Facial Action Coding System
Encyclopedia
Facial expression
A facial expression one or more motions or positions of the muscles in the skin. These movements convey the emotional state of the individual to observers. Facial expressions are a form of nonverbal communication. They are a primary means of conveying social information among humans, but also occur...
s, originally developed by Paul Ekman
Paul Ekman
Paul Ekman is a psychologist who has been a pioneer in the study of emotions and their relation to facial expressions. He has been considered one of the 100 most eminent psychologists of the twentieth century...
and Wallace V. Friesen in 1978. It is a common standard to systematically categorize the physical expression of emotion
Emotion
Emotion is a complex psychophysiological experience of an individual's state of mind as interacting with biochemical and environmental influences. In humans, emotion fundamentally involves "physiological arousal, expressive behaviors, and conscious experience." Emotion is associated with mood,...
s, and it has proven useful to psychologist
Psychologist
Psychologist is a professional or academic title used by individuals who are either:* Clinical professionals who work with patients in a variety of therapeutic contexts .* Scientists conducting psychological research or teaching psychology in a college...
s and to animator
Animator
An animator is an artist who creates multiple images that give an illusion of movement called animation when displayed in rapid sequence; the images are called frames and key frames. Animators can work in a variety of fields including film, television, video games, and the internet. Usually, an...
s.
Uses
Using FACS, 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 Dr. 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 smile
Smile
A smile is a facial expression formed by flexing the muscles near both ends of the mouth. The smile can also be found around the eyes . Among humans, it is an expression denoting pleasure, joy, happiness, or amusement, but can also be an involuntary expression of anxiety, in which case it is known...
s as follows:
- Insincere and voluntary Pan American smile: contraction of zygomatic major alone
- Sincere and involuntary Duchenne smile: contraction of zygomatic major and inferior part of orbicularis oculi.
Although the labeling of expressions currently requires trained experts, researchers have had some success in using computers to automatically identify FACS codes, and thus quickly identify emotions.
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
Clinical depression
Major depressive disorder is a mental disorder characterized by an all-encompassing low mood accompanied by low self-esteem, and by loss of interest or pleasure in normally enjoyable activities...
, and the measurement of pain in patients unable to express themselves verbally.
FACS is designed to be self-instructional. People can learn the technique from a number of sources including manuals and workshops, and obtain certification through testing. A variant of FACS has been developed to analyze facial expressions in chimpanzee
Chimpanzee
Chimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:...
s.
FACS can also be modified such that it can be used to compare facial repertoires across similar species, such as humans and chimpanzees. 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 FACS present in humans and chimpanzees, to show that the facial expressions of both species result from extremely notable appearance changes. It is through comparing such detailed cross-species analysis of facial expressions that we can begin to understand what it is that makes us uniquely human.
(Coding System) and FACSAID (Facial Action Coding System Affect Interpretation Dictionary) which consider only emotion-related facial actions. For example:
| Emotion | Action Units |
|---|---|
| Happiness | 6+12 |
| Sadness | 1+4+15 |
| Surprise | 1+2+5B+26 |
| Fear | 1+2+4+5+20+26 |
| Anger | 4+5+7+23 |
| Disgust | 9+15+16 |
| Contempt | R12A+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-maximial 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
Main Codes
| AU Number | FACS Name | Muscular Basis |
|---|---|---|
| 0 | Neutral Face | |
| 1 | Inner Brow Raiser | frontalis Frontalis Frontalis may refer to:* Crista frontalis, the frontal crest, a crest on the internal surface of the squama frontalis of the frontal bone* Frontalis muscle, a thin, quadrilateral fascia muscle located on the front of the head... (pars medialis) |
| 2 | Outer Brow Raiser | frontalis Frontalis Frontalis may refer to:* Crista frontalis, the frontal crest, a crest on the internal surface of the squama frontalis of the frontal bone* Frontalis muscle, a thin, quadrilateral fascia muscle located on the front of the head... (pars lateralis) |
| 4 | Brow Lowerer | depressor glabellae, depressor supercilii, corrugator supercilii |
| 5 | Upper Lid Raiser | levator palpebrae superioris |
| 6 | Cheek Raiser | orbicularis oculi (pars orbitalis Pars orbitalis The orbital or horizontal part of the frontal bone consists of two thin triangular plates, the orbital plates, which form the vaults of the orbits, and are separated from one another by a median gap, the ethmoidal notch.- Surfaces :... ) |
| 7 | Lid Tightener | orbicularis oculi (pars palpebralis Pars palpebralis Pars palpebralis in a medical context means "relating to the eyelids." It is the source of the English word "palpebral".... ) |
