Why do I grimace when I concentrate?

The parts of your brain that do your abstract thinking are very tightly interconnected with the parts that control your muscles. In fact, some of that abstract thinking is done by the same brain regions that control your muscles. We don’t yet know why a specific brain region produces a given specific thought, but the overall pattern is clear: you grimace when you concentrate because in your brain (and in a lot of other peoples’ too), the brain regions controlling your facial muscles are also focusing your attention.

My musician friends use the term “jazz face” to describe the sometimes ridiculous expressions they have when they’re most deeply immersed in the music. Think also of Michael Jordan sticking his tongue out in the heat of play. And consider the fact that some people need to pace in order to think, or gesticulate, or perform repetitive manual tasks like knitting or splitting wood.

Original post on Quora