The model indicates that the development of the oracy skills of speaking and auding are built upon the prior development of prelinguistic knowledge through information processing activities. It is important that it be understood that this early, prelinguistic cognitive content, or knowledge, will form the foundation for the acquisition of new knowledge over the person's lifetime, including that knowledge known as "literacy."

Much of this knowledge will remain personal, and will not be explicitly represented in language for communication to others. Nonetheless, such personal, tacit knowledge, which includes perceptual [earnings and general knowledge of "how the world works," will be absolutely necessary for learning to comprehend the spoken, and later the written, language. This reflects the fact that language is selective in the features and concepts chosen to be represented. We may think of language as producing a verbal figure, which can be comprehended only in terms of its relationship to a nonlinguistic conceptual ground of "world knowledge." A simple illustration of the role of "world knowledge" in literacy training is seen in the recommendation to give students experience with objects and events in the world through field trips, demonstrations, movies, etc., before they read about them. This approach provides an experiential base or a "world knowledge" which will permit a deeper comprehension of the words and concepts the students read, and greater "access" to prior knowledge via perceptual learning.

A final aspect of the model is that it recognizes that, on the one hand, the literacy skills of reading and writing utilize the same knowledge base that is used in auding and speaking, plus the special decoding and encoding skills of reading and writing. On the other hand, the very nature of the written language display -- characterized by being more or less permanent, being arrayed in space, and utilizing the features of light (color, contrast) -- makes possible (i.e., affords) the development of skills and knowledge entirely different from those involved in oral language.

The model incorporates the role of prelinguistic looking and marking abilities as contributors to later utilization of the visual display of written language in conjunction with graphic marks such as lines, white space, and color to develop graphic tools for thinking and problem solving like matrices, flow charts, color coded graphs, and so forth. These tools combine with written language and non-language graphic symbols, such as arrowheads and geometric figures, to produce analytical products beyond those obtainable through the fleeting, temporal, oral language.

A point to be emphasized is that much of the acquisition of literacy is not simply learning to read; that is, it is not just learning a graphic language system that can be substituted for the oral language system. Rather, a large part of learning to be literate, and perhaps the most important part for acquiring higher levels of literacy, is learning how to perform the many tasks made possible by the unique characteristics of printed displays -- their permanence, spatiality, and use of light, and using that knowledge to develop large amounts of new knowledge (see the discussion of the Army's Beta test in Part I to learn how "literacy," considered here as reasoning while engaged in visual information processing in working memory, was used by military psychologists to assess "intelligence" without having the person access much information in long term memory).

The foregoing, and Figure 2 briefly summarize the structure of the developmental model of literacy and emphasize:

• An architecture for a human cognitive system that contains a long term memory (knowledge base) and a working memory. The mind draws upon certain procedural knowledge, including language, that is in the long term memory and uses that procedural knowledge for processing information taken both from the long term memory and from the external world. The latter serves as a sort of "external memory" that displays information to be picked up by the sensory systems and internal processing skills and merged with prior knowledge in the process generally called "learning."