What is a reader looking for when he is scanning print? In some cases subheadings -- often in a larger, darker typeface -- inform him that there is something of interest; at other times he may be scanning the text for an interesting word or phrase (either one he has in mind or one that will just catch his eye); sometimes he wants a quick idea of what the whole text contains -- and then he may never read it again, or he may go back and read all or part of it closely.
For a hypertext environment that follows something like an architectural metaphor (i.e., one consisting of virtual rooms), a map can provide an overview. However, while the user is moving within the environment, there is essentially no way to scan ahead.
The practice of scanning for later references to a word or phrase is made unnecessary when a link from "robots," for example, will take the user to other information about robots. If there is no link, the user can assume there is no more about robots in this cluster of information, and no one has provided a "hallway" or door to another cluster elsewhere.
A hypertext chunk can be construed as a room containing several objects (or links) for examination. An astute use of rooms, or chunks, may make scanning seem unnecessary -- but only if the user does not become trapped in a long linear sequence.
Lacking the option to scan, the user needs to be able to jump in and out of the linked environment and check the overview, or map, to see whether there are still things of interest here.
The screen environment is not well suited to the kind of scanning we use in print environments. Hypertext does not re-create a print environment on a screen; rather, it offers a wholly different way of moving through and among texts. Because of this, hypertext can vastly improve the usability of texts within a screen, or frame, structure. But because the screen is so different from print, it must be understood that hypertext requires a different handling of text.