YSLEXIA is an extreme difficulty experienced by a minority of children in learning to read and spell. The recurrence in families suggests a genetic origin and there is evidence that the language areas of the brain and the visual and auditory pathways may be affected. The possible involvement of the cerebellum, a part of the brain concerned with movement control, is the basis of the "miracle cure" proposed by Wynford Dore's Dyslexia, Dyspraxia and Attention Disorder Treatment (DDAT) Centre.
A great deal of research has been directed at attempts to understand dyslexia. One approach is to search for the causes of the problem. Another is to analyse the nature of the difficulty. If the problem in the development of reading and spelling can be understood, then it may be possible to design effective remedial programmes.
Causes can be defined at two levels. There are the cognitive causes, psychological processes, such as memory, which might affect learning to read. According to current research, the most probable cause is a disturbance of a child's understanding of the way in which speech can be divided into segments.
Other causes are described in biological terms. The evidence from brain imaging establishes that reading and spelling processes normally take place in the cortical language areas of the left hemisphere. Damage to these areas in adulthood can disrupt reading or spelling, producing an "acquired dyslexia".
For the DDAT theory to be correct, it seems necessary to believe that learning to read involves the left hemisphere working in conjunction with the cerebellum. If this was so, and if a malfunction in the cerebellum was the crucial cause of the disruption of learning, then it might be true that special exercises which somehow produced a physiological improvement in the internal structure of the cerebellum could serve as a "cure".
The theory is founded on many questionable assumptions and an extended research programme would be essential before it could be accepted. We need to know how close an association exists between success in learning to read and the tests used to detect cerebellar and middle-ear dysfunction. How many dyslexic children do not show these problems? How many normal readers do show them?
The rates at which dyslexic children learn to read in response to instruction needs to be determined; then, some of these children should undertake a programme of exercises while others engage in equivalent activities; all should then complete a further period of reading instruction. If the intervention group differs statistically from the control group by showing an improvement in balance and an increase in rate of literacy acquisition, the theory will gain support.
In the meantime, it is important to be clear that the major problem in dyslexia is the difficulty in learning to read and write. To understand this properly we need valid cognitive and linguistic theories about the way in which mastery of written language is achieved.
Languages differ in difficulty. Recent European research co-ordinated in Dundee shows that learning to read in a complex language such as English is much slower and more arduous. The nature of dyslexia also differs. In English, dyslexic children have great difficulty in learning to "decode" (to use their knowledge of letters and sounds to read or write new words), while in simple spelling systems dyslexic reading appears accurate but lacking in fluency.
Specially designed teaching programmes, such as the one developed by the Dyslexia Institute, are needed which draw attention to these peculiarities in a direct and explicit way. Research is needed to determine the optimal ways of scheduling and teaching these structures for children at different developmental levels and with differing kinds of problem. So-called "miracle cures", such as training in balance and co-ordination, or wearing coloured spectacles, appear remote from the essentially linguistic nature of the dyslexic difficulty.
Philip Seymour is professor of cognitive psychology at Dundee University.