Word form access dyslexia: understanding the basis of visual reading errors

We report the case of a patient V.E.M. who exhibits the infrequently described syndrome of visual dyslexia. V.E.M. read many single words accurately and rapidly; however, when words were read inaccurately, the majority of responses were alternate real words bearing a strong visual relationship to the target items. A series of observational and experimental investigations of her reading skills revealed that response accuracy was strongly affected by word frequency and mildly affected by concreteness but not influenced by word length, orthographic neighbourhood size, or semantic priming. It is argued that V.E.M.'s visual dyslexia results from a deficit of the visual word form system. More specifically, we propose that this deficit has an “access” quality, with visual word form representations remaining relatively intact despite an impairment in the processes by which these representations are activated. Taking the results of this study together with previous reports of dyslexic patients who make a high proportion of visual paralexic errors, we also suggest that visual dyslexia represents a multicomponent dyslexic syndrome for which phonological impairment and not semantic impairment may be a necessary condition.     

Paying attention to reading errors in acquired dyslexia

The important role of selective attention in normal reading is illustrated by a relatively rare form of acquired dyslexia known as 'attentional dyslexia'. Theories of the functional deficit underlying this disorder differ as to the locus of the attentional dysfunction. A recent study by Mayall and Humphreys has contributed to this debate by studying letter migration errors in an attentional dyslexic.     

Word length effect in early reading and in developmental dyslexia

Vocal reaction times were measured in Italian dyslexics and in proficient readers while they read single words. Three groups of control participants (for a total of 79) were tested. All were in the first, second or third grade of elementary school. Nine third graders with a low level of reading ability when assessed by standard reading procedures were also tested. Results indicated that vocal RTs of control participants were faster and less sensitive to word length as a function of age; also, there was a particularly marked change between first and second graders. Dyslexics' vocal RTs and errors were much worse than those of peer control participants and resembled those of first grade controls. It is suggested that normal readers in an orthographically transparent language (Italian) adopt a lexical strategy quite early in their learning. On the contrary, dyslexics seem unable to learn this mode of processing and continue to use a sub-lexical reading procedure.     

Letter form as a constraint for errors in neglect dyslexia and letter position dyslexia

Does letter-form constrain errors in peripheral dyslexia? In Hebrew, 5 of the 22 letters have two different letter forms, one is used only when the letter occurs in word-final position, the other form is used in initial and middle positions. Is the information on final-forms encoded in the letter identity information and used for word identification, or is it discarded? The current research explored this question through the effect of final vs. non final letter form on the error pattern in neglect dyslexia (neglexia) and letter position dyslexia (LPD). Left word-based neglexia results in errors of omission, substitution and addition of letters in the left side of words, which in Hebrew is the end of the word. We examined whether final letter form blocks the addition of letters to the end of the word and whether omissions of letters after letters in non-final form are avoided. The predominant error type in LPD is migration of letters within words. We tested whether migrations also occur when they cause form change of either final-form letters that move to middle position or middle-form letters that move to final position. These questions were assessed in both acquired and developmental neglexia and LPD. The results indicated a strong effect of final letter-form on acquired neglexia and on acquired and developmental LPD, which almost completely prevented form-changing errors. This effect was not found in developmental neglexia, where words that end in final-form letters were actually more impaired than other words, probably because final-form letters appear only on the neglected side of the word for Hebrew-reading children with left developmental neglexia. These data show that early visuo-orthographic analysis is sensitive to final letter form and that final letter form constrains errors in peripheral dyslexia.     

Direct visual access in reading for meaning

Two experiments examined whether phonological receding is an obligatory stage in reading for meaning or whether direct access to a word's semantic representation is the general rule. The first study demonstrated that the time to make a semantic decision about a pair of words was much more delayed by misspelling than was the time to make a phonological one. The second study investigated the effect of varying the syllabic length of a word on reaction time in a category decision task. While reaction time varied with the semantic difficulty of the category decision, it generally proved invariant with respect to syllabic length. It is argued that reading for meaning generally uses a direct route from visual form to semantic representation.     

