Facial Action Coding System

Defining FACS

First published by Paul Ekman and Wallace Friesen in 1978, and updated in 2002, FACS was designed to collect empirical data on facial expressions without introducing emotional interpretation. Previous coding systems focused on the messages underlying expressions (e.g., Is this a happy or sad expression?). Ekman and Friesen argued that this was a subjective approach. Raters did not have a standardized system for determining the emotional state; instead, they relied on their own judgments and experiences. FACS offers a more objective measurement system, which is divorced from emotional valuation from the beginning. Instead of interpreting the message the expression is conveying, FACS coders focus on describing facial behaviors. Interpretation can be added later when researchers examine which facial behaviors are related to emotional situations or self-reports.

How FACS Works

To create FACS, Ekman and Friesen began by electrically stimulating each individual muscle of the face and attempting to replicate those movements voluntarily. FACS action units are defined as the smallest movements of the face that can be reliably distinguished from another, and each one is associated with one or more muscle movements. Readers interested in a comprehensive list of the FACS action units can seek out the updated FACS manual published by Ekman, Friesen, and Joseph C. Hager in 2002. The FACS manual includes codes for 27 action units in the face, 25 head and eye position codes, and an additional 28 codes that include miscellaneous movements (such as showing the tongue) and visibility codes.

The 27 facial action units are broken down into upper and lower facial movements. The upper facial action units include brow raising (action units 1 and 2 for inner and outer edges of the brow, respectively), brow lowering (4), eyelid raising [Page 488](5), and cheek raising (6). Lower facial actions are more complex and include vertical, horizontal, oblique, and orbital action units. An example of a vertical action unit would be number 15, which pulls the corners of the lips straight down, whereas an oblique action unit would be action unit 12, which pulls the lip corners up and out. Most facial expressions include a combination of upper and lower action units, and some combinations are more common than others. Head and eye movement codes are broader and less commonly used but can provide important emotional information about what is happening on the face. They include head tilting, turning, and general eye direction.

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