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Theory of information processing deficits
The brain is a computer that has been ‘pre-wired’ to learn. Information goes to the brain from the sense organs and is analysed and then stored in the memory for later recall, or is dealt with in some other way. These processes can be shown on a flowchart in the way that one can study the workings of a computer. Some workers have focused their attention on the particular problems experienced by children with specific learning difficulties, and have formulated theories about the precise deficits in information processing in their brains.
A model of the different steps involved in processing information is produced and hypotheses are put forward about where deficits could occur. Research studies are then designed to test these hypotheses. This field has provided great insights into specific learning difficulties over the last decade.
Figure 3.2 shows a simplified flowchart that illustrates the information processing that occurs when an adult reads aloud. A printed word is transmitted via the eyes to the brain, where it undergoes a number of steps. First, it is analysed to detect whether it is a familiar word or not. If familiar, it is processed along a
Figure 3.2 The reading process in the brain.
lexical route (A). If the word is completely unrecognizable, it will be processed along a phonological route (B). The existence of these two different routes has now been established from clinical and research data.
The first step on route A is for the word to enter a lexicon, or dictionary, which is connected to a semantic system where the meanings of all words already known by the individual are stored. Once the meaning is matched to the word, the word can be sounded by the speech generator, where the movements required to speak the word are initiated and controlled by the brain.
An unfamiliar word may be processed via route B. Here, the meaningless letters of the word are broken up into its component sounds (phoneme segmentation). Before the word can be spoken, the sounds must be joined back together (phoneme blending). Speech is then initiated by the speech generator in the same way as for a familiar word.
With this model in mind, one can check whether a child with specific reading difficulty has a deficit in lexical or phonological procedures. For example, is the child significantly better when reading actual words (lexical system) than nonsense words (phonological system)? If so, teaching may need to focus on ways to help the child develop his weak phonological skills.
It should be realized that children with specific learning difficulties are a heterogeneous group, and that the research findings in one group of children may not apply to all children with the disorder.
Another difficulty in interpreting data is the chicken or the egg problem: do the findings reflect the underlying cause of the difficulty, or are they the result of the difficulty? For example, because a child with specific reading difficulty cannot read well, he reads less and, therefore, has less reading experience to draw on than other children of his age. Some of the deficits in information processing that are regarded as a cause of specific reading difficulty may be the result of this lack of reading experience rather than a primary cause. For this reason, research data from studies that compare children with specific learning difficulties with other children of the same chronological age should be interpreted with caution. It may be more appropriate to compare such children with normal children of a younger age, who are at the same level of ability in the area being studied and at the same stage of learning.
A third important aspect of interpreting information processing data in children is the need to take into account so-called ‘critical periods’. Certain methods of processing information in the brain may be required at certain stages of learning a skill such as reading. A process may be present when we test a child with established difficulties, and we may not realize that it was the absence of this very process, at some crucial stage in the past, that was responsible for the child’s disorder. A developmental approach must, therefore, always be taken in interpreting information processing deficits in children.
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