Dogs were able to distinguish between human breath and perspiration samples taken before and after a stressful task.
According to a recent study, canines can accurately identify acute psychological stress responses with 93.75% accuracy by detecting changes in human breath and sweat.
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According to a new study by Clara Wilson of Queen's University Belfast, UK, and colleagues, dogs can accurately identify changes in human breath and perspiration that are caused by the physiological processes connected to an acute psychological stress response with a 93.75% accuracy rate.
The body emits chemical messages called odors that have developed primarily for communication within species. Researchers questioned whether dogs could be sensing chemical signals to respond to their owners' psychological states given their remarkable sense of smell, close history of domestication with humans, and use to support human psychological conditions like anxiety, panic attacks, and post-traumatic stress disorder (PTSD).
In the latest study, non-smokers who had not recently consumed food or liquids had their breath and perspiration samples collected. Samples were taken both before and after a demanding math task, along with objective physiological measurements like heart rate (HR) and blood pressure and self-reported stress levels (BP). Within three hours of being collected, samples from 36 participants who reported feeling more stressed as a result of the exercise and who also saw an increase in HR and BP throughout the task were presented to trained dogs.
Four dogs of various breeds and breed mixes had been trained to match odors in a discriminating task using a clicker and kibble. Dogs were asked to locate the participant's relaxed sample, which was collected just minutes before the activity began, while the participant's stressed sample was collected after the task's conclusion.
Overall, dogs were able to recognize and act in an alert manner on the sample collected under stress in 675 out of 720 trials, or 93.75% of the time, which is significantly more often than would be predicted by chance (p 0.001). The canines accurately alerted to the stressed sample 94.44% of the time when they were first presented with a participant's relaxed and stressed samples. The accuracy of the individual dogs ranged from 90% to 96.88%.
The authors come to the conclusion that dogs are capable of smelling odors linked to changes in the Volatile Organic Compounds (VOCs) that humans produce in response to stress. This finding sheds light on the relationship between humans and dogs and may have implications for the training of service dogs for anxiety and PTSD who are currently trained to respond primarily to visual cues.
The authors further say: "This study shows that canines are able to distinguish between human breath and sweat samples taken before and after a stressful task. This result demonstrates that dogs are able to identify changes in the olfactory profile of our breath or perspiration caused by an acute, negative, psychological stress response."
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ine Reeve, Zachary Petzel, and Clara Wilson. Dogs are able to distinguish between normal human odors and those associated with psychological stress. 2022;17 (9):e0274143 in PLOS ONE; DOI: 10.1371/journal.pone.0274143