Date Published: 11 February 2016
Horses respond to human facial expressions
Horses can 'read' human facial expressions, according to researchers in psychology at Sussex University near Brighton on the south coast of England. This study claims to be "the first evidence of horses' abilities to spontaneously discriminate between positive (happy) and negative (angry) human facial expressions in photographs". While showing photographs to horses might be a fairly new idea, anyone who has worked with horses, ponies and other equines will be familiar with their ability to 'sense' the mood of the people around them.
This scientific study of horses' reactions to photographs of faces of people involved the researchers showing a limited set of large photographs of two unfamilar men to 28 horses at a total of 5 riding or livery stables in Sussex and Surrey, England. Some of the photos were of 'happy' human expressions while others were of 'angry' facial expressions. The experiment was arranged in such a way as to prevent the researchers from seeing which photographs were being displayed so that they couldn't inadvertently, or even unknowingly, influence the horses.
According to the university's website:
" When viewing angry faces, horses looked more with their left eye, a behaviour associated with perceiving negative stimuli. Their heart rate also increased more quickly and they showed more stress-related behaviours."
The horses had been fitted with heart monitors to enable collection of the heart rate data. Taken together, the horses' responses were interpreted in terms of them having a functionally relevant understanding of the visual stimuli of the angry faces. The authors of the study said that such an effect of facial expressions on heart rate in interactions between animals and humans had not been studied before.
Lead author Amy Smith, a doctoral student in the Mammal Vocal Communication and Cognition Research Group, 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 rate, and the horses moved their heads to look at the angry faces with their left eye."
It might surprise some people to know that research has found that many species tend to view negative events with their left eye, perhaps due to the right brain hemisphere's specialisation for processing threatening stimuli. (It is more comonly known that visual information received through the left eye is processed in the right hemisphere of the brain.) A tendency for viewing negative human facial expressions with the left eye specifically has also been documented in dogs1.
" It's interesting to note that the horses had a strong reaction to the negative expressions but less so to the positive. This may be because it is particularly important for animals to recognise threats in their environment. In this context, recognising angry faces may act as a warning system, allowing horses to anticipate negative human behaviour such as rough handling" continued Ms Smith.
Co-author Prof Karen McComb (Sussex University), explained that the observations made during this research could be explained in various ways. She mentioned the theoretical possibilities of horses as a species having adapted their ability to 'read' emotional cues in other horses in order to respond appropriately to people, or, alternatively, of individual horses having learned to interpret human expressions during their own lifetime. Research examining the relationship between emotional skills and social behaviour is on-going.
This research has been published in the journal Biology Letters (ref. below)2 and has also featured on various news websites including the BBC3.