Since mathematicians tend to be experts in mathematics, and not on how their brains process mathematics, I think this question will quickly degenerate into a bunch of anecdotes and get very discussion-y. In other words, I think this belongs on a (mathematics) blog, or on a forum for different professional, and not on MO.
It would also be a perfect question for AfternoonTea, though who knows if that's going to happen or not.
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