The nature of attention-direction, the way it moves and such, be it a choice or otherwise, is indeed mysterious. One phenomenon that you might consider is that

The nature of attention-direction, the way it moves and such, be it a choice or otherwise, is indeed mysterious. One phenomenon that you might consider is that when you direct your attention at one thing (be it a thought or whatatever) you become blind to other things. And this blindness is proportional to the intensity of the attention-directing.