Simanaitis Says

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“Whether it’s a tricky maths problem or an unexpected bill,” Nicola Davis of The Guardian reports, “daily life is full of stressful experiences. Now researchers have found that humans produce a different odour when under pressure – and dogs can sniff it out.”

Here are tidbits on this scientific assessment, with special attention paid to methodology of the research. 

Background. Nicola Davis writes, “While previous studies have suggested canines might pick up on human emotions, possibly through smell, questions remained over whether they could detect stress and if this could be done through scent.”

Recent Research. Answers are given in “Dogs Can Discriminate Between Human Baseline and Psychological Stress Condition Odours,” PLOS ONE, September 28, 2022. “This study has definitively proven that people, when they have a stress response, their odour profile changes,” said Clara Wilson, a PhD student at Queen’s University Belfast, and first author of the research.

She and her colleagues “tested whether baseline and stress odours were distinguishable to dogs, using a double-blind, two-phase, three-alternative forced-choice procedure.”

Methodology. The researchers trained four dogs to identify containers holding a particular breath and sweat sample, selected among other samples of unused gauze, of other persons, or the same person taken at a less-stressful time. The samples were obtained from participants at baseline, and after a stress-inducing (mental arithmetic) task.

This and a following image from PLOS ONE.

How to Induce Stress? Davis writes, “With the team confident the dogs understood the approach, they turned to breath and sweat samples collected from 36 people asked to count backwards from 9000 in units of 17. The participants reported feeling stressed by the task and, for the 27 who carried it out in the laboratory, their blood pressure and heart rate rose.”

Counting Backwards by 17s from 9000?? This sounds like that sobriety test of reciting the alphabet backwards. (I’m okay with z, y, x, and then I slow down….) However, being mathematically trained and having taught everything from remedial to college level math, I performed a little Gedankenexperiment: 9000, 8983….

This is easy; er… 8983-17=….  All this “borrowing” is a pain. There must be a less stressful way.

Arithmetic Trickery. Subtracting 10s are easy, then the -7s are straightforward: 8983 to 8973, 8973-7=8966. Then 8956-7=8949. 8939-7=8932. 8922-7=8915. 8905-7=8898….

There. I wouldn’t say it’s easy-peasy, but perhaps this approach is less stressful.

Back to the Doggies. Davis reports, “The results reveal that the dogs chose the ‘stressed’ sample in 675 out of the 720 trials.”

“It was pretty amazing to see them be so confident in telling me ‘nope, these two things definitely smell different,’ ” said Wilson.

Davis continues, “The team say while it was unclear what chemicals the dogs were picking up on, the study shows humans produce a different odour when stressed—confirming previous research that used instruments to analyse samples. Wilson added that while the dogs were trained to communicate that they could tell different samples apart, it is possible that even untrained pet dogs might detect changes in odour when a human becomes stressed.”

Service Dog Benefits. Davis says, “Wilson added the findings could prove useful when training service dogs, such as those that support people with post-traumatic stress disorder (PTSD).”

Image from The Guardian.

The PLOS ONE paper stresses the importance of enhanced training for such service dogs: “The results of the current study could have further applications to the training of anxiety and PTSD service dogs, that are, currently, predominantly trained to respond to visual cues.”

Wilson notes, “They’re often trained to look at someone either crouching down on the floor, or starting to do self-injurious behaviours…. There is definitely a smell component, and that might be valuable in the training of these dogs in addition to all of the visual stuff.”

Fido can evidentally identify anxieties more crucial than those of the math sort. ds 

© Dennis Simanaitis,, 2022.


  1. Michael Rubin
    October 4, 2022

    An acquaintance has a service dog that warns when she’s going to have a seizure. The dog, a Pekinese, barks at her a certain way. Apparently people with epilepsy emit some sort of smell before seizuring. Truly amazing.

  2. Jack Albrecht
    October 5, 2022

    I have to do a lot of math in my job. Lots of it is algebra where the little tricks you mention come in very handy even if you haven’t memorized times tables (eg. 15×15 = 225).

    Even if you don’t have the exact answer easily, you can judge if a number is in the ballpark e.g. 15×15 =225, 15×20 = 300, so 14×17 is gonna be more than 225, but much closer to 225 than 300 (238).

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