NoticelyThe seven basic facial expressions and their cues (FACS)
The Facial Action Coding System (FACS) describes faces as small muscle movements called action units. Seven commonly studied emotions are linked to typical combinations: raised lip corners and cheeks for happiness, high brows and a dropped jaw for surprise, wide eyes for fear, raised inner brows for sadness, lowered brows and tense lids for anger, a wrinkled nose for disgust, one tightened lip corner for contempt.
§ 1What FACS is
The Facial Action Coding System was published by Paul Ekman and Wallace Friesen in 1978 and revised in 2002. It does not describe emotions. It describes movements: each visible change produced by the facial muscles gets a number, called an action unit (AU). AU1 raises the inner ends of the brows, AU4 lowers the brows and draws them together, AU12 pulls the lip corners up. Coders record which units moved and how strongly, on a scale from A (trace) to E (maximum).
Researchers then asked which combinations of units people associate with particular emotions. The answer is a reference model, not a law: it describes typical posed expressions that observers label consistently, mostly in Western samples.
§ 2The seven expressions at a glance
| Emotion | Typical action units | What you see |
|---|---|---|
| Happiness | AU6 + AU12 | Lip corners pulled up and back; in stronger smiles the cheeks rise and lines appear at the outer eye corners. |
| Surprise | AU1 + AU2 + AU5 + AU26 | Whole brows raised high in a curve, eyes a little wider, jaw dropped loosely. |
| Fear | AU1 + AU2 + AU4 + AU5 + AU20 | Brows raised but straighter and drawn together, white showing above the iris, lips stretched sideways. |
| Sadness | AU1 + AU4 + AU15 | Inner ends of the brows raised and drawn together, lip corners down, chin sometimes pushed up (AU17). |
| Anger | AU4 + AU5 + AU7 + AU23/24 | Brows lowered and pulled together, a hard stare, tense lower lids, lips pressed or narrowed. |
| Disgust | AU9 and/or AU10 | Nose wrinkled, upper lip raised; the brows come down a little as a side effect. |
| Contempt | AU14 on one side | One lip corner tightened and slightly raised; the eyes stay neutral. |
§ 3Where to look: eyes or mouth?
Different emotions are carried by different parts of the face. When Wegrzyn and colleagues (2017) revealed faces patch by patch, fear, anger and sadness depended most on the eyes and brows, happiness and disgust on the mouth and nose, and surprise on both. The most useful single cue for fear was the raised upper lid (AU5); for anger it was the tightened lower lid (AU7).
This matters because many people look mainly at the mouth. Checking the brows and upper lids first catches the expressions that the mouth does not show.
§ 4Subtle and partial expressions
Real expressions are often weak or involve only one region. Matsumoto and Hwang (2014) showed 273 observers 110 subtle expressions with nine answer options. Average accuracy was 59%, far above the 11% expected by chance, and partial versions, such as only the lip corners for happiness or only the raised inner brows for sadness, were still recognised above chance. Contempt was hardest, at about 32%.
§ 5A note on “genuine” smiles
A popular rule says that a smile with raised cheeks and crinkled eye corners (AU6, the “Duchenne” smile) is always genuine. Research does not support the rule. Girard and colleagues (2021) found that the cheek raise mostly tracks how strong a smile is, and it appeared in most smiles whether or not people reported feeling positive. People can also produce it on purpose. The cheek raise tells you about intensity, not sincerity.
§ 6Limits of the model
Faces and feelings are only loosely linked. A large review by Barrett and colleagues (2019) concluded that the same facial movements can mean different things depending on the situation, the person and the culture. People across cultures recognise these expressions above chance, but more accurately within their own culture (Elfenbein and Ambady, 2002). Treat the seven expressions as a shared vocabulary for describing faces, not as a way to read minds.
Questions and answers
What are the seven basic emotions?
In facial expression research the seven most commonly studied are happiness, surprise, fear, sadness, anger, disgust and contempt. The list is a research convention; scientists still debate how “basic” these emotions are.
What is an action unit?
A single visible facial movement in FACS, numbered by the muscle action that produces it. For example, AU12 pulls the lip corners up and AU4 lowers the brows.
Which expression is the hardest to recognise?
Contempt. It is one-sided and subtle, and in research it is the least consistently recognised of the seven.
Are facial expressions universal?
Partly. People in many cultures recognise them above chance, but accuracy is higher within one’s own culture, and context can change how a face is read.