In physiology, a smile is a facial expression formed by flexing the muscles most notably near both ends of the mouth. The smile can be also around the eyes. Among humans, it's customarily an expression of pleasure, happiness, or amusement, but can also be an involuntary expression of anxiety, in which case it can be known as a grimace. There is much evidence that smiling is a normal reaction to certain stimuli and occurs regardless of culture. Happiness most often causes the smile to occur, though. Among animals, the exposure of teeth, which may bear a resemblance to a smile, are often used as a threat or warning display - known as a snarl - or a sign of submission. In chimpanzees, it can be a sign of fear.
Types of smilesResearchers have identified two main varieties of smiles:
The "Duchenne smile", after the researcher Guillaume Duchenne, is the most studied, and involves the movement of both the zygomaticus major muscle near the mouth and the orbicularis oculi muscle near the eyes. An example of the smile is shown in the girl's smile in the middle of the page. It is believed that the Duchenne smile is only produced as an involuntary response to genuine emotion, and is therefore what one could call the "genuine" smile. Due to the involvement of the muscle near the eyes, it is sometimes said that one can tell whether or not a smile is "real" by whether or not it "reaches the eyes". The "Pan American smile", on the other hand, is the voluntary smile involving only the zygomaticus major muscle to show politeness; for example, by a flight attendant on the former airline of the same name. Considered "insincere", this type of smile has also been called the "Professional Smile" by David Foster Wallace in his comedic short story "A Supposedly Fun Thing I'll Never Do Again".
Facial Action Coding System (FACS) is a system originally developed by Paul Ekman and Wallace Friesen in 1976, to taxonomize every conceivable human facial expression ( (1976) Facial Action Coding System: A technique for the measurement of facial movement. Consulting Psychologist. ). It is the most popular standard currently used to systematically categorize the physical expression of emotions, and it has proven useful both to psychologists and to animators. FACS and its action units are based on the book of Carl-Herman Hjortsjö "Man's Face and Mimic [i.e. Facial] Language" (Swedish version: “Människans ansikte och mimiska språket”, 1969: Malmö, Studentlitteratur). Hjortsjö was professor of Anatomy at Lund University in Sweden.
The original FACS was published in 1976 by Paul Ekman and Wallace V. Friesen. While using the system for several years in their lab and training new FACS coders, they updated the rules and definitions of the system. At first the changes were handed out to the new FACS coders in form of an addendum. However, as changes became more structural, a new version of FACS was needed.
In 2002, a new version of FACS was finally published, with large contributions by Joseph Hager ( (2002) Facial Action Coding System. A human face. ). Most co-occurrence rules were removed, a number of AUs were removed and some added, minimum requirements were eliminated and a novel intensity scoring definition was introduced. Unfortunately, the authors decided not to rename the system. It is still simply known as FACS, not as FACS2, FACS 2002 revision or FACS version 2. The website of Paul Ekman' lab refers to it as the "new" FACS.
Using FACS, human coders can manually code nearly any anatomically possible facial expression, decomposing it into the specific AUs 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.
FACS defines 32 "Action Units" (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:
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.
Types of smilesResearchers have identified two main varieties of smiles:
The "Duchenne smile", after the researcher Guillaume Duchenne, is the most studied, and involves the movement of both the zygomaticus major muscle near the mouth and the orbicularis oculi muscle near the eyes. An example of the smile is shown in the girl's smile in the middle of the page. It is believed that the Duchenne smile is only produced as an involuntary response to genuine emotion, and is therefore what one could call the "genuine" smile. Due to the involvement of the muscle near the eyes, it is sometimes said that one can tell whether or not a smile is "real" by whether or not it "reaches the eyes". The "Pan American smile", on the other hand, is the voluntary smile involving only the zygomaticus major muscle to show politeness; for example, by a flight attendant on the former airline of the same name. Considered "insincere", this type of smile has also been called the "Professional Smile" by David Foster Wallace in his comedic short story "A Supposedly Fun Thing I'll Never Do Again".
Facial Action Coding System (FACS) is a system originally developed by Paul Ekman and Wallace Friesen in 1976, to taxonomize every conceivable human facial expression ( (1976) Facial Action Coding System: A technique for the measurement of facial movement. Consulting Psychologist. ). It is the most popular standard currently used to systematically categorize the physical expression of emotions, and it has proven useful both to psychologists and to animators. FACS and its action units are based on the book of Carl-Herman Hjortsjö "Man's Face and Mimic [i.e. Facial] Language" (Swedish version: “Människans ansikte och mimiska språket”, 1969: Malmö, Studentlitteratur). Hjortsjö was professor of Anatomy at Lund University in Sweden.
The original FACS was published in 1976 by Paul Ekman and Wallace V. Friesen. While using the system for several years in their lab and training new FACS coders, they updated the rules and definitions of the system. At first the changes were handed out to the new FACS coders in form of an addendum. However, as changes became more structural, a new version of FACS was needed.
In 2002, a new version of FACS was finally published, with large contributions by Joseph Hager ( (2002) Facial Action Coding System. A human face. ). Most co-occurrence rules were removed, a number of AUs were removed and some added, minimum requirements were eliminated and a novel intensity scoring definition was introduced. Unfortunately, the authors decided not to rename the system. It is still simply known as FACS, not as FACS2, FACS 2002 revision or FACS version 2. The website of Paul Ekman' lab refers to it as the "new" FACS.
Using FACS, human coders can manually code nearly any anatomically possible facial expression, decomposing it into the specific AUs 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.
FACS defines 32 "Action Units" (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:
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.
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