ABSTRACT
Our faces are moving most of the time — we don't keep them still for long. These movements fall into two different broad types — rigid movements that don't alter the shape of facial features (for example, movements of the head), and non-rigid movements of the facial features themselves (moving the lips, widening the eyes, raising an eyebrow, and so on). Rigid movements of the head (and, independently, the eyes) often signal the direction of social attention, a topic that has become so important in its own right that we will consider it in a separate chapter. Here, we will primarily be concerned with social signals conveyed through nonrigid facial movements, the most obvious of which are speaking and using our faces to signal moods and feelings.
