The eye is certainly capable of moving to any point on the page extremely rapidly. Yet, when we browse, we do not move about randomly around the printed page. Typically, we move to the next paragraph, next line, or previous word. This seems to indicate that the eye infers some structure in the printed document, which is used to move around effectively. Since each of these actions are being performed extremely rapidly, owing to the eye's inherent scanning ability, these atomic actions are difficult to pinpoint.
We therefore conjecture the following:
Every well-formatted document presents inherent
logical structure, which the eye is capable of perceiving. All
visual browsing actions
can be characterized as
movements around this structure.