Carlo Siracusa of the School of Veterinary Medicine commented on a study that found dogs were more stimulated by seeing other dogs than people. “Mother Nature will not invest in something that is not relevant to survival, either in dog-to-dog or even wolf-to-wolf interactions,” he said. “They use other ways of communicating such as ear position—which can be seen from the front and from behind. The ear position will tell about the mood of the dog. We humans don’t move our ears.”