We all know that dogs are incredibly in tune with our emotions. But did you know that our emotional state can affect them not just through our body language or tone, but through scent as well? New research from the University of Bristol shows that the smell of human stress, released through our sweat and breath, can significantly impact a dog’s mindset, making them more likely to show signs of pessimism—a behavioral marker of a negative emotional state.
“Dog owners know how attuned their pets are to their emotions,” said Dr. Nicola Rooney, Senior Lecturer in Wildlife and Conservation at the Bristol Veterinary School and the study’s lead author. “But here we show that even the odor of a stressed, unfamiliar human affects a dog’s emotional state, perception of rewards, and ability to learn.”
Sniffing Out Negativity: How the Study Worked
In this study, 18 dogs of various breeds—including Labradors, Cocker Spaniels, Whippets, and mixed breeds, ranging in age from eight months to ten years—participated in a series of behavioral tests to measure their response to different emotional scents.
The first test involved training the dogs to recognize two food bowls: one containing a treat and the other empty. Once the dogs learned which bowl was the reward holder, they became faster at approaching the treat-filled bowl. The next step introduced a third “ambiguous” bowl placed between the two original bowls. The idea was that if the dogs approached the new bowl quickly, they were optimistic about it containing a treat. A slower approach suggested the opposite: a more pessimistic or cautious response.
Stress Smells Trigger Emotional Shifts
The dogs were then exposed to three conditions: no odor, the odor of a relaxed human (who was listening to calming sounds), and the odor of a stressed human (who was under pressure doing a math test). The odors were collected from the humans’ breath and sweat.
The results were striking. Dogs exposed to the odor of human stress became slower to approach the ambiguous bowl, especially when it was near the location of the empty bowl. “The stress smell made dogs slower to approach the ambiguous bowl location nearest the trained location of the empty bowl,” said the researchers. “This pessimistic response reflects a negative emotional state and could possibly be a way for the dog to conserve energy and avoid disappointment.”
Stress in the Air—Not Just Down the Leash
This research emphasizes the deep bond between humans and dogs—and just how much our emotions can affect them, even without us saying a word. As Dr. Rooney explained, “Working dog handlers often describe stress traveling down the lead, but we’ve also shown it can travel through the air.”
These findings could have significant implications for dogs in kennels and training programs, and for dogs in assistance roles. The stress of humans nearby may unintentionally impact a dog’s ability to stay focused, motivated, or emotionally balanced.
Dogs Keep Learning—Even When Stressed
Fascinatingly, the research showed that although stress scents impacted the dogs’ emotional well-being, they still retained their capacity to learn effectively. The dogs kept getting better at spotting the rewarding bowls, even when faced with challenging scents. The researchers propose that this could reflect the dogs’ capacity to adjust, even in the face of emotional challenges—a genuine testament to their strength and adaptability.
The Takeaway
This study serves as a reminder of how intertwined our lives are with our canine companions. Our emotions—particularly stress—don’t just affect us; they can shape how our pets feel, behave, and make decisions.
Understanding this connection is crucial, especially for those working closely with dogs in high-stress environments. “Understanding how human stress affects dogs’ wellbeing is an important consideration,” said Dr. Rooney, “for dogs in kennels and when training companion dogs and dogs for working roles such as assistance dogs.”
So, next time you’re feeling overwhelmed, remember: your dog might not just see it—they might smell it too.
