What is EquiFACS?

The Equine Facial Action Coding System (EquiFACS) is a scientific observational tool for identifying and coding facial movements in domestic horses (Equus caballus). The system is based on the facial anatomy of horses and has been adapted from the original FACS system used for humans created by Ekman and Friesen (1978). The EquiFACS manual details how to use the system and code the facial movements of horses objectively. The manual is freely available to the scientific community.


EquiFACS is a standardized system that requires certification to use. The EquiFACS Manual identifies each muscle movement that causes visible changes in facial appearance. These are called Action Units (AUs) and each AU is listed in the manual with a numerical code. For each AU, the muscular basis is described along with a list of observable appearance changes and subtle differences between AUs.


The EquiFACS Manual and the EquiFACS Test are freely available through this website. Please contact us for the passwords. We keep a record of who is using the system so we can maintain standardisation.


For a correct visualization of the EquiFACS Manual, please install the latest version of Adobe Reader on your computer. To decompress the files (manual and test), please install WinRar.


Click here to download the EquiFACS manual.


To use the system you need to take a test after training. This ensures that all users are coding in the same way, and maintains the standardisation of the system.


Please contact us to access the EquiFACS Test clips.

Please notice that you can attempt the EquiFACS Test several times if you don't pass initially. For each additional attempt, however, you may need to wait for several weeks to receive your scores, especially during busy periods. It is also important that the trainee takes enough time to revise the Manual before a second attempt.

How to use it?

EquiFACS is not an ethogram of horse facial expressions and does not detect emotions per se. Instead, the system allows the user to code the unitary facial movements of horses in detail, with no a priori assumptions about what represents a facial expression in this species.

Until now, there has been no methodology available that documented all of the facial movements of the horse, allowing a record of all potential facial configurations. There are a number of studies that focus on the facial expressions of horses in one specific context, for example pain. However, EquiFACS provides a comprehensive list of all the facial movements that horses can produce, which can be used to document facial expressions across a wide range of contexts.

The people behind it

EquiFACS was developed thanks to the joint effort of:

  • Jennifer WathanUniversity of Sussex
  • Anne M. BurrowsDuquesne University and University of Pittsburgh
  • Bridget M. WallerCentre for Comparative and Evolutionary Psychology, University of Portsmouth
  • Karen McCombUniversity of Sussex


We would like to thank countless owners for letting us video their horses. Particular thanks must go to Sussex Horse Rescue Trust, Bowler’s Riding School, and Little Park Farm. Katie Slocombe, Will Teasley and Becky Spooner helped with the collection of video data. We are grateful to Cátia Caeiro and Karen Schmidt for valuable advice, and also thanks to Cátia, Kate Grounds, Amy Smith, and Charlotte Lillis for help with the reliability coding. We must credit and thank Tim Smith for the anatomical drawing. Perry Habecker at the New Bolton Centre, University of Pennsylvania, sourced the specimen for the dissection. Emily Durham deserves a huge thank you for dealing with the specimen and thanks to Helen Spence for giving a second opinion on the age of the horse.

Contact us

Psychology Department

University of Portsmouth

Portsmouth, UK

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