Actually, the 10% of the brain thing is a cultural myth.
We use a much larger percentage—in the 90%’s IIRC . . . Greater imaging technologies have confirmed it repeatedly.
That 10% came from a spurious broadside guess/illustration by a famous person—I forget who. It never was based on any research even initially.
Except in the case of Rush Limbaugh who has half his brain tied behind his back to make it fair. Just sayin’