Facial Action Coding System (FACS)

Paul Ekman and W V Friesen, in the 1970s, developed the Facial Action Coding System (FACS). It is a way to measure, describe, and interpret facial behaviours. It has been designed to measure even the slightest facial muscle contractions and determine what category or categories each facial action fits into. It can detect what the naked eye can't and is used by law enforcement agencies, film animators, and researchers of human behaviour.