Dogs Can Act Jealous: Study

Apparently humans aren't the only ones who can act jealous. Dogs can also be green with envy, according to a new study from the University of California, San Diego.

Charles Darwin had suspected for years that dogs could feel emotion, but researchers argued over whether jealousy required complex cognition. Some have even said that it's an entirely social construct - not seen in all human cultures and wired in our brains differently than other emotions, like fear or anger.

The current study, published in the journal PLOS ONE, is the first to look at jealousy in dogs, and find that there may be a more basic form of jealousy, which evolved to protect social bonds from intruders.

For dogs, acts of jealousy appear as snapping at other dogs or their owners and pushing at their own owner - especially when their master showed affection towards another dog (even if it was a stuffed animal). This behavior was amplified compared to if their owner simply was distracted.

"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," lead author Christine Harris said in a statement. "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 researchers observed 36 dogs and their reaction when their owners ignored them in favor of a stuffed, animated dog or a jack-o-lantern pail (treating them as they would a dog). Dogs were twice as likely to nudge their owner when they paid more attention to the faux dog (78 percent) than with the pail (42 percent). About 30 percent of the animals tried to get between their owner and the stuffed dog, while 25 percent snapped at the other dog.

The UC San Diego team believes this aggression suggests the dogs were jealous of the affection their owners bestowed on the other objects. The dog participants believed that these objects were dogs so much, 86 percent of them even sniffed the toy dog's rear.

"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 said. "Our results challenge these ideas, showing that animals besides ourselves display strong distress whenever a rival usurps a loved one's affection."