Cambridge, Jan 24 (The Conversation) Humans have long believed horses can “smell fear”. Nervous riders are often told to “relax, or the horse will feel it”. Until recently, though, there was little scientific
evidence to show whether this was anything more than folklore.
A new study has found that this belief is no myth. Its results show that horses can detect chemical signals linked to human emotions, and that these signals can influence their behaviour and physiology.
Previous research has pointed to a form of emotional contagion between humans and horses. This is a phenomenon in which the emotional state of one person or animal influences the emotional state of another. But this is the first study to find evidence horses can detect human fear using their sense of smell.
Horses rely heavily on their sense of smell to understand the world around them. Their olfactory system is far more sensitive than ours, allowing them to detect subtle chemical differences in the environment.
There is scientific evidence that horses can select the most nutritious food by smelling it. A 2016 found that horses select foods based on nutrient content (such as protein), not just flavour, and that the way their body responds after eating influences future choices they make about food.
So how can horses smell our fear? Well, human emotions come with physiological changes. When people experience fear or stress, their body, face and voice changes. Their body also releases hormones such as adrenaline and cortisol, heart rate increases, and their sweat composition changes. These changes alter the chemical profile of a person’s body odour, which can carry information about their emotional state.
The scent of fear
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The new study found evidence horses not only detect but also respond to human emotional odours. Horses in the study were exposed to human body odours collected via cotton pads wiped under the armpits of people.
These research participants watched either an excerpt from the 2012 horror movie Sinister (to induce fear) or clips, like the Singing in the Rain’s dance scene (to induce joy). The researchers also collected control odours with no emotional association.
The horses showed distinct behavioural and physiological changes when exposed to fear-related odours through the cotton pads, which were secured by a nylon mask on the horses’ noses. They were more alert, more reactive to sudden events and less inclined to approach humans.
And they showed increases in maximum heart rate, which indicates stress, during the exposure to the fear smell from sweat. Crucially, these responses happened without any visual or vocal cues from humans displaying fear.
This finding shows that smell alone can influence a horse’s emotional state. Horses were not reacting to tense body language, facial expressions or nervous movements – they were responding to chemical signals carried in human scent.
Previous research has shown horses seem to be sensitive to humans’ emotional states. In a May 2025 study, horses were shown videos of humans expressing fear, joy or neutral emotions in their facial expressions and voice.
Researchers measured the horses’ heart rate, behaviour and facial expressions while they watched the videos. The horses showed increased heart rates when exposed to fearful or joyful human expressions compared with neutral ones, which indicates heightened emotional arousal.
Fearful expressions depicted in the videos were associated with alert postures in the horses, like holding their head high and pointing their ears back and stress-related facial movements, like wide eyes. Joyful expressions depicted in the videos were linked to patterns associated with positive emotional states, like relaxed nostrils and ears.
Together, these findings are consistent with emotional contagion. Emotional contagion has been documented between humans and dogs, for instance, and these results suggest horses may also be affected by human emotions.
What this does – and doesn’t – mean
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These studies do not suggest that horses understand fear in the same way humans do, or that they know why a person is afraid. Instead, the evidence shows horses are highly sensitive to the chemical, visual and vocal cues associated with emotional states.
Smell is probably just one part of a broader physiological system. Horses are adept at reading human posture, muscle tension, breathing patterns, heart rate and movement – all of which change when a person is anxious. These cues shape how a horse perceives and responds to a human.
Understanding how horses perceive human emotions has important implications for welfare, training and safety. Riders, handlers and therapists working with horses may unintentionally influence an animal’s emotional state through their own stress or calmness.
More broadly, the research challenges outdated assumptions about animal perception. Horses are not passive responders to human commands, as equine professionals and researchers thought until recently. They are sensitive social partners, finely tuned to the emotional signals we give off.
Horses evolved as social prey animals living in large herds on open grasslands, where survival depended on detecting danger quickly. Although humans began domesticating horses around 5,500 years ago, this is evolutionarily recent, meaning modern horses still retain highly sensitive sensory systems adapted for vigilance and social awareness.
So, when people say horses can smell fear, science now suggests they may be closer to the truth than we originally thought. And next time you are close to a horse, try to relax, and make the interaction more enjoyable for both of you. (The Conversation)
GSP
