Dogs Can Smell Your Stress and Act Accordingly

The smell of human stress affects dogs’ emotions – and their decision-making – according to a study conducted by the University of Bristol, Cardiff University, and the British charity Medical Detection Dogs. Their research appears in Scientific Reports.

First, the researchers tested 18 dogs' responses to food bowls, some full and some empty. A third, ambiguous, food bowl was placed in a neutral spot. Meanwhile, human subjects were put through stressful paces, such as being pressed into delivering an impromptu speech or calculating complex math problems under duress. Another group of humans relaxed in comfy chairs and watched calming videos. 

The participants’ cortisol levels, heart rate, and self-reported anxiety were recorded, with samples of their breath and sweat collected on rags. The dogs – which included Springer and Cocker spaniels, Labrador and golden retrievers, a Braque d’Auvergne, a whippet, a miniature poodle, and seven mixed breeds – took a whiff of the rags and then were presented with the food-bowl options.

The dogs exposed to the stress-induced aromas were reluctant to approach the bowl in the ambiguous location – indicating their pessimism that it would have any food in it. The relaxed-scented rags, on the other hand, didn’t have a measurable effect.

The researchers speculate that the “pessimistic” response reflects a negative emotional state, which might be a way for the dog to conserve energy and avoid disappointment. In other words, lowered expectations.

“These findings may indicate an effect of human odor on the emotional state of dogs and/or how dogs perceive risks and rewards,” the authors of the study conclude. 

“If the odor from stressed humans affects a dog’s emotional state, perception of rewards, or ability to learn, it suggests that stress may not just travel down the lead (as is often stated) but also through the air. These findings highlight the need to consider dogs’ training and working environments from an olfactory perspective.”

Photo credit: University of Bristol