A team of psychologists in the United Kingdom has published evidence that horses can distinguish between human facial expressions. They can “read” us by watching our faces: horses in the British study were able to distinguish between angry and happy human facial expressions, and reacted differently to happy and angry faces.
But if you think that making your horse’s heart beat faster is a positive sign, think again. Turn that frown upside down and the equine pulse may well go back down to normal.
University of Sussex psychologists studied how 28 horses in five different stables reacted to seeing photographs of positive versus negative human facial expressions. They held up large photos of smiling and angry images of the same man. When viewing angry faces, horses looked more with their left eyes, a behavior associated with perceiving negative stimuli. Their heart rate also increased more quickly and they showed more stress-related behaviors.
Student volunteers held the big photos in a way that prevented them from seeing whether the angry or happy face was in their hands. Did the horses recognize the man in the photo? The research says they did not.
The study, published this month in the Royal Society’s Biology Letters, concludes that this response indicates that the horses had a functionally relevant understanding of the angry faces they were seeing. The effect of facial expressions on heart rate has not been seen before in interactions between animals and humans.
Amy Smith, a doctoral student in the Mammal Vocal Communication and Cognition Research Group at Sussex, co-led the research. She said: “What’s really interesting about this research is that it shows that horses have the ability to read emotions across the species barrier. We have known for a long time that horses are a socially sophisticated species but this is the first time we have seen that they can distinguish between positive and negative human facial expressions.
“The reaction to the angry facial expressions was particularly clear – there was a quicker increase in their heart rates, and the horses moved their heads to look at the angry faces only with their left eyes.”
Research shows that many species view negative events with their left eyes because the right brain hemisphere is specialized for processing threatening stimuli, and information from the left eye is processed in the right hemisphere of the brain.
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Note: While the article presenting this research is fully protected by copyright, the publishers are allowing full text views and downloading of the PDF version from the Royal Society website. Click on the link of the study’s title in the citation to open the web page for this paper.
Citation for this research:
Functionally relevant responses to human facial expressions of emotion in the domestic horse (Equus caballus) Amy Victoria Smith, Leanne Proops, Kate Grounds, Jennifer Wathan, Karen McComb Biology Letters 2016 12 20150907; DOI: 10.1098/rsbl.2015.0907. Published 10 February 2016