Carmen Martínez Torrón / Getty Images Horses can sniff out fear in humans, according to a new study published Wednesday in the journal PLOS One . The study used cotton pads placed in human participants’ armpits to collect odor samples while they watched scary, joyful, or neutral videos. Those samples were then presented to the nostrils of 43 horses to observe their reactions. Researchers monitored the horses’ behavior and stress-related biomarkers, including heart rate, cortisol levels, and saliva indicators. Horses exposed to scent samples from frightened humans showed heightened stress responses, appearing more easily startled and more cautious around unfamiliar people and objects. “The fearful odors from humans amplify the reactions of horses,” the study’s lead author, Plotine Jardat, told CNN, noting that the animals appear particularly sensitive to chemical signals associated with stress. Researchers say this initial study focused on fear because of the practical implications the results would have on horse riders and handlers. Future studies will examine whether horses can also distinguish other human emotions through scent, including sadness and disgust. Read it at CNN Read more at The Daily Beast.