Horses can smell fear in humans, scientists have found in a discovery that suggests emotions are contagious between both species.
The researchers predict their new findings will affect riders and trainers as well as anyone else who works with horses, warning that humans should be aware of the emotional impact they can have, as people are “closely connected” with animals.
In the study, horses smelled body odour from people watching scary videos and then from those engaging with joyful footage. The animals were found to be more jumpy, have increased heart rates and be less interactive with their handlers after smelling sweat from the former group.
If the research holds up in the future, then this suggests fear between humans and horses is contagious. The scientists say the contagious nature of fear could have developed for animals to warn each other of danger, even across different species.
Dr Lea Lansade, of the University of Tours in France, told The Guardian: “This study shows how closely connected animals and humans are. Unconsciously, we can transmit our emotions to animals, with quite important effects on their own emotions in return.”
Smell is among the most common and primitive senses used to communicate, with people picking up on the cocktail of compounds that make up fear in others’ sweat, even if this is not conscious. However, this research has made the unusual move of focusing on scent signals crossing species barriers.
Writing in the journal Plos One, researchers explained that, for the experiment, volunteers wore cotton pads in their armpits while watching clips from content like horror movie Sinister and feel-good film Singing in the Rain.
The cotton swabs were then stapled to the horses’ muzzles directly over their nostrils before tests were carried out, including establishing how often the animals approached and touched their handler, and their reaction to an umbrella suddenly opening.
It was found that, when exposed to odours from the frightened people, the horses startled more, had increased peak heart rates, and interacted less with their handlers.
In light of the findings, Dr Plotine Jardat, the first author on the study and a researcher at the French Horse and Riding Institute near Tours, warned that those who come into contact with horses should be mindful of the impact their emotions could have.
She told The Guardian: “Arriving relaxed and in a positive mood can foster a better interaction with the horse, whereas if you are afraid yourself, the horse can feel afraid in response and react more strongly to a potentially scary situation.”
Prof Biagio D’Aniello, from the University of Naples Federico II, who has shown that both horses and dogs can smell human fear, added: “The findings add to growing evidence that emotional signals can cross species boundaries, with horses reacting to human fear via smell.
“This raises intriguing questions about how human stress or calmness might shape everyday human-horse interactions, from training to clinical handling.”