It might educational systems at play here. I've never been to China, and have no idea if this is wide-spread — I saw a documentary on children in China being t

It might educational systems at play here. I've never been to China, and have no idea if this is wide-spread — I saw a documentary on children in China being taught mathematics at an early age using an abacus. Eventually, they remove the abacus but the child still mimes using it. And then gradually this disappears too. Essentially they're training their muscle-memory to do their maths for them. It was quite extraordinary to see, especially since I, while I flatter myself I'm reasonably intelligent in some areas, and worked in programming and related areas for many years, my ability to do any maths without a pencil and paper is abysmal. OTOH, it's not impossible I have un-diagnosed dyscalculia.