August 12, 2024, 6:24 am | Read time: 4 minutes
When we are stressed, this is also transferred to our dogs. This leads to them making more “pessimistic” decisions, as new research findings show. For the first time, British scientists were able to show that even the stressful odors of strangers have an effect on the learning and emotional state of dogs.
It’s well established that dogs can detect when humans feel stress, and this emotional state can also be transferred to them. How exactly this perception influences our four-legged friends in their decisions, however, has been studied little. Scientists at the University of Bristol in England have now investigated for the first time how the stressful odors of strangers affect the learning and emotional state of dogs. The results were published in the scientific journal “Scientific Reports“.
How do you test emotions in dogs?
To investigate the influence of strangers’ stress on dogs’ emotions and decision-making, the team employed a test measuring “optimism” or “pessimism”. The idea behind this is that animals that make optimistic decisions have a positive emotional state. Pessimistic decisions, on the other hand, indicate negative emotions.
A total of 18 dogs took part in the study. They were taught that a food bowl contained a treat in one place, but was empty in another. Once a dog had learned the difference between these bowl locations, it approached the location with the treat faster than the empty bowl. But what would happen if a third bowl location, previously unknown to the dog, was introduced? Would the dog be more optimistic and expect a treat in it? Or would it be pessimistic and approach the new location rather slowly? And how could smells influence this decision?
Smell stress from a math test
When a person is stressed, others notice this, primarily through their behavior. Dogs also sense our stress through smell. In order to create an authentic stress smell for the study, the human test subjects had to pass a math test. This is likely to induce sweating in most people.
It was important that the human participants were not the owners of the dogs in the test but strangers. As a counterpart to this, the smell of strangers who were in a relaxed state of mind was used. The dogs were then exposed to either one or the other odor during the test with the bowls.
Stress from strangers influences dogs’ feelings
In fact, the stress odor caused the dogs to approach the bowls in new locations more slowly compared to the dogs exposed to the human relaxation odor. This suggests that the stress odor may have increased the dogs’ expectations that this new location would not contain food. This behavior could be a way for the dog to conserve energy and avoid disappointment.
The researchers were thus able to show for the first time that the stress of strangers influences dogs’ feelings and decisions. The scent alone was enough, as the dogs were unable to see or hear the people. Even so, they still detected their stress.
Stress is not only transmitted via the leash, but also via the air
“Dog owners know how responsive their pets are to their emotions. Here we show that even the smell of a stressed, unfamiliar human affects a dog’s emotional state. Also, its perception of rewards and its ability to learn”, said Dr. Nicola Rooney, lecturer in wildlife and conservation at Bristol Veterinary School and lead author of the study. She summarized the findings in a university press release. “Dog handlers often report that stress is transmitted through the leash. We have also shown that it can be transmitted through the air.”
Dr. Rooney further emphasized the importance of understanding the impact of human stress on dogs’ well-being. Both in domestic settings and in the training of companion and working dogs, such as assistance dogs.
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The results should be interpreted with caution
Given that this is a pioneering study, the results warrant cautious interpretation. For one thing, the number of dogs tested is very small. Secondly, the results were not statistically clear in all test runs, as the authors note in the discussion of the results.
Consequently, the researchers cautiously present their conclusions: “Our study is the first to demonstrate that olfactory signals of human stress, in the absence of visual or auditory cues, can influence dogs’ cognitive processes and learning abilities, which could significantly affect their well-being and task performance.”