Facial Action Units

Facial Action Units (AUs) are specific movements or contractions of facial muscles that produce observable changes in facial appearance. Developed by experts like Paul Ekman, AUs help identify and categorize genuine facial expressions by analyzing muscle activity, such as raising eyebrows or smiling. They provide a systematic way to interpret emotions and reactions by breaking down complex facial behaviors into measurable components. This approach is used in psychology, security, and human-computer interaction to understand non-verbal communication accurately and objectively.