AU15 — Lip Corner Depressor
The Action Unit produced by the depressor anguli oris, which pulls the corners of the mouth downward — a primary signal of sadness or displeasure.
AU15 lowers the lip corners and is one of the most reliable visible markers of sadness, often appearing in combination with AU1 and AU4. It can also indicate disappointment, disagreement, or empathic response to another person's distress.
AU15 is widely tracked in healthcare empathy training, customer-experience analytics, and behavioral research.
Related terms: action unit, au1 inner brow raiser, au4 brow lowerer
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