Horses can detect fear in humans by smell, becoming more likely to startle and more wary of people who are scared, a new study has found.Researchers collected samples of odor compounds from the armpits of human study participants and then observed how the horses behaved when they were exposed to the different odors during standardized tests, according to research published Wednesday in the journal PLOS One.While previous research has found that horses can pick up on human emotions through speech and facial expressions, the idea that they can smell our fear has remained just a theory due to the difficulties of studying smell, said lead study author Plotine Jardat, a researcher at the French Institute for Horse and Riding (IFCE).AdvertisementAdvertisementAdvertisementAdvertisement“As humans, we are not really aware of all the smells that are around us compared to what other animals apparently perceive, so that’s not so easy to study,” Jardat told CNN.Horses were found to become more fearful when exposed to odor compounds produced by humans who had watched a scary film. – ViewStock/Getty ImagesTo overcome this problem, researchers developed a novel method that involved placing cotton pads in the armpits of the human study participants, where odor compounds are released by the sweat glands.Samples were taken from people while they watched a scary video and a joyful video, as well as a neutral sample, and these pads were later placed on the nostrils of 43 different female horses, held in place by small nets.The researchers were careful to prevent contamination by other odor compounds by making sure the pads were only handled by the human providing the sample, and the compounds were preserved by freezing the pads, said Jardat.AdvertisementAdvertisementAdvertisementAdvertisementThe horses were then exposed to a series of tests conducted by experimenters familiar to the animals — for example, whether or not they would freely approach a human in their paddock, or startle at the sudden opening of an umbrella.Researchers observed the horses’ behavior, as well as collecting data on their heart rate and the level of cortisol in their saliva, a key biomarker for stre …
