Although it's well known, that faces and eye contact play an important role in the communication between dogs and humans, this was the first study, where facial recognition of dogs was investigated with eye movement tracking.
Typically animals' ability to discriminate different individuals has been studied by training the animals to discriminate photographs of familiar and strange individuals.
The researchers, led by Professor Outi Vainio at the University of Helsinki, tested dogs' spontaneous behavior towards images to determine if the dogs, who are not trained to recognize faces, would be able to see faces in the images and if they naturally look at familiar and strange faces differently.
Vainio said that dogs were trained to lie still during the image presentation and to perform the task independently and they seemed to experience the task rewarding, because they were very eager to participate.
Dogs' eye movements were measured while they watched facial images of familiar humans and dogs being displayed on the computer screen. As a comparison, the dogs were shown facial images from dogs and humans that the dogs had never met.
The results indicate that dogs were able to perceive faces in the images.
Dogs looked at images of dogs longer than images of humans, regardless of the familiarity of the faces presented in the images.
This corresponds to a previous study by Vainio's research group, where it was found that dogs prefer viewing conspecific faces over human faces.
Dogs fixed their gaze more often on familiar faces and eyes rather than strange ones, i.e. dogs scanned familiar faces more thoroughly.
The study is published in the journal Animal Cognition.