HORSES AND HUMAN SHARE FACIAL EXPRESSIONS
Horses share some
surprisingly similar facial expressions to humans and chimps, according to new
University of Sussex research.
Mammal communication
researchers have shown that, like humans, horses use muscles underlying various
facial features -- including their nostrils, lips and eyes -- to alter their
facial expressions in a variety of social situations.
The findings,
published in PLOS ONE today (05 August 2015), suggest
evolutionary parallels in different species in how the face is used for
communication.
The study builds on
previous research showing that cues from the face are important for horses to
communicate, by developing an objective coding system to identify different
individual facial expressions on the basis of underlying muscle movement.
The Equine Facial
Action Coding System (EquiFACS), as devised by the Sussex team in collaboration
with researchers at the University of Portsmouth and Duquesne University,
identified 17 "action units" (discrete facial movements) in horses.
This compares with 27 in humans, 13 in chimps and 16 in dogs.
The study's co-lead
author, doctoral researcher Jennifer Wathan, said: "Horses are
predominantly visual animals, with eyesight that's better than domestic cats
and dogs, yet their use of facial expressions has been largely overlooked. What
surprised us was the rich repertoire of complex facial movements in horses, and
how many of them are similar to humans.
"Despite the differences
in face structure between horses and humans, we were able to identify some
similar expressions in relation to movements of the lips and eyes.
"What we'll now
be looking at is how these expressions relate to emotional states."
The researchers analysed
video footage of a wide range of naturally occurring horse behaviours to
identify all the different movements it is possible for horses to make with
their face. They also carried out an anatomical investigation of the facial
muscles that underpin these movements. Each individual facial movement that was
identified was given a code.
Co-lead author
Professor Karen McComb said: "It was previously thought that, in terms of
other species, the further away an animal was from humans, the more rudimentary
their use of facial expressions would be.
"Through the
development of EquiFACS, however, it's apparent that horses, with their complex
and fluid social systems, also have an extensive range of facial movements and
share many of these with humans and other animals. This contributes to a
growing body of evidence suggesting that social factors have had a significant
influence on the evolution of facial expression."
She added that a
systematic way of recording facial expressions would have a wide range of uses.
"With EquiFACS we can now document the facial movements associated with
different social and emotional contexts and thus gain insights into how horses
are actually experiencing their social world. As well as enhancing our
understanding of social cognition and comparative psychology, the findings
should ultimately provide important information for veterinary and animal
welfare practices."
Comments
Post a Comment