Facial Action Coding System

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In 2009, a study was conducted to study spontaneous facial expressions in sighted and blind judo athletes. They discovered that many facial expressions are innate and not visually learned.Matsumoto, D., & Willingham, B. (2009). "Spontaneous facial expressions of emotion of blind individuals". Journal of Personality and Social Psychology, 96(1), 1-10

Using the FACS{{cite book|title=Encyclopedia of Human Behavior|vauthors=Freitas-Magalhães|date=2012|publisher=Elsevier/Academic Press|isbn=978-0-12-375000-6|veditors=Ramachandran VS|volume=2|location=Oxford|pages=173–183|chapter=Microexpression and macroexpression}} human coders can manually code nearly any anatomically possible facial expression, deconstructing it into the specific "action units" (AU) and their temporal segments that produced the expression. As AUs are independent of any interpretation, they can be used for any higher order decision making process including recognition of basic emotions, or pre-programmed commands for an ambient intelligent environment. The FACS manual is over 500 pages in length and provides the AUs, as well as Ekman's interpretation of their meanings.

The FACS defines AUs, as contractions or relaxations of one or more muscles. It also defines a number of "action descriptors", which differ from AUs in that the authors of the FACS have not specified the muscular basis for the action and have not distinguished specific behaviors as precisely as they have for the AUs.

For example, the FACS can be used to distinguish two types of smiles as follows:{{cite journal | vauthors = Del Giudice M, Colle L | title = Differences between children and adults in the recognition of enjoyment smiles | journal = Developmental Psychology | volume = 43 | issue = 3 | pages = 796–803 | date = May 2007 | pmid = 17484588 | doi = 10.1037/0012-1649.43.3.796 }}

• the insincere and voluntary Pan-Am smile: contraction of zygomatic major alone
• the sincere and involuntary Duchenne smile: contraction of zygomatic major and inferior part of orbicularis oculi.

The FACS is designed to be self-instructional. People can learn the technique from a number of sources including manuals and workshops,{{Cite web |last=Rosenberg |first=Erika L. |name-list-style=vanc |title=Example and web site of one teaching professional |url=http://www.erikarosenberg.com/FACS.html |url-status=dead |archive-url=https://web.archive.org/web/20090206232546/http://www.erikarosenberg.com/FACS.html |archive-date=2009-02-06 |access-date=2009-02-04}} and obtain certification through testing.{{Cite web |title=Facial Action Coding System |url=https://www.paulekman.com/facial-action-coding-system/ |access-date=2019-10-23 |website=Paul Ekman Group |language=en-US}}

Although the labeling of expressions currently requires trained experts, researchers have had some success in using computers to automatically identify the FACS codes.[http://www.cs.wpi.edu/~matt/courses/cs563/talks/face_anim/ekman.html Facial Action Coding System.] Retrieved July 21, 2007. One obstacle to automatic FACS code recognition is a shortage of manually coded ground truth data.{{Cite arXiv |last1=Song |first1=Juan |last2=Liu |first2=Zhilei |date=10 Mar 2023 |title=Self-supervised Facial Action Unit Detection with Region and Relation Learning |class=cs.CV |eprint=2303.05708 }}

Baby FACS (Facial Action Coding System for Infants and Young Children){{cite book |last1=Oster |first1=Harriet |title=Baby FACS: Facial Action Coding System for Infants and Young Children |date=2006 |publisher=Unpublished monograph and coding manual. New York University. |location=New York}} is a behavioral coding system that adapts the adult FACS to code facial expressions in infants aged 0–2 years. It corresponds to specific underlying facial muscles, tailored to infant facial anatomy and expression patterns.

It was created by Dr. Harriet Oster and colleagues to address the limitations of applying adult FACS directly to infants, whose facial musculature, proportions, and developmental capabilities differ significantly.

The use of the FACS has been proposed for use in the analysis of depression,{{cite journal | vauthors = Reed LI, Sayette MA, Cohn JF | title = Impact of depression on response to comedy: a dynamic facial coding analysis | journal = Journal of Abnormal Psychology | volume = 116 | issue = 4 | pages = 804–9 | date = November 2007 | pmid = 18020726 | doi = 10.1037/0021-843X.116.4.804 | citeseerx = 10.1.1.307.6950 }} and the measurement of pain in patients unable to express themselves verbally.{{cite journal | vauthors = Lints-Martindale AC, Hadjistavropoulos T, Barber B, Gibson SJ | title = A psychophysical investigation of the facial action coding system as an index of pain variability among older adults with and without Alzheimer's disease | journal = Pain Medicine | volume = 8 | issue = 8 | pages = 678–89 | year = 2007 | pmid = 18028046 | doi = 10.1111/j.1526-4637.2007.00358.x | doi-access = free }}

