FACS Definition

The Facial Action Coding System(developed by Ekman and Friesen 1976) is an anatomically based for measuring all visually discernible facial movement, described on the basis of 44 Action Units (AU's) as well as several head and eye positions and movements. An AU has a fairly arbitrarily assigned numeric code and can consist of one or more muscle (groups). The coding procedure also allows for the coding of the intensity of the facial action on a five point intensity scale, for the timing of facial action and for the coding of facial expressions in terms of events (one or more AU's composing the facial expression)