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Now there’s scientific evidence that Barkley has a list of cute traits that shed more light on one of his impressive skills: the ability to smell when you’re stressed.
Dogs can tell the difference between smells from humans when they’re stressed and when they’re calm, according to a study published Wednesday. The journal PLOS ONE.
Previous research has found that dogs can smell when a person is happy or afraidhowever, this latest study eliminated other competing odors and measured the stress levels of its human participants to increase the accuracy of the results.
The researchers first collected breath and sweat samples from the study participants. These people then performed a mental arithmetic task in front of two researchers for three minutes, counting backwards from 9000 in units of 17.
“If the participant answered correctly, they were given no feedback and expected to continue, and if they answered incorrectly, the researcher would interrupt them with ‘no’ and give them their last correct answer,” said Clara Wilson, lead author of the study. , PhD candidate at Queen’s University Belfast, Northern Ireland.
The research team collected another breath and sweat sample after the task was completed.
In addition, the researchers collected data on stress levels, heart rate, and blood pressure before and after the assigned task. The dogs were shown samples of 36 participants who reported feeling stressed and reported an increase in heart rate and blood pressure.
The researchers provided one to 20 subjects with post-task breath and sweat samples dogs and two other blank control samples. The dogs had to choose the correct pattern at least seven out of 10 times to advance to the next stage.
In the second and final phase, the research team showed the four dogs that passed the first phase the same samples they had smelled in the first phase, a sample from the same person before the task, and a blank. Dogs presented with these options 20 times had to successfully identify the post-task “stress” odor at least 80% of the time for the results to be conclusive.
Wilson said the dogs chose the correct pattern in 93.8% of trials, indicating that the stress odors were quite different from the prime patterns.
“It was fascinating to see how well the dogs could distinguish between these odors when the only difference was a psychological stress response,” he said.
dogs have it 220 million olfactory receptors compared to humans 50 million, which makes dogs “extremely effective at distinguishing and identifying odors,” Dr. Mark Freeman, assistant clinical professor in the department of small animal clinical sciences at Virginia Tech in Blacksburg. He was not involved in the study.
Olfactory receptors are tiny nerve endings located inside the nostrils that allow for smell, he said.
“While we don’t know exactly why dogs develop such a keen sense of smell, it’s likely related to the need to identify prey, potential threats, reproductive status, and family relationships, among others,” Freeman said.
Twenty domestic dogs from around Belfast, Northern Ireland were recruited and four completed the entire study.
Most of the dogs either failed to finish the task because they showed signs of anxiety when separated from their owner, or were unable to concentrate the entire time.
If the canines in the study had been trained from birth to sniff out stress, it is likely that more dogs would have completed the study.
There was a male cocker spaniel, a female cockapoo, a male lucher type known as a crossbreed dog, and a female terrier type. Their ages ranged from 11 months to 36 months.
All dogs have a strong sense of smell, Freeman said, but spaniels, terriers and luchers would likely use their olfactory receptors more regularly than hunting dogs. This may have been a factor in their success in the study, or it may have been coincidental, as other breeds, such as retrievers, have excellent scenting skills.
Service dogs that help people with mental health conditions such as anxiety and post-traumatic stress disorder may benefit from these findings, Wilson said.
“Knowing that there is a detectable olfactory component to stress may enhance the debate about the value of olfactory training using samples from individuals during periods of stress and calm,” he said.
More experiments need to be done outside the lab to see how applicable the results of this research are 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 can be detected.
