Expression implies a revelation about the characteristics of a person, a message about something internal to the expresser. In the context of the face and nonverbal communication, expression usually implies a change of a visual pattern over time, but as a static painting can express a mood or capture a sentiment, so too the face can express relatively static characteristics (sometimes called physiognomy). The concept of facial expression, thus, includes:
- a characteristic of a person that is represented, i.e., the signified;
- a visual configuration that represents this characteristic, i.e., the signifier;
- the physical basis of this appearance, or sign vehicle, e.g., the skin, muscle movements, fat, wrinkles, lines, blemishes, etc.; and
- typically, some person or other perceive that perceives and interprets the signs.
Facial expressions are an important channel of nonverbal communication. Many animal species display facial expressions, but expressions are highly developed particularly in the primates, and perhaps most of all, in humans. Even though the human species has acquired the powerful capabilities of a verbal language, the role of facial expressions in person-to-person interactions remains substantial. Messages of the face that provide commentary and illustration about verbal communications are significant in themselves.
Other types of expressions provide another, different mode for understanding the private, hidden side of the inner person, a side which may not be accessible in the form of verbalization For example, the facial behaviors related to emotion can reveal part of the feeling side of a person's private life. Such emotion indicators range from stereotyped, full-face expressions that are obvious to fleeting, partial-face movements that are hard to see.
Facial Expression Has Many Messages And Multiple Sources
The expression of a given face at a specific time is conveyed by a composite of signals from several sources of facial appearance. These sources include the general shape, orientation (pose), and position of the head, the shapes and positions of facial features (e.g., eyes, mouth), coloration and condition of the skin, shapes of wrinkles, folds, and lines, and so forth. Some of these sources are relatively fixed; others, more changeable. The most important source of change in facial expression is the set of muscular movements produced by facial muscles, which provide the most substantial changes in facial appearance over short time duration and contribute most to nonverbal communication by the face. Other shorter term origins that may contribute to expressions are blood flow and glandular secretions. As a generalization, muscular activity contributes expressive variation on a background of more slowly changing or static expressive sources. These latter sources include the sizes, positions, and shapes of fleshy tissues, hair, teeth, cartilage, and bones.
Multiple Messages In Nonverbal Communication
Corresponding to the several sources of expressive information in the face are the many nonverbal communication messages that the face can provide. Some of these messages are validly related to characteristics of the person behind the face, some are fabrications of the viewer unrelated to the real person, and others lie somewhere between these two extremes. Much of the research on the face is centered on discovering the messages that fit into these different categories. Another perspective on the range of facial messages is to consider objective description, such as a list of physical anatomical measurements, as an anchor for veridical information, and ever more abstract generalizations or inferences about characteristics more remote from these specific observations becoming increasingly difficult to verify.
A further difficulty for interpreting the face is that the appearances produced by one source of facial information can interact with another, producing a mixture, as mentioned above, that can hide, mask, or interfere with the messages conveyed by each source. The structure of facial nonverbal communication is complex.