Facial Action Coding System - Uses

Uses

Using FACS, human coders can manually code nearly any anatomically possible facial expression, deconstructing it into the specific Action Units (AU) and their temporal segments that produced the expression. As AUs are independent of any interpretation, they can be used for any higher order decision making process including recognition of basic emotions, or pre-programmed commands for an ambient intelligent environment. The FACS Manual is over 500 pages in length and provides the AUs, as well as Ekman’s interpretation of their meaning.

FACS defines AUs, which are a contraction or relaxation of one or more muscles. It also defines a number of Action Descriptors, which differ from AUs in that the authors of FACS have not specified the muscular basis for the action and have not distinguished specific behaviors as precisely as they have for the AUs.

For example, FACS can be used to distinguish two types of smiles as follows:

• Insincere and voluntary Pan-Am smile: contraction of zygomatic major alone
• Sincere and involuntary Duchenne smile: contraction of zygomatic major and inferior part of orbicularis oculi.

Although the labeling of expressions currently requires trained experts, researchers have had some success in using computers to automatically identify FACS codes, and thus quickly identify emotions. Computer graphical face models, such as CANDIDE or Artnatomy, allow expressions to be artificially posed by setting the desired action units.

The use of FACS has been proposed for use in the analysis of depression, and the measurement of pain in patients unable to express themselves verbally.

FACS is designed to be self-instructional. People can learn the technique from a number of sources including manuals and workshops, and obtain certification through testing. A variant of FACS has been developed to analyze facial expressions in chimpanzees.

FACS can also be modified such that it can be used to compare facial repertoires across similar species, such as humans and chimpanzees. A study conducted by Vick and others (2006) suggests that FACS can be modified by taking differences in underlying morphology into account. Such considerations enable a comparison of the FACS present in humans and chimpanzees, to show that the facial expressions of both species result from extremely notable appearance changes. A cross-species analysis of facial expressions can help to answer the question of which emotions are uniquely human.

EMFACS (Emotional Facial Action Coding System) and FACSAID (Facial Action Coding System Affect Interpretation Dictionary) consider only emotion-related facial actions. Examples of these are: