Facial Action Coding System

Facial Action Coding System (FACS) is a system to taxonomize human facial movements by their appearance on the face, based on a system originally developed by a Swedish anatomist named Carl-Herman Hjortsjö.[1] It was later adopted by Paul Ekman and Wallace V. Friesen, and published in 1978.[2] Ekman, Friesen, and Joseph C. Hager published a significant update to FACS in 2002.[3] Movements of individual facial muscles are encoded by FACS from slight different instant changes in facial appearance.[4] It is a common standard to systematically categorize the physical expression of emotions, and it has proven useful to psychologists and to animators. Due to subjectivity and time consumption issues, FACS has been established as a computed automated system that detects faces in videos, extracts the geometrical features of the faces, and then produces temporal profiles of each facial movement.[4]

Muscles of head and neck.

Uses

Using FACS [5] 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 meaning.

FACS defines AUs, which are a contraction or relaxation of one or more muscles. It also defines a number of Action Descriptors, which differ from AUs in that the authors of 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, FACS can be used to distinguish two types of smiles as follows:[6]

Although the labeling of expressions currently requires trained experts, researchers have had some success in using computers to automatically identify FACS codes.[7] Computer graphical face models, such as CANDIDE or Artnatomy, allow expressions to be artificially posed by setting the desired action units.

The use of FACS has been proposed for use in the analysis of depression,[8] and the measurement of pain in patients unable to express themselves verbally.[9]

FACS is designed to be self-instructional. People can learn the technique from a number of sources including manuals and workshops,[10] and obtain certification through testing.[11] The original FACS has been modified to analyze facial movements in several non-human primates, namely chimpanzees,[12] rhesus macaques,[13] gibbons and siamangs,[14] and orangutans.[15] More recently, it was developed also for domestic species, including the dog,[16] the horse[17] and the cat.[18] Similarly to the human FACS, the animal FACS have manuals available online for each species with the respective certification tests.[19]

Thus, 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 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.[20]

EMFACS (Emotional Facial Action Coding System)[21] and FACSAID (Facial Action Coding System Affect Interpretation Dictionary)[22] consider only emotion-related facial actions. Examples of these are:

EmotionAction units
Happiness6+12
Sadness1+4+15
Surprise1+2+5B+26
Fear1+2+4+5+7+20+26
Anger4+5+7+23
Disgust9+15+17
ContemptR12A+R14A

Codes for action units

For clarification, 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 FACS, the main muscles involved in the facial expression have been added here for the benefit of the reader.

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 hasn't been specified and specific behaviors haven't been distinguished as precisely as for the AUs.

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

Intensity scoring

Intensities of 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

Other letter modifiers

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 unilateral but has a stronger side is indicated with an "A."

Main codes

AU numberFACS nameMuscular basis
0Neutral face
1Inner brow raiserfrontalis (pars medialis)
2Outer brow raiserfrontalis (pars lateralis)
4Brow lowererdepressor glabellae, depressor supercilii, corrugator supercilii
5Upper lid raiserlevator palpebrae superioris, superior tarsal muscle
6Cheek raiserorbicularis oculi (pars orbitalis)
7Lid tightenerorbicularis oculi (pars palpebralis)
8Lips toward each otherorbicularis oris
9Nose wrinklerlevator labii superioris alaeque nasi
10Upper lip raiserlevator labii superioris, caput infraorbitalis
11Nasolabial deepenerzygomaticus minor
12Lip corner pullerzygomaticus major
13Sharp lip pullerlevator anguli oris (also known as caninus)
14Dimplerbuccinator
15Lip corner depressordepressor anguli oris (also known as triangularis)
16Lower lip depressordepressor labii inferioris
17Chin raisermentalis
18Lip puckerincisivii labii superioris and incisivii labii inferioris
19Tongue show
20Lip stretcherrisorius w/ platysma
21Neck tightenerplatysma
22Lip funnelerorbicularis oris
23Lip tightenerorbicularis oris
24Lip pressororbicularis oris
25Lips partdepressor labii inferioris, or relaxation of mentalis or orbicularis oris
26Jaw dropmasseter; relaxed temporalis and internal pterygoid
27Mouth stretchpterygoids, digastric
28Lip suckorbicularis oris

