EquiFACS: The Equine Facial Action Coding System
Jen Wathan1*, Anne M. Burrows2, Bridget M. Waller3, Karen McComb1*
1 Mammal Communication and Cognition Research, School of Psychology, University of Sussex, Brighton, United Kingdom, 2 Centre for Comparative and Evolutionary Psychology, Department of Psychology,
University of Portsmouth, Portsmouth, United Kingdom, 3 Department of Physical Therapy, Duquesne
University, Pittsburgh, Pennsylvania, United States of America
* j.wathan@sussex.ac.uk (JW); karenm@sussex.ac.uk (KM)
FULL Article:EquiFACS: The Equine Facial Action Coding System
Abstract
Although previous studies of horses have investigated their facial expressions in specific contexts, e.g. pain, until now there has been no methodology available that documents
all the possible facial movements of the horse and provides a way to record all potential
facial configurations. This is essential for an objective description of horse facial expressions
across a range of contexts that reflect different emotional states.
Facial Action Coding Systems (FACS) provide a systematic methodology of identifying and coding facial expressions
on the basis of underlying facial musculature and muscle movement. FACS are
anatomically based and document all possible facial movements rather than a configuration
of movements associated with a particular situation. Consequently, FACS can be applied
as a tool for a wide range of research questions. We developed FACS for the domestic
horse (Equus caballus) through anatomical investigation of the underlying musculature and
subsequent analysis of naturally occurring behaviour captured on high quality video. Discrete
facial movements were identified and described in terms of the underlying muscle contractions,
in correspondence with previous FACS systems. The reliability of others to be
able to learn this system (EquiFACS) and consistently code behavioural sequences was
high—and this included people with no previous experience of horses. A wide range of
facial movements were identified, including many that are also seen in primates and other
domestic animals (dogs and cats). EquiFACS provides a method that can now be used to
document the facial movements associated with different social contexts and thus to
address questions relevant to understanding social cognition and comparative psychology,
as well as informing current veterinary and animal welfare practices.