The taxonomy
of the face.
Building on Darwin, Paul Ekman and Wallace Friesen catalogued every distinct movement the human face can make and assigned each one a number. Forty-six muscle groups, hundreds of combinations, seven universal expressions every human face produces regardless of culture.
Inner Brow Raiser
FRONTALIS (MEDIAL)
Reads as appeal — something internal is being offered for the other person to notice. Pairs with AU 4 in sadness, AU 5 in surprise.
Outer Brow Raiser
FRONTALIS (LATERAL)
Surprise, fear, performative interest. The brow that lifts at the news anchor. Easy to fake, hard to sustain.
Brow Lowerer
CORRUGATOR SUPERCILII
Concentration, suspicion, anger. The most common baseline AU — many people hold a slight AU 4 by default and read as critical without knowing it.
AU 5
PAIRS · AU 1 · AU 2 · AU 26
Upper Lid Raiser
LEVATOR PALPEBRAE SUPERIORIS
Eyes opening past their resting line. Surprise, fear, intense interest. In poker players, the involuntary tell.
Cheek Raiser
ORBICULARIS OCULI (PARS ORBITALIS)
The Duchenne mark. The eye-corner crinkle that proves a smile is real. Cannot be summoned at will by most people. Its presence is the difference between social warmth and felt warmth.
Lid Tightener
ORBICULARIS OCULI (PARS PALPEBRALIS)
The narrowed eyes of someone calculating, working out a lie, or refusing to release attention. Often holds during silence, drops the moment they speak.
AU 9
PAIRS · AU 15 · AU 17
Nose Wrinkler
LEVATOR LABII SUPERIORIS ALAEQUE NASI
Disgust. The single AU that almost never blends — when you see it, the person is repulsed by something specific. Often momentary.
Lip Corner Puller
ZYGOMATICUS MAJOR
The mouth half of a smile. Without AU 6, it reads as polite, posed, social. With AU 6, it reads as felt. Both are useful — they just say different things.
Lip Corner Depressor
DEPRESSOR ANGULI ORIS
The downturn at the mouth corners. Sadness, disappointment, dignified loss. In sustained form it becomes a baseline tell of a person carrying weight they will not name.
AU 17
PAIRS · AU 9 · AU 15
Chin Raiser
MENTALIS
The pucker under the lower lip. Doubt, contempt, the small involuntary mark of disagreement before words arrive. Often visible right before someone politely rejects a proposal.
PART TWO · THE SEVEN UNIVERSAL EXPRESSIONS
Seven faces every human makes.
Across cultures, languages, and even isolated populations, Ekman documented these seven facial expressions as cross-cultural constants. Their AU encodings, their giveaway tells, and how to read them in someone else.
Cheek raiser + lip corner puller. Eye crinkle is the tell.
AU 12 alone is social. AU 6 + AU 12 is felt. Most posed photographs lack AU 6. When you see AU 6 in a still image you are seeing someone who was actually amused at the moment of capture.
Inner brow raise + brow lowerer + lip corner depressor.
The signature is the contradiction in the brow — both pulled together (AU 4) and lifted at the inner edge (AU 1). It is the face that says I am working hard not to show this. Often visible for less than half a second.
AU 1 + AU 2 + AU 4 + AU 5 + AU 20
Brows up and together, eyes wide, lips stretched horizontally.
The most distorted of the seven. AU 20 (lip stretcher) is what separates fear from surprise — the mouth pulls sideways rather than dropping open.
AU 4 + AU 5 + AU 7 + AU 23
Lowered brow, raised upper lid, tight lid, pressed lips.
Anger lives in the eyes more than the mouth. AU 4 + AU 7 together — brow down and lid tight — is the hold-back face of contained anger. The lip press (AU 23) is the rest. When that lip press releases, words arrive.
Nose wrinkler + lip corner depressor + lower lip depressor.
The shortest-lived of the seven. AU 9 alone is enough to register. Often involuntary and almost always specific — the person is reacting to a thing, not a state.
AU 1 + AU 2 + AU 5 + AU 26
Brows up, eyes wide, jaw slightly dropped.
Genuine surprise lasts under one second. If the expression holds for two or more, it is performed. The held-open mouth at the end of a long story is theatre.
One-sided lip corner pull. The only asymmetric universal expression.
The most diagnostic of the seven. A single-side lip pull is contempt. Useful in negotiation: if you watch for it, contempt is often visible on the face of the side that has decided you are beneath the deal — even while the rest of their face stays cooperative.