Dogs can smell stress in humans

Dogs see the world through their noses. Their ability to recognize specific smells – much better than humans – helps them find bombs, weapons, drugs and human remains, and can indicate certain diseases. Now, a study has found that dogs can also do something remarkable: sniff out stress in humans.

The dogs were able to smell changes in human breath and sweat, and with high accuracy they identified the chemical odors that people emit when they are stressed. The findings “provide a deeper understanding of the human-dog relationship and increase our understanding of how dogs perceive and interact with human psychological states,” said Clara Wilson. Wilson, a PhD student at Queen’s University Belfast’s school of psychology, is one of the study’s authors.

Noting that previous research with sniffer dogs and human biospecimens has focused mostly on disease detection, he added that it’s exciting to see that “they can smell other parts of the human experience.”

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The latest research adds to a growing body of evidence on canine behavior – how dogs see, think and smell – and their positive psychological effects. Dogs can make people feel better by relieving symptoms of anxiety and depression. Therefore, they are often used to support people with anxiety disorders or recovering from trauma. Dogs’ ability to smell human stress could be valuable in training service and therapy dogs, which now respond primarily to visual cues, according to researchers.

“I think this work helps to confirm that dogs can be astute at reading our emotional states, and this study in particular shows that it can be done through olfactory cues,” said Nathaniel Hall.

Hall, director of the Canine Olfaction Research and Education Laboratory at Texas Tech University, was not involved in the study. “The results reinforce what many owners feel: their dogs can be quite sensitive to their emotional states.”

There are many anecdotal stories of such moments shared by pet parents. Ben Goldberg of Scottsdale, Arizona, remembers how Yadi crawled into his wife’s arms after learning his initial fertility treatments had failed. (The couple now has a 10-month-old son.) “He could tell right away that she was nervous,” Goldberg said. “Yadi did the same thing again recently. “My wife found out that her grandmother passed away last month, and as soon as the call ended, she immediately hugged her.”

Victoria Allen of Goochland, Washington, tells a similar story about her rooster, Spes. On the beach, he and Spes encountered a group of young men, one of whom was crying. “Space ignored everyone and immediately went to the young woman who was crying to see him,” Allen said. “He loves people, so it wasn’t surprising, but in this situation, it was clear that this woman was the only person he wanted to see. Without hesitation, Spes walked right up to him and simply slapped his hand on his nose.

In real-life situations, Wilson said, dogs use a variety of contextual cues, such as our body language, tone of voice or breathing rate, to understand a situation. The results of the study “provide strong evidence that smell is also a component that can be acquired by dogs,” he said.

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The study did not determine whether the dogs could sense human emotions, such as whether the participants were feeling happy, sad, angry or fearful – only that they were experiencing stress as measured by the physiological signs of heart rate and blood pressure. pressure.

“Dogs can distinguish something about human odors in stressful and non-stressful situations, but they don’t necessarily know anything about how a person feels or what that means when stressed,” Evan MacLean said. MacLean, director of the Arizona Canine Cognition Center at the University of Arizona, was not part of the study. “Maybe – but we don’t know that from this study.”

Soot, a rescue female terrier mix, was one of four dogs included in a study at Queen’s University Belfast that tested canine stress scents. (Video: Matt Donnelly / Queen’s University Belfast)

The researchers collected sweat and breath samples from human participants before and after giving them a difficult math problem to solve, and only used samples from those who showed increased blood pressure and heart rate — signs of stress from completing the task. Samples were collected from 36 non-smokers who did not eat or drink anything before the test. Breath and sweat samples were collected from each subject by wiping gauze on the back of their neck, placing the gauze in a sterile glass vial, and then exhaling three times into the vial.

Four dogs, Treo, a male Cocker spaniel; Winnie, the female cockatoo; Fingal, male brindle rescue Lurcher/hound mix; and Soot, a female mixed-terrier breed rescue, were pets selected from a larger group of dogs after preliminary tests showed they were highly motivated to choose between different samples of human scents.

To train the dogs to recognize the scent, the scientists first exposed a stressed person’s sweat and breath sample to two control vials with clean gauze and used clicks and treats to train the dogs to identify the correct ones.

Each dog was then provided with breath and sweat samples taken from the same participant before and after experiencing stress. In about 94 percent of 720 trials, the dogs correctly alerted the researchers to each human’s pattern of stress, Wilson said.

He said he hopes future research can determine whether dogs can distinguish between positive and negative stress.

“Although we doubted that the dogs would be able to distinguish between the relaxed and stressed patterns of each person, it was fascinating to see how confident they were,” Wilson said. “I hope that we can build on this and discover more about these talented animals and what they can do.”

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