According to a 2005 survey, 81% of dog owners and 66% of cat owners believed their pets had shown signs of jealousy. But as we all know, a pet owner’s judgment isn’t always the most reliable—humans are incredibly prone to projecting their own emotions onto animals. So, are scientific studies actually trustworthy in this area?Jealousy itself is a subjective emotion, a psychological state. We can only judge another being’s jealousy through external behaviors and our own experience. When it comes to dogs and cats, behaviors that seem like “jealousy” can often be explained in other ways—such as alertness, territorial instincts, or attention-seeking.But to put it simply: if you feel it’s jealousy, then it probably is.Maybe dogs truly believe they’re humans’ best friends—and they certainly don’t want a “third party” getting in the way.Early experimental results showed that if a stuffed toy dog drew the owner’s attention, the real dog absolutely wouldn’t let it slide. Newer research suggests that jealousy is a primitive emotion, not unique to humans and not necessarily dependent on an advanced brain. Jealousy can drive us to behave destructively, which makes understanding its nature even more important.Kristin Harris, the lead researcher of this study and an emotion scientist at the University of California, San Diego, explained:“In many countries, jealousy is the third leading cause of homicide.”Many people assume jealousy is exclusive to humans, especially since emotional conflicts can quickly become complicated.
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Dogs Get Jealous Too
Since no one had previously studied jealousy in dogs, researchers borrowed inspiration from experiments done on human infants—such as having mothers interact with doll-like figures to observe the reactions of six-month-old babies. These studies showed that even infants already display jealousy.For this dog experiment, 36 dogs participated, all small or medium-sized (weighing under 15.8 kg and shorter than 38.1 cm), ensuring that owners could physically control their pets if jealousy was triggered. The setup was simple: owners were instructed to completely ignore their own dogs while taking turns interacting with a toy dog that wagged its tail and made sounds, a Halloween pumpkin lantern, and a children’s pop-up sound book.Owners had to treat the toy dog and the pumpkin lantern as if they were real dogs—petting them gently and speaking to them affectionately. As for the book, owners read it aloud in an animated manner.The results showed that dogs were far more likely to get jealous of the toy dog. When owners interacted with the toy dog, the dogs were much more likely to push or nudge their owners—twice as likely compared to the pumpkin lantern and three times as likely compared to the sound book. One-third of the dogs physically inserted themselves between their owner and the toy dog; one-quarter barked at the toy dog. Only one dog barked at the pumpkin lantern and the book.Harris added, “Besides showing aggressive behaviors, dogs also use charm—they’ll act cute to win their owner back.” All these signs suggest that, in a dog’s mind, the toy dog seemed like a real rival. In fact, during or after the experiment, 86% of the dogs even sniffed the toy dog’s rear end.“Many people believe jealousy is a uniquely human social reaction, or that it only relates to romance and sexuality,” Harris wrote. “But our findings challenge this: when a close bond is threatened by a third party, animals can also become deeply distressed.”
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Why Dogs Get Jealous
The researchers explained that their findings shed new light on the question of whether jealousy exists only in humans, a species known for complex emotional processing. “The results show that complex cognitive abilities are not a necessary requirement for jealousy,” Harris said. “Simply realizing that your affection is being divided is enough.”As for the dogs that didn’t show jealousy, Harris offered several possibilities: “Not all dogs display jealous behaviors. Some may be less sharp and simply don’t interpret the objects as rivals. Others may be too smart—they can see through the setup and aren’t fooled by it. Another possibility is that the dog’s bond with its owner isn’t strong enough for jealousy to arise.”Future experiments could refine the research further—for example, testing how dogs react to toy dogs that don’t bark or wag their tails, or to non-dog objects like cats or dolls.“I suspect two factors trigger jealousy in dogs: first, how much attention and affection the owner gives the object; and second, how closely the object resembles a dog,” Harris explained. “My guess is that dogs get jealous of more than just dog-shaped things.”Future studies may also broaden the scope of the tested species.
The researchers suggested that animals whose offspring compete for parental attention, food, or mates would be worth studying next. Domestic cats might be a good option, as their kittens do compete with one another—unfortunately, however, cats do not have fixed mating partners.
