What is OrangFACS?

Orangutan Facial Action Coding System (OrangFAC)  is a modification of the original human FACS system (Ekman & Friesen 1978), for use with orangutans and was established following the same methods used in the development of previous primate FACS systems.

The resulting OrangFACS Manual is an additional, freely available tool for scientists interested in comparative communication research, supporting already existing facial action coding systems to studying facial expressions.


OrangFACS is a standardized system that requires certification to use.

The OrangFACS 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 and several topics to aid understanding and clarification. These include the proposed muscular basis for the AU, a list of appearance changes, subtle differences between AUs and a comparison with FACS of other species. The manual contains pictures and videos throughout to aid training as well as a section related to broad muscular movements (Action Descriptors).

The OrangFACS Manual and the OrangFACS 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.


Click here to download the OrangFACS 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 so maintains the standardisation of the system.


To access the OrangFACS Test clips click herePlease contact us for the passwords.

Please notice that you can attempt the OrangFACS 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?

OrangFACS is not an ethogram of orangutan facial expressions and does not detect emotions per se. Instead, the system allows the user to code the unitary facial movements of orangutans in detail, with no a priori assumptions about what represents a facial expression in this species. Since the coding is based on individual muscle movements and not on the perception of a composed facial expression, it avoids any emotional context biases.

The OrangFACS Manual is an objective and reliable tool, which is freely available to the scientific community. OrangFACS increases potential for the study of communication, emotion and inter-species comparisons.

The people behind it

OrangFACS was developed thanks to the joint effort of:

  • Cátia C. CaeiroDepartment of Psychology, University of Lincoln
  • Bridget M. Waller, Department of Psychology, University of Portsmouth
  • Elke Zimmermann, Institute of Zoology, University of Veterinary Medicine Hannover
  • Anne M. BurrowsDepartment of Physical Therapy, Duquesne University (PA, USA)
  • Marina Davila-RossDepartment of Psychology, University of Portsmouth


The authors would like to thank all the institutions and people that somehow contributed to make this project

  • To the funding institutions/grants:
    • European Commission Leonardo da Vinci grant,
    • Center for Systems Neuroscience Hannover, Forschungszentrum Jülich,
    • Gesellschaft der Freunde der TiHo,
    • University of Veterinary Medicine Hannover;
  • To the institutions where the data collection took place:
    • Apenheul Primate Park (The Netherlands),
    • Leipzig Zoological Garden (Germany),
    • Sepilok Rehabilitation Centre (Malaysia),
    • Tierpark Carl Hagenbeck (Germany),
    • Zoo Wilhelma (Germany);
  • To the people who assisted in collecting part of the audio-visual material:
    • C. Schopf, E. Ey,
    • M. Wessels,
    • S. Johnson;
  • To the people that sent additional photographs:
    • C. Rodrigues,
    • F. Lasmana,
    • N. Baptista,
    • R. Sharma;
  • To collaborators that were involved on the reliability assessment:
    • M. Lembeck,
    • P. Kuchenbuch;
  • To the institutions that established a mobility partnership acting as host/sending organizations:
    • Faculty of Sciences of the University of Lisbon,
    • University of Portsmouth.

Contact us

Psychology Department

University of Portsmouth

Portsmouth, UK

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