When that happens read those few words. You can quickly recognise if it answers one of your questions. That is when you notice a certain 'T' or whatever, a quick read of the words that follow is in order. It could something new or even highly important that your mind is pulling you in for. It sounds to me like that is one of you inner minds tricks, to pull you into reading. There can be others. That is the whole idea of superreading noticing what attracts your attention. In the beginning you may not get perfect results, if you keep following the pattern of going in for a dip when you notice or are attracted by something, you train both the inner mind and conscious mind how to pull out the answers or what is important quickly.
The straigh down the middle scan is one of the techniques of superreading and dipping. There are other method. Skittering techniques, where you develop your own way of quickly looking over the text on a page is another. It could be something like the backward S, where your eyes just curve over the page tracing a S or Z pattern. Sometimes I'm moved to zig zag each paragraph orther times the whole page. I've even just glanced down the middle and circled back...
I might be at the end of the page and something draws me back to dip. It works much better when you find your own way to superread.
Scanning down the center of the page is the starting point. Notice what happens do what works and let go of what doesn't. 
Alex
