What super quick, small changes in someone's face does an expert notice to know their true feelings and adjust their own plan in that very moment?

An expert identifies super quick, small changes in someone's face, primarily focusing on microexpressions and subtle facial shifts, to discern true feelings. A microexpression is an involuntary, extremely brief facial display, lasting typically between 1/25 and 1/5 of a second, which reveals a genuine emotion a person may be trying to conceal. Subtle expressions are less intense but still short-lived muscle movements that indicate underlying emotion. These observations are based on the Facial Action Coding System, which categorizes individual muscle movements into "Action Units" (AUs). An expert rapidly scans specific facial regions for these AUs.

In the forehead and brows, the inner corners of the eyebrows pulling upwards (Action Unit 1) signals sadness or distress. The entire brow raising (Action Unit 2), often with the eyes widening (Action Unit 5), indicates surprise. The eyebrows drawing together and down (Action Unit 4) suggests anger, concentration, or frustration.

Around the eyes, tightening of the lower eyelids and raising of the cheeks, creating "crow's feet" (Action Unit 6), indicates genuine enjoyment (a Duchenne smile). The upper eyelids raising significantly, exposing the whites above the iris (Action Unit 5), is a marker for fear or intense surprise. Tension in the eyelids, sometimes with a slight squint (Action Unit 7), can denote anger or focused effort.

The nose wrinkling (Action Unit 9) and the upper lip raising (Action Unit 10) are key indicators of disgust.

In the mouth and lips, the corners of the lips pulling back and up (Action Unit 12) signifies happiness. However, without Action Unit 6, it may not be a genuine smile. One side of the lip corner pulling up in a smirk (Action Unit 14) often indicates contempt or superiority. The corners of the lips pulling straight down (Action Unit 15) indicates sadness. The lower lip pushing up and out (Action Unit 17) suggests sadness or doubt. Lips pressing tightly together (Action Unit 23) indicates anger, frustration, or determination. The jaw dropping (Action Unit 26) is a strong sign of surprise.

The expert rapidly processes these specific, momentary shifts, recognizing patterns of AUs that correspond to core emotions: anger, fear, disgust, sadness, joy, surprise, and contempt. By detecting these involuntary emotional leakages, especially when they contradict a person's verbal statements or consciously displayed emotions, the expert gains insight into the person's true emotional state. This immediate, factual understanding of underlying feelings allows the expert to instantly adjust their communication, strategy, or approach in that very moment to better align with the other person's actual state, manage the interaction effectively, or achieve their objective.