A glimpse inside dog’s brains suggests that our furry companions can identify certain emotions in people’s faces, according to a new first-of-its-kind study.
A team from the University of Vienna scanned the brains of several dogs to reveal how the animals’ brains respond differently depending on humans facial expressions, which was published in the Cell Press journal iScience.
Researchers first showed eight dogs — six border collies, a labrador and a golden retriever — images of strangers with either a happy or neutral expression, finding that the images with happy expressions triggered a stronger response in a region of a canine’s brain.
In addition, researchers showed 12 dogs — one mixed breed, three golden retrievers, and eight border collies — pictures of people feeling happy, angry, fearful or sad, with whole-brain activity patterns distinguishing sad faces from fearful ones, and angry faces from fearful ones.
There was no evidence that the dogs could distinguish angry faces from sad ones. Fearful expressions stood out from the other negative emotions.
The authors describe the findings as the first direct evidence that dogs’ brains can distinguish between two human faces showing different negative expressions.
“I would like people to see dogs as emotional beings,” senior author Laura Cuaya of the University of Vienna said in a press release.
“They have evolved with us to understand our expressions and cooperate with us, and recognizing that can change how we communicate with and care for them.”
Happy images trigger 'reward' part of dog's brain
In the first experiment, the researchers trained eight dogs to sit completely still for several minutes in a functional magnetic resonance imaging (fMRI) machine, showing the dogs strangers’ faces with either a happy or neutral expression.
The happy images “elicited a stronger response than neutral faces in a right temporal cluster extending to the caudate nucleus,” which the study states are also activated in dogs by representations of “food reward” and “familiar scents.”
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These two areas of the brain were only activated when happy images were shown.
However, the study does note that just because a dog recognized a happy face, it does not conclude that the animal is in turn feeling happy.
“The expression labels (i.e., happiness, anger, sadness, and fear) used here were defined in human-validated stimulus databases, and thus should be interpreted as descriptors of the stimuli rather than descriptors of dogs’ subjective experience.”
Sad, fearful or angry photos tell different story
When the 12 dogs were shown images of strangers that were either sad, fearful or angry, researchers found distinct activity patterns that “differentiate some specific negative human facial expressions, showing that dogs’ brains can distinguish between expressions.”
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This provided the first evidence that dogs can tell apart specific negative facial expressions.
The study found that images of strangers angry, fearful, and sad expressions appeared to stimulate different areas of the dogs’ brains, particularly the right rostral supra sylvian gyrus, the right ectosylvian gyrus and the left splenal gyrus.
The right rostral supra sylvian gyrus parts of the human brain contribute to the processing of visual information.
While the dogs displayed differing responses to fear and anger, and to fear and sadness, they did not seem able to differentiate anger and sadness.
“This suggests that the dog brain separates human facial expressions by valence and shows separability among some negative human facial contrasts, particularly those involving fear,” the study states.
“When we compare humans with primates, we are looking at abilities that may have come from a common ancestor,” Cuaya stated. “With dogs, the story is totally different. They followed a very different evolutionary path, yet through domestication, they developed the social abilities needed to understand and cooperate with us.”
The study added that all the furry participants in the study were all pets from loving families and cautioned that dogs outside such environments may respond to human emotional cues differently.
The researchers next plan to investigate how dogs integrate other cues, including voice nuances, body language and scent, to interpret the humans around them.
They also hope to compare how human and canine brains process the same emotional signals.
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