Agnieszka Sabiniewicza and co-workers at the Institute of Psychology, University of Wrocław, looked at whether body odours collected from humans in a state of fear or of happiness produced different behavioural responses in horses that were exposed to them.
The research team collected body odour samples from ten fearful or happy humans. They achieved this by showing them a fear-inducing horror video or a cartoon.
Prior to viewing the films, the human subjects washed in perfume-free detergent and had avoided smoking, alcohol, odorous food, or hard exercise for a couple of days. While watching the films the “odour donors” had sterile pads in their armpits. The pads were subsequently collected and frozen.
Twenty-one adult Thoroughbred and Arabian horses took part in the study. Their response to the smell of fear, or happiness, or a control (no odour) was recorded.
Two people, one known to the horse, the other unknown, stood quietly in different corners of the stable. They made no attempt to interact with the horse. The investigators then presented the horse with a pole to which odour pads were attached (pads from four fearful or four happy people were combined to reduce the risk of individual variation between odour donors) and recorded the horse’s response.
The researchers found that horses showed different behaviours in response to odours from fearful or happy humans.
Horses lifted their heads significantly more frequently and for longer in response to the fear odour and the control, compared to the happiness odour.
Also, when exposed to the fear odour, there was a tendency for horses to touch, more frequently and for longer, a familiar person that was present during the test, than they did when exposed to the happiness odour.
The researchers conclude that, using human body odour as the only source of information about a human’s emotion is enough to induce some differential behaviour in horses.
For more details, see:
Olfactory-based interspecific recognition of human emotions: Horses (Equus ferus caballus) can recognize fear and happiness body odour from humans (Homo sapiens)
Agnieszka Sabiniewicza, Karolina Tarnowska, Robert Świątek, Piotr Sorokowski, Matthias Laska
Applied Animal Behaviour Science (2020) vol 230; 105072