The Selective Preservation of Phonological Reading

Chapter 4 began with the programme of understanding dyslexic difficulties using a multiple-route model of the normal reading process. On this programme, the selective impairment of any individual route would correspond to a form of central dyslexia. However, the one candidate reading disorder considered, surface dyslexia, has proved a disappointment. Far from consisting of a selective impairment of the semantic reading route, in its best known form, it seems to consist of compensatory behaviour for an underlying peripheral dyslexic difficulty.

Can an improvement be obtained using the dissociation approach? Can one adapt the method of defining syndromes by dissociations in order to lessen the probability that the dissociation reflects only the operation of a compensatory procedure? One approach is to insist that the better performed task is not merely ‘better’ than the poorly performed task, but also normal or nearly so on any relevant measure. In the terminology to be developed in chapter 10, this dissociation is a ‘classical’ or near-classical one. In this case, it would be unlikely to arise as a result of the operation of a laborious compensatory strategy. Having made this distinction, I will, however, immediately relax it. The critical aspects that distinguish the use of, say, a normal phonological reading procedure – if somewhat impaired – from the compensatory strategies discussed in chapter 4 are the speed and fluency of reading.