Editing Affective computing (section)

====Facial Action Coding System====
{{Main|Facial Action Coding System}}

A system has been conceived by psychologists in order to formally categorize the physical expression of emotions on faces. The central concept of the [[Facial Action Coding System]], or FACS, as created by Paul Ekman and Wallace V. Friesen in 1978 based on earlier work by [[Carl-Herman Hjortsjö]]<ref>[http://face-and-emotion.com/dataface/facs/description.jsp "Facial Action Coding System (FACS) and the FACS Manual"] {{webarchive |url=https://web.archive.org/web/20131019130324/http://face-and-emotion.com/dataface/facs/description.jsp |date=October 19, 2013 }}. A Human Face. Retrieved 21 March 2011.</ref> are action units (AU).
They are, basically, a contraction or a relaxation of one or more muscles. Psychologists have proposed the following classification of six basic emotions, according to their action units ("+" here mean "and"):

{| class="wikitable sortable"
|-
! 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
|}