Jealousy is not strictly a human emotion, a study suggests; dogs can feel it to, possibly in a more basic form that evolved to defend social bonds against interlopers.
Whether jealousy is only the result of complex cognition at a human level not attained by animals has been the subject of spirited debate among emotion researchers, some of whom say they believe jealousy is a completely social construct that isn't hard-wired or fundamental in the same ways anger and fear are.
In an experiment described in the journal PLOS ONE, researchers at the University of California, San Diego, set out to test the capacity for jealous behavior in dogs.
In the experiment, psychology Professor Christine Harris and student Caroline Prouvost found that when dog owners displayed affection toward a stuffed dog that could bark, whine and wag it tail, the owners' pets reacted by snapping at the stuffed animal, pushing it away, or touching their owners.
The study involved 36 puppies, none older than 6 months, and the researchers looked for signs of aggression, attention-seeking and interest in their owner as possible signs of jealousy.
"Our study suggests not only that dogs do engage in what appear to be jealous behaviors but also that they were seeking to break up the connection between the owner and a seeming rival," Harris says. "We can't really speak to the dogs' subjective experiences, of course, but it looks as though they were motivated to protect an important social relationship."
The dogs' behavior arose only when the owners paid attention to the stuffed dog and was not in evidence when they where engaged with other objects, like a book they were reading, the researcher said.
If human jealousy requires complex cognition, the behavior in the puppies may constitute a basic, specific form in dogs and other social creatures meant to protect social bonds against outsiders, the researchers say.
"Many people have assumed that jealousy is a social construction of human beings -- or that it's an emotion specifically tied to sexual and romantic relationships," Harris says. "Our results challenge these ideas, showing that animals besides ourselves display strong distress whenever a rival usurps a loved one's affection."
The behavior in dogs may be similar to a primitive form of jealously seen in human infants that may have evolved to help babies compete with siblings for parental resources including food, care, attention and love, the researchers said.
They suggest their study may show some form of that primitive jealously exits in at least one other social animal -- dogs.