The original FACS has been modified to analyze facial movements in several non-human primates, namely chimpanzees,{{cite journal | vauthors = Parr LA, Waller BM, Vick SJ, Bard KA | title = Classifying chimpanzee facial expressions using muscle action | journal = Emotion | volume = 7 | issue = 1 | pages = 172–81 | date = February 2007 | pmid = 17352572 | pmc = 2826116 | doi = 10.1037/1528-3542.7.1.172 }} rhesus macaques,{{cite journal | vauthors = Parr LA, Waller BM, Burrows AM, Gothard KM, Vick SJ | title = Brief communication: MaqFACS: A muscle-based facial movement coding system for the rhesus macaque | journal = American Journal of Physical Anthropology | volume = 143 | issue = 4 | pages = 625–30 | date = December 2010 | pmid = 20872742 | pmc = 2988871 | doi = 10.1002/ajpa.21401 }} gibbons and siamangs,{{Cite journal | vauthors = Waller BM, Lembeck M, Kuchenbuch P, Burrows AM, Liebal K | title = GibbonFACS: A Muscle-Based Facial Movement Coding System for Hylobatids | doi = 10.1007/s10764-012-9611-6 | journal = International Journal of Primatology | volume = 33 | issue = 4 | pages = 809–821 | year = 2012 | s2cid = 18321096 }} and orangutans.{{Cite journal | vauthors = Caeiro CC, Waller BM, Zimmermann E, Burrows AM, Davila-Ross M | title = OrangFACS: A Muscle-Based Facial Movement Coding System for Orangutans (Pongo spp.) | doi = 10.1007/s10764-012-9652-x | journal = International Journal of Primatology | volume = 34 | pages = 115–129 | year = 2012 | s2cid = 17612028 | url=http://irep.ntu.ac.uk/id/eprint/41473/1/1383920_Waller.pdf}} More recently, it was developed also for domestic species, including dogs,{{cite journal | vauthors = Waller BM, Peirce K, Caeiro CC, Scheider L, Burrows AM, McCune S, Kaminski J | title = Paedomorphic facial expressions give dogs a selective advantage | journal = PLOS ONE | volume = 8 | issue = 12 | pages = e82686 | year = 2013 | pmid = 24386109 | pmc = 3873274 | doi = 10.1371/journal.pone.0082686 | bibcode = 2013PLoSO...882686W | doi-access = free }} horses{{cite journal | vauthors = Wathan J, Burrows AM, Waller BM, McComb K | title = EquiFACS: The Equine Facial Action Coding System | journal = PLOS ONE | volume = 10 | issue = 8 | pages = e0131738 | date = 2015-08-05 | pmid = 26244573 | pmc = 4526551 | doi = 10.1371/journal.pone.0131738 | bibcode = 2015PLoSO..1031738W | doi-access = free }} and cats.{{Cite journal| vauthors = Caeiro CC, Burrows AM, Waller BM |date=2017-04-01|title=Development and application of CatFACS: Are human cat adopters influenced by cat facial expressions?|journal=Applied Animal Behaviour Science|volume=189|pages=66–78|doi=10.1016/j.applanim.2017.01.005|issn=0168-1591|url=http://eprints.lincoln.ac.uk/25940/1/25940%20Proof_APPLAN_4392.pdf}} Similarly to the human FACS, the animal FACS has manuals available online for each species with the respective certification tests.{{Cite web|url=http://animalfacs.com|title=Home|website=animalfacs.com|access-date=2019-10-23}}

Thus, the FACS can be used to compare facial repertoires across species due to its anatomical basis. A study conducted by Vick and others (2006) suggests that the FACS can be modified by taking differences in underlying morphology into account. Such considerations enable a comparison of the homologous facial movements present in humans and chimpanzees, to show that the facial expressions of both species result from extremely notable appearance changes. The development of FACS tools for different species allows the objective and anatomical study of facial expressions in communicative and emotional contexts. Furthermore, a cross-species analysis of facial expressions can help to answer interesting questions, such as which emotions are uniquely human.{{cite journal | vauthors = Vick SJ, Waller BM, Parr LA, Smith Pasqualini MC, Bard KA | title = A Cross-species Comparison of Facial Morphology and Movement in Humans and Chimpanzees Using the Facial Action Coding System (FACS) | journal = Journal of Nonverbal Behavior | volume = 31 | issue = 1 | pages = 1–20 | date = March 2007 | pmid = 21188285 | pmc = 3008553 | doi = 10.1007/s10919-006-0017-z }}

The Emotional Facial Action Coding System (EMFACS){{citation | vauthors = Friesen W, Ekman P | title = EMFACS-7: Emotional Facial Action Coding System. Unpublished manuscript | publisher = University of California at San Francisco | date = 1983 | volume = 2 | issue = 36 | pages = 1 }} and the Facial Action Coding System Affect Interpretation Dictionary (FACSAID){{Cite web |url=http://www.face-and-emotion.com/dataface/facsaid/description.jsp |title=Facial Action Coding System Affect Interpretation Dictionary (FACSAID) |access-date=2011-02-23 |archive-url=https://web.archive.org/web/20110520164308/http://face-and-emotion.com/dataface/facsaid/description.jsp |archive-date=2011-05-20 |url-status=dead }} consider only emotion-related facial actions. Examples of these are:

