So far the specialised skill for recognising facial features holistically has been assumed to be a quality that only humans and possibly primates possess.
Although it is 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, scientists say.
Typically animals' ability to discriminate different individuals has been studied by training the animals to discriminate photographs of familiar and strange individuals.
"Dogs were trained to lie still during the image presentation and to perform the task independently. Dogs seemed to experience the task rewarding, because they were very eager to participate," said Vainio.
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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 canines had never met.
The pooches fixed their gaze more often on familiar faces and eyes rather than strange ones, ie dogs scanned familiar faces more thoroughly.
In addition, part of the images was presented in inverted forms ie upside-down. The inverted faces were presented because their physical properties correspond to normal upright facial images.
It is known that the human brain process upside-down images in a different way than normal facial images.
This study shows that the gazing behaviour of dogs is not only following the physical properties of images, but also the information presented in the image and its semantic meaning.
Dogs are able to see faces in the images and they differentiate familiar and strange faces from each other.