Emily Chan
Dogs are very in tune with the emotions of humans. They know when we are happy, sad, or even stressed. But how do they know? What kind of canine superpower is this?
Researchers from the University of Bristol in England may have found the answer—and it’s through their powerful sense of smell. In the first study of its kind, the researchers tested how the odors of human stress affect the emotional state of dogs.
Evidence suggests that humans subconsciously react to the smell of a stressed person. Dr. Nicola Rooney, senior lecturer in wildlife and conservation at Bristol Veterinary School, and her team set out to explore whether dogs do the same.
They recruited 18 dog-owner partnerships to participate in a series of trials. During the trials, the dogs were trained to associate the location of a food bowl with the presence or absence of a treat. Once they learned the arrangement, they were faster to approach the bowl with a treat than an empty one.
Then, the researchers switched it up by placing bowls in new, ambiguous locations between the two original bowls. If the dogs approached the bowls in the ambiguous locations quickly, that meant they were “optimistic” about the presence of food—a sign of a positive emotional state.
On the other hand, if they approached slowly, that indicated “pessimism” and a negative emotional state.
Each dog was also exposed to no odor or the odors of human stress, which were sweat and breath samples that were taken after an arithmetic test.
The researchers discovered that when the dogs were exposed to the smell of stress, they became slower to approach the ambiguous bowl location nearest the empty bowl location.
The “pessimistic” response was not seen when dogs were exposed to relaxed smells, which were samples from humans listening to calming soundscapes.
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