A new study shows that a dog can be just as green with envy as a human if it thinks another dog is homing in on its owner.

Has your dog ever seemed envious of another dog in the house, or the attention you devote to a pup you meet in the park? According to a new study from the University of California, San Diego, dogs may snap at or push their owners if they feel jealous that their humans are paying attention to other canines.

In general, scientists think jealousy is an emotion that requires a complex thought process, but new research indicates there may be a more basic form of jealousy that has evolved to protect relationships from outsiders.

That’s what Christine Harris, Ph.D., from U.C. San Diego, and her colleague Caroline Prouvost, now a doctoral student at Rosalind Franklin University in North Chicago, Ill., found when they studied the behavior of 36 dogs. They modified a test that can evaluate jealousy in infants. The dogs’ owners ignored their own dogs and instead interacted with three objects: a lifelike stuffed dog, a jack-o’-lantern bucket, and a book.

Next, the scientists evaluated the dogs’ behavior for signs of attention seeking, aggression, or interest in the owner or object. Harris and Prouvost found that dogs exhibited significantly more jealous behaviors, such as snapping, getting between the owner and the object, and pushing or touching the object or their owner, when their owners showed affection to the stuffed dog than they did when their owners focused on the other two objects.

Read More: Rabies, Used as a Bioweapon in Ancient Times, Still a Threat Today »

“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 told Healthline. “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.”

Harris said she found variability in how dogs responded to the jealousy-inducing test.

“A few didn’t show any behaviors that could be interpreted as jealousy,” she said, adding that it raises interesting questions about what was different about those dogs. Perhaps the differences could be documented according to breed.

“Were they the less cognitively sophisticated ones, the more cognitively sophisticated ones, or perhaps just weren’t as bonded with the owners?” she asked. “Our hope is that this is one direction to go for future studies. We didn’t have enough of any particular type of breed to assess possible breed differences.”

Related News: Exposure to Dogs May Keep Kids from Developing Allergies »

The researchers say their findings show that jealousy is something primal that exists not just in humans but in other animals as well. They believe jealousy evolved to secure resources such as food, attention, care, and affection — it’s not solely a behavior related to sexual relationships.

“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. She believes her research shows that animals other than humans experience distress when a rival captures the attention of a loved one.

The new study was published yesterday in PLOS ONE.

Study: Dogs Can Benefit Families with Autistic Children »