Still not convinced? Then try this experiment: Think about the taste of chocolate (that glorious silky rush of sweet earthy flavor) at the exact same time as you add 47 and 56. Really try. At the same time. If it makes your brain fuzzy in the way your mouth feels after you’ve had an unripe banana, you’re in good company: it’s impossible. You can switch back and forth really quickly, but you can’t actually think about both things at the same time.