| 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 The levator labii superioris is a muscle of the human body used in facial expression. It is a broad sheet, the origin of which extends from the side of the nose to the zygomatic bone.... , caput infraorbitalis Levator labii superioris The levator labii superioris is a muscle of the human body used in facial expression. It is a broad sheet, the origin of which extends from the side of the nose to the zygomatic bone.... |
| 11 | Nasolabial Deepener | zygomaticus minor |
| 12 | Lip Corner Puller | zygomaticus major |
| 13 | Sharp Lip Puller | levator anguli oris Levator anguli oris The levator anguli oris is a facial muscle of the mouth arising from the canine fossa, immediately below the infraorbital foramen.... (also known as caninus) |
| 14 | Dimpler | buccinator Buccinator The buccinator muscle is a muscle at the side of the face.Buccinator may also refer to:* Buccinator artery * Buccinator lymph node* Buccinator nerve * An ancient Roman buccina player... |
| 15 | Lip Corner Depressor | depressor anguli oris (also known as triangularis) |
| 16 | Lower Lip Depressor | depressor labii inferioris |
| 17 | Chin Raiser | mentalis Mentalis The Mentalis is a paired central muscle of the lower lip, situated at the tip of the chin. It raises and pushes up the lower lip, causing wrinkling of the chin, as in doubt or displeasure... |
| 18 | Lip Pucker | incisivii labii superioris and incisivii labii inferioris |
| 19 | Tongue Show | |
| 20 | Lip Stretcher | risorius Risorius The risorius is a muscle of facial expression which arises in the fascia over the parotid gland and, passing horizontally forward, superficial to the platysma, inserts onto the skin at the angle of the mouth... w/ 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 Mentalis The Mentalis is a paired central muscle of the lower lip, situated at the tip of the chin. It raises and pushes up the lower lip, causing wrinkling of the chin, as in doubt or displeasure... or orbicularis oris |
| 26 | Jaw Drop | masseter; relaxed temporalis and internal pterygoid Medial pterygoid muscle The medial pterygoid , is a thick, quadrilateral muscle of mastication.The mandibular branch of the fifth cranial nerve, the trigeminal nerve, innervates the medial pterygoid muscle.-Origin and insertion:... |
| 27 | Mouth Stretch | pterygoids, digastric |
| 28 | Lip Suck | orbicularis oris |
| 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 (pars alaris) Nasalis muscle The nasalis is a sphincter-like muscle of the nose whose function is to compress the nasal cartilage.It consists of two parts, transverse and alar:... |
| 39 | Nostril Compressor | nasalis (pars transversa) Nasalis muscle The nasalis is a sphincter-like muscle of the nose whose function is to compress the nasal cartilage.It consists of two parts, transverse and alar:... and depressor septi nasi Depressor septi nasi muscle The depressor septi arises from the incisive fossa of the maxilla.Its fibers ascend to be inserted into the nasal septum and back part of the alar part of nasalis muscle.... |
| 41 | Glabella Lowerer | Separate Strand of AU 4: depressor glabellae (aka procerus) |
| 42 | Inner Eyebrow Lowerer | Separate Strand of AU 4: depressor supercilii |
| 43 | Eyes Closed | Relaxation of levator palpebrae superioris |
| 44 | Eyebrow Gatherer | Separate Strand of AU 4: corrugator supercilli |
| 45 | Blink | Relaxation of levator palpebrae superioris; contraction of orbicularis oculi (pars palpebralis Pars palpebralis Pars palpebralis in a medical context means "relating to the eyelids." It is the source of the English word "palpebral".... ) |
| 46 | Wink | orbicularis oculi |
Head Movement Codes
| 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 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 and/or tilted to either the left or right. |
Eye Movement Codes
| 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 | 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 and/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
| 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.| AU Number | FACS Name |
|---|---|
| 40 | Sniff |
| 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
- MicroexpressionMicroexpressionA microexpression is a brief, involuntary facial expression shown on the face of humans according to emotions experienced. They usually occur in high-stakes situations, where people have something to lose or gain. Unlike regular facial expressions, it is difficult to fake microexpressions...
- Facial feedback hypothesisFacial feedback hypothesisThe facial feedback hypothesis states that facial movement can influence emotional experience. For example, an individual who is forced to smile during a social event will actually come to find the event more of an enjoyable experience.-Background:...
- Facial electromyographyFacial electromyographyFacial Electromyography refers to an electromyography technique that measures muscle activity by detecting and amplifying the tiny electrical impulses that are generated by muscle fibers when they contract....
- Computer facial animationComputer facial animationComputer facial animation is primarily an area of computer graphics that encapsulates models and techniques for generating and animating images of the human head and face. Due to its subject and output type, it is also related to many other scientific and artistic fields from psychology to...
- Facial musclesFacial musclesThe facial muscles are a group of striated muscles innervated by the facial nerve that, among other things, control facial expression. These muscles are also called mimetic muscles.-Structure:...
External links
- Paul Ekman’s articles relating to FACS
- FACS Overview (accessed 21/02/2011)
- Sample of FACS Manual (accessed 21/02/2011)
- More information on the CHIMPFACS project
- New Yorker article discussing FACS
- Details from 1978 edition of FACS
- Site at WPI