FACS coding is also used extensively in computer animation, in particular for computer facial animation, with facial expressions being expressed as vector graphics of AUs.{{Cite news |last=Walsh |first=Joseph |date=2016-12-16 |title=Rogue One: the CGI resurrection of Peter Cushing is thrilling – but is it right? |language=en-GB |work=The Guardian |url=https://www.theguardian.com/film/filmblog/2016/dec/16/rogue-one-star-wars-cgi-resurrection-peter-cushing |access-date=2023-10-23 |issn=0261-3077}} FACS vectors are used as weights for blend shapes corresponding to each AU, with the resulting face mesh then being used to render the finished face.{{Cite journal |last1=Gilbert |first1=Michaël |last2=Demarchi |first2=Samuel |last3=Urdapilleta |first3=Isabel |date=October 2021 |title=FACSHuman, a software program for creating experimental material by modeling 3D facial expressions |url=https://link.springer.com/10.3758/s13428-021-01559-9 |journal=Behavior Research Methods |language=en |volume=53 |issue=5 |pages=2252–2272 |doi=10.3758/s13428-021-01559-9 |pmid=33825127 |issn=1554-3528}}{{Cite web |title=Discover how to create FACS facial blendshapes in Maya {{!}} CG Channel |url=https://www.cgchannel.com/2021/04/discover-how-to-create-facs-facial-blendshapes-in-maya/ |access-date=2023-10-23 |language=en-US}} Deep learning techniques can be used to determine the FACS vectors from face images obtained during motion capture acting, facial motion capture or other performances.{{Cite book |url=https://ieeexplore.ieee.org/document/7284873 |access-date=2023-10-23 |date=2015 |doi=10.1109/FG.2015.7284873 |language=en-US |last1=Gudi |first1=Amogh |last2=Tasli |first2=H. Emrah |last3=Den Uyl |first3=Tim M. |last4=Maroulis |first4=Andreas |title=2015 11th IEEE International Conference and Workshops on Automatic Face and Gesture Recognition (FG) |chapter=Deep learning based FACS Action Unit occurrence and intensity estimation |pages=1–5 |isbn=978-1-4799-6026-2 |s2cid=6283665 }}

{{See also|List of muscles in the human body#The muscles of the head}}

For clarification, the FACS is an index of facial expressions, but does not actually provide any bio-mechanical information about the degree of muscle activation. Though muscle activation is not part of the FACS, the main muscles involved in the facial expression have been added here.

Action units (AUs) are the fundamental actions of individual muscles or groups of muscles.

Action descriptors (ADs) are unitary movements that may involve the actions of several muscle groups (e.g., a forward‐thrusting movement of the jaw). The muscular basis for these actions has not been specified and specific behaviors have not been distinguished as precisely as for the AUs.

For the most accurate annotation, the FACS suggests agreement from at least two independent certified FACS encoders.

Intensities of the FACS are annotated by appending letters A–E (for minimal-maximal intensity) to the action unit number (e.g. AU 1A is the weakest trace of AU 1 and AU 1E is the maximum intensity possible for the individual person).

• A Trace
• B Slight
• C Marked or pronounced
• D Severe or extreme
• E Maximum

There are other modifiers present in FACS codes for emotional expressions, such as "R" which represents an action that occurs on the right side of the face and "L" for actions which occur on the left. An action which is unilateral (occurs on only one side of the face) but has no specific side is indicated with a "U" and an action which is bilateral but has a stronger side is indicated with an "A" for "asymmetric".

These codes are reserved for recording information about gross behaviors that may be relevant to the facial actions that are scored.

• Computer facial animation
• Computer processing of body language
• Emotion classification
• Facial electromyography
• Facial feedback hypothesis
• Facial muscles
• Microexpression

{{Reflist}}

• [https://web.archive.org/web/20150324015937/https://www.paulekman.com/research/ Paul Ekman's articles relating to FACS]
• [https://web.archive.org/web/20080606005626/http://www.face-and-emotion.com/dataface/facs/description.jsp Paul Ekman's Facial Action Coding System (FACS)]
• [http://www.animalfacs.com/ More information on the different animal FACS projects]
• [https://www.newyorker.com/magazine/2002/08/05/the-naked-face New Yorker article discussing FACS]
• [http://www-2.cs.cmu.edu/afs/cs/project/face/www/facs.htm Details from 1978 edition of FACS]
• [http://www.cs.wpi.edu/~matt/courses/cs563/talks/face_anim/ekman.html Site at WPI]
• download of [http://diglib.uibk.ac.at/ulbtirol/content/titleinfo/782346 Carl-Herman Hjortsjö, Man's face and mimic language"] {{Webarchive|url=https://web.archive.org/web/20220806115847/https://diglib.uibk.ac.at/ulbtirol/content/titleinfo/782346 |date=2022-08-06 }} (the original Swedish title of the book is: "Människans ansikte och mimiska språket". The correct translation would be: "Man's face and facial language")

{{Nonverbal communication}}

Category:Facial expressions

Category:Encodings

Category:Anatomical simulation

Category:Animal communication

Category:1978 introductions