Stress-sniffing dogs can detect human distress with about 94% accuracy

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A new study shows that physiological processes associated with stress produce changes in breath, sweat, or both that can be detected by dogs. Tim Trzoska/EyeEm/Getty Images
  • In a new study, dogs detected breath and sweat samples from a person experiencing psychological stress with 93.75% accuracy.
  • The results show that stress-related physiological processes cause changes in compounds that flow from breath, sweat, or both, and that dogs can detect these changes.
  • Four dogs were trained for about an hour each week for about 10 months, according to the researchers.

Humans have developed many ways to activate the canine olfactory system. Trained diabetic dogs alert owners when they smell changes in blood sugar. Researchers have trained dogs to detect people malaria parasites because of their smells.

Dogs can even be trained to distinguish individuals’ inhaled breath patterns Lung cancer and healthy people.

When under stress, people can experiment physiological changesincluding the release of epinephrine and cortisol into the bloodstream, as well as increased heart rate, blood pressure, and respiration.

Recently, researchers from the UK’s Queen’s University Belfast and the University of Newcastle tried to find out whether these physiological changes cause a stressed person’s sweat and breath to smell differently than normal sweat and breath. If they are different, I wonder if dogs can detect them.

For this proof-of-concept published study PLOS ONEthe researchers reported that dogs could indeed pick out breath and sweat samples from a person experiencing psychological stress with 93.75% accuracy.

“It was fascinating to see how the dogs were able to distinguish between these odors when the only difference was the occurrence of a psychological stress response,” said Clara Wilson, Ph.D., lead author of the study. candidate at Queen’s University who studies canine smell and behavior explained Medical news today.

The researchers recruited domestic dogs from the Belfast area for the study.

The researchers selected 20 dogs for the review. Four dogs completed the training process after some dogs were withdrawn from the study for a number of reasons, including loss of interest as training progressed.

The four dogs selected included a male cocker spaniel, a female cockapoo and two mixed breed dogs, one male and one female. The age of the dogs ranged from 11 to 36 months.

Researchers have trained dogs using operative conditioning (where dogs repeat behaviors that lead to desired outcomes) and positive reinforcement.

The study started in December 2019. According to Wilson, dog training had to be put on hold for about a year during the pandemic. In total, he said, the dogs trained for about an hour each week for about 10 months.

“The training was extensive because the main goal was for the dogs to be able to consistently distinguish between two very similar human odors with known differences with over 80% accuracy over several sessions,” Wilson said. MNT.

For the study, the researchers used a contraceptive: a base with three aluminum arms. Each arm came with a cylindrical port with a removable cap.

First, the dogs were trained to stand or sit in front of the apparatus with their noses touching for 5 seconds.

The researchers then placed a sweat sample from the volunteers into gauze and a piece of food into one of the ports. The other two ports were filled with unused gauze.

When the dog successfully identified a port containing food, the researcher clicked the clicker and gave the dog a food reward. After the dog was able to correctly identify the food port on 8 out of 10 trials, the food was removed.

The dogs were then presented with three ports, none of which contained food. One port contained a sample of human sweat and breath, and the other two contained blank samples. One dog chose the port that held the human’s sweat and breath sample in seven out of 10 trials; they passed to the next stage.

In this training phase, dogs were presented with a piece of gauze containing sweat and breath of the same person used in the previous challenge (target), a sample from a new person, and a blank. Dogs had to select the target on 16 out of 20 trials for two consecutive sessions before moving on to the next training phase.

For this phase, the researchers presented the dog with breath samples taken from the same person at two different times of the day. The sample used in the morning was usually used as the target sample. After the dogs were successful with this challenge, the researchers allowed them to move on to the test phase.

The researchers recruited 53 human participants. 40 of them completed the study in person, and 13 completed it remotely due to the pandemic.

Participants were not allowed to smoke and were asked not to eat or drink flavored beverages for 1 hour before providing a breath sample. Participants either did not take mood-altering drugs or abstained from taking those drugs for 1 hour before providing a breath sample.

Participants wiped a piece of gauze on the back of their neck, depending on whether the sample was collected remotely or in person, or the researchers wiped a piece of gauze on the back of the participants’ neck. Then the gauze was placed in the vial. Participants took three deep breaths into the vial before closing the cap. Participants then completed a self-report questionnaire regarding their current level of stress.

Participants were then asked to perform a mental arithmetic task in front of the researchers, which involved counting backwards from 9,000 in 17 units without using pencil or paper.

As they calculated, two researchers followed up either in person or using an online dating app. During the task, the researchers would sternly say things like “you must continue until the task is complete”.

If the participant answered correctly, they were given no feedback and expected to continue. However, a participant who answered incorrectly would be told “no” by the researcher and would then report the participant’s last correct answer. The task lasted 3 minutes.

After completion, the participants again wiped a piece of gauze on the back of their neck, or the researchers wiped a piece of gauze on the participants’ necks. Gauze was placed in a vial. Participants took three deep breaths into the vial again before closing the cap. The same process was performed a second time with another vial. Participants then completed a second self-report questionnaire regarding their current level of stress.

In addition, the researchers monitored the heart rate and blood pressure of the participants who completed the study in person.

Samples were used only when participants’ self-report increased by two points from the time they took the baseline questionnaire to the time they took the questionnaire after completing the mental task. Participants who completed the study in person had to demonstrate an increase in mean heart rate and mean arterial pressure to be included.

Nine participants who conducted the study in person and two participants who conducted it remotely were excluded because they did not demonstrate a sufficient stress response. The sample of five other participants was excluded for various reasons. A total of 36 participants were tested.

Samples were collected from 30 women and six men with an average age of 25.42 years. Participants included 30 people who were white, three were Asian or Asian British, two were of mixed or multiple ethnicities and one was black, African, Caribbean or black British.

The samples were shown to the dogs within 3 hours of collection.

In the first phase of the trial, the researchers filled the port with a sweat and breath sample from a stressed participant and two blank samples.

In the next step, the researchers filled one port with a sweat and breath sample taken from the stressed participant, the other port with a sweat and breath sample taken before the participant performed the mental task, and a blank.

Each dog completed 10 phase 1 trials and 20 phase 2 discrimination trials. For the study, the researchers focused on the stage at which the dogs had to discriminate between stressful and baseline patterns.

Overall, the dogs detected the stress pattern in 93.75% of trials. The performance of individual dogs revealed the stress pattern from 90% to 96.88%.

“The way we tested this provides much-needed controlled evidence that the human stress response alters our emitted odor profile and that dogs can detect it,” Wilson said.

said Alan Beck, director of the Center for Animal-Human Interactions at the Purdue University College of Veterinary Medicine in Indiana, who was not involved in the study. MNT said he wasn’t surprised to read that dogs can pick up a stressed person’s sweat and breath pattern.

“This is part of a long history of literature showing that dogs have this ability,” he said. “We know that dogs have a very good sense of smell.”


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