The following is from p. 40 of “How to Read a Book“, by Mortimer Adler and Charles Van Doren. Note that the author points out that speed reading is often benefitial to inspectional reading, but not always to analytical reading.
Fixation and Regression
Speed reading courses properly make such of the discovery–we have known it for half a century of more–that most people continue to sub-vocalize for years after they are first taught to read. Films of eye movements, furthermore, show that the eyes of young or untrained readers “fixate” as many as five or six times in the course of each line that is read. (The eye is blind when it moves; it can only see when it stops.) Thus single words or at the most two-word or three-word phrases are being read at a time, in jumps across the line. Even worse than that, the eyes of incompetent readers regress as often as once every two or three lines–that is, they return to phrases or sentences previously read.
All of these habits are wasteful and obviously cut down reading speed. They are wasteful because the mind, unlike the eye, does not need to “read” only a word or short phrase at a time. The mind, that astounding instrument, can grasp a sentence or even a paragraph at a “glance”–if only the eyes will provide it with the information it needs. Thus the primary task–recognized as such by all speed reading courses–is to correct the fixations and regressions that slow so many readers down. Fortunately, this can be done quite easily. Once it is done, the student can read as fast as his mind will let him, not as slow as his eyes make him.
There are various devices for breaking eye fixations, some of them complicated and expensive. Usually, however, it is not necessary to employ any device more sophisticated than your own hand, which you can train yourself to follow as it moves more and more quickly across and down the page. You can do this yourself. Place your thumb and first two fingers together. Sweep this “pointer” across a line of type, a little faster than it is comfortable for your eyes to move. Force yourself to keep up with your hand. You will very soon be able to read the words as you follow you hand. Keep practicing this, and keep increasing the speed at which your hand moves, and before you know it you will have doubled or trebled your reading speed.