That dogs have a wonderful sense of smell is no secret. Not in vain do they have odor receptors 10,000 times more precise than those of humans. Now, a study conducted by researchers at Queen’s University Belfast and published in Plos One concludes that dogs can tell when we’re stressed by the smell we give off.
Four dogs of different breeds participated in the experiment: Treo, Fingal, Soot and Winnie and 36 people. To measure stress, human participants had to solve a difficult math problem and report to the researchers the stress they felt before and after performing the task. The researchers, meanwhile, took sweat and breath samples before and after they were set on the task. Only the samples in which the person’s blood pressure and heart rate had increased were used in the experiment.
The dogs were taught to look for a lineup of scents and to alert the researchers when they came across the correct sample, that is, the stress sample. Next, the stress and relaxation samples were introduced, but at this stage the researchers didn’t know if there was an odor difference that the dogs could detect.
In each testing session, each animal received two samples from a person, the relaxed and the stressed, collected just four minutes apart. The result was that all the dogs correctly notified the researchers when they were faced with the stress sample.
“The findings show that we as humans produce different odors through our sweat and breath when we are stressed and dogs can distinguish this from our odor when we are relaxed, even if it is from someone they don’t know,” said Clara Wilson. , one of the authors of the study. “The research shows that dogs do not need visual or auditory cues to perceive human stress . It is the first study of its kind and shows that dogs can smell stress through breath and sweat alone, which could be useful for training service and therapy dogs,” said Wilson.
The researchers emphasize in the publication that the small size of the sample does not compromise the results, since the objective of the study is not to generalize the results to all dogs, but to demonstrate that, if we carefully select a few and train them, they can differentiate success the samples.
The results also contribute to our better understanding of the relationships between humans and dogs and how dogs interpret their environment and interactions with us through smell. It is also shown that there is a certain detectable odor associated with negative stress that some trained dogs can detect.
Service dogs that support people suffering from post-traumatic stress or anxiety are primarily trained to respond to certain visual cues. This study opens the door to the possibility of training animals also with smell, to detect stress by their smell.
Referencia: Wilson, C., Campbell, K. et.al. Dogs can discriminate between human baseline and psychological stress condition odours. 2022. Plos One. DOI: https://doi.org/10.1371/journal.pone.0274143
