Your dog is perfectly capable of sensing when you are stressed

Dogs have a long history with our species, which gives them an amazing ability to decipher the signals we send them. They also have an incredible sense of smell, which allows them to detect certain diseases that affect humans, such as Covid-19 or lung cancer, just by smell. On the other hand, the issue of whether these abilities extend to the detection of odors associated with psychological states has been little investigated.

My colleagues and I wanted to determine whether dogs could use their sense of smell to distinguish odor samples from the same person before and after exposure to stress. It should be known that when we are stressed, hormonal changes and modifications occur in the nervous system and change the odors produced by our body.

To determine whether our canine companions could indeed detect such differences, we were inspired by protocols applied to biomedical detection dogs with talents in the laboratory. We combined them with techniques used to test how these animals perceive smells. Our results were published in the journal PLOS One on September 28, 2022.

Sweat and breathe before and after the mental calculation

We first fitted (human) study participants with sensors to continuously measure heart rate and blood pressure. We also asked them to rate their perceived stress level before and after participating in a task we asked them to perform as part of this experiment. It was about doing a quick mental calculation that caused stress.

Before starting the task, participants wiped their necks with a piece of gauze, placed them in a sterile glass vial, and then inhaled. After mental arithmetic, participants presented two more sweat-breath samples.

Sample collection was separated by four minutes in the “relaxed state” (before the task) and the “stressed state” (after). This short delay makes it less likely that changes due to events other than exercise stress will affect the participants.

We included in the study only vials from participants who said they found the task stressful and had elevated heart rates and blood pressure. Finally, we presented the dogs with samples from thirty-six individuals.

Dog learning through positive reinforcement

The dogs included in this study were companion animals offered by their owners. They were also trained once a week in the laboratory by researchers using positive reinforcement, which involves associating exercise with something that represents a reward for the animal.

Before data collection began, the dogs were trained to indicate that they had chosen a sample by standing for a few seconds and walking over it or sitting in front of it—a behavior we call “startle behavior.”

The animals were then introduced to a matching game, through which they learned to distinguish patterns with different odors. Once it was determined that they had passed this game, they were ready to take part in the actual test.

During the latter, we asked the dogs to discriminate between samples taken from participants before and after arithmetic training. To teach them which odor to look for during each test session, we first showed them a sample of sweat or breath from a stressed person, as well as two “control” samples – pieces of clean gauze placed in sterile glass bottles, without sweat or breath. . The dogs were allowed to sniff three samples and were rewarded if they could signal a sweat-breath sample to the researchers.

After ten exposures, a second breath-sweat sample was added to the list: the same person, but relaxed. It was from this moment that the “discrimination” test began, which continued for the next twenty trials.

Effective ability

In this phase, the dogs had to alertly show a pattern that they perceived as identical to the pattern shown to them during the previous ten trials, i.e., the pattern containing the odor of the stress pattern. Controls were applied to verify that the animals did not rely on information other than information about the tested pattern (eg, the ongoing odor or visual aid unconsciously provided by the presentation devices in the patterns) to help them make their choices. experimenter).

If the two odors presented are similar to the sniffer, it can be expected to choose one or the other at random. If the two odors seem different to him, he should on the other hand be able to systematically find the first odor (the “stress” odor) presented to him during training. Each set of samples was used only once, so dogs were presented with vials from a different participant during each session.

Conclusion: From their first exposure to the post-stress samples, the dogs found that they had a specific odor. Indeed, they correctly selected the pattern in 94% of 720 trials. The fact that they were exposed to a mental arithmetic exercise that emphasized them actually caused a change in the odors produced by the participants’ bodies.

Better train assistance dogs

However, it should be emphasized that this study does not determine whether dogs perceive this odor as reflecting a negative emotional state. It is likely that in real life they use various contextual cues such as our body language, tone of voice or breathing rate to understand the situation.

However, these results provide strong evidence that the smell of stress is something that dogs can also sense. They allow us to better understand how our canine companions perceive and interact with human psychological states.

In addition to better understanding the bond that binds us to our four-legged friends, this knowledge may also be useful for better training assistance dogs for people suffering from anxiety and post-traumatic stress disorder. .

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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