Horses can smell fear in humans, researchers say

"Horses can smell fear, or at least whether you have scared yourself witless watching a horror movie, according to researchers who say the effect has consequences for riders, trainers and others who work with the animals. In a series of tests, horses that smelled body odour from people watching scary films startled more easily, had higher heart rates and approached their handlers less often than when the odour came from people watching more joyful scenes."

"If the finding holds up in future studies, it would suggest that fear is contagious between humans and horses, with volatile compounds in human sweat acting as a warning signal that danger may lurk nearby. This study shows how closely connected animals and humans are, said Dr Lea Lansade at the University of Tours in France. Unconsciously, we can transmit our emotions to animals, with quite important effects on their own emotions in return."

"Smell is one of the most common and primitive senses used to communicate, but research often focuses on scent signals that pass between members of the same species to find mates, for example rather than those that cross species barriers. Lansade and her colleagues investigated whether horses responded to the smell of fear in human sweat, the product of a cocktail of compounds that other people can sense even if they are never aware of it."

Human sweat produced during fear contains volatile compounds that can be detected by horses. Volunteers wore cotton pads in their armpits while watching horror or joyful film clips; pads were later stapled over horses' nostrils. Horses exposed to fear odour started more easily, exhibited higher heart rates, and approached handlers less frequently than when exposed to joyful odour. An umbrella pop test measured reactions while horses ate. Smell functions as a primitive communication channel that can cross species and may convey warning signals, with practical implications for riders, trainers, and others who work with horses.

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