If you’re an observant dog owner, you’re almost sure to have noticed how Fido seems to pick up on your moods, and now scientists think they’ve pinned down one of the big reasons why.
It’s your stink or, put more politely, your smell.
The scent of human breath and sweat changes when people are stressed, and researchers in the United Kingdom say they’ve found that dogs can detect this change nine times out of 10 or better.
The results of their work are, however, somewhat constrained by the fact only four dogs were involved in the study. Dogs, like people and most other animals, differ in their performance capabilities.
Some dogs were specifically bred for their sense of smell, among other things. Some were bred to run fast. Some were bred to swim strong. And some were simply bred to look cute with the definition of cute constantly changing through the ages.
Still, it is generally agreed the worst dog nose is way more sensitive than the best human nose, and even humans have been shown to have the ability to smell fear, which is brought on by extreme psychological stress.
Previous research had already indicated that dogs can detect human psychological states by scent, but as the authors of the latest work noted, that “study did not record any physiological measures from the human participants during sample collection, therefore confirmation that the sweat samples collected in the ‘happy,’ ‘fearful,’ and ‘neutral’ conditions represented physiologically distinct states associated with each condition could not be established.”
The new study – led by Clara Wilson a doctoral student working in the Animal Behaviour Centre at Queen’s University Belfast – pinned down the fact dogs can separate the smell of neutral breath and sweat from that of stressed breath and sweat.
The study also makes it clear not all dogs are as good at this as others. Or, in some cases, too sensitive to stress to perform reliable work in a laboratory.
The four dogs that qualified as official sweat and breathe sniffers for the Belfast study came from among 20 that were recruited for training at the university. Eighty percent of the dogs washed out before testing began.
Two “were unable to continue with training because their owners were shielding from Covi-19,” the researchers reported. “Three dogs were excluded for behavior reasons (the researchers interpreted stress-indicative behaviors from the dogs when their owners left), and nine dogs started to show behaviors of disinterest (for example, lying down between trials, slow to approach the apparatus) as training progressed, or were unable to achieve our performance criteria in stage one” when they were tested to see if they could reliably discriminate between the scents of different people.
The four dogs that made the cut, Wilson and colleagues reported, “ranged in age from 11 to 36 months and consisted of a male Cocker Spaniel, a female Cockapoo, and two undetermined, mixed breeds (one male Lurcher-type and one female terrier-type). The Cocker Spaniel and Cockapoo were raised by their owners from the age of ten weeks and the mixed breed dogs were rehomed from rescue centres.”
Interestingly, the dogs did not appear to display any emotional reaction to the scent of human fear as has been reported in other studies. The researchers suggested this might have been because of the way they were trained.
The dogs were schooled to sniff samples of human scents while separated from the people who provided the scents. Thus they got no visual clues as to the scents might connect to human behavior.
One earlier study, Wilson and her colleagues noted, suggested “that not only could dogs detect an odour, but (that) it also had a mirroring effect on the dog’s own emotional state. It is possible that dogs in the current study were able to recognize the odor of stress as having an emotional context,” but that the positive reinforcement training used to teach them to recognize only the smell of the fearful kept them focused on the job at hand and emotionally uninvolved.
Or at least emotionally uninvolved in a fearful way.
“Although dog behaviour was not coded in this study, it can be anecdotally noted that no dog showed signs of distress when encountering the human stress samples,” the researchers wrote “On the contrary, dogs appeared excited when they came to the stress sample as they were anticipating the clicker and food reward for a correct alert. Future studies may wish to examine the interaction between the emotional contagion of stress and positive reinforcement directly to add insight into this area.”
There could be advantages to training some dogs to avoid emotional contagion. Being able to maintain an even keel would be helpful for those working as service dogs assisting people suffering from post-traumatic stress disorder (PTSD) or anxiety.
Anxiety and PTSD service dogs are now ” trained to respond to visual cues,” the authors wrote. “Knowing that there is a detectable odour component to stress may raise discussion into the value of olfactory-based training (e.g., taking samples from a person when relaxed and experiencing stress) and positively reinforcing the dog to attend, or perform attention seeking behaviours in response to, this odor, similarly to how medical assistance dogs are trained,” Wilson wrote.
Some earlier research has shown owner stress translates into dog stress, but a recent study of service dogs trained to aid “in stress reduction for veterans…found that cortisol values (a proxy measure for stress) did not differ between service and companion animals, which may seem at odds with the results of (the) Sundman et al study which found that owner and dog cortisol levels mirrored each other. ”
The service dogs in question were trained to avoid stress contagion, but given the dueling studies, Wilson and colleagues suggested more research into the interaction between stress contagion and training is warranted given that “service dogs for those with anxiety, panic attack disorders and PTSD are growing in popularity….”
Meanwhile, everyday dog owners might want to think about how their stress is stressing their canine companion and remember that going for a walk together could be good for both of you.
A long list of studies has now documented that taking a walk, especially in a natural area, is a major stress reducer for people. The Mayo Clinic is very blunt about this with its declaration to “get moving to manage stress.”
Getting moving is reported to provide the same stress relief or more for your canine companion, but even if it doesn’t, simply de-stressing your stink will likely be a relief to that oversensitive canine nose.