Head movement codes

AU numberFACS nameAction
51Head turn left
52Head turn right
53Head up
54Head down
55Head tilt left
M55Head tilt leftThe onset of the symmetrical 14 is immediately preceded or accompanied by a head tilt to the left.
56Head tilt right
M56Head tilt rightThe onset of the symmetrical 14 is immediately preceded or accompanied by a head tilt to the right.
57Head forward
M57Head thrust forwardThe onset of 17+24 is immediately preceded, accompanied, or followed by a head thrust forward.
58Head back
M59Head shake up and downThe onset of 17+24 is immediately preceded, accompanied, or followed by an up-down head shake (nod).
M60Head shake side to sideThe onset of 17+24 is immediately preceded, accompanied, or followed by a side to side head shake.
M83Head upward and to the sideThe onset of the symmetrical 14 is immediately preceded or accompanied by a movement of the head, upward and turned and/or tilted to either the left or right.

Eye movement codes

AU numberFACS nameAction
61Eyes turn left
M61Eyes leftThe onset of the symmetrical 14 is immediately preceded or accompanied by eye movement to the left.
62Eyes turn right
M62Eyes rightThe onset of the symmetrical 14 is immediately preceded or accompanied by eye movement to the right.
63Eyes up
64Eyes down
65Walleye
66Cross-eye
M68Upward rolling of eyesThe onset of the symmetrical 14 is immediately preceded or accompanied by an upward rolling of the eyes.
69Eyes positioned to look at other personThe 4, 5, or 7, alone or in combination, occurs while the eye position is fixed on the other person in the conversation.
M69Head and/or eyes look at other personThe onset of the symmetrical 14 or AUs 4, 5, and 7, alone or in combination, is immediately preceded or accompanied by a movement of the eyes or of the head and eyes to look at the other person in the conversation.

Visibility codes

AU numberFACS name
70Brows and forehead not visible
71Eyes not visible
72Lower face not visible
73Entire face not visible
74Unscorable

Gross behavior codes

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

AU numberFACS nameMuscular basis
29Jaw thrust
30Jaw sideways
31Jaw clenchermasseter
32[Lip] bite
33[Cheek] blow
34[Cheek] puff
35[Cheek] suck
36[Tongue] bulge
37Lip wipe
38Nostril dilatornasalis (pars alaris)
39Nostril compressornasalis (pars transversa) and depressor septi nasi
40Sniff
41Lid droopLevator palpebrae superioris (relaxation)
42SlitOrbicularis oculi muscle
43Eyes closedRelaxation of Levator palpebrae superioris
44SquintCorrugator supercilii and orbicularis oculi muscle
45BlinkRelaxation of Levator palpebrae superioris; contraction of orbicularis oculi (pars palpebralis)
46Winkorbicularis oculi
50Speech
80Swallow
81Chewing
82Shoulder shrug
84Head shake back and forth
85Head nod up and down
91Flash
92Partial flash
97*Shiver/tremble
98*Fast up-down look

