Many dog owners are sure their pooches get jealous, particularly when the person pays too much attention to someone else’s Fido. Now, scientists have confirmed that these dog lovers are right. Our canine pals can act every bit as resentful, bitter, and hostile as a jealous child—even if the interloper is nothing more than a stuffed toy hound. The researchers modified a test originally developed to assess the emotion in 6-month-old infants. They videotaped 36 dogs as they watched their owners completely ignore them while turning their attention to three different objects: a realistic-looking stuffed dog (which briefly barked and wagged its tail after a button was pushed), a plastic jack-o’-lantern, and a book. The dogs’ behaviors were then rated for aggressiveness, attention seeking, and interest in the owner or object. The fake pooch elicited the strongest response, the researchers report today in PLOS ONE. All the dogs pushed at their owners when the people talked to and petted the toy, and nearly 87% bumped it or tried to get between it and their beloved human. Almost 42% of the dogs actually snapped at the stuffed interloper. The fact that the rival was faux didn’t seem to matter—even pooches that sniffed the toy’s rear end (which 86% of the subjects did) behaved aggressively toward it. The study supports the idea that not all jealousy requires the ability to reflect on one’s self and to understand conscious intentions, as some scientists have argued, but that there is a more basic form of the emotion that likely evolved as a way of securing resources such as food and affection. Infants experience it if their mothers gaze affectionately at other babies, and so do members of another social species: dogs.