My eldest was more overtly mathy as a small child (addition requiring fingers and toes while in her baby car seat so just before or just after 3 I would guess, as she was out of that seat by 3.5 or before). As much as IQ can be measured by a test she's a full SD less gifted than her sister, who was never the less much less naturally mathy, possibly through complete lack of interest. Though I suspect that they will both be better at problem solving than facts.