You know your dog knows who you are, right? That enthusiastic greeting when you come home is proof positive that he recognizes you. But what clues him in to your identity—the sound of your footsteps, your voice, your unique smell, that palpable charm? That may all be possible, but recent evidence suggests that dogs can actually recognize faces.
The ability to recognize faces is important for social animals. When living in a group, identifying individual members and being able to distinguish them from one another is essential for keeping track of specific social interactions. For dogs as well as humans, this skill is highly developed.
In a recent study called How dogs scan familiar and inverted faces: an eye movement study  published in the journal Animal Cognition, researchers investigated facial recognition in the domestic dog. They concluded that:
These results are similar to those found when studying humans and other primates with the same technique used in this study—tracking eye movement. Across the many species that have been studied previously, primates are more interested and spend more time looking at faces of members of their own species. Similarly, primates look at the eyes of faces, just as dogs did.
This study also investigated dogs’ responses to faces that are shown upside down. Such inversions are interesting to cognitive scientists because there is evidence in other species that inverted faces are not processed the same way as faces that are oriented in the normal way.
Humans are able to identify faces quickly and accurately because we have a mechanism to identify faces that is separate from the system used to identify other sorts of objects. The face is looked at as a complete structure with tiny differences in the configuration of its parts rather than as separate parts as we do with other objects. When faces are upside down, the process of facial recognition is disrupted and we are forced to identify the face as we would other objects, as parts that must be looked at and evaluated individually rather than as a whole. The facial recognition that is usually so effective doesn’t work well on inverted faces. They are processed as other sorts of objects are—piece by piece—rather than as an integrated whole, which is why we are not as good at identifying faces in this way.
Dogs, according to this study, fixate on upside down faces longer, suggesting that it is more difficult for them to identify them than when they are upright. They do spend a lot of time looking at the eyes even in upside down faces, which suggests that they do recognize these images as faces despite their position.
Because dogs have lived with humans for so long, they provide an interesting model for studying facial recognition since they are adept at identifying individual faces in their own as well as in our species.