Word skipping in reading: On the interplay of linguistic and visual factors

An eye movement experiment is reported in which target words of two and four letters were presented in sentences that strongly raised the expectation of a particular word. There were three possible conditions: The expected word was present in the sentence, an unexpected word of the same length was present, or an unexpected word of a different length was present (all continuations were acceptable, but the latter two were difficult to predict). Our first purpose was to test one of the core assumptions of the Extended Optimal Viewing Position model of eye guidance in reading (Brysbaert & Vitu, 1998). This model states that word skipping is primarily a function of the length of the upcoming word. It leads to the prediction that an unpredicted two‐letter word will be skipped more often than a predicted four‐letter word, which is indeed what we observed. Our second aim was to determine if we could obtain an interaction between context predictability and parafoveal word length, by looking at what happens when the length of the parafoveal word does not agree with the length of the expected word. No such interaction was observed although the effects of both word length and predictability were substantial. These findings are interpreted as evidence for the hypothesis that visual and language‐related factors independently affect word skipping.     

Attentional gating in primary visual cortex: a physiological basis for dyslexia

The visual magnocellular pathway is known to play a central part in visuospatial attention and in directing attention to specific parts of the visual world in serial search. It is proposed that, in the case of reading, this mechanism is trained to perform a sequential gating of visual information coming into the primary visual cortex to enable further orderly processing by the ventral stream. This scheme, taken together with the potential for plasticity between the different afferent channels in the case of a relative impairment of the magnocellular system, can provide some limited rationale for the beneficial effects that have been claimed for the use of coloured overlays and glasses.     

Understanding reading as a form of language-use: A language game hypothesis

Reading research and research on conversation have followed different paths: While the research program for reading committed itself to a relatively static view of language, where objective text properties serve to elicit specific effects on cognition and behavior of a reader, research on conversation has embraced a language-use perspective, where language is primarily seen as a dynamic, context dependent process. In this essay I contrast these two perspectives, and argue that in order to reach a unified understanding of natural language – be it reading, talking, or conversing – one needs to adopt a language-use perspective. Furthermore, I describe how reading can be seen as a form of language-use, and how the current landscape of research on reading can be re-interpreted in terms of a dynamic, context-sensitive perspective on language. In particular, I propose that the concept of ‘language games’ serves as a good starting point to conceive reading as a form of language-use, describe how one can derive first concrete hypotheses by re-interpreting reading in terms of language games, and show how they can be readily operationalized using tools from dynamic systems analysis.     

The visual word form area: expertise for reading in the fusiform gyrus

Brain imaging studies reliably localize a region of visual cortex that is especially responsive to visual words. This brain specialization is essential to rapid reading ability because it enhances perception of words by becoming specifically tuned to recurring properties of a writing system. The origin of this specialization poses a challenge for evolutionary accounts involving innate mechanisms for functional brain organization. We propose an alternative account, based on studies of other forms of visual expertise (i.e. bird and car experts) that lead to functional reorganization. We argue that the interplay between the unique demands of word reading and the structural constraints of the visual system lead to the emergence of the Visual Word Form Area.     

Semantic ambiguity and the failure of inhibition hypothesis as an explanation for reading errors in deep dyslexia

We report evidence for dissociation between explicit and implicit access to word representations in a deep dyslexic patient (JO). JO read aloud a series of ambiguous (e.g., bank) and unambiguous (e.g., food) words and performed a lexical decision task using these same items. When required to explicitly access the items (i.e., naming), JO showed relative impairment for ambiguous compared with unambiguous words. In contrast, the same stimuli produced an advantage for ambiguous words in lexical decision. The results are discussed within a framework of deep dyslexia that considers errors in production to arise through a failure to inhibit spuriously activated candidate representations.     

Semantics and semantic errors: implicit access to semantic information from words and nonwords in deep dyslexia

In this paper we describe dissociations of implicit versus explicit access to semantic information in a patient with deep dyslexia. This acquired reading disorder is characterized by the production of morphological (e.g., SLEEP read as SLEEPING) and semantic errors (e.g., HEART read as BLOOD) and consequently provides a potential window into the operation of both aspects of the language system. The deep dyslexic patient in this study (JO) demonstrated implicit semantic access to items in a number of tasks despite the fact that she was unable to correctly read these items aloud. The findings from this study are consistent with a model of lexical deficits that distinguishes between explicit and implicit access to lexical representations on the basis of inhibitory processes.     

