Dog owners have long suspected that canines get jealous, but this new study provides scientific evidence for the idea for the first time.
Canines were found to become extremely jealous when their human caretakers pay attention to a dog from outside their family. This behavior occurs even when the other "dog" is nothing more than a stuffed toy, researchers report.
Researchers studied dog owners and their canine wards, using a modified test, originally designed to measure jealousy in six-month-old children. The 36 animals were recorded as their human caretakers played with a realistic stuffed dog, a plastic jack-o-lantern, and a book. They looked for attention-getting behaviors, aggressiveness and interest in both the target of interest and the person.
"We found that dogs exhibited significantly more jealous behaviors (e.g., snapping, getting between the owner and object, pushing/touching the object/owner) when their owners displayed affectionate behaviors towards what appeared to be another dog as compared to nonsocial objects," researchers wrote in an article announcing their discovery.
When human companions paid attention to, and petted, the stuffed dogs, the real canines bumped into the person or the faux animal 87 percent of the time. A total of 42 percent of the dogs even snapped at the supposed interlopers. The real canines sniffed the rumps of the stuffed canines 86 percent of the time. This should have revealed to the dogs the stuffed creature was not real, but aggression among dogs continued.
"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," Christine Harris, psychology professor at the University of California San Diego, said.
The study was conducted in the homes shared by the dogs and their Homo Sapien companions. The human subjects petted the stuffed dogs, as well as the jack-o-lanterns used in the experiment and the read from pop-up books, which also played a musical melody.
Some scientists believe that jealousy requires the ability for self-reflection and an understanding of conscious intentions. This new investigation suggests a more primitive form of jealousy may have evolved in human ancestors and dogs as a way of securing both affection and nutrition.
Human infants have been shown to act jealous when parents pay attention to other babies. These behaviors are much like those seen in dogs in this new study.
Investigation of jealousy in dogs was detailed in the journal Plos One.