Can Horses Smell Fear?

When learning to ride a horse, many of us are told not to be afraid because the horse can sense our fear and anxiety. If you are like me, you weren’t precisely dubious but skeptical to the notion that horses can literally smell fear. Surely, the instructor simply uses a turn of phrase to explain the natural connection between horse and humans emotions. Well, according to scientific studies, my skepticism was misplaced: Yes, horses can LITERALLY smell fear (and other emotions too.)The Study

According to Paolo Baragli, DVM, Ph.D., a researcher in the University of Pisa Department of Veterinary Sciences in Italy who conducted the study, horses can smell emotions through the secretion of our sweat. As it turns out, human sweat smells differently depending on how we feel, and a horse’s susceptible nose can smell that odor and determine what emotions we are feeling at that moment.

“We noticed that horses had increased levels of arousal when they smelled human ‘fear’ and ‘happiness’ odors,” said Paolo Baragli.

“We know that horses perform unexpected reactions when being ridden by a nervous person. This research background led us to suspect that the olfactory system of horses is likely to enable them to read human emotional states using the axial chemosignals humans emit.”

To conduct his study, Dr. Baragli and his colleagues from the University of Pisa collected sweat samples from male college students while watching horror or comedy movies -- basically, movie genres specifically designed to evoke emotions in their viewers.

The young male volunteers were instructed not to wear any kind of cologne or any other scented skin topicals that might interfere with their findings. After collecting the underarm sweat of the volunteers, the scientists showed them to seven different horses that varied in breed and age. The scientists recorded the horses' cardiac activity as the horses smelled the cotton swabs containing the volunteer’s sweat and fresh cotton swabs for control purposes.

Astonishingly, the research team found that smelling the various cotton swabs visibly affected the autonomous nervous system of the horses. While incredible in its own right, the study couldn’t conclusively prove whether or not the horses’ were able to specifically discern between the person’s emotions whose sweat it came from. The researchers could only prove that horses can smell the emotions of humans through our sweat glands.

The study also included dogs. Biagio D’Aniello, Ph.D., of the University of Naples Federico II Department of Biology, who conducted this portion of the experiment, found that dogs tend to stay closer to their owners when they smell fear or anxiety. However, when the dogs smelled happy emotions, they were likelier to be friendly and approach strangers.

Dr. D’ Aniello states that to test a horse's emotional valence when smelling fear or happiness, additional experiments similar to the dogs’ portion of their study must be conducted in the future. 

Dr. Baragli points out that it might be difficult to scientifically determine the effect of our smells on horses when we display or feel strong emotions. This is because we humans typically wear or wash with fragrances or in an environment with distinct smells (food, home spray, and cleaning products) that may interfere with practical studies on the subject.  

The point isn’t really to have a direct practical application in riding centers,” Baragli said. “However, the study does draw our attention to certain points worth considering about the transfer of emotions between species—which seems to be multifactorial, including sights, sounds, touch, and smell.”

And it could give clues about how our odors—whatever they might be—could affect horses’ emotions, he added. “For example, if you misuse your whip… that horse might learn to associate your combination of smells (personal smells, shampoo, food, and more) with a negative experience,” he said.

Contrarily, associating positive emotions with human smells could be advantageous for the human-horse bond and relationship -- Given that we make sure the surrounding environment permits that to happen.

Welfare-compromising training tactics or stable management could reduce a horse’s sensitivity to picking up “good” associations through smells, said Baragli.

Baragli also says that if we feel bad psychologically, our ability to pick up on other's feelings could be impaired due to our poor perception within ourselves or even disappear entirely.

This study, titled, A Case for the InterspeciesTranserence of Emotions, is considered to be a preliminary investigation, namely, how human odors specifically affect the autonomic nervous system in horses. It was published in the 40th Annual International Conference of the IEEE, Engineering in Medicin and Biological Study.