Ordinary mathematical writing is two-dimensional. In $\frac{x+1}{2}$, what is above the bar is divided by what is below it; in $x^2$, the $2$ is up high and therefore an exponent; in $\sqrt{x+1}$, the stroke of the root covers exactly what is inside. Position is part of the sign, like the place of a digit in a numeral. The eye reads all this at once. But what about someone who does not read with the eye?