Facial Action Coding System - Codes For Action Units

Codes For Action Units

See also: List of muscles in the human body#The muscles of the head

For clarification, FACS is an index of facial expressions, but does not actually provide any bio-mechanical information about the degree of muscle activation. Though muscle activation is not part of FACS, the main muscles involved in the facial expression have been added here for the benefit of the reader.

Action Units (AUs) are the fundamental actions of individual muscles or groups of muscles.

Action Descriptors (ADs) are unitary movements that may involve the actions of several muscle groups (e.g., a forward‐thrusting movement of the jaw). The muscular basis for these actions hasn’t been specified and specific behaviors haven’t been distinguished as precisely as for the AUs.

For most accurate annotation, FACS suggests agreement from at least two independent certified FACS encoders.

Read more about this topic:  Facial Action Coding System

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