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Dogs can detect changes in breathing and sweating that occur in response to stress
The physiological processes associated with an acute psychological stress response lead to changes in human breath and sweat that dogs can detect with 93.75% accuracy, according to a new study published this week in the open access journal PLOS ONE by Clara Wilson of Queen's University Belfast, UK, and colleagues. Smells emitted by the body represent chemical signals that have evolved for communication, especially within species. Given dogs' remarkable sense of smell, their close domestication history with humans, and their use to alleviate human mental illnesses such as anxiety, panic attacks, and post-traumatic stress disorder (PTSD), we wondered...
Dogs can detect changes in breathing and sweating that occur in response to stress
The physiological processes associated with an acute psychological stress response lead to changes in human breath and sweat that dogs can detect with 93.75% accuracy, according to a new study published this week in the open access journal PLOS ONE by Clara Wilson of Queen's University Belfast, UK, and colleagues.
Smells emitted by the body represent chemical signals that have evolved for communication, especially within species. Given dogs' remarkable sense of smell, their close domestication history with humans, and their use to alleviate human mental illnesses such as anxiety, panic attacks, and post-traumatic stress disorder (PTSD), researchers wondered whether dogs could sense chemical signals to respond to their owners' psychological state.
In the new study, researchers collected breath and sweat samples from non-smokers who hadn't eaten or drunk recently. Samples were collected both before and after a quick arithmetic task, along with self-reported stress levels and objective physiological measures: heart rate (HR) and blood pressure (BP). Samples from 36 participants who reported an increase in stress due to the task and experienced increases in heart rate and blood pressure during the task were shown to trained dogs within three hours of collection. Four dogs of different breeds and breed mixes were trained to assign odors in a discrimination task using a clicker and dry food. During the test, the dogs were asked to find the participant's stress sample (taken at the end of the task), while the same person's relaxed sample (taken just minutes before the task began) was also included in the sample set.
Overall, dogs were able to recognize and execute their alarm behavior from the sample taken under stress in 675 of 720 trials, or 93.75% of cases, much more than expected by chance (p < 0.001). When first exposed to a participant's stressed and relaxed samples, the dogs correctly called attention to the stressed sample 94.44% of the time. Individual dog performance ranged from 90% to 96.88% accuracy.
The authors conclude that dogs can detect an odor that is related to changes in volatile organic compounds that humans produce in response to stress. This finding tells us more about the human-dog relationship and could be applied to training anxiety and PTSD service dogs, which are currently trained to respond primarily to visual cues.
The authors add: "This study shows that dogs can distinguish between people's breath and sweat before and after a stressful task. This finding tells us that an acute, negative, psychological stress response changes the odor profile of our breath." Sweat, and that dogs can detect this change in smell.
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Reference:
Wilson, C., et al. (2022) Dogs can distinguish between basic human odors and psychological stress odors. PLUS ONE. doi.org/10.1371/journal.pone.0274143.