Dogs Can Identify Owner Stress By Smell, Study Says

There is now scientific evidence that sheds more light on one of the most impressive abilities of dogs in a long list of endearing traits: the ability to sniff when the owner is stressed.

Dogs can sense the difference between human odors when they are stressed and when they are calm, according to a study published in the journal PLOS ONE.

Previous research has found that dogs can smell when a person is happy or scared, but this latest study eliminated other competing scents and measured the stress levels of its human participants to increase the accuracy of the results.

First, scientists collected breath and sweat samples from study participants to use as a baseline. Afterwards, these people performed a mental arithmetic task, counting backwards from 9,000 in units of 17 in front of two researchers for three minutes.

“If the participant gave a correct answer, they received no feedback and were expected to continue, and if they gave an incorrect answer, the researcher would interrupt with ‘no’ and say their last correct answer,” said the study’s lead author, Clara Wilson. , PhD student at Queen’s University Belfast, Northern Ireland.

The study team collected another round of breath and sweat samples after completing the task.

The researchers presented post-task breath and sweat samples from one person to 20 dogs, along with two other blank control samples. The animals needed to select the correct sample at least seven out of 10 times to move on to the next phase.

In the second and final phase, the study team showed the four dogs that passed phase one the same samples they sniffed in phase one, along with a sample from the same individual collected before the task and a blank.

Presented with these options 20 times, dogs had to successfully identify the original post-task “stress” scent at least 80% of the time for the results to be conclusive.

The animals chose the right sample in 93.8% of the tests, which suggested that the stress odors were quite different from the baseline samples, Wilson said.

“It was fascinating to see how dogs were able to discriminate between these odors when the only difference was that a psychological stress response had taken place,” she said.

a powerful nose

Dogs have 220 million olfactory receptors compared to 50 million in humans, which makes canines “extremely effective at differentiating and identifying odors,” said Mark Freeman, clinical assistant professor in the Virginia Department of Small Animal Clinical Sciences. Tech in Blacksburg. He did not participate in the study.

“While we can’t know for sure why dogs have developed such keen senses of smell, this is likely related to the need to identify prey, potential threats, reproductive status, and family relationships in a pack environment, among others,” Freeman said.

Twenty pet dogs were recruited from around Belfast, Northern Ireland, and four completed the entire study.

Most dogs couldn’t finish because they either showed signs of anxiety when separated from their owners or couldn’t stay focused all the time.

If the canines in the study were bred from birth for the purpose of sniffing stress, more dogs would likely have finished the study, he said.

There was a male cocker spaniel, a female cockatoo, a male lurcher type, also known as a crossbreed dog, and a female terrier type. The age ranged from 11 to 36 months.

All dogs have a strong sense of smell, but spaniels, terriers and lurchers would likely use their olfactory receptors more regularly as hunting dogs, Freeman said.

This could have been a success factor in the study, or it could be coincidence because other breeds, such as retrievers, also have excellent olfactory abilities.

Real world implementation

Service dogs that help people with mental health issues such as anxiety and post-traumatic stress disorder could benefit from these findings, Wilson said.

“Knowing that there is a detectable odor component in stress may raise discussion about the value of scent-based training using samples from individuals in times of stress versus calm,” she said.

More experimentation needs to be done outside of a lab to see how the results of this study are applicable in the real world, Wilson said.

These findings also open the door for future research to investigate whether dogs can discriminate between emotions, as well as how long odors are detectable, she said.