A
facial expression is one or more motions or positions of the
muscles beneath the
skin of the face. According to one set of controversial theories, these movements convey the
emotional state of an individual to observers. Facial expressions are a form of
nonverbal communication. They are a primary means of conveying social information between
humans, but they also occur in most other
mammals and some other animal
species. (For a discussion of the controversies on these seemingly obvious claims, see Fridlund and Russell & Fernandez Dols.)