Terminology

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In order to describe changes in facial appearance you must learn a few terms which refer to particular areas and features of the face and the changes in them. Figure 1-1 illustrates some of the features of the face, which are explained in Table 1-1. Tables 1-2, 1-3, and 1-4 define additional terms that describe other aspects of the face. Check the definitions of each of these terms with the illustrations in Figure 1-1. Rather than trying to memorize all these new terms now, simply read them and look carefully at any illustrations of them. These terms are used to describe Action Units in Chapter 2. When you encounter each term there, you can return to the illustration and tables to look up the definition. The terms will become understandable in the context of their use. By the time you have finished Chapter 2, you will have learned the terminology.

GLABELLA	Area of the forehead between the eyebrows.
ROOT OF NOSE	The beginning of the nose between the eyes; also called the nasal root.
EYE APERTURE	The degree to which the eye is open; the eye opening.
EYE COVER FOLD	The skin between the eyebrows and the palprebral part of the upper eyelid (the part that contacts the eyeball), which folds into the eye socket.
LOWER EYELID FURROW	A place below the lower eyelid where a line or wrinkle may appear. A line or wrinkle may be permanently etched into the face; if so, it will deepen with certain AUs. If not, it should appear when these AUs are contracted.
INFRAORBITAL FURROW	A place where a line or wrinkle may appear parallel to and below the lower eyelid running from near the inner corner of the eye and following the cheek bone laterally.
NOSTRIL WINGS	The fleshy skin of the side of the nose that forms the outside of each nostril.
NASOLABIAL FURROW	A place where a line or wrinkle may appear which begins adjacent to the nostril wings and runs down and outwards beyond the lip corners. In some people it is permanently etched in the face; if so, it will deepen with certain AUs. If not, it will appear on most peoples' faces with certain AUs.
PHILTRUM	The vertical depression in the center of the upper lip directly under the tip of the nose.
CHIN BOSS	The skin covering the bone of the chin.
SCLERA	The white part of the eyeball.

Table 1-1: Terms that name areas and features of the face

Figure 1-1: Names and locations of facial areas and parts.

The appearance of the lips can change in so many ways that it is necessary to define a few terms specifically for this feature. Table 1-2 contains these terms and definitions.

ELONGATE	The mouth appears to be longer than usual in the horizontal plane.
DE-ELONGATE	The mouth appears to be shorter than usual in the horizontal plane.
NARROW	The red part of the lip is less visible or narrower than usual (opposite of widen).
WIDEN	The red part of the lip is revealed more or wider than usual (opposite of narrow).
FLATTEN	The lips appear flattened against the teeth. They protrude less than usual. Does not involve sucking in the lips.
PROTRUDE	The lips come forward or out away from the face more than usual, (opposite of flatten).
TIGHTEN	The lips appear tight, the lips are not relaxed or loose. The muscle within the lips has contracted.
STRETCH	The lips are pulled and the skin stretched like a rubber band.
ROLLED IN	The lips are turned, or rolled, inwards, disappearing entirely or almost entirely, but they are not tightened, pressed, or stretched.

Table 1-2: Terms that describe appearance changes in the lip and other features

Some of the terms used to describe the lip in Table 1-2 are also used to describe other parts of the face, but the same basic meaning applies. Examples are:

· Narrow is used to describe a decrease in the eye aperture.

· Widen is used to describe an increase in the eye aperture.

· Widen is used in reference to enlarging the opening of the nostril and may also be used to refer to the extent of mouth opening in AUs 25, 26, 27.

· Flatten is used to refer to the effect of AU 20 on the cheek area that reduces its curvature.

· Tighten is used to describe the appearance of the lower and upper eyelids.

In discussing changes in the appearance of the skin, the words bulge, bag and pouch are used. These terms have somewhat overlapping meaning, but can be distinguished as described in Table 1-3.

BULGE	A protrusion of the skin, where the skin is pushed outward by muscle, or by skin being stretched over the eyeball or bone.
BAG	Loose skin which wrinkles as it is gathered together or pushed; a bag remains loose, not taut; it may be permanent, but will thicken or become larger or more prominent with certain actions.
POUCH	A pocket-like shape, often protrudes like a bulge; also, may be permanent in some faces, but certain actions will make it more evident.

