The lexiaProject GUI is based on key design premises drawn from traditional graphic design principles and a survey of the literature concerning traditional paper-based reading (within the realms of developmental, educational and cognitive psychology) and the design of electronic text delivery systems (within the domains of human-computer interactions, user interface design, educational multimedia and hypertext). Very briefly:
- Users have a wide range of reading abilities and strategies for approaching texts of various levels of difficulty. To grossly generalize: Better readers sometimes read grammatically related groups of words as a single thought unit (called a lexia
 ) versus reading one - word - at - a - time, they usually make fewer references to the surrounding text for support of meaning, and frequently maintain a relatively consistent pace while reading (often resorting to guessing or contextual meaning equivalents for difficult terms rather than slowing down).
- Most readers can only focus on a small part of a page or screen within each moment in time. I call this area of limited focus a "reading moment" to emphasize the temporal nature of reading.
- Elements that are not focused on during a reading moment (the surrounding text and interface elements) can be considered background noise when these elements are not being used to provide a sense of global context (e.g., referring to a scroll bar's thumb button to determine position within a document). However, since important contextual clues are often found in nearby text (e.g., who's he? or what's that?), we must be careful not to suppress too much of this type of noise or else we might unintentionally devalue the meaning of some words altogether.
- Although text that scrolls smoothly upward, as found in movie credits and teleprompter systems, closely mimics our own progress through a text, it may cause a kind of visual motion sickness called the "waterfall effect" during sustained viewing sessions. Rapid serial visual presentations (RSVP), where individual words flash in sequence, have tested well but seem deficient both in terms of control and of providing any sense of global context. Thus, I have attempted to marry the two concepts to create a vertical serial interface for reading.
- Readers have a wide range of physical abilities; both in terms of visually resolving on-screen text (based on eyesight and environmental conditions) and in terms of manipulating control devices such as a mouse or keyboard.
- The physical manipulation of a mouse or keyboard, which is required to interact with typical interface elements for navigation, is distracting to the user on a cognitive level. Simple events, such as scrolling (via scrollbars) or paging (via keyboard buttons) through a text document, require a cognitive shift from a reading mode to a task mode to a manipulation mode and then finally back to a reading mode. This modality shifting should also be considered a form of background noise.
- It is generally agreed upon by graphic artists that it's easier to read body copy set in a serif typeface (such as Times Roman) of larger point sizes that are set using relatively short measures (with fewer words before beginning a new line).
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