There's also the question of what to learn. I don't know if this has really been proven but it seems to me that some people who seem to learn quickly are those

There's also the question of what to learn. I don't know if this has really been proven but it seems to me that some people who seem to learn quickly are those that have mastered the art of learning the minimum needed to accomplish their goal. And then there's those that go deep and venture into every nook and cranny of the subject and gather immensely more knowledge than what is needed for the task at hand.