Dogs can smell the difference between stressed and relaxed humans from their sweat and breath alone. The finding could be used to inform training programs for service dogs.
When we are stressed, our body responds with a host of physical changes. Our heart rate jumps, we get clammy and the cocktail of chemicals in our sweat and saliva changes. Previous studies have found that dogs can smell things like fear, and in humans. at Queen鈥檚 University Belfast in the UK wanted to know if dogs could also smell human stress.
To find out, she and her team had 36 people perform a taxing mathematical exercise. 鈥淭hey had to count backwards from 9000 in chunks of 17 out loud in front of the research panel. And if they got anything wrong, we would interrupt them,鈥� says Wilson. After 3 minutes, they stopped the participants.
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The researchers collected sweat and breath samples before and after the exercise. This was done by the volunteers wiping gauze on their forehead and neck, and then breathing on it three times before sealing it in a glass vial.
Within 3 hours of the exercise, the team then used the vials to test four dogs trained to pick out a matching scent in a line-up. The dogs were presented with a piece of gauze from the participant taken after the task and directed to find a match from three vials: one containing gauze from the person before the task, another from after the task and one blank piece.
The dogs correctly identified the stressed sample in the line-up in 675 out of 720 tests, giving an accuracy of around 94 per cent.
at the Max Planck Institute in Germany says the ability may have arisen from our long history of companionship with canines. 鈥淢aybe other animals can also distinguish a stressed human, but they wouldn鈥檛 care,鈥� she says.
Wilson hopes the discovery could inform training for service dogs that support people with panic attacks or post-traumatic stress disorder, as the dogs are currently trained primarily on visual and body posture cues. For example, dogs could be trained to detect changes in their owner鈥檚 scent, which may be present even when visual signs of stress aren鈥檛.
Next, Wilson wants to see if dogs can smell other emotional states via sweat and breath, including positive ones like happiness.
PLoS ONE
