Biological constraints on literacy acquisition

Abstract

This paper investigates some of the biological constraints that shape the process of literacy acquisition. It explores the possibility of isolating processing components of reading which correspond to computational units of equivalent size in the neural architecture. After reviewing and evaluating the current approaches to the biology of literacy acquisition, the paper considers three interconnected topics: (a) developmental dissociations, (b) early stages of literacy acquisition (in a transparent orthography), and (c) effects of remedial intervention for children with reading disorders. Developmental dissociations between reading and severe mental retardation, motor impairment, congenital anarthria and inaccuracy in phonemic awareness tasks reveal the functional independence of the reading processes. The early stages of literacy acquisition in a transparent orthography show a very steep increase in word and non-word reading accuracy; a speed that could hardly be accounted for by unconstrained learning. Finally, rehabilitation treatments of reading disorders either produce no specific effects, or marginal improvements in reading accuracy, which fade away in the long term. Concurrently, these data suggest that the process of literacy acquisition is largely constrained by a specific biological architecture which mimics the functional properties of a modular system. It is speculated that the core component of reading is a metaphonological parser, designed to perform automatic cross-modal associations between visual and sublexical units, according to the paradigms set up by any orthographic system. The phylogenetic implications of the ‘specificity hypothesis’ are discussed.