Why the Acquired Dyslexias?

In this chapter and the next, I consider whether the cognitive neuropsychology research programme is working at a level more complex than a single functional syndrome. Can the approach provide information about the organisation of a group of subsystems, and not just about the functioning of a single one? If each potential subsystem could be shown to be damaged by a pure syndrome specific to it, the power and plausibility of the approach would be greatly increased.

What domain should one choose to explore in detail in order to assess whether the breakdown of related functions in different patients is caused by damage to different components of a modular organisation? It might seem natural to take a domain like language or object perception, in which any such modular organisation would have been honed by evolution. Instead, I am going to consider the breakdown of reading, a skill that is specific not only to one species, but also to what is, from an evolutionary perspective, a tiny time period. A prerequisite for taking such a domain as a prototype is that contrary to one of Fodor's (1983) assumptions, the human modular structure must be affected by the experience of the organism, with respect to not only the operation of individual subsystems, but also the organisation of the functional architecture itself.

There are a number of reasons for choosing the reading system and the syndromes that occur when it is damaged – the acquired dyslexias.