Christine Harris
Left: Psychology professor Christine Harris. Right: Dogs were study subjects in research on jealousy

Humans’ Best Friend Gets Jealous, Too

Researchers have been debating for years whether jealousy, the third leading cause of nonaccidental homicide, requires complex cognitive abilities. Some scientists have described jealousy as an entirely social construct—not seen in all human cultures and not fundamental or hard-wired in the way that fear and anger are.

Not so, according to UC San Diego alumnus and psychology professor Christine Harris and former honors student Caroline Prouvost, who recently performed the first experimental test of jealous behaviors in dogs. Harris, who earned her bachelor’s degree and doctorate at UC San Diego, has shown through her research with dogs that there may be an innate form of jealousy that does not require complicated reasoning and did not evolve to protect social bonds from interlopers.

Adapting a test used with six-month-old human babies, the researchers worked with thirty-six dogs and videotaped the owners, who ignored their pets by favoring either a stuffed dog that barked, whined, and wagged its tail; or a plastic jack-o-lantern. The owners were instructed to treat the objects as though they were real dogs—by petting them and talking to them affectionately. The third scenario involved reading aloud from a pop-up children’s book that played songs.

The pets exhibited more jealous behaviors, such as snapping and pushing at their owner or their rival, when the owner showed affection to what appeared to be another dog. Dogs were about twice as likely to push or touch the owner who was interacting with the faux dog (78 percent) as when the owner was attending to the jack-o-lantern (42 percent). Only 22 percent did this in the book scenario. While 25 percent snapped at the “other dog,” only one dog snapped at the jack-o-lantern and book. During the experiment or post experiment phase, about 85 percent of the dogs sniffed the fake dog’s rear end, which suggests they viewed the stuffed animal as a true rival.

Many people have assumed that jealousy is a social invention of human beings—or an emotion specifically tied to sexual and romantic relationships. The findings of the current study challenges these ideas— by showing that nonhumans may display strong distress when a rival usurps a loved one’s affection.