When stressed, humans emit a distinct odor that can only be recognized by dogs.
According to previous studies, dogs can pick up on human emotions through their sense of smell. However, it remains unclear whether they can detect stress through sniffing.
Clara Wilson, a research fellow at Queen’s University Belfast and the lead researcher, stated: “Our work demonstrates that when a person is in a state of stress, their scent changes.”
Wilson affirmed to The Guardian that this finding could be beneficial in training therapy dogs, such as those assisting individuals with post-traumatic stress disorder (PTSD).
“They are often trained to observe someone who is crouching on the floor or beginning self-harming behaviors,” Wilson explained.
Untrained dogs can also detect signs of stress through changes in human body odor. (Photo: The Guardian)
Wilson and her colleagues published a paper in the journal Plos One, detailing their experiment.
In the study, the team created a holder for three boxes with holes, where one box contained a sample of sweat and breath from one person, another box contained a sample from the same person at a different time, and the last box held a sample from a completely different individual.
The results showed that the dogs focused on the box containing the breath and sweat samples of 36 individuals who were asked to count backwards from 9,000. These individuals admitted to feeling stressed while following this instruction, with 27 of them experiencing increased heart rates and blood pressure.
Subsequently, they tested with unused samples and samples taken from the same person before they were asked to participate in the experiment, which meant they felt more relaxed at that time.
Each set of samples was presented to the same dog 20 times. The results indicated that all the dogs selected the “stressed” sample a total of 675 times out of 720 trials.
Although it is unknown how dogs recognize this, Wilson confirmed that humans produce a different body odor when stressed. She also added that even untrained dogs can detect changes in human body odor.
