DOgs have a long history with humans, giving them the amazing ability to read human cues. Dogs also have an incredible sense of smell, which enables them to detect diseases, such as COVID And lung cancer, in humans by smell alone. Whether the ability of dogs to detect odors is associated with psychological states has been little known.
When people are under stress, hormonal and nervous system changes occur that alter the type of odor produced by the body. My colleagues and I wanted to know whether dogs could discriminate between odor samples taken from the same person before and after they were stressed. To do this, we took ideas from the field of biomedical detection dogs (sniffer dogs in a laboratory setting) and combined these ideas with techniques used to test dogs’ perception of odors.
Our results are published in the journal one more,
To test whether dogs could detect odors associated with psychological stress, we attached sensors to study participants to continuously measure their heart rate and blood pressure. Participants also rated how stressed they were feeling before and after participating in the task.
Before the task began, participants wiped gauze on the back of their neck, placed it in a sterile glass vial, and dropped it into the vial. We then asked the participants to perform rapid mental arithmetic tasks to create tension in them.
After the task, participants provided another rating of their stress and two additional sweat/breath samples.
The total time between the collection of relaxed (pre-task) and stressed (post-task) samples was four minutes, allowing participants to experience changes other than the onset of stress.
We only included samples in the study if the individual found the task stressful, and both their heart rate and blood pressure increased during the task. We submitted samples to 36 people for dogs.
training process
The dogs involved in this study were pets, volunteered by their owners, that were trained once a week using positive reinforcement by researchers in the laboratory. Before formal data collection began, dogs were taught to communicate that they were selecting a sample by standing on top of it or sitting in front of it for several seconds – we called this their “vigilant behavior.”
The dogs were then taught a matching game, where they learned to discriminate between samples with known odor differences. Once it was established that the dogs were successful in this, they were ready for testing.
At the time of testing, we tasked the dogs to discriminate between samples from an individual taken before and after the arithmetic task. To teach the dogs what odor they should be looking for in each test session, they were first shown a sample of the individual’s stress sweat/breath along with two “control samples”—in glass vials without sweat or breath. Clear mist.
The dogs were allowed to smell all three samples and were rewarded for alerting the researchers to the sweat/breath sample.
After ten exposures, a second breath/sweat sample was added to the line-up: a sample from the same person at rest. Here the test of discrimination began, which took place over the next 20 trials. It was the dogs job to communicate through their alert behavior which sample they perceived to be similar to the sample shown in the previous ten trials, i.e. which sample smelled like the stress sample. Since dogs can use other information to help them make choices, we included both visual and odor control.
If both of these odors smell the same to a dog, we would expect them to choose one of them by chance. If two odorants smell different, they will be able to consistently find the odor previously presented to them: the stress odor. Each sample set from the participants was used only once, so the dogs saw a different individual sample during each session.
The first time the dogs were exposed to these samples, they perceived the samples as smelling different. The dogs correctly selected the stress sample in 94% of the 720 trials, indicating that the participants’ psychological experience of the arithmetic task resulted in their breath and sweat emitting odors from their bodies that the dogs could detect.
It should be noted that this study did not determine whether dogs perceived stress samples as reflecting a negative emotional state. It is likely that in real-life settings dogs use a variety of contextual cues, such as our body language, tone of voice, or breathing rate, to help them understand a situation. However, the results provide strong evidence that odor is also a component that dogs can pick up on.
Establishing that dogs can detect odors associated with human stress provides a deeper understanding of the human-dog relationship and adds to our understanding of how dogs perceive and interact with human psychological states. This knowledge may also be useful for training anxiety and PTSD service dogs that are currently trained to respond primarily to visual cues.
Clara WilsonPhD Candidate, Psychology, Queen’s University Belfast
This article is republished from Conversation Under Creative Commons license. read the original article,
Read also: Raw meat can be good for your pet’s health – but only if you do it well.