A new study has suggested that jealously in dogs may be a basic emotion that evolved to protect social relationships from external threats. This jealously seems to stem from a desire to protect their owner-dog relationship.

The researchers included Caroline Prouvost, a former honors student at University of California-San Diego (UCSD) and Christine Harris, professor of psychology at UCSD. They said that there have been no previous studies that assessed jealousy in dogs. Studying jealous behavior in dogs may lead to better understanding of the behavior in humans.

For this study, 36 dogs underwent a series of tests that were modified from an experiment for six-month-old human babies. These tests included owners ignoring their dogs, treat objects as a dog, and more. The researchers videotaped each test and assessed the records for disruptive, attention-seeking or aggressive dog behavior.

On analysis, the researchers found that 78% of dogs touched or pushed their owners when they paid attention to stuffed dogs and 42% did the same when owners focused on a jack-o-lantern pail. Also, only 22% of dogs showed the behavior when reading a pop-up book aloud.

Moreover, 30% pushed themselves between the owner and stuffed dog and 25% snapped at the stuffed dog. The animals believed that the stuffed dogs were real, with 86% of them even sniffing the stuffed dog. Harris said, “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.”