The development of reading skill and bases of developmental dyslexia were explored using connectionist models. Four issues were examined: the acquisition of phonological knowledge prior to reading, how this knowledge facilitates learning to read, phonological and non phonological bases of dyslexia, and effects of literacy on phonological representation. Compared with simple feedforward networks, representing phonological knowledge in an attractor network yielded improved learning and generalization. Phonological and surface forms of developmental dyslexia, which are usually attributed to impairments in distinct lexical and nonlexical processing “routes,” were derived from different types of damage to the network. The results provide a computationally explicit account of many aspects of reading acquisition using connectionist principles.

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xi 1 Introduction 1 1.1 Intuitions and Evidence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2 Previous Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.2.1 The Classical Dual Route Model . . . . . . . . . . . . . . . . . . . . . . . 6 1.2.2 Seidenberg and McClelland 1989 . . . . . . . . . . . . . . . . . . . . . . 10 1.2.3 Plaut and Shallice 1993 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1.2.4 Plaut et al. 1996: Naming . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1.2.5 Bullinaria 1996 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 1.2.6 Plaut 1997: Lexical Decision . . . . . . . . . . . . . . . . . . . . . . . . . 15 1.2.7 Harm and Seidenberg 1998: Naming . . . . . . . . . . . . . . . . . . . . 16 1.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2 A New Computational Model 18 2.1 Principles . . . . . . . . . . . . . . . . . . . . . . . . ...

this paper. Correspondence concerning this article should be addressed to Michael W. Harm, Center for the Neural Basis of Cognition, 115 Mellon Institute, 4400 Fifth Avenue, Pittsburgh, Pennsylvania, 15213. Electronic mail may be sent to mharm@cnbc.cmu.edu

This research investigated the effects of prior knowledge on learning in psychologically-plausible connectionist networks. This issue was examined with respect to the benchmark orthography-to-phonology mapping task (Sejnowski & Rosenberg, 1986; Seidenberg & McClelland, 1989). Learning about the correspondences between orthography and phonology is a critical step in learning to read. Children (unlike the networks mentioned above) bring to this task extensive knowledge about the sound-structure of their language. We first describe a simple neural network that acquired some of this phonological knowledge. We then summarize simulations showing that having this knowledge in place facilitates the acquisition of orthographicphonological correspondences, producing a higher level of asymptotic performance with fewer implausible errors and better nonword generalization. The results suggest that connectionist networks may provide closer approximations to human performance if they incorporate more...

Findings in infant speech perception suggest that early phonologicalperceptions may be syllabic in nature, and that there is a loss of sensitivity to nonnative contrasts toward the end of the first year of life. We present a neural network model that simulates these two phenomena. In addition, the model and simulations (1) demonstrate how information about stress can be utilized in generating syllable-like perceptions; (2) provide a simple means of extracting static representations from a dynamic and co-articulated signal; and (3) indicate that the development of "attractor " states may be necessary in network models of these phenomena.

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We investigated the relationship between dyslexia and three aspects of language: speech perception, phonology and morphology. Reading and language tasks were administered to dyslexics aged 8-9 years, and two normal reader groups (age-matched and reading-level matched). Three dyslexic groups were identified: phonological dyslexics (PD), developmentally language impaired (LI), and globally delayed (delay-type dyslexics). The LI and PD groups exhibited similar patterns of reading impairment, attributed to low phonological skills. However, only the LI group showed clear speech perception deficits, suggesting that such deficits affect only a subset of dyslexics. Results also indicated phonological impairments in children whose speech perception was normal. Both the LI and PD groups showed inflectional morphology difficulties, with the impairment being more severe in the LI group. The Delay group's reading and language skills closely matched those of younger normal readers, suggesting these children had a general delay in reading and language skills, rather than a specific phonological impairment. The results are discussed in terms of models of word recognition and dyslexia.