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

Three eye movement experiments were conducted to examine the role of letter identity and letter position during reading. Before fixating on a target word within each sentence, readers were provided with a parafoveal preview that differed in the amount of useful letter identity and letter position information it provided. In Experiments 1 and 2, previews fell into 1 of 5 conditions: (a) identical to the target word, (b) a transposition of 2 internal letters, (c) a substitution of 2 internal letters, (d) a transposition of the 2 final letters, or (e) a substitution of the 2 final letters. In Experiment 3, the authors used a further set of conditions to explore the importance of external letter positions. The findings extend previous work and demonstrate that transposed-letter effects exist in silent reading. These experiments also indicate that letter identity information can be extracted from the parafovea outside of absolute letter position from the first 5 letters of the word to the right of fixation. Finally, the results support the notion that exterior letters play important roles in visual word recognition.

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.

output lexicon

& The visual system of literate adults develops a remarkable perceptual expertise for printed words. To delineate the aspects of this competence intrinsic to the occipitotemporal ‘‘what’ ’ pathway, we studied a patient with bilateral lesions of the occipitoparietal ‘‘where’ ’ pathway. Depending on critical geometric features of the display (rotation angle, letter spacing, mirror reversal, etc.), she switched from a good performance, when her intact ventral pathway was sufficient to encode words, to severely impaired reading, when her parietal lesions prevented the use of alternative reading strategies as a result of spatial and attentional impairments. In particular, reading was disrupted (a) by rotating word by more than 508, providing an approximation of the invariance range for words encoding

Attentional dyslexia is a reading deficit in which letters migrate between neighboring words, but are correctly identified and keep their correct relative position within the word. Thus, for example, fig tree can be read as fig free or even tie free. This study reports on 10 Hebrew-speaking individuals with developmental attentional dyslexia and explores in detail the characteristics of their between-word errors. Each participant read 2,290 words, presented in word pairs: 845 horizontally presented word pairs, 240 vertically presented word pairs, and 60 nonword pairs. The main results are that almost all migrations preserve the relative position of the migrating letter within the word, indicating that the between-word position can be impaired while the within-word position encoding remains intact. This result is also supported by the finding that the participants did not make many letter position errors within words. Further analyses indicated that more errors occur in longer words, that most migrations occur in final letters (which are the leftmost letters in Hebrew), and that letters migrate both horizontally and vertically, and more frequently from the first to the second word in horizontal presentation. More migrations occurred when the result of migration was an existing word. Similarity within word pairs did not increase error rates, and more migrations occurred when the words shared fewer letters. The betweenword errors included migration of a letter between words, intrusion of a letter from one word to the corresponding position in the neighboring word without erasing the original letter in the same position, and omission of one instance of a letter that appeared in the same position in the two words (these omissions made up a considerable percentage of the between-word errors). 1.

The article describes AE, a Hebrew-speaking individual with acquired dysgraphia, who makes mainly letter position errors in writing. His dysgraphia resulted from impairment in the graphemic buffer, but unlike previously studied patients, most of his errors related to the position of letters rather than to letter identity: 80 % of his errors were letter position errors in writing, and only 7 % of his errors were letter omissions, substitutions, and additions. Letter position errors were the main error type across tasks (writing to dictation and written naming), across output modalities (writing and typing), and across stimuli (migratable words [words in which letter migration forms another word], irregular words, and nonwords). Letter position errors occurred mainly in the middle letters of a word. AE’s writing showed a significant length effect, and no lexicality, migratability, or frequency effects. His letter position deficit was manifested selectively in writing; he made no letter position errors in reading, demonstrating the dissociability of letter position encoding in reading and writing. These data support the existence of a letter order function in the graphemic buffer that is separate from the function responsible for activating letter identities. 1.

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Letter position dyslexia (LPD) is a deficit in the encoding of letter position within words. It is characterized by errors of letter migration within words, such as reading trail as trial and form as from. In order to examine whether LPD is domain-specific, and to assess the domain specificity of the visual analysis system, this study explored whether LPD extends to number reading, by testing whether individuals who have letter migrations in word reading also show migrations while reading numbers. The reading of words and numbers of 12 Hebrews-peaking individuals with developmental LPD was assessed. Experiment 1 tested reading aloud of words and numbers, and Experiment 2 tested same-different decisions in words and numbers. The findings indicated that whereas the participants with developmental LPD showed a large number of migration errors in reading words, 10 of them read numbers well, without migration errors, and not differently from the control participants. A closer inspection of the pattern of errors in words and numbers of two individuals who had migrations in both numbers and words showed qualitative differences in the characteristics of migration errors in the two types of stimuli. In word reading, migration errors appeared predominantly in middle letters, whereas the errors in numbers occurred mainly in final (rightmost) digits. Migrations in numbers occurred almost exclusively in adjacent digits, but in words migrations occurred both in adjacent and in nonadjacent letters. The results thus indicate that words can be selectively impaired, without a parallel impairment in numbers, and that even when numbers are also impaired they show different error pattern. Thus, the visual analyzer is actually an orthographic-visual analyzer, a module that is domain-specific for the analysis of words.

This study reports the reading of 4 Arabic-speaking individuals with letter position dyslexia (LPD), and the effect of letter form on their reading errors. LPD is a peripheral dyslexia caused by a selective deficit to letter position encoding in the orthographic-visual analyzer, which results in migration of letters within words, primarily of middle letters. The Arabic orthography is especially interesting for the study of LPD because Arabic letters have different forms in different positions in the word. As a result, some letter position errors cause letter form change. We compared the rate of letter migrations that change letter form with migrations that do not change letter form in 3 Arabic-speaking individuals with developmental LPD, and one bilingual Arabic and Hebrewspeaking individual with acquired LPD. The results indicated that the participants made 85 % letter position errors in migratable words when the resulting word included the letters in the same form, whereas migrations that caused letter form change almost never occurred. The error rate of the Arabic-Hebrew bilingual reader was smaller in Arabic than in Hebrew, but when only words in which migrations do not change letter form were counted, the rate was similar in Arabic and Hebrew. Namely, whereas orthographies with multiple letter forms for each letter might seem more difficult in some respects, these orthographies are in fact easier to read in some forms of dyslexia. Thus, the diagnosis of LPD in Arabic should consider the effect of letter forms on migration errors, and use stimuli that are migratable words that do not require letter-form change. The theoretical implications for the reading model are that letter form is part of the information encoded in the abstract letter identity, and thus affects further word recognition processes, and that there might be a pre-lexical graphemic buffer in which the checking of orthographic well-formedness takes place.