Dogs have a specialised region in the brain that is hard-wired to recognise human faces, according to a new study that may explain the canines' extreme sensitivity to human social cues.
The study provides the first evidence for a face-selective region in the temporal cortex of dogs, researchers said. "Our findings show that dogs have an innate way to process faces in their brains, a quality that has previously only been well-documented in humans and other primates," said Gregory Berns, a neuroscientist at Emory University and the senior author of the study.
Having neural machinery dedicated to face processing suggests that this ability is hard-wired through cognitive evolution, Berns said, and may help explain dogs' extreme sensitivity to human social cues.
Berns heads the Dog Project in Emory's Department of Psychology, which is researching evolutionary questions surrounding man's best friend.
In previous research, the Dog Project identified the caudate region of the canine brain as a reward centre. It also showed how that region of a dog's brain responds more strongly to the scents of familiar humans than to the scents of other humans, or even to those of familiar dogs.
For the current study, the researchers focused on how dogs respond to faces versus everyday objects. "Dogs are obviously highly social animals, so it makes sense that they would respond to faces. We wanted to know whether that response is learned or innate," Berns said.
The study involved dogs viewing both static images and video images on a screen while undergoing functional magnetic resonance imaging (fMRI). It was a particularly challenging experiment since dogs do not normally interact with two-dimensional images, and they had to undergo training to learn to pay attention to the screen.
Only six of the eight dogs enrolled in the study were able to hold a gaze for at least 30 seconds on each of the images to meet the experimental criteria.
The results were clear, however, for the six subjects able to complete the experiment. A region in their temporal lobe responded significantly more to movies of human faces than to movies of everyday objects.
This same region responded similarly to still images of human faces and dog faces, yet significantly more to both human and dog faces than to images of everyday objects.
If the dogs' response to faces was learned - by associating a human face with food, for example - you would expect to see a response in the reward system of their brains, but that was not the case, Berns said.
"That study identified only a few face-selective cells and not an entire region of the cortex," said Daniel Dilks, an Emory assistant professor of psychology and the first author of the current dog study. The researchers have dubbed the canine face-processing region they identified the dog face area, or DFA. The study appears in the journal PeerJ.