead of their child, and other objects. An infant was reportedly more likely to respond with "negative" behavior if its mother diverted her attention to the doll.

In the dog experiment, authors instructed the dog owners to push the bark button on the stuffed dog's head and then speak to it sweetly while ignoring their own dog. After that, they showed attention to the pumpkin pail, then read the children's book, while also ignoring their dog.

Researchers said that the dogs were far more likely to act aggressively when their owners spoke to the stuffed dog than when they paid attention to the other objects. One-fourth of the dogs snapped at the stuffed dog, while only one dog snapped at the pail or the book. The dogs were also more likely to push or touch their owners as they interacted with the stuffed dog and tried to get in between the owner and the stuffed dog more frequently than the other objects. Whining also occurred more frequently with the stuffed dog.

"The data present a strong case that domestic dogs have a form of jealousy," the authors wrote.

The researchers said that although the vast majority of studies that examine jealousy in humans focus on jealousy within romantic relationships, their findings suggest a deeper cause.

"One possibility is that jealousy evolved in species that have multiple dependent young that concurrently compete for parental resources such as food, attention, care, and affection," they concluded.

"It is easy to imagine the advantages that might be gained by a young animal that is not only alert to interactions between siblings and parents, but also motivated to interpose itself in such interactions."

Information for this report was contributed by Monte Morin of the Los Angeles Times and Rachel Feltman of The Washington Post.

SundayMonday on 07/27/2014