Laugh and your best friend will probably join in. Her face will also instantly mimic your mirthful expression. Scientists call this emotional contagion (it also happens when someone yawns), and regard it as a basic form of empathy—the ability to experience what someone else is feeling. But humans aren’t the only animals who automatically and rapidly mimic each other’s expressions. Orangutans, chimpanzees, and geladas do as well. Now, researchers report online today in the Royal Society Open Science that dogs do, too. The scientists’ video recorded the play sessions of 49 dogs (26 female and 23 male), ranging in age from 3 months to 6 years, at a dog park in Palermo, Italy. They evaluated the videos for evidence of rapid mimicry—that is, dogs who in less than 1 second matched their playmate’s play postures (such as a bow) or facial expressions. In the video above, for example, one dog gives the other what the researchers call a “relaxed open mouth” expression—a dog’s signal for “let’s play.” And the second dog automatically makes the same expression with his mouth. Seventy-seven percent of the dogs rapidly mimicked the play bows and play faces of their dog pals, the scientists report. And like humans and other primates, the dogs most often experienced this emotional sharing with canines they knew well and played with on a regular basis. Dogs that shared at least one moment of rapid mimicry also played together longer—further evidence, the scientists say, that dogs are likely empathetic.