FACS is used across many different personal and professional settings. It is often used in various scientific settings for research. It is also used by animators and computer scientists interested in facial recognition. FACS may also enable greater awareness and sensitivity to subtle facial behaviors. Such skills are useful for psychotherapists, interviewers, and anyone working in communications. It also describes how AUs appear in combinations. The Paul Ekman Group offers the manual for sale. The FACS manual is self-instructional.
Head Movement Action Units
Used by Researchers and Animators
Friesen, and published in Hager published a significant update to FACS in Due to subjectivity and time consumption issues, FACS has been established as a computed automated system that detects faces in videos, extracts the geometrical features of the faces, and then produces temporal profiles of each facial movement. 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. 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: .
There is broad interest in the application of FACS for assessing consumer expressions as an indication of emotions to consumer product-stimuli. However, the translation of FACS to characterization of emotions is elusive in the literature. The aim of this systematic review is to give an overview of how FACS has been used to investigate human emotional behavior to consumer product-based stimuli. The search was limited to studies published in English after , conducted on humans, using FACS or its action units to investigate affect, where emotional response is elicited by consumer product-based stimuli evoking at least one of the five senses. The search resulted in an initial total of 1, records, of which 55 studies were extracted and categorized based on the outcomes of interest including i method of FACS implementation; ii purpose of study; iii consumer product-based stimuli used; and iv measures of affect validation. This review illuminated some inconsistencies in how FACS is carried out as well as how emotional response is inferred from facial muscle activation. This may prompt researchers to consider measuring the total consumer experience by employing a variety of methodologies in addition to FACS and its emotion-based interpretation guide. A variety of methods exist to capture the human affectual experience in response to stimuli; however, the nature of emotions makes them difficult to measure and interpret.
Many researchers code muscle movements to learn more about how and why the face moves. They use the Facial Action Coding System which provides them with a technique for the reliable coding and analysis of facial movements and expressions. They indicate which AUs moved to produce the changes observed in the face. This makes FACS coding quite objective. In scoring, it will be necessary to apply slow motion and frame-by-frame viewing to identify the AUs that occur, always alternating with real time viewing.