Facial expression
A visible configuration or movement of the face that communicates emotion, intention, or other social information.
Facial muscles: The muscles that move facial skin and features, producing expressions and other movements. Their coordinated contractions create the visible movements that make up an expression.
Emotion: A coordinated state involving subjective experience, physiological change, expression, and action tendencies. Expressions can be outward signals of emotional states, but do not reveal them infallibly.
Charles Darwin: The English naturalist who developed the theory of evolution by natural selection. His 1872 book argued that emotional expressions have evolutionary origins and cross-cultural similarities.
Basic emotion theory: A family of theories proposing a limited set of biologically grounded, distinct emotions. It links recurring facial patterns to discrete emotion categories.
Facial action coding system: A system for describing facial movements in terms of observable muscular actions called action units. It decomposes expressions into measurable movements without assuming what they mean.
Nonverbal communication: Communication through signals other than spoken or written language, including gesture, posture, and facial movement. Facial expression is one channel within this broader system of social signaling.
The Expression of the Emotions in Man and Animals: Charles Darwin's 1872 book examining the expression of emotions in humans and other animals. It established an influential evolutionary account of facial and bodily expression.
Theory of constructed emotion: A theory that emotions are constructed from brain predictions, bodily signals, and learned concepts. It challenges the idea that each emotion has a fixed, reliably diagnostic facial signature.
Facial feedback hypothesis: The hypothesis that facial movements can influence emotional experience. It proposes that expression may affect emotion as well as communicate it.
Facial gesture: A deliberate or conventional facial movement used to convey meaning or manage interaction. Some expressions function as communicative gestures rather than direct displays of emotion.