Editing Facial Action Coding System

{{Short description|System of classifying human facial movements}}
[[File:1106 Side Views of the Muscles of Facial Expressions.jpg|thumb|upright=1.3|Muscles of head and neck]]

The '''Facial Action Coding System''' ('''FACS''') is a system to [[taxonomize]] human [[facial expression|facial movements]] by their appearance on the face,  based on a system originally developed by a Swedish [[anatomist]] named [[Carl-Herman Hjortsjö]].<ref>{{cite book|url=https://books.google.com/books?id=BakQAQAAIAAJ|vauthors=Hjortsjö CH|title=Man's face and mimic language|year=1969}} free download: [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 }}</ref> It was later adopted by [[Paul Ekman]] and [[Wallace V. Friesen]], and published in 1978.<ref>{{cite book | vauthors = Ekman P, Friesen W | title = Facial Action Coding System: A Technique for the Measurement of Facial Movement. | publisher = Consulting Psychologists Press | location = Palo Alto | date = 1978 }}</ref> Ekman, Friesen, and Joseph C. Hager published a significant update to FACS in 2002.<ref>{{cite book | first1 = Paul | last1 = Ekman | first2 = Wallace V. | last2 = Friesen | first3 = Joseph C. | last3 = Hager | name-list-style = vanc | title = Facial Action Coding System: The Manual on CD ROM. | publisher = A Human Face | location = Salt Lake City | date = 2002 }}</ref> Movements of individual [[facial muscles]] are encoded by the FACS from slight different instant changes in facial appearance. It has proven useful to [[psychologist]]s and to [[animator]]s.

==Background==
[[File:Rio2016 0809 MARTINET ©G-Picout 22.jpg|thumb|Blind athlete expressing joy in athletic competition. The fact that unsighted persons use the same expressions as sighted people shows that expressions are innate.]]
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.<ref>Matsumoto, D., & Willingham, B. (2009). "Spontaneous facial expressions of emotion of blind individuals". ''[[Journal of Personality and Social Psychology]]'', 96(1), 1-10</ref>

== Method ==
Using the FACS<ref>{{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}}</ref> 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 [[emotion recognition|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 [[smile]]s as follows:<ref name="pmid17484588">{{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 }}</ref>
* 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,<ref>{{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}}</ref> and obtain certification through testing.<ref>{{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}}</ref>

Although the labeling of expressions currently requires trained experts, researchers have had some success in using computers to automatically identify the FACS codes.<ref>[http://www.cs.wpi.edu/~matt/courses/cs563/talks/face_anim/ekman.html Facial Action Coding System.] Retrieved July 21, 2007.</ref> One obstacle to automatic FACS code recognition is a shortage of manually coded ground truth data.<ref>{{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 }}</ref>

== Uses ==

=== Baby FACS ===
Baby FACS (Facial Action Coding System for Infants and Young Children)<ref>{{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}}</ref> 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.

=== Use in medicine ===
The use of the FACS has been proposed for use in the analysis of [[Clinical depression|depression]],<ref name="pmid18020726">{{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 }}</ref> and the measurement of pain in patients unable to express themselves verbally.<ref name="pmid18028046">{{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 }}</ref>

=== Cross-species applications ===
The original FACS has been modified to analyze facial movements in several non-human primates, namely [[Common chimpanzee|chimpanzee]]s,<ref name="pmid17352572">{{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 }}</ref> rhesus macaques,<ref>{{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 }}</ref> gibbons and siamangs,<ref>{{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 }}</ref> and orangutans.<ref>{{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}}</ref> More recently, it was developed also for domestic species, including dogs,<ref>{{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 }}</ref> horses<ref>{{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 }}</ref> and cats.<ref>{{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}}</ref> Similarly to the human FACS, the animal FACS has manuals available online for each species with the respective certification tests.<ref>{{Cite web|url=http://animalfacs.com|title=Home|website=animalfacs.com|access-date=2019-10-23}}</ref>

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.<ref>{{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 }}</ref>

The  Emotional Facial Action Coding System (EMFACS)<ref>{{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 }}</ref> and the  Facial Action Coding System Affect Interpretation Dictionary (FACSAID)<ref>{{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 }}</ref> consider only emotion-related facial actions. Examples of these are:
{| class="wikitable sortable"
|-
! Emotion !! Action units
|-
| Happiness ||6+12
|-
| Sadness || 1+4+15
|-
| Surprise ||  1+2+5B+26
|-
| Fear || 1+2+4+5+7+20+26
|-
| Anger || 4+5+7+23
|-
| Disgust || 9+15+17
|-
| Contempt || R12A+R14A
|}

