For the
first time horses have been shown to be able to distinguish between angry and
happy human facial expressions.
Researchers at the University of Sussex examined the reactions of 28 horses to photographs of people
making positive and negative expressions, noting stronger reactions to
anger.
Amy Smith, a doctoral student in the Mammal Vocal Communication and Cognition Research Group at Sussex, co-led the research. She said: “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.”
Research shows that many species view negative events
with their left eye due to the right brain hemisphere’s specialisation for
processing threatening stimuli (information from the left eye is processed in
the right hemisphere). The effect of facial expressions on heart rate has not been
seen before in interactions between animals and humans.
Amy continued: “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.”
A tendency for viewing negative human facial
expressions with the left eye specifically has also been documented in dogs.
Professor Karen McComb, a co-lead author of the
research, said: “Emotional awareness is likely to be very important in highly
social species like horses – and our ongoing research is examining the
relationship between a range of emotional skills and social behaviour.”
The details of the study are published in Biology
Letters.
