Three is a different kind of middle. It’s the logarithmic middle, which means it’s a middle with respect to multiplication rather than addition: 1 × 3 = 3; 3 × 3 = 9. You can go from one to nine either by adding equal steps of four or multiplying by equal steps of three. So the “multiplication middle” is three, and that is what humans do by default, until we are taught otherwise.
