similarity effects in masked associative priming One issue that all models of visual word recognition in alphabetic orthographies must ultimately take a position on is how the human processing system encodes letter positions when creating internal orthographic representations. Furthermore, although the choice of a coding scheme might seem to be a secondary aspect of these models, it can have a large impact on a model’s predictions (Andrews, 1996). For example, virtually all of the current models assume that the derived orthographic representation activates the lexical representations of formally similar words

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This article focuses on applying the SERIOL model of orthographic processing to dyslexia. The model is extended to include a phonological route and reading acquisition. We propose that the temporal alignment of serial orthographic and phonological representations is a key aspect of learning to read, driving the formation of a phonemic encoding. The phonemic encoding and the serial representations are mutually reinforcing, leading to automatic, proficient processing of letter strings. A breakdown in any component of this system leads to the failure to form stringspecific phonological and visual representations, resulting in impaired reading ability. Following the pioneering work of Liberman and colleagues (1974), research into dyslexia has focused on phonological deficits. As discussed by Castles and Colheart (2004), there is a wide range of evidence that dyslexics are impaired in phonological awareness tasks, such as phoneme deletion, phoneme counting and phoneme lending. This correlation has largely been taken to reflect causality. That is, impaired phonological awareness is thought to reflect abnormal phonological representations, which are thought to be the fundamental cause of dyslexia. However, a causal relationship between phonological awareness and

Recent research has shown that letter identity and letter position are not integral perceptual dimensions (e.g., jugde primes judge in word-recognition experiments). Most comprehensive computational models of visual word recognition (e.g., the interactive activation model, J. L. McClelland & D. E. Rumelhart, 1981, and its successors) assume that the position of each letter within a word is perfectly encoded. Thus, these models are unable to explain the presence of effects of letter transposition (trial–trail), letter migration (beard–bread), repeated letters (moose–mouse), or subset/superset effects (faulty–faculty). The authors extend R. Ratcliff’s (1981) theory of order relations for encoding of letter positions and show that the model can successfully deal with these effects. The basic assumption is that letters in the visual stimulus have distributions over positions so that the representation of one letter will extend into adjacent letter positions. To test the model, the authors conducted a series of forced-choice perceptual identification experiments. The overlap model produced very good fits to the empirical data, and even a simplified 2-parameter model was capable of producing fits for 104 observed data points with a correlation coefficient of.91.

Dividing attention across multiple words occasionally results in misidentifications whereby letters apparently migrate between words. Previous studies have found that letter migrations preserve withinword letter position, which has been interpreted as support for position-specific letter coding. To investigate this issue, the authors used word pairs like STEP and SOAP, in which a letter in 1 word could migrate to an adjacent letter in another word to form an illusory word (STOP). Three experiments show that both same-position and adjacent-position letter migrations can occur, as well as migrations that cross 2 letter positions. These results argue against position-specific letter coding schemes used in many computational models of reading, and they provide support for coding schemes based on relative rather than absolute letter position. A key issue that must be addressed in any theory of visual word recognition is how to code for letter position: Without coding of position, it is not possible to distinguish anagrams like CAT and ACT. Although relatively little empirical work has been directed at assessing the relative merits of different letter coding schemes, the choice of coding scheme plays a central role in the performance of

Five theories of how letter position is coded are contrasted: position-specific slot-coding, Wickelcoding, open-bigram coding (discrete and continuous), and spatial coding. These theories make different predictions regarding the relative similarity of three different types of pairs of letter strings: substitution neighbors, neighbors-once-removed, and double-substitution neighbors. In Experiment 1, we used an illusory word paradigm and found that neighbor-once-removed similarity contexts resulted in fewer illusory word reports than substitution neighbors but more illusory words than double-substitution neighbors. In Experiments 2 and 3, we used a masked form priming technique with a lexical-decision task. The pattern of facilitation was as predicted by spatial coding but was incompatible with slot-coding, Wickelcoding, and both versions of open-bigram coding. These results provide further support for the SOLAR (self-organizing lexical aquisition and recognition) model of visual word identification.

Two questions regarding the non-local nature of long-distance agreement in consonantal harmony patterns (Hansson 2001, Rose and Walker 2004) are addressed: (1) How can such patterns be learned from surface forms alone? (2) How can we understand a a major feature of the typology—the absence of blocking effects? It is shown that a learner which generalizes only by making distinctions with respect to the order of sounds (and by not making distinctions with respect to the distance between sounds) is able to learn major classes of long-distance phonotactic patterns, and is unable to learn hypothetical long-distance phonotactic patterns with blocking effects. Thus not only is the learner able to acquire attested patterns, it explains the absence of unattested ones. Furthermore, this result lends support to the idea that long distance phonotactic patterns are phenomonologically distinct from spreading patterns contra the hypothesis of Strict Locality (Gafos 1999, et seq).

This paper defines a collection of functions which define classes of languages, which have the property that they are identifiable in the limit from positive data from a very simple kind of learner. Furthermore these learners are always incremental, maximally consistent, and locally conservative. They are also efficient provided the function itself is efficient. These learners are called string extension learners because components of the grammar are read directly from strings in the language via the defining function. A number of classes of languages in the literature can be described this way including varieties of k-Locally Testable languages (McNaughton and Papert 1971) and k-Piecewise Testable languages (Simon 1975), as well as some classes not discussed in the literature, such as the k-Piecewise Testable languages in the Strict Sense. Potential applications of string extension learning exist for models of natural languages, particularly phonotactics, aspects of cognition and natural language processing.

The split fovea theory proposes that visual word recognition of centrally presented words is mediated by the splitting of the foveal image, with letters to the left of fixation being projected to the right hemisphere (RH) and letters to the right of fixation being projected to the left hemisphere (LH). Two lexical decision experiments aimed to elucidate word recognition processes under the split fovea theory are described. The first experiment showed that when words were presented centrally, such that the initial letters were in the left visual field (LVF/RH), there were effects of orthographic neighborhood, i.e., there were faster responses to words with high rather than low orthographic neighborhoods for the initial letters (Ôlead neighborsÕ). This effect was limited to leadneighbors but not end-neighbors (orthographic neighbors sharing the same final letters). When the same words were fully presented in the LVF/RH or right visual field (RVF/LH, Experiment 2), there was no effect of orthographic neighborhood size. We argue that the lack of an effect in Experiment 2 was due to exposure to all of the letters of the words, the words being matched for overall orthographic neighborhood count and the sub-parts no longer having a unique effect. We concluded that the orthographic activation found in Experiment 1 occurred because the initial letters of centrally presented words were projected to the RH. The results support the split fovea theory, where the RH has primacy in representing lead neighbors of a written word.

Revised (revised date) Communicated by Editor's name ABSTRACT A new notion, that of semi-lossless text compression, is introduced, and its applicability in various settings is investigated. First results suggest that it might be hard to exploit the additional redundancy of English texts, but the new methods could be useful in applications where the correct spelling is not important, such as in short emails, and the new notion raises some interesting research problems in several different areas of Computer Science.