See also

References

  1. Hjortsjö CH (1969). Man's face and mimic language. free download: Carl-Herman Hjortsjö, Man's face and mimic language"
  2. Ekman P, Friesen W (1978). Facial Action Coding System: A Technique for the Measurement of Facial Movement. Palo Alto: Consulting Psychologists Press.
  3. Ekman P, Friesen WV, Hager JC (2002). Facial Action Coding System: The Manual on CD ROM. Salt Lake City: A Human Face.
  4. Hamm J, Kohler CG, Gur RC, Verma R (September 2011). "Automated Facial Action Coding System for dynamic analysis of facial expressions in neuropsychiatric disorders". Journal of Neuroscience Methods. 200 (2): 237–56. doi:10.1016/j.jneumeth.2011.06.023. PMC 3402717. PMID 21741407.
  5. Ramachandran VS (2012). "Microexpression and macroexpression". In Ramachandran VS (ed.). Encyclopedia of Human Behavior. 2. Oxford: Elsevier/Academic Press. pp. 173–183. ISBN 978-0-12-375000-6.
  6. Del Giudice M, Colle L (May 2007). "Differences between children and adults in the recognition of enjoyment smiles". Developmental Psychology. 43 (3): 796–803. doi:10.1037/0012-1649.43.3.796. PMID 17484588.
  7. Facial Action Coding System. Retrieved July 21, 2007.
  8. Reed LI, Sayette MA, Cohn JF (November 2007). "Impact of depression on response to comedy: a dynamic facial coding analysis". Journal of Abnormal Psychology. 116 (4): 804–9. CiteSeerX 10.1.1.307.6950. doi:10.1037/0021-843X.116.4.804. PMID 18020726.
  9. Lints-Martindale AC, Hadjistavropoulos T, Barber B, Gibson SJ (2007). "A psychophysical investigation of the facial action coding system as an index of pain variability among older adults with and without Alzheimer's disease". Pain Medicine. 8 (8): 678–89. doi:10.1111/j.1526-4637.2007.00358.x. PMID 18028046.
  10. Rosenberg EL. "Example and web site of one teaching professional". Archived from the original on 2009-02-06. Retrieved 2009-02-04.
  11. "Facial Action Coding System". Paul Ekman Group. Retrieved 2019-10-23.
  12. Parr LA, Waller BM, Vick SJ, Bard KA (February 2007). "Classifying chimpanzee facial expressions using muscle action". Emotion. 7 (1): 172–81. doi:10.1037/1528-3542.7.1.172. PMC 2826116. PMID 17352572.
  13. Parr LA, Waller BM, Burrows AM, Gothard KM, Vick SJ (December 2010). "Brief communication: MaqFACS: A muscle-based facial movement coding system for the rhesus macaque". American Journal of Physical Anthropology. 143 (4): 625–30. doi:10.1002/ajpa.21401. PMC 2988871. PMID 20872742.
  14. Waller BM, Lembeck M, Kuchenbuch P, Burrows AM, Liebal K (2012). "GibbonFACS: A Muscle-Based Facial Movement Coding System for Hylobatids". International Journal of Primatology. 33 (4): 809–821. doi:10.1007/s10764-012-9611-6.
  15. Caeiro CC, Waller BM, Zimmermann E, Burrows AM, Davila-Ross M (2012). "OrangFACS: A Muscle-Based Facial Movement Coding System for Orangutans (Pongo spp.)". International Journal of Primatology. 34: 115–129. doi:10.1007/s10764-012-9652-x.
  16. Waller BM, Peirce K, Caeiro CC, Scheider L, Burrows AM, McCune S, Kaminski J (2013). "Paedomorphic facial expressions give dogs a selective advantage". PLOS ONE. 8 (12): e82686. Bibcode:2013PLoSO...882686W. doi:10.1371/journal.pone.0082686. PMC 3873274. PMID 24386109.
  17. Wathan J, Burrows AM, Waller BM, McComb K (2015-08-05). "EquiFACS: The Equine Facial Action Coding System". PLOS ONE. 10 (8): e0131738. Bibcode:2015PLoSO..1031738W. doi:10.1371/journal.pone.0131738. PMC 4526551. PMID 26244573.
  18. Caeiro CC, Burrows AM, Waller BM (2017-04-01). "Development and application of CatFACS: Are human cat adopters influenced by cat facial expressions?" (PDF). Applied Animal Behaviour Science. 189: 66–78. doi:10.1016/j.applanim.2017.01.005. ISSN 0168-1591.
  19. "Home". animalfacs.com. Retrieved 2019-10-23.
  20. Vick SJ, Waller BM, Parr LA, Smith Pasqualini MC, Bard KA (March 2007). "A Cross-species Comparison of Facial Morphology and Movement in Humans and Chimpanzees Using the Facial Action Coding System (FACS)". Journal of Nonverbal Behavior. 31 (1): 1–20. doi:10.1007/s10919-006-0017-z. PMC 3008553. PMID 21188285.
  21. Friesen W, Ekman P (1983), EMFACS-7: Emotional Facial Action Coding System. Unpublished manuscript, 2, University of California at San Francisco, p. 1
  22. "Facial Action Coding System Affect Interpretation Dictionary (FACSAID)". Archived from the original on 2011-05-20. Retrieved 2011-02-23.
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