Dogs can detect the physiological processes associated with an acute psychological stress response, which produces changes in human breath and sweat, with an accuracy of 93.75 percent.
The new study was conducted by Clara Wilson and colleagues of Queen’s University Belfast, UK, published this week in the open-access journal PLOS ONE.
Researchers wondered whether dogs could sense chemical signals and respond to their owner’s psychological states since these signals which are emitted by the body through odors have primarily evolved for communication within species.
The research focused on dogs not only because of their remarkable sense of smell but also due to their close domestication history with humans and their use in supporting human psychological conditions such as anxiety, panic attacks, and post-traumatic stress disorder.
Samples of breath and sweat were collected from non-smokers who had not eaten or drunk recently. These samples were collected both before and after a fast-paced mathematical task. Research subjects were also required to self-report stress levels, and objective physiological measures, including heart rate (HR) and blood pressure (BP), were also assessed.
Tests conducted on 36 participants with stress increase
Researchers collected samples from thirty-six participants who reported both an increase in stress and showed HR and BP during the mathematical task. Trained dogs were then exposed to these samples within three hours of collection.
To match odors in a discrimination task, researchers used a clicker and a kibble to train the four different breeds and mixed-breed dogs. The dogs were asked to identify a participant’s stress sample which was collected at the end of the mathematical task. The same person’s sample collected during a stress-free moment only minutes prior to the beginning of the task was also in the sample line-up.
After only a single time the dogs were exposed to a participant’s “stressed” and “relaxed” samples so to say, the dogs were able to accurately alert of stress samples 94.44 percent of the time. Accuracy rates of individual dogs in the task ranged from 90 percent to 96.88 percent.
Overall, dogs could accurately detect and alert of stress using the samples provided in 675 out of 720 trails, or 93.75 percent of the time. This is a much greater rate than initially estimated and expected by chance (p˂0.001).
Findings revealed human-dog relationship
This new finding tells us more about the human-dog relationship and could have implications in the training of anxiety and PTSD service dogs currently trained to respond predominantly to visual cues.
Dogs can detect odors associated with the change in Volatile Organic Compounds produced by humans in response to stress as revealed by the researchers and authors.
According to researchers, “This study demonstrates that dogs can discriminate between the breath and sweat taken from humans before and after a stress-inducing task.”
“This finding tells us that an accurate, negative, psychological stress response alters the odor profile of our breath and sweat and that dogs are able to detect this change in odor,” the researchers concluded.