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We develop a connectionist approach to processing in quasi-regular domains, as exemplified by English word reading. A consideration of the shortcomings of a previous implementation (Seidenberg & McClelland, 1989, Psych. Rev.) in reading nonwords leads to the development of orthographic and phonological representations that capture better the relevant structure among the written and spoken forms of words. In a number of simulation experiments, networks using the new representations learn to read both regular and exception words, including low-frequency exception words, and yet are still able to read pronounceable nonwords as well as skilled readers. A mathematical analysis of the effects of word frequency and spelling-sound consistency in a related but simpler system serves to clarify the close relationship of these factors in influencing naming latencies. These insights are verified in subsequent simulations, including an attractor network that reproduces the naming latency data directly in its time to settle on a response. Further analyses of the network's ability to reproduce data on impaired reading in surface dyslexia support a view of the reading system that incorporates a graded division-of-labor between semantic and phonological processes. Such a view is consistent with the more general Seidenberg and McClelland framework and has some similarities with---but also important differences from---the standard dual-route account.

Does knowledge of language consist of mentally-represented rules? Rumelhart and McClelland have described a connectionist (parallel distributed processing) model of the acquisition of the past tense in English which successfully maps many stems onto their past tense forms, both regular (walk/walked) and irregular (go/went), and which mimics some of the errors and sequences of development of children. Yet the model contains no explicit rules, only a set of neuron-style units which stand for trigrams of phonetic features of the stem, a set of units which stand for trigrams of phonetic features of the past form, and an array of connections between the two sets of units whose strengths are modified during learning. Rumelhart and McClelland conclude that linguistic rules may be merely convenient approximate fictions and that the real causal processes in language use and acquisition must be characterized as the transfer of activation levels among units and the modification of the weights of their connections. We analyze both the linguistic and the developmental assumptions of the model in detail and discover that (1) it cannot represent certain words, (2) it cannot learn many rules, (3) it can learn rules found in no human language, (4) it cannot explain morphological and phonological regularities, (5) it cannot explain the differences between irregular and regular forms, (6) it fails at its assigned task of mastering the past tense of English, (7) it gives an incorrect explanation for two developmental phenomena: stages of overregularization of irregular forms such as bringed, and the appearance of doubly-marked forms such as ated, and (8) it gives accounts of two others (infrequent overregularization of verbs ending in t/d, and the order of acquisition of different irregula...

Pinker, S. & Bloom, P. (1990). Natural language and natural selection. Behavioral and Brain Sciences 13

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this article. PRINCIPLES UNDERLYING THE CONNECTIONIST APPROACH The connectionist approach instantiates a number of computational principles that are relevant to morphological processing (see Figure 2). We discuss #ve central ones in some detail because they are important for understanding the conditions under which the approach predicts morphological effects in the absence of semantic and/or phonological similarity (for additional background on principles of connectionist modelling, see Chauvin &Rumelhart, 1995; Hertz, Krogh, &Palmer, 1991; McClelland et al., 1986; Rumelhart, Hinton, & Williams, 1986a; Smolensky, Mozer, & Rumelhart, 1996)

seeing a toy car in it she says car; taking i::'..'. the ear out she says out; putting it on the floor she says down. In the world at large these little remarks do not command much attention. But to people i interested in how children learn to talk, the first steps into language raise fas- :7' "? elnating and difficult questions. In this chapter, we are concerned with the enal puzzle of where children's early word meanings come from. Are they ' introduced through language? Do they reflect concepts that arise spontane~ -. ously through infants' perceptual and cognitive development? Do language ":.: and cognition interact to produce early word meanings, and, if so, how? ",..., The idea that children learn how to structure meanings through exposure to language is' usually associated with Whorl (1956). Whorf stressed that ':: languages differ in the way they partition the world, and he proposed that in learning the semantic categories of their language, children also acquire a 'world vie

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ally - positing boundaries inside phoneme transitions which are unlikely to occur word-internally. This has implications for complex words. If the phonology across a morpheme boundary is unlikely to occur morpheme-internally, then the preprocessor will posit a boundary, and so facilitate decomposition. For example the /pf/ transition in pipeful is unlikely to occur within a simple word in English. The whole-word route will therefore be disadvantaged relative to the decomposed route, because it doesn't align with hypothesized boundaries. Three experiments demonstrate that phonotactics are relevant to morphological decomposition. In experiment 1, a simple recurrent network was trained to spot the boundaries between monomorphemes, and then tested on multimorphemic words. Despite never having previously encountered a morphologically complex word, the network hypothesized a boundary at 60% of word-internal morpheme boundaries. This demonstrates that English is conf

The proposition that the mental lexicon is a `dual route' system, advanced by Pinker and others to account for regular and irregular morphology, overlooks the important fact that morphological regularity correlates inversely with phonological regularity --`regular' past-tense beeped being phonologically irregular (exceptional syllable), while `irregular' past-tense kept is phonologically just regular. I argue that the correlation, which is general, can only be captured under a single-rather than `dual'- architecture, and an associational-rather than rule based- theory of morphology. Where morphological associations are strong, morphology looks regular and phonological alternations are inhibited, making phonology look irregular. In a system in which regularities are attributed to `rules', rules should be able to coexist with other rules, and morphological and phonological regularities should correlate directly, rather than inversely. 1.