Dogs affected by the smell of human stress, study finds

He smell of human stress affects dogs’emotions and could lead them to make more pessimistic decisions, new research suggests.

The study found that the scent of stress released through human sweat and breath can change the behavior of man’s best friend.

A pessimistic response reflects a negative emotional state and could possibly be a dog’s way of conserving energy and avoiding disappointment, the researchers suggest.

Researchers led by the University of Bristol suggest the findings are important for dogs in kennels and when animals are being trained for roles such as assistance dogs.

Dr Nicola Rooney, Senior Lecturer in Wildlife and Conservation at Bristol Veterinary School and lead author on the paper, said: “Understanding how human stress affects dog welfare is an important consideration for kenneled dogs and when training companion dogs and dogs for working roles such as assistance dogs.

“Dog owners know how in tune their pets are with their emotions, but here we show that even the scent of a stressed, unfamiliar human affects a dog’s emotional state, perception of rewards, and ability to learn.

“Working dog trainers often describe stress as being transmitted through the leash, but we have shown that it can also travel through the air.”

The researchers used an optimism or pessimism test in animals, which is based on the finding that people’s optimistic or pessimistic choices indicate positive or negative emotions, respectively.

In the study, 18 dogs were trained so that when a food bowl was placed in one location, it would contain a treat, but when it was placed in another location, it would be empty.

Once the dog learned the difference, he was quicker to approach the spot with the treat.

The researchers then tested how quickly the dog would approach a third container, in a new location between the original two.

A fast approach reflected optimism about the presence of food in these new locations (a positive emotional state), while a slow approach indicated pessimism and negative emotion, the researchers say.

These trials were repeated with each dog exposed to no odor or to the odors of sweat and breath samples from humans in a stressed or relaxed state.

According to the results, the stressful odor caused the dogs to approach the new bowl location more slowly, closer to the trained location for the empty bowl.

This did not occur after the animals were exposed to the relaxing scent.

The findings, published in the journal Scientific Reports, suggest that the stress scent may have heightened the dogs’ expectations that this new location did not contain food, similar to the nearby empty bowl location.

This pessimistic response reflects a negative emotional state and could possibly be a way for the dog to conserve energy and avoid disappointment, the researchers suggest.

The scientists also found that the dogs continued to improve their learning about the presence or absence of food and that they improved faster when the stress scent was present.

The 18 dogs included were between eight months and ten years old, and included two springer spaniels, two cocker spaniels, two labrador retrievers, two braque d’Auvergnea whippet, a golden retriever, a miniature poodle and seven mixed-breed dogs.