Routes From Print To Sound

Suppose you were asked to read out the following list of words and non-words:

CAT FOG COMB PINT MANTINESS FASS You would probably find it a simple task, but it actually involves some hidden complexities. For example, how do you know that the "b" in "comb" is silent, and that "pint" does not rhyme with "hint"? Presumably you have specific information stored in long-term memory about how to pronounce these words. However, this cannot explain how you are able to pronounce non-words such as "mantiness" and "fass", because you do not have any stored information about their pronunciation. Perhaps non-words are pronounced by analogy with real words (e.g., "fass" is pronounced to rhyme with "mass"). Another possibility is that rules governing the translation of letter strings into sounds are used to generate a pronunciation for non-words.

This description of the reading of individual words is oversimplified. The study of adult patients whose reading skills have been impaired due to brain damage suggests that there are several reading disorders, depending on which parts of the cognitive system involved in reading are damaged. Some of the major findings from the cognitive neuropsychological approach are discussed in the next section.

Cognitive neuropsychology

Some of the processes and structures that may be involved in reading are shown in Figure 11.8. Ellis and Young (1988) identified these components on the basis of the study of acquired dyslexias (i.e., impairments of reading produced by brain damage in adults who were previously skilled readers). Only selected aspects of the cognitive neuropsychological account of reading will be presented here.

The most important message of Figure 11.8 is that there are three routes between the printed word and speech. All three routes start with the visual analysis system, which has the functions of identifying and grouping letters in printed words. We will consider each of the three routes in turn.

Route 1 (grapheme-phoneme conversion)

Route 1 differs from the other routes between the printed word and speech in making use of the process of grapheme-phoneme conversion. This process may well involve working out pronunciations for unfamiliar words and non-words in a piecemeal way by translating letters or letter groups into phonemes by the application of rules. However, not everyone agrees with this view. Kay and Marcel (1981) argued that unfamiliar words and non-words are actually pronounced by analogy with familiar words. They found that the pronunciations of non-words by normal readers were sometimes altered to rhyme with real words that had just been presented. For example, a non-word such as "raste" is generally pronounced to rhyme with "taste", but is more likely to be pronounced to rhyme with "mast" if preceded by the word "caste".

If a brain-damaged patient could use only Route 1 when pronouncing words and non-words, what would one expect to find in their pronunciation performance? The use of grapheme-phoneme conversion rules should permit accurate pronunciation of words having regular spelling-sound correspondences, but not of irregular words. If an irregular word such as "pint" has grapheme-phoneme conversion rules applied to it, it should be pronounced to rhyme with "hint"; this is known as regularisation. Finally, the graphemephoneme conversion rules can be used to provide pronunciations of non-words.

Patients who adhere most closely to exclusive use of Route 1 were labelled as surface dyslexics by Marshall and Newcombe (1973). Surface dyslexia is a condition in which patients have particular problems in reading irregular words. The surface dyslexic JC, could read 67 out of 130 regular words correctly, but he was successful with only 41 out of 130 irregular words. More striking findings were reported by Bub, Cancelliere, and Kertesz (1985). Their patient, MP, read non-words well, and had a reading accuracy of over 90% with common and rare regular words. In contrast, although common irregular words were read with an accuracy of about 80%, only 40% of rare irregular words were read accurately.

The evidence from surface dyslexics such as JC and MP suggests they have a strong (but not exclusive) reliance on Route 1. If all words were read by means of grapheme-phoneme conversion, then all irregular words would be mispronounced, and this simply does not happen. Presumably surace dyslexics can make some use of routes other than Route 1, even though these other routes are severely damaged.

Finally, surface dyslexics vary considerably in the nature of the impairment that led them to adopt the strategy of grapheme-phoneme conversion. For example, JC had no problem with understanding words that he pronounced correctly, whereas MP often failed to understand words she could pronounce. Thus, the syndrome of "surface dyslexia" may be of limited usefulness.

Route 2 (lexicon plus semantic system)

Route 2 is the route generally used by adult readers. The basic idea is that representations of thousands of familiar words are stored in a visual input lexicon. Visual presentation of a word leads to activation in the visual input lexicon. This is followed by obtaining its meaning from the semantic system after which the word can be spoken (see Figure 11.8).

How could we identify patients who use Route 2 but not Route 1? Their intact visual input lexicon means that they should experience little difficulty in pronouncing familiar words. However, their inability to use

Adult Dyslexia

Adult Dyslexia

This is a comprehensive guide covering the basics of dyslexia to a wide range of diagnostic procedures and tips to help you manage with your symptoms. These tips and tricks have been used on people with dyslexia of every varying degree and with great success. People just like yourself that suffer with adult dyslexia now feel more comfortable and relaxed in social and work situations.

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