Eyebrows raised and pulled together, upper eyelids raised exposing white, and the mouth is often open with lips stretched horizontally.
Creates oblique eyebrows, often associated with sadness or worry
Creates arched eyebrows, often seen in surprise
Creates frown lines between brows, associated with concentration or anger
Widens eye appearance, shows more of the eyeball
Creates tense, stretched mouth in fear
Passive movement from muscle relaxation
This expression maximizes sensory input. The combination of raised brows (AU 1+2), raised upper lids (AU 5), and an open mouth (AU 26) creates the characteristic "deer in the headlights" look.
These are the most commonly confused expressions because both involve wide eyes and an open mouth.