Explained: How dogs can sniff and tell if they’re stressed

Stress is a part of everyday life for everyone, and researchers have found that when people are stressed, they produce a different scent that dogs can detect with their sense of smell.

A study recently published by the Public Library of Science found that dogs can distinguish between stressful and non-stressful situations by detecting this scent. Clara Wilson, one of the authors of the study and a PhD student at Queen’s University Belfast, said: “This research has shown that the olfactory profile changes in humans in response to stress.” This finding may be useful in training service dogs that support people with post-traumatic stress disorder (PTSD) and help understand the human-dog relationship.

How does research define “stress”?

Research views “stress” as “a physiological and psychological response to a challenging situation (ie, a stressor) that is exacerbated when the individual does not feel confident in their ability to cope with the stressor.” The term is further classified as “negative” when the individual lacks adequate measures to cope with the stressful situation and “positive” when the individual has adequate resources to cope with the stressful situation. Negative stress is accompanied by an increase in heart rate and blood pressure, while positive stress is often accompanied by a decrease in blood pressure levels.

While the research avoids conceptualizing stress as an emotion in humans, it points out that negative stress produces “relatively automatic emotional responses based on a person’s perception of the stressor.” This response involves the same areas of the brain involved in fear. When people are stressed or afraid, they experience negative stress and, as research shows, they create changes in their olfactory profiles.

How do dogs detect human emotions?

While humans use primarily sight to assess the world, dogs are believed to use both sight and smell to perceive and communicate with their surroundings. According to VCA Animal Hospitals veterinarians Ryan Llera and Lynn Buzhardt, dogs have more than 100 million olfactory receptors, compared to 6 million in humans. Moreover, the area of ​​the brain responsible for interpreting smells in dogs is about 40 times larger than in humans.

How was the research conducted?

Given the close relationship dogs have with humans, it is possible that they can detect changes in humans through their sense of smell, beyond what previous research has revealed. Breath and sweat samples were obtained from thirty-six participants in combination, at baseline (starting point) and after challenging them with some stress level (tasking them to count down from 9000 in 17 units). The study was conducted over 36 sessions and in two phases.

A dog was trained in Phase One to detect an arousal pattern by presenting the participant with a stress sample (obtained immediately after engaging in the stressful task) and two samples without breathing or sweating.

The second phase included a stress sample, a prime sample from the same participant, and a blank sample. The performance of the dog’s warning behavior was measured in the stress sample.

Dogs were observed to select the stress pattern in 675 of 720 trials (pooled accuracy 93.75%). This observation suggests that each participant’s patterns were different at baseline and after stress-induction. In addition, odor control procedures ensured that dogs did not rely on external cues to discriminate between samples. This performance suggests that humans can distinguish between core and stress odors.

What is the relevance of this research?

The study claims that this finding is crucial to understanding how dogs “interpret and interact with human psychological states.” Service dogs trained to help people with anxiety, panic attack disorder, and PTSD can detect the psychological changes associated with these conditions through their olfactory detection abilities alone—the olfactory component of dog training can help them. detect acute stress reactions in their owners.

What else can dogs detect?

The finding that dogs can detect changes in the scent profiles of humans is based on the fact that humans release volatile organic compounds that are exhaled by their breath, adhere to the skin surface, and are found in urine, feces, and saliva. This is further demonstrated in the ability of dogs to detect complex medical conditions in humans such as lung, bladder, prostate and breast cancer by sniffing samples of breath, urine and feces.

Claire Guest, co-founder and chief scientist at the charity Medical Detection Dogs, points out that “medical alert dogs are trained to alert people with complex medical conditions when they are in danger of experiencing a potentially life-threatening medical event. detection of changes in smell”.

In addition to their nose, Jacobson’s organ (or vomeronasal organ) serves as a unique part of the canine olfactory system dedicated to chemical communication. Its nerves lead directly to the brain, unlike ordinary olfactory nerves, and facilitate the detection of “ambiguous” odors.


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