NATIONAL NEWS

Dogs can smell when humans are stressed, study suggests

Sep 28, 2022, 4:28 PM | Updated: Oct 6, 2022, 3:12 pm
FILE: The life expectancy of dogs can be six to 12 times shorter than humans....
FILE: The life expectancy of dogs can be six to 12 times shorter than humans.

(CNN) — There’s now scientific evidence shedding more light on one of Barkley’s impressive skills in a long list of endearing traits: the ability to smell when you’re stressed.

Dogs can smell the difference between odors from humans when they’re stressed and when they’re calm, according to a study published Wednesday in the journal PLOS ONE.

Earlier research found that canines may be able to smell when a person is happy or fearful, but this latest study eliminated other competing scents and measured its human participants’ stress levels to increase the accuracy of the results.

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

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

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

Additionally, the researchers collected reported stress levels, heart rate and blood pressure before and after the assigned task. Thirty-six participants who reported feeling stressed and had increased heart rate and blood pressure had their samples shown to the dogs.

The researchers presented post-task breath and sweat samples from one person to 20 dogs along with two other blank control samples. The canines needed to select the correct sample at least seven out of 10 times to move onto 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, the dogs needed to successfully identify the original post-task “stress” scent at least 80% of the time for the results to be conclusive.

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

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

A powerful nose

Dogs have 220 million olfactory receptors compared with humans’ 50 million, which makes canines “extremely effective at differentiating and identifying odors,” said Dr. Mark Freeman, clinical assistant professor in the department of small animal clinical sciences at Virginia Tech in Blacksburg. He was not involved in the study.

Olfactory receptors are small nerve endings located inside your nostrils that allow you to smell, he said.

“While we can’t know with certainty why dogs developed such keen olfactory senses, it is very probably related with the need to identify prey, potential threats, reproductive status, and familial relationships in a pack setting among others,” Freeman said.

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

Most of the dogs failed to finish because they either showed signs of anxiety when separated from their owner, or they were not able to stay focused the entire time.

If the canines in the study were raised from birth with the purpose of sniffing out stress, more dogs would have most likely finished the study, he said.

There was a male cocker spaniel, female cockapoo, male lurcher type, also known as a crossbred hound, and a female terrier type. Their ages ranged from 11 to 36 months.

All dogs have a strong sense of smell, but spaniels, terriers and lurchers would have likely used their olfactory receptors more regularly as hunting dogs, Freeman said. This could have been a factor in their success in the study, or it might be coincidental because others breeds like retrievers have excellent smelling skills as well.

Real-world implementation

Service dogs who assist people with mental health conditions like anxiety and post-traumatic stress disorder may benefit from these findings, Wilson said.

“Knowing that there is a detectable odor component to stress may raise discussion into 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 laboratory to see how applicable the results of this study are in the real world, Wilson said.

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


The-CNN-Wire™ & © 2022 Cable News Network, Inc., a Warner Bros. Discovery Company. All rights reserved.

KSL 5 TV Live

Top Stories

National News

Gate to the Duke Energy West End substation in Moore County, North Carolina, on Dec. 4, 2022. (John...
Nicole Grether, Gloria Pazmino and Tina Burnside, CNN

Gunfire at power substation cause North Carolina outages

Two power substations in a North Carolina county were damaged by gunfire in what is being investigated as a criminal act.
18 hours ago
Lava flowing from Mauna Loa Volcano during the night. (KSL-TV's Carissa Hutchinson)...
Shelby Lofton

‘It’s kind of an eerie feeling;’ Utah man living in Hawaii witnesses Mauna Loa eruption

A Utah man has a front-row seat to the Mauna Loa Volcano eruption happening on the Big Island of Hawaii.
18 hours ago
Body camera footage taken from a traffic stop last month. (Pinellas County Sheriff's Office)...
Keith Allen, CNN

Tampa police chief placed on leave after flashing badge during traffic stop

Tampa Police Chief Mary O'Connor has been placed on administrative leave after body camera footage taken from a traffic stop last month revealed she told a deputy she was "hoping that you'll just let us go tonight" and flashed her badge.
18 hours ago
Former President Donald Trump speaks at a rally on Sept. 25, 2021, in Perry, Georgia. (Photo by Sea...
HOPE YEN, Associated Press

Trump rebuked for call to suspend Constitution over election

Former President Donald Trump is facing rebuke from both parties after calling for the “termination” of parts of the Constitution over his lie that the 2020 election was stolen.
18 hours ago
tetson Bennett #13 of the Georgia Bulldogs celebrates with the trophy...
Associated Press

SEC halftime contest booed, both students awarded $100,000

Two college students have won $100,000 in tuition after a confusing finish in the SEC championship game's halftime competition. Boos rained down from the fans in attendance for the game between No. 1 Georgia and No. 11 LSU when one of the two students appeared to win the Dr Pepper ball toss competition in overtime on a technicality. The winner was due to get $100,000 and the runner-up $20,000. Baylor student Reagan Whitaker and St. Augustine student Kayla Gibson exchanged leads multiple times in regulation. In overtime, they tied again, but Whitaker was declared the winner. It was announced on the broadcast in the fourth quarter of the game that Dr Pepper would gift both Whitaker and Gibson with $100,000 in tuition.
18 hours ago
A police car in Tampa, Florida....
Associated Press

Tampa police chief on leave after golf cart traffic stop

The police chief of Tampa has been placed on leave after a video emerged of her flashing her badge from the passenger seat of a golf cart to get out of a traffic ticket. Tampa Mayor Jane Castor placed Chief Mary O'Connor on administrative leave Friday pending an investigation of the Nov. 12 traffic stop. The body camera video shows O'Connor identifying herself as the Tampa police chief and asking the Pinellas County sheriff's deputy not to ticket her and her husband, who she says was driving the golf cart without a tag. O'Connor later released a statement saying the incident reflected "poor judgement."
18 hours ago

Sponsored Articles

house with for rent sign posted...
Chase Harrington, president and COO of Entrata

Top 5 reasons you may want to consider apartment life over owning a home

There are many benefits of renting that can be overshadowed by the allure of buying a home. Here are five reasons why renting might be right for you.
Festive kitchen in Christmas decorations. Christmas dining room....
Lighting Design

6 Holiday Decor Trends to Try in 2022

We've rounded out the top 6 holiday decor trends for 2022 so you can be ahead of the game before you start shopping. 
Happy diverse college or university students are having fun on their graduation day...
BYU MBA at the Marriott School of Business

How to choose what MBA program is right for you: Take this quiz before you apply!

Wondering what MBA program is right for you? Take this quiz before you apply to see if it will help you meet your goals.
Diverse Group of Energetic Professionals Team Meeting in Modern Office: Brainstorming IT Programmer...
Les Olson

Don’t let a ransomware attack get you down | Protect your workplace today with cyber insurance

Business owners and operators should be on guard to protect their workplace. Cyber insurance can protect you from online attacks.
Hand turning a thermostat knob to increase savings by decreasing energy consumption. Composite imag...
Lighting Design

5 Lighting Tips to Save Energy and Money in Your Home

Advances in lighting technology make it easier to use smart features to cut costs. Read for tips to save energy by using different lighting strategies in your home.
Portrait of smiling practitioner with multi-ethnic senior people...
Summit Vista

How retirement communities help with healthy aging

There are many benefits that retirement communities contribute to healthy aging. Learn more about how it can enhance your life, or the life of your loved ones.
Dogs can smell when humans are stressed, study suggests