You know how people, when interested in something, will lean forward, even if that doesn't really change anything about their ability to see what it is they are

You know how people, when interested in something, will lean forward, even if that doesn't really change anything about their ability to see what it is they are interested in? I believe reclining convinces your brain that you are ready to sleep, or at least relax, which means it is not in that "activated interested" mode any more than you could be when lying in bed or on the beach. There is a difference in productivity between passive and active interest, so you should be able to use the feedback loop to your advantage. Remember all those teachers begging you to stop slouching? It's that. It's similar to forcing yourself to smile, until you actually start to feel a little happier. Your body not only gives off clues of your internal state, but your brain also takes clues for what your internal state should be. If you are letting your body kick back and slack off, what is your brain to perceive about the work at hand?