Dogs can detect when their humans are stressed, and it seems to affect their mood negatively.
For around 30,000 years, humans and dogs have shared a close bond, evolving together. This deep connection allows dogs to interpret human emotions through verbal and visual cues.
Now, new research shows that dogs can also smell stress, specifically through the odor of cortisol in human sweat, and this makes them feel downhearted.
The Study
A recent study published in Scientific Reports by scientists at the University of Bristol involved 18 dogs of various breeds and their owners. The researchers also recruited 11 volunteers unfamiliar to the dogs.
These volunteers were subjected to a stress test involving public speaking and arithmetic, during which sweat samples were collected. They then underwent a relaxation exercise, and new sweat samples were taken.
The study used sweat samples from three of these volunteers.
The dogs were divided into three groups and exposed to the sweat samples from the stressed volunteers.
Before this, the dogs were trained to associate a food bowl at one location with a treat and another bowl without a treat. During the testing, bowls without treats were placed in ambiguous locations.
When the dogs smelled the stressed sweat sample, they were less likely to approach the bowl in the ambiguous location, suggesting they expected a negative outcome.
This behavior indicates a down mood in dogs.
The results suggest that dogs are more pessimistic about uncertain situations when they are around stressed individuals. Conversely, the relaxed odor did not have the same effect.
Emotional Contagion
Zoe Parr-Cortes, the lead study author and a Ph.D. student at Bristol Veterinary School, explained, "For thousands of years, dogs have learned to live with us, and a lot of their evolution has been alongside us. Both humans and dogs are social animals, and there's an emotional contagion between us."
Katherine A. Houpt, a professor emeritus of behavioral medicine at Cornell University's College of Veterinary Medicine, noted that the smell of stress might reduce the dogs' motivation for food, impacting their decision-making.
This research indicates that dogs have empathy based on smell in addition to visual and verbal cues.
When their humans are stressed, dogs may display unusual behaviors.
Houpt added that it would be interesting to see how dogs respond to more intense stress, such as an impending tornado or a significant life event like job loss.
