Dunno. I do think it's important to distinguish between the procedural knowledge of arithmetic and the logical reasoning of algebra and beyond of mathematics.
Watching my kids operate, I've always attributed DD's extraordinary mathematics ability to her verbal ability, and DS's extraordinary math ability to some sort of black magic. Neither kids' math scores seem predicted by their IQ index scores. Their PRI scores are high, but not nearly as high as Broad Math.
I can see how WM should be important in arithmetic, but my kids' scores in that are are closer to average, but we haven't seen any impact on arithmetic.