=== Computer-generated imagery ===
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.<ref>{{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}}</ref> FACS vectors are used as weights for [[Morph target animation|blend shape]]s corresponding to each AU, with the resulting face mesh then being used to render the finished face.<ref>{{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}}</ref><ref>{{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}}</ref> [[Deep learning]] techniques can be used to determine the FACS vectors from face images obtained during [[Motion capture|motion capture acting]], [[facial motion capture]] or other performances.<ref>{{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 }}</ref>

== Codes for action units ==
{{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.

=== Intensity scoring ===
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

=== 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 bilateral but has a stronger side is indicated with an "A" for "asymmetric".

=== List of AUs and ADs (with underlying facial muscles) ===

==== Main codes ====
{| class="wikitable sortable"
|-
! AU number !! FACS name !! Muscular basis
|-
| 0 || Neutral face ||
|-
| 1 ||Inner brow raiser || ''[[frontalis muscle|frontalis]]'' (''[[pars medialis]]'')
|-
| 2 || Outer brow raiser || ''frontalis'' (''[[pars lateralis]]'')
|-
| 4 || Brow lowerer || ''[[depressor glabellae]]'', ''[[depressor supercilii]]'', ''[[corrugator supercilii]]''
|-
| 5 || Upper lid raiser || ''[[levator palpebrae superioris]]'', [[superior tarsal muscle]]
|-
| 6 || Cheek raiser || ''[[orbicularis oculi]]'' (''[[Orbital part of frontal bone|pars orbitalis]]'')
|-
| 7 || Lid tightener || ''orbicularis oculi'' (''[[pars palpebralis]]'')
|-
| 8 || Lips toward each other || ''[[orbicularis oris]]''
|-
| 9 || Nose wrinkler || ''[[levator labii superioris alaeque nasi]]''
|-
| 10 || Upper lip raiser || ''levator labii superioris'', ''[[levator labii superioris|caput infraorbitalis]]''
|-
| 11 || Nasolabial deepener || ''[[zygomaticus minor]]''
|-
| 12 || Lip corner puller || ''[[zygomaticus major]]''
|-
| 13 || Sharp lip puller || ''[[levator anguli oris]]'' (also known as ''[[caninus]]'')
|-
| 14 || Dimpler || ''[[buccinator]]''
|-
| 15 || Lip corner depressor || ''depressor anguli oris'' (also known as ''[[triangularis]]'')
|-
| 16 || Lower lip depressor || ''[[depressor labii inferioris]]''
|-
| 17 || Chin raiser || ''[[mentalis]]''
|-
| 18 || Lip pucker || ''[[incisivii labii superioris]]'' and ''[[incisivii labii inferioris]]''
|-
| 19 || Tongue show ||
|-
| 20 || Lip stretcher || ''[[risorius]]'' with ''[[platysma]]''
|-
| 21 || Neck tightener || ''platysma]''
|-
| 22 || Lip funneler || ''[[orbicularis oris]]''
|-
| 23 || Lip tightener || ''orbicularis oris''
|-
| 24 || Lip pressor || ''orbicularis oris''
|-
| 25 || Lips part || ''[[depressor labii inferioris]]'', or relaxation of ''mentalis'' or ''orbicularis oris''
|-
| 26 || Jaw drop || ''[[masseter]]''; relaxed ''[[temporalis]]'' and [[Medial pterygoid muscle|internal ''pterygoid'']]
|-
| 27 || Mouth stretch || ''[[Pterygoid bone|pterygoids]]'', ''[[digastric]]''
|-
| 28 || Lip suck || ''orbicularis oris''
|}

