What does it mean to ask whether cognitive skills are prerequisite for learning to read and write?—A response to cossu and marshall

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Abstract
In this issue of Cognitive Neuropsychology (pp. 21–40) Cossu and Marshall report the case of a 9-year-old Italian child (TA) who (like other “hyperlexics”) has learned to transcode print to sound and vice versa, to a certain level of competence, and yet appears to lack several other abilities which various theorists have implicated in learning to read alphabetic script. The authors infer that these other abilities are not prerequisites for, nor even implicated in, learning to transcode in either direction, and that this is the strongest evidence for the “modularity of transcoding skill”. While the data add little to the literature on hyperlexia, it is most useful to examine the implications of confronting different research literatures which rarely make contact. However, the status, treatment, and theoretical interpretation of the data in Cossu and Marshall's paper are worrying. They raise issues that go beyond this individual publication. Among such issues are the following: 1. The nature of a dissociation in behaviour and how it can be interpreted. 2. Constraints on inferences from pathology to theory of different kinds and to characterisation of normality. 3. What the term “modularity” means when applied to different questions, e.g. the mode of operation versus the acquisition of some process. 4. Appropriateness of the data for the questions addressed. In essence my argument is that the inferences made by Cossu and Marshall are invalid, that their data are inappropriate for such inferences, and that the view that they infer is either unspecified or incoherent.