Every dog owner knows what it is like to return home to a pup that has been awaiting their arrival after a long day at work. The moment that door flings open, your best friend is sitting there with an anxious look on its face. Their tail might be wagging 100 MPH, the ears pinned back, and its front paws barely able to stay on the floor as it braces to jump up and give you a warm welcome.

During this reunion with your pup, is it simply excited to see another person in its environment, or is this reaction uniquely for you as the owner because the dog recognizes your face?

It begs the question: can a dog actually recognize human faces?

A study conducted four years ago, and published in the journal Animal Behavior, found that dogs do have the capacity to recognize the face of their human owners in person. In the study, a dog was placed in a sterile room with no distractions or toys to excite the animal. The experiment began with the dog's owner and another individual entering the room, crisscrossing their paths several times in front of the dog, and then exiting the room through two separate doors.

The scientists following the dog's head and eye movement found that most of the dogs participating in the study fixed their gaze on the movement of their owners. When the owner and the other individual had departed, the dogs were then allowed free movement in the room. Again, the vast majority of dogs would move toward the door their owner had exited through, sitting in front of (or near) it waiting for their owner to return.

In order to establish the importance of facial recognition, the scientists had the owner and another individual repeat their movements through the room wearing a bag over their heads to disguise their faces. During this phase, the dogs involved in the experiment paid less attention to their owners. The eye and head movement of most dogs was random and, in many cases, the dogs spent equal time watching the movements of both individuals. 

The only question that remained regarding dogs and facial recognition was whether or not they could recognize their owners' faces when they did not see them in person. Could a dog recognize a simple image of its owner's face? A new study from December 2013 suggests that dogs can indeed recognize their owner's face in an image alone.

The new eye-movement study was conducted at the University of Helsinki in Finland. The study tracked the eye movements of thirty one participant dogs. The animals were shown images of human faces, as well as the faces of other dogs, on the screen in front of them. The scientists leading the experiment found that dogs would fix their gaze on the face of their owners for longer periods of time compared to the faces of strangers.

Another not so shocking finding from the study revealed that dogs fixed their gaze for the longest period of time on the face of other dogs. The thirty one participants all gazed at images of other dogs, from the same house or unknown dogs, for longer periods of time than their human owners' faces. Then again, any dog owner knows how fixated their dog becomes when another dog has the nerve to waltz through the yard, so this fact shouldn't come as a surprise.