Chapter 1 - Purpose and Overview

The Facial Action Coding System (FACS) Manual teaches you how to recognize and score the Action Units (AUs), which represent the muscular activity that produces momentary changes in facial appearance. The changes in facial appearance for each AU are explained in words and illustrated in images (usually made from original still photographs) and digital video (usually made from original film or videotape). The images and videos of the Action Units and Action Unit combinations are listed in Appendix II, approximately in the order in which they are first mentioned in the Manual. The reference example images appear in the first part in Appendix II, followed by the video examples. This table contains the final scoring for the reference example images and videos. An index of the videos ordered by AU comprises Appendix I, the Index to Video Examples, which is cross-referenced to the filename of the video on CD ROM and the scoring commentary in Appendix II. These files can be used to play the video separately from using the Manual.

The illustrations are not meant to be taken literally - they exemplify but do not typify. The exact appearance change varies from one person to another depending upon their bone structure, variations in the facial musculature, fatty deposits, permanent wrinkles, shape of features, etc. Common elements appear across people in the changes that occur in an Action Unit. These elements are detailed and emphasized in the manual, and you will learn with experience to recognize them. One important way to focus upon these common elements is to make each action on your own face and observe in a mirror how it differs and how it is similar to what is shown in the images and video. Also, examine the similarities and differences shown by other people who are learning this facial measurement procedure with you. Finally, score the practice images and videos to help you learn the common elements.

The AUs are presented and are to be learned in groups. The groups are based upon the location and/or type of action involved. First, you learn the AUs in the Upper Face, which affect the eyebrows, forehead, and eyelids. Then, the Lower Face AUs are presented in five groups: Up/Down, Horizontal, Oblique, Orbital, and Miscellaneous Actions. After learning each group, you practice scoring facial behavior and verify your scores before proceeding to the next group of AUs.

Within each group of AUs, each AU is explained in three sections that have the following names:

Later, in referring to a particular part of the Manual, these abbreviations, A, B, and C will be used. Thus, if you read the instruction, "see 4secC" you should look under Action Unit number 4 in Section C ("Intensity Scoring for AU 4"). A more detailed presentation of these three sections can be found later in this chapter.

This Manual is written so that it can serve two purposes: as a basis for initial learning and as a reference when scoring facial behavior. To be useful as a reference, the Manual contains information that is not relevant or even understandable until you have learned the entire system. Usually, such materials are listed separately under the Reference heading. When you encounter such a section, disregard it until after you have learned the Action Units that are mentioned in the chapter. Sometimes, other parts of the Manual besides the Reference section will mention Action Units that you have not yet learned. For example, the chapter on the Upper Face contains some mention of Lower Face Action Units. You do not need to look those AUs up or understand them in your initial learning. You will return to the chapters many times when scoring, and then you will understand how these sections are useful.

After the Manual introduces you to all of the individual AUs within a group, it explains the subtle differences among these AUs. Then, the Manual describes some of the combinations of two or more AUs, including the subtle differences among these combinations, and the specific difficulties in scoring two or more co-occurring AUs, such as how to score the AUs when one AU interferes with detecting another.

Initially, on first reading, you may find that certain issues are not clear. Instead of trying to clarify such issues immediately, you should continue reading up to the AU Combinations section of a chapter before returning and working harder to understand the material in the A, B, and C sections for individual AUs. Avoid skimming, but if you cannot figure something out, at least continue through the single AUs and the first Subtle Difference Table. If the difficulty is in recognizing the changes due to a particular AU, you may be able to understand the distinction better after reading about the AU in combination with the other AUs.