Ekman's Facial Action Coding System

Ekman's Facial Action Coding System (FACS) is a comprehensive method for describing and categorizing every facial expression by analyzing muscle movements, called "action units." Developed by psychologist Paul Ekman, it provides a detailed language for understanding facial expressions associated with emotions, such as happiness, sadness, anger, or surprise. FACS allows trained observers to accurately identify subtle facial muscle movements that reveal what someone might be feeling or thinking, enhancing communication, psychological research, and lie detection. It is a tool that systematically maps the expressive capabilities of the face, serving as a bridge between observable behavior and emotional states.