Why Do We Furrow Our Brows When Concentrating?

Watch someone solve a tricky puzzle, read a dense email, or line up a difficult shot in a game. There’s a good chance their brows will drift down and together, forming that small, serious frown between the eyes.

Most people do it. Almost nobody decides to. So why does concentration show up in the middle of our foreheads?

Meet the muscle behind the frown

The main muscle at work is the corrugator supercilii, a small muscle that sits just above the inner end of each eyebrow. When it contracts, it pulls the brows down and toward each other. A neighboring muscle, the procerus, works alongside it at the top of the nose.

Together, these muscles create the vertical creases between the brows that dermatologists call glabellar lines. You may know them by their nickname, the “11s,” because of their shape. A 2024 paper in the Journal of Cosmetic Dermatology describes the typical frowning pattern as vertical wrinkles formed by the contraction of the corrugator supercilii and procerus muscles.

Your face keeps track of effort

Researchers who study the body’s responses to thinking (psychophysiologists) can measure tiny muscle movements in the face using sensors on the skin, a technique called facial electromyography, or EMG. The corrugator has turned out to be especially interesting to them.

In a 1993 study published in Psychophysiology, researchers A. van Boxtel and M. Jessurun recorded facial muscle activity while people completed a demanding reaction-time task. Activity in the brow muscle, along with muscles in the forehead and lower lip, rose as the task got harder. The authors concluded that this activity could serve as a sensitive index of the mental effort a person was putting in.

More recent work has looked at what happens when a task involves conflict, the kind you feel in the classic test of naming the ink color of a word that spells out a different color. Using conflict tasks of this general type, a 2020 study by Berger and colleagues found that corrugator activity increased after conflict moments in some of their experiments, and interpreted it as a sign of the mildly unpleasant signal that conflict creates. Interestingly, the effect didn’t appear reliably in every version of their task, which is a good reminder that faces are complicated.

These are laboratory studies with specific tasks, so they don’t tell us exactly what any one person’s face is doing while they scroll. But together they point to a simple idea: when something takes effort, the brow often responds, whether or not we notice.

Why screens make it more likely

A lot of what we do on our phones involves exactly the kind of effort these studies describe:

• Reading long messages or articles in small type
• Working through emails, documents, and to-do lists
• Playing games that reward fast decisions
• Searching for something specific in a crowded feed

Add a squint at small text or a bright screen, and you have a face that’s working pretty hard while the rest of you is sitting still.

Is brow furrowing a problem?

Not in itself. Expressions are part of how we think, feel, and communicate, and a furrowed brow is a perfectly normal one.

What some people want to notice is the held frown, the one that settles in during a long session and stays there. Sometimes that’s simply about comfort, since a tense face can feel tiring. For others it’s about appearance, because repeated expressions are one of several things linked to lasting lines over time. We go into that more in Facial Expressions, Frown Lines, and Everyday Habits.

How to soften a furrow

Letting go of brow tension is easy once you catch it. Try this the next time you notice your forehead working:

1. Exhale slowly. A long breath out is a natural cue to release tension.
2. Let your brows drop and widen. Imagine the space between your eyebrows getting a little wider.
3. Soften your gaze. Let your eyes relax rather than staring hard at one spot.
4. Check your setup. Is the text too small, or the screen too bright? A quick fix can remove the reason for the frown.
5. Do one thing at a time. Juggling several tasks can add effort. If you can, finish one thing before starting the next.

Catching it in the moment

The tricky part, again, is noticing. Squintly tracks brow furrowing separately from eye squinting, so you can see which habit shows up more for you. When it notices sustained brow tension while you’re using your phone, it sends a gentle vibration, your reminder to let your forehead rest. Over time, its activity insights can help you spot the moments when the furrow tends to appear.

Your brows are working hard on your behalf. Every so often, it’s nice to let them take a break.

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This article is for general information and isn’t medical advice.