The Facial Action Coding System Manual

The Facial Action Coding System (FACS) Manual is a detailed guide that categorizes and describes every observable movement of facial muscles. Developed by psychologists, it allows trained users to identify and document specific facial expressions and muscle activations, which reflect emotions, reactions, or communication cues. By systematically coding facial muscle actions, FACS helps in research, psychology, forensics, and human-computer interaction, providing a precise method to interpret non-verbal signals and understand underlying emotional states without relying on subjective judgment.