Are words read visually (by means of a direct mapping from orthography to semantics) or phonologically (by mapping from orthography to phonology to semantics)? The authors addressed this long-standing debate by examining how a large-scale computational model based on connectionist principles would solve the problem and comparing the model's performance to people's. In contrast to previous models, the present model uses an architecture in which meanings are jointly determined by the 2 components, with the division of labor between them affected by the nature of the mappings between codes. The model is consistent with a variety of behavioral phenomena, including the results of studies of homophones and pseudohomophones thought to support other theories, and illustrates how efficient processing can be achieved using multiple simultaneous constraints.

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 nonphonological 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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Older and younger adults' abilities to use context information rapidly during ambiguity resolution were investigated. In Experiments 1 and 2, younger and older adults heard ambiguous words (e.g., fires) in sentences where the preceding context supported either the less frequent or more frequent meaning of the word. Both age groups showed good context use in offline tasks, but only young adults demonstrated rapid use of context in cross-modal naming. A 3rd experiment demonstrated that younger and older adults had similar knowledge about the contexts used in Experiments 1 and 2. The experiment results were simulated in 2 computational models in which different patterns of context use were shown to emerge from varying a single speed parameter. These results suggest that age-related changes in processing efficiency can modulate context use during language comprehension.

Two hypotheses have been advanced concerning the basis of acquired phonological dyslexia. According to the dual-route model, the pattern derives from impaired grapheme-phoneme conversion. According to the phonological impairment hypothesis, it derives from impaired representation and use of phonology. Effects of graphemic complexity and visual similarity observed in studies by Howard and Best (1996), orthographic effects on phoneme counting (Berndt, Haendiges, Mitchum, & Wayland, 1996), and data from patient LB (Derouesné & Beauvois, 1985) have been taken as evidence for an orthographic impairment in phonological dyslexia and therefore against the impaired phonology hypothesis (Coltheart, 1996). We present a computational simulation, results of two behavioral studies, and a critical analysis of the MJ and LB data, which suggest that the "orthographic" deficits in such patients arise from phonological impairments that interact with orthographic properties of stimuli.