As a first step towards developing an effective audio analogue, let us examine communication through the printed page. The printed page is passive: it is a two-dimensional visual display with marks on it. The person reading the printed page can either scan the material linearly or browse through parts of the document. Visual layout (the way the marks appear on paper) enables such browsing. Thus, rather than laying all the text in a naive manner on the page, we exploit concepts such as line and paragraph breaks to allow the reader to perceive chunks of the printed matter and to selectively read specific portions of the text being presented.
The dpower of the printed medium lies in the eye's ability to browse text laid out on a two-dimensional display. When reading a paper, we are able to skim through the text, focusing on paragraphs of interest, and quickly scan across to the bottom of a page when we see a reference being made to a footnote.