Table 1-3: Terms that describe transient excrescences of the skin

The distinctions between bulge, bag and pouch are subtle; often the three occur together, or what happens involves something in between them. When they are discussed in the context of a particular action, appearance change, and visual example, you will understand the terms better.

The terms furrow, wrinkle, and line are used to describe another aspect of the appearance of the skin as described in the following table:

LINE	A surface line with no depth, usually quite fine in terms of width. Some faces may show permanent surface lines; these may deepen to a wrinkle when certain actions occur.
WRINKLE	A line which has some depth and often has more width than a surface line; some faces may show no permanent wrinkles, but they will appear with certain actions. Other faces may show permanent wrinkles but they will deepen with certain actions.
FURROW	This term describes a place on the face where certain wrinkles may appear: lower eyelid furrow; infraorbital furrow; or nasolabial furrow (see Figure 1-1). In some faces there is no wrinkle or line in such a facial location until there is action. Some faces show a line permanently, but it will deepen to a wrinkle with certain actions, e.g., some faces show a permanent line in the lower eyelid furrow, infraorbital furrow or nasolabial furrow, which will deepen with an action.

Table 1-4: Terms that describe marks in the skin

These distinctions might not be clear now, but when you read Chapter 2, where these terms are used in context with visual examples, their meaning will clarify. You may find it useful to refer back to these definitions.

In discussing Intensity Scoring for an Action Unit, we explain how to score variations in the strength of the actions, which result in variations in the intensity of the appearance change. You will learn to score intensity, with the terms A, B, C, D, and E referring to how strong the action is, from barely detectable to the highest levels. In assessing the intensity of an AU, we use the following terminology to distinguish different levels of Action Unit involvement. An Action Unit can be totally uninvolved, or it can be involved to the following degrees:

.Trace..Slight...Marked...Pronounced...Severe...Extreme..Maximum.

The meaning of this scale of evidence will become apparent as you study the FACS illustrations in each chapter. You will learn what is meant by trace, slight, etc., in practice scoring where you will apply this scale. We provide intensity scoring criteria for each AU and explanations with behavioral examples that establish what we mean.

The chapters that describe AUs discuss the differences among them, their inter-relationships, and how the co-occurrence or simultaneous presence of AUs can affect the detection and scoring of an AU. For example, one AU can affect the appearance or mask the presence of another AU. In such situations, the AU that obscures another AU is referred to as the dominant AU, and the obscured AU as the non-dominant or subordinate AU¹. These issues are usually found in descriptions of appearance changes due to an AU and in tables of subtle differences between AUs and AU combinations. Another issue is alternative scores, when it is up to you to choose which AU best describes the appearance change. These relationships are explained further near the end of this chapter and are applied to specific AUs in tables at the end of chapters.

Other terms describe separate aspects of scoring. The apex of an action is the point of greatest excursion or change within that action. For example, if an Action Unit raises the inner corner of the eye brow, the apex is the moment when the greatest raise first occurs. The apex is not an absolute amount of change, but the greatest change that occurs for a particular Action Unit in a particular instance or event. It is when the action is strongest for that event. In some research, the first frame when apex is reached is noted; in other scoring, the duration of the apex, before the action begins to decline, is measured. Scoring of unilateral actions, where the action occurs on only one side of the face, uses the abbreviation "L" for left and "R" for right placed in front of the AU number. To indicate a unilateral score, but without indicating the side on which the action occurs, a "U" prefix is used (e.g., a wink is U46). The asymmetry of an action, where the action occurs on both sides, but is stronger on one side of the face than the other, is noted simply by the "A" prefix, but also has a more detailed scoring notation. Unilateral and asymmetry scoring is explained fully in Chapter 11.

¹

In the first edition of this manual, there were many scoring rules based on the consideration of dominance that were designed to improve scoring reliability. Further experience with FACS showed that these co-occurrence rules were unnecessary and hard to follow, and most were formally eliminated in 1992 and are not found in this edition.