Raising Eyebrows by Brad J. Guigar

The mouth makes a face pleased or displeased and the eyes control the overall intensity of the expression. But this leaves an entire range of emotion, aggression, untouched. Although it would seem that eyebrows are directly linked to the eyes, they play a completely different role. The eyebrows regulate the amount of aggressiveness — or lack thereof — displayed on the face.

Interestingly, the closer the eyebrows are to the eyeballs, the more focused the overall emotion. When the eyebrows drift away from the eyes, the emotion loses focus and a neutral expression becomes quizzical or surprised.

Arched Down/Slanted Up Eyebrows

Eyebrows that slant downward toward the middle specify aggression. A formerly happy face grins with evil once the eyebrows arch. Similarly, a frown becomes an expression of anger.

Eyebrows that curve upward toward the middle of the forehead indicate the opposite of aggression. This feature makes the expression passive. This is useful for expressing an apologetic or helpless expression. If you'll notice, cartoon eyebrows can curve upward in two ways — as U shapes and as curved arches. Both modify the entire expression toward the passive, but the U-shaped brows seem to be more apologetic.

Straight Eyebrows

Eyebrows that form a straight line across the forehead are neutral. Sometimes the expression is so bland that two eyebrows merge into one. Paired with other neutral features, this helps to create a look of boredom. Eyebrows, like the mouth, tend to disappear when they're expressing a neutral emotion.