Ekman and Friesen's FACS (Facial Action Coding System)

Ekman and Friesen's Facial Action Coding System (FACS) is a technique used to analyze and categorize facial expressions by identifying specific muscle movements, called Action Units (AUs). It systematically codes facial behaviors to decode emotions and internal states. For example, raising eyebrows or tightening lips corresponds to particular AUs. FACS helps researchers, psychologists, and law enforcement understand genuine emotions, detect deception, or study non-verbal communication by providing a detailed, objective framework for interpreting facial cues. It is applicable across cultures and provides a scientific basis for recognizing subtle facial changes associated with different feelings.