“Horses can smell fear you know”. A phrase many equestrians will have heard, but how true is it? A recent study1 suggests there might be some truth in this statement and the results may have some interesting consequences for human-horse relationships.
The ability to recognize emotional states in members of your own species (intraspecific) is critical for successful social interactions. Increasing research suggests that this ability is not just limited to members of the same species however, and that recognition of emotional states in members of different species (interspecific) is increasingly common. For example, horses appear to recognize human emotions from facial expressions and speech2. Dogs can also respond to human facial expressions3 and have also been shown to display stressful behaviors when presented with fearful human body odours4.
From a human care-giver perspective, appreciating that the animals we work with can recognize and respond to human emotional states, might be useful in training and management regimes.
In order to explore if horses can use human body odor to identify emotional state in the same way that dogs can, a study was conducted to identify whether horses exhibited different behaviors when exposed to human “fearful” and “happy” body odors. Odor samples were collected on sterile pads from the arm pits of ten human participants (three female, seven male) after they watched either a short cartoon (“happy” odor) or a horror movie (“fear” odor). Control samples consisted of unused sterile pads.
A total of 21 horses (ten female, five geldings, six stallions) were presented with “happy”, “fear” or control odor pads over three consecutive weeks. The researchers presenting the pads to the horse were blinded as to the condition being tested, to prevent unintentional behavioral influences in the test horses. The behaviors (frequency and duration) of the experimental horses were then filmed and scored according to known equine social and emotional behaviors.
Results showed that horses lifted their heads (suggestive of alertness and vigilance) significantly more often and for longer when exposed to “fear” versus “happy” odor and in control versus “happy”. Ears were also held back significantly more in the control presentation versus the “fear” condition. It appears that horses can thus recognize different emotional states in humans and respond accordingly through sight, hearing and now smell, further evidence of how human-animal relationships have developed through domestication.
1. Sabiniewicz, A., Tarnowska, K., Świątek, R., Sorokowski, P. & Laska, M. (2020). Olfactory-based interspecific recognition of human emotions: Horses (Equus ferus caballus) can recognize fear and happiness body odour from humans (Homo sapiens). Applied Animal Behaviour Science 230, 105072. Available HERE
2. Nakamura, K., Takimoto-Inose, A. & Hasegawa, T. (2018). Cross-modal perception of human emotion in domestic horses (Equus caballus). Sci Rep 8, 8660. Available HERE
3. Merola, I., Prato-Previde, E., Lazzaroni, M. & Marshall-Pescini, S. (2014). Dogs’ comprehension of referential emotional expressions: familiar people and familiar emotions are easier. Anim Cogn 17(2), 373–385. Available HERE
4. D’Aniello, B., Semin, G.R., Alterisio, A. & Aria, M. (2018). Interspecies transmission of emotional information via chemosignals: from humans to dogs (Canis lupus familiaris). Anim Cogn 21, 67–78. Available HERE