Kirby and Williams (1991) argue that the cognitive processing associated with reading passes through eight distinct and increasingly complex levels of abstractions: (a) features (components of letters), (b) letters, (c) sound or syllable units, (d) words, (e) phrases, (f) ideas, (g) main ideas, and (h) themes. At each level, items of information are recognized (simultaneous processing) and ordered (successive processing). In other words, both simultaneous and successive processing are required at each level.
1. Each letter consists of various features—vertical, horizontal or oblique lines, and semicircles.
2. The letter has to be recognized as a whole after its components have been put together successively. Uppercase letters (A, B) have to be distinguished from lowercase letters (a, b), yet the child must recognize that A = a, B = b. Thus, simultaneous processing is also required.
3. The various sounds of letters, especially vowels, have to be distinguished (simultaneous processing) and put together serially.
4. Words must then be read, either as whole patterns or as strings of phonemes (when the words are long or unfamiliar).
5. Meaning must be obtained from phrases; it is not enough to know the meaning of each individual word in phrases like hot-headed comment or bone-chilling cold. We need to understand their meaning in the context of other words in the phrase, and this requires both processes.
6. The ideas represented by words, phrases, and sentences need to be understood.
7. The ideas need to be sorted into main and secondary ideas. For example, what is the main idea in the sentence While walking on ice, he fell through it?
8. Finally, themes have to be identified in order to make sentences, paragraphs, and the entire text meaningful. “In small proportions we just beauties see”, when combined with “In short measures life may perfect be”, gives the reader a theme to understand the two sentences. Simultaneous and successive processing are both needed for comprehension, as are attention to the sequence and combination of words, and a plan to extract the meaning of the lines. Moreover, it the child does not have an adequate knowledge base, he or she may read the poem and understand each word but still miss its meaning.
In the case of a child who fails to learn to read, the failure is primarily due to a problem with successive processing, that is, the process that helps the child to sequence different items, letters, or words. A child cannot read if he/she cannot remember the exact sequence of letters in each word and then convert these words into speech. Thus, difficulties in successive processing may cause difficulties in acquiring and/or using phonological coding, which may, in turn, lead to reading failure.
On the other hand, when a child can read but struggles to under-stand what he or she is reading, the difficulty probably stems from weaknesses in simultaneous processing. Comprehension as an aspect of reading is very different from basic word decoding and is also more difficult to remediate.
The PREP approach seeks to identify the most important processing needs of the child and to concentrate remediation in those areas.
Thus, a PREP facilitator will focus on successive processing to develop decoding skills or, alternatively, focus on simultaneous processing to develop comprehension.
It is important to note, however, that no cognitive task requires one process alone. It is a matter of emphasis. Depending on the task requirements and individual preference, the child may focus most strongly on one of the processes.
To sum up, then, PREP provides:
• alternatives for children who cannot use simultaneous or successive processes well,
• experience and practice for children who have not developed simultaneous or successive processes, and
• specific training in recognizing which method is most efficient for a given task (Kirby and Williams, 1991).