One possible cause of dyslexia is that it emanates from neurological (brain) factors. This is a biological explanation. There is some evidence that dyslexic people share a group of genes on part of chromosome 6 which is close to the MHC genes that control the immune system. This idea is supported by the evidence that dyslexics often tend to suffer from disorders of the immune system such as asthma and rhemutoid arthritis.
One theory which attempts to explain how dyslexia may be caused by problems in the brain is Gerschwinds theory. He claims that high testosterone in the foetus could lead to damage of the left hemisphere of the brain, which ultimately may cause dyslexia to arise. There is some evidence to support this theory - it is taken from post mortems. Gershwind studied the brains of two dyslexic people (after death) and found that there was damage in the left hemisphere of the brain, which had been caused either before or during birth.
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A fMRI scan showing regions of activation in orang...
Tursiops truncatus (bottlenose dolphin) brain comp...Animal studies also show that testosterone interferes with brain development in the foetus. However, there are problems with this evidence. The brains studied were of males, but females get dyslexia too. Males and females hear sounds in different parts of the brain therefore evidence relating to males cannot be generalised to apply to both sexes. Also, the sample size of only 2 dyslexic brains is very small, so the results cannot even be applied with confidence to all male dyslexics either. The brains studied were 'dead' and there is no way of determining that the living brains of dyslexics would display the same damage in the left hemisphere that the 'dead' brains did. Another problem is that only dyslexics were studied - the results were not compared to non-dyslexics therefore it can't be said whether this...