I went to medical school with a big hunk of a guy who never paid much attention at first year anatomy lectures but when asked whether he had read the assignment, could recite page after page of the textbook with perfect accuracy - he had a photographic memory. Of course when I asked him how he did it he couldn't tell me, except to say that ever since he was a kid, after he read something it was all right there in his visual memory, page upon page.
There were other kids in the class who didn't have a photographic memory but learned every last fact and could spit them back with commendable precision. My best friend, though, was tops. He would take class notes on one 3X5" card while the rest of us were scribbling like mad and filling a notebook.
At the end of what we thought might be the "key" lecture, the one from which the final exam was soon coming, Bill said,
"I got it all right here, Tom! Come over tonight and we'll go over it all for the exam." And he waved the inevitable 3X5 card before slipping it into his shirt pocket.