Experts at Eötvös Loránd University in Hungary have compared how dogs and humans process visual information about others. The study showed some striking similarities, but also revealed that faces do not matter nearly as much to dogs as they do to people.
In humans, faces are central to visual communication – we have an entire brain network that is dedicated to face processing. While dogs pay attention to faces and use them to read our emotions, they also rely on other body signals to communicate. Prior to this study, it was not yet clear whether dog brains are specialized for face processing like human brains.
To explore how the brains of both species respond to visual information about others, the researchers tested 20 dogs and 30 people people in the same functional magnetic resonance imaging (fMRI) experiment. The study subjects were all presented with short videos of dog and human faces, as well as the back of the heads for comparison.
The experts identified brain regions in both dogs and humans that had a different response to the images depending on whether they contained individuals of their own species.
“Earlier, our research group already showed a similar correspondence between dog and human brains for voice processing,” said study senior author Attila Andics. “We now see that species-sensitivity is an important organizing principle in the mammalian brain for processing social stimuli, in both the auditory and the visual modality. ”
On the other hand, the researchers found no brain areas in dogs that encode whether the images showed a face or the back of a head. For humans, there was an obvious distinction made between the two.
“A preference analysis of the brain response patterns confirmed that in dogs, conspecific-preference is primary over face-preference and in humans, face-preference is primary over conspecific-preference,” said study co-first author Nóra Bunford. “This is an essential difference. It demonstrates that there can be substantial dissimilarities in cortical specialization for face perception across mammals.”
“Actually, these findings also shed new light on previous dog fMRI studies claiming to have found ‘face areas’: we now think that the stronger activity to dog faces in those studies indicated dog-preferring rather than face-preferring brain areas.”
The team also identified dog and human brain regions that showed a similar activity pattern in response to the videos.
“This so-called representational similarity analysis can directly compare brain activity patterns across species,” said study co-first author Raúl Hernández-Pérez.
“Interestingly, similarities between dog and human activity patterns were stronger for what we named functional matching (comparing activity for dog face in the dog brain to activity for human face in the human brain), than for physical matching (comparing activity for dog face in the dog brain to activity for dog face in the human brain).”
“This shows that here we may have tapped into high-level categorical processing of social information rather than low-level visual processing, in dogs as well as in humans.”
According to Andics, similarities in species-sensitivity yet differences in face-sensitivity show that the visual processing of social information is not organized in the same way among dogs and humans.
“This is another demonstration that comparative neuroimaging with phylogenetically distant mammalian species can advance our understanding of how social brain functions are organized and how they evolved,” said Andics.
The study is published in the Journal of Neuroscience.