==== Head movement codes ====
{| class="wikitable sortable"
|-
! AU number !! FACS name !! Action
|-
| 51 || Head turn left ||
|-
| 52 || Head turn right ||
|-
| 53 || Head up ||
|-
| 54 || Head down ||
|-
| 55 || Head tilt left ||
|-
| M55 || Head tilt left || The onset of the symmetrical 14 is immediately preceded or accompanied by a head tilt to the left.
|-
| 56 || Head tilt right ||
|-
| M56 || Head tilt right || The onset of the symmetrical 14 is immediately preceded or accompanied by a head tilt to the right.
|-
| 57 || Head forward ||
|-
| M57 || Head thrust forward || The onset of 17+24 is immediately preceded, accompanied, or followed by a head thrust forward.
|-
| 58 || Head back ||
|-
| M59 || Head shake up and down || The onset of 17+24 is immediately preceded, accompanied, or followed by an up-down head shake (nod).
|-
| M60 || Head shake side to side || The onset of 17+24 is immediately preceded, accompanied, or followed by a side to side head shake.
|-
| M83 || Head upward and to the side || The onset of the symmetrical 14 is immediately preceded or accompanied by a movement of the head, upward and turned or tilted to either the left or right.
|}

==== Eye movement codes ====
{| class="wikitable sortable"
|-
! AU number !! FACS name !! Action
|-
| 61 || Eyes turn left ||
|-
| M61 || Eyes left || The onset of the symmetrical 14 is immediately preceded or accompanied by eye movement to the left.
|-
| 62 || Eyes turn right ||
|-
| M62 || Eyes right || The onset of the symmetrical 14 is immediately preceded or accompanied by eye movement to the right.
|-
| 63 || Eyes up ||
|-
| 64 || Eyes down ||
|-
| 65 || [[Strabismus|Walleye]]||
|-
| 66 || Cross-eye ||
|-
| M68 || Upward rolling of eyes || The onset of the symmetrical 14 is immediately preceded or accompanied by an upward rolling of the eyes.
|-
| 69 || Eyes positioned to look at other person || The 4, 5, or 7, alone or in combination, occurs while the eye position is fixed on the other person in the conversation.
|-
| M69 || Head or eyes look at other person || The 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 ====

{| class="wikitable sortable"
|-
! AU number !! FACS name
|-
| 70 || Brows and forehead not visible
|-
| 71 || Eyes not visible
|-
| 72 || Lower face not visible
|-
| 73 || Entire face not visible
|-
| 74 || Unscorable
|}

==== Gross behavior codes ====
These codes are reserved for recording information about gross behaviors that may be relevant to the facial actions that are scored.
{| class="wikitable sortable"
|-
! AU number !! FACS name !! Muscular basis
|-
| 29 || Jaw thrust ||
|-
| 30 || Jaw sideways ||
|-
| 31 || Jaw clencher || ''[[masseter]]''
|-
| 32 || [Lip] bite ||
|-
| 33 || [Cheek] blow ||
|-
| 34 || [Cheek] puff ||
|-
| 35 || [Cheek] suck ||
|-
| 36 || [Tongue] bulge ||
|-
| 37 || Lip wipe ||
|-
| 38 || Nostril dilator  || ''[[Nasalis muscle|nasalis (pars alaris)]]''
|-
| 39 || Nostril compressor || ''nasalis'' (''pars transversa'') and ''[[Depressor septi nasi muscle|depressor septi nasi]]''
|-
| 40 || Sniff
|-
| 41 || Lid droop || ''[[levator palpebrae superioris]]'' (relaxation)
|-
| 42 || Slit || ''[[orbicularis oculi muscle]]''
|-
| 43 || Eyes closed || relaxation of ''levator palpebrae superioris''
|-
| 44 || Squint || ''[[corrugator supercilii]]'' and ''orbicularis oculi'' muscle
|-
| 45 || Blink || relaxation of ''levator palpebrae superioris''; contraction of ''orbicularis oculi'' (''pars palpebralis'')
|-
| 46 || Wink || ''orbicularis oculi''
|-
| 50 || Speech
|-
| 80 || Swallow
|-
| 81 || Chewing
|-
| 82 || Shoulder shrug
|-
| 84 || Head shake back and forth
|-
| 85 || Head nod up and down
|-
| 91 || Flash
|-
| 92 || Partial flash
|-
| 97* || Shiver/tremble
|-
| 98* || Fast up-down look
|}

== See also ==
* [[Computer facial animation]]
* [[Computer processing of body language]]
* [[Emotion classification]]
* [[Facial electromyography]]
* [[Facial feedback hypothesis]]
* [[Facial muscles]]
* [[Microexpression]]

== References ==
{{Reflist}}

== External links ==
* [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]]