A Computer Model of Reading Development

Abstract

Current theories of reading development fail to specify the details of the procedures and representations used by children when they first begin to read. This has led to confusion when the interaction between the different procedures used by the beginning reader are discussed. This thesis provides a detailed set of hypotheses about the first procedures used in reading. The developmental theory presented is based on two computational models. The first model implements a visual word recognition procedure based on a lexicon of stored representations accessed via visual cues. Words are stored initially as an unordered set of letter tokens. This representation is incomplete in that some letters may be replaced by markers and others may be omitted altogether. As the reading procedure develops, the representation becomes more accurate and the order of letter tokens is also stored. The way that words are selected from the lexicon changes so that initial and final letters are used as cues. This developmental pattern is explored in a series of 'snapshot' simulations which model the procedure under a given set of parametric assumptions. The simulations are used to predict the characteristics of the reading procedure, including the types of errors made at each stage. The error profile of the hypothesised developmental sequence for visual reading is shown to correspond to published data from longitudinal studies of children's reading. The second model learns letter-to-sound rules from examples of print words and their phonological forms. Three different phonological segmentation assumptions are made in the learning simulations corresponding to the child's awareness of onset-rime, onsetnucleus-coda or phoneme segmentation of phonology. The capabilities of the different rule sets are explored in word and non-word naming experiments. The prerequisites for the rule-learning procedure are used to constrain the relative timing of the visual word recognition procedure and a phonologically based procedure. A theory of reading development is described that makes use of the detailed descriptions of the visual and phonological reading procedures derived from the computational models. The theory applies Karmiloff-Smith's (1990) ideas on representational redescription as a framework for the development of the reading procedure. Representational redescription provides a mechanism for qualitative change in the visual lexicon through the integration of knowledge from other areas of cognitive skill. The theory provides an account of the relationship between visual reading skills and phonological knowledge.