Advocates of rich views of conscious experience, such as Searle (one of my graduate advisors) and William James think that there's a constant stream of conscious experience outside of attention -- that we have a constant peripheral consciousness of the hum of traffic in the background, of the feeling of our feet in our shoes, of subtle emotional conditions, etc. James (as he so often does) puts things beautifully:
The next thing to be noticed is this, that every one of the bodily changes, whatsoever it be, is felt, acutely or obscurely, the moment it occurs.... Our whole cubic capacity is sensibly alive; and each morsel of it contributesits pulsations of feeling, dim or sharp, pleasant, painful, or dubious, to that sense of personality that every one of us unfailingly carries with him (1890/1981, p. 1066-1067).
Advocates of thin views of consciousness (e.g., Dennett, Mack and Rock, Blackmore) deny this. When something is out of attention, it is generally not experienced -- not even in a secondary, peripheral way. One does not go through life constantly feeling one's shoes against one's feet. It's only when one thinks about one's feet that one experiences the tightness of one's shoes. It may seem that we have constant experience in our feet, but that's a "refrigerator light error": Just as a child might think the refrigerator light is always on because it's on whenever he checks it, so also someone might think we constantly experience our feet because we experience our feet whenever we think about whether there is experience in our feet.
This is a crucial, foundational issue in the study of consciousness, and in my view no one has given a satisfying argument one way or another on it. All arguments either rely upon doubtful (and conflicting) intuitive, armchair reports or they rely on experimental data that beg exactly the crucial question (by assuming one or another relationship between the reportability of a stimulus and whether it's consciously experienced).
The only way to get started addressing such a question, it seems to me, is to ask people about their experience -- but not about their current experience (which is subject to the refrigerator light problem). Rather, we should ask them to go about their normal business and then periodically interrupt them with questions like "were you, just then, experiencing your feet in your shoes or not?" But of course we can't follow people around: We should give them random beepers (a la Hurlburt) and prime them in advance to ponder one specific such question (was I having tactile experience in my feet? was I having visual experience?).
I did this. The results, are here -- in a rather long-winded paper, I'm afraid.
I'm also afraid that the beeper method is subject to all sorts of biases and distortions. But as far as I can see there is no better method for studying this question. (Suggestions welcome.)