The ability of dogs to sniff out stress levels in humans has been known for some time.
But the relationship between woman and man’s four-legged best friend is a two-way street, and scientists now believe they have discovered that when a dog senses a person in need, it has an effect on the animal’s behavior – in particular, it makes they pessimistic.
New research is believed to be the first to test how dog owners’ emotional states can affect their pets.
Dr Nicola Rooney, senior lecturer at the University of Bristol’s veterinary school and lead author of a paper on the subject, said: “Dog owners know how attuned their pets are to their emotions, but here we show that even the smell of a stressful, unfamiliar human affects a dog’s emotional state, perception of rewards and ability to learn.
“Working dog handlers often describe stress moving along the lead, but we’ve also shown it can also travel through the air.”
She added that understanding how human stress affects dogs’ well-being is important for dogs in kennels and training companion, working and assistance dogs.
The team used a test of “optimism” or “pessimism” in animals to determine whether they felt positive or negative emotions after exposure to people’s stressful and relaxing smells.
The researchers recruited 18 dog-owner partnerships to participate in trials in which dogs were trained that when a food bowl was placed in one location, it contained a treat, but when placed in another location, it was blank.
Once dogs learned the difference between these trays, they were faster to approach the location with a treat than the empty location. Researchers then tested how quickly the dog would approach new, ambiguous bark locations between the original two.
A fast approach reflected optimism about food being present in these ambiguous locations—a marker of a positive emotional state—while a slow approach indicated pessimism and negative emotion. These trials were repeated while each dog was exposed to either no odor or the odors of sweat and breath samples from people who felt stressed from a math test or relaxed after listening to soundscapes.
Researchers discovered that the stress odor made dogs slower to approach the ambiguous bowl location closest to where they had been trained to expect empty bowls. This effect was not replicated after exposure to the relaxing odor.
These findings suggest that the stress odor may have heightened the dogs’ expectations that this new location contained no food, similar to the nearby empty litter box. The researchers suggested that this could be a way for the dog to conserve energy and avoid disappointment.
The team also found that dogs continued to improve their learning about the presence or absence of food in the two trained bowls and that they learned the difference faster when the stress odor was present.