Patterns of visual dyslexia

This study reports two Hebrew-speaking individuals with acquired visual dyslexia. They made predominantly visual errors in reading, in all positions of the target words. Although both of them produced visual errors, their reading patterns crucially differed in three respects. KD had almost exclusively letter substitutions, and SF also made letter omissions, additions, letter position errors, and between-word migrations. KD had difficulties accessing abstract letter identity in single-letter tasks, and in letter naming, unlike SF, who named letters well. KD did not show lexical effects such as frequency and orthographic neighbourhood effects and produced nonword responses, whereas SF showed lexical effects, with a strong tendency to produce word responses. We suggest that these two patterns stem from two different deficits - KD has letter identity visual dyslexia, which results from a deficit in abstract letter identification in the orthographic-visual analysis system, yielding erroneous letter identities, whereas SF has visual-output dyslexia, which results from a deficit at a later stage, a stage that combines the outputs of the various functions of the orthographic-visual analyzer.     

Spelling dyslexia: A form of cross-cuing

A patient with spelling dyslexia maintained the ability to write, spell, and pronounce spelled nonsense words and words that require knowledge of orthographic rules of language. He was unable to perform grapheme-phoneme conversions except after naming the letter involved. We propose that he uses a letter-naming strategy to circumvent the disconnection of visual areas from the area of visual word images and that his letter-naming strategy represents a compensatory cross-cuing strategy.     

Word recognition in developmental dyslexia: A connectionist interpretation

We present a study of the accuracy, consistency, and speed of word naming in a dyslexic boy, JM, who has severe impairments in the ability to use sub-lexical, phonological reading strategies. For words that he can recognise, JM's naming latencies do not differ from those of control subjects matched for reading age, and he is generally consistent from one occasion to the next. He can also match printed homophones with their definitions--a skill that requires access to well-specified orthographic representations. The data are interpreted as evidence for the creation of efficient recognition devices for words within JM's sight vocabulary. However, he shows a continuing inability to use phonological decoding strategies to deal with words that he cannot recognize by sight. Overall we argue our results pose problems for stage models of reading development, and that they may best be interpreted within a connectionist framework of the development of word recognition skills.     

Developmental dyslexia: the visual attention span deficit hypothesis

The visual attention (VA) span is defined as the amount of distinct visual elements which can be processed in parallel in a multi-element array. Both recent empirical data and theoretical accounts suggest that a VA span deficit might contribute to developmental dyslexia, independently of a phonological disorder. In this study, this hypothesis was assessed in two large samples of French and British dyslexic children whose performance was compared to that of chronological-age matched control children. Results of the French study show that the VA span capacities account for a substantial amount of unique variance in reading, as do phonological skills. The British study replicates this finding and further reveals that the contribution of the VA span to reading performance remains even after controlling IQ, verbal fluency, vocabulary and single letter identification skills, in addition to phoneme awareness. In both studies, most dyslexic children exhibit a selective phonological or VA span disorder. Overall, these findings support a multi-factorial view of developmental dyslexia. In many cases, developmental reading disorders do not seem to be due to phonological disorders. We propose that a VA span deficit is a likely alternative underlying cognitive deficit in dyslexia.     

Phonological dyslexia: a test case for reading models

Following brain damage, skilled readers may encounter more severe problems in reading nonwords than familiar words, a type of deficit referred to as phonological dyslexia. We report on 2 individuals with Alzheimer's disease who show phonological dyslexia. Although highly accurate in reading familiar words aloud (even those with irregular spelling, such as sew), they were quite impaired in nonword reading. Both patients performed well in phonological tasks involving the repetition, identification, and manipulation of phonemes of orally presented words and nonwords. These results challenge the idea, proposed in the context of connectionist and evolutionary theories, that phonological dyslexia originates from a phonological deficit. However, the results are consistent with reading models, such as the dual-route model, that attribute phonological dyslexia to a deficit that selectively affects the reading mechanisms responsible for deriving the sounds of nonwords. According to these models, such a deficit is not necessarily accompanied by a more general phonological impairment.     

The role of visual form in lexical access: Evidence from Chinese classifier production

The interface between the conceptual and lexical systems was investigated in a word production setting. We tested the effects of two conceptual dimensions – semantic category and visual shape – on the selection of Chinese nouns and classifiers. Participants named pictures with nouns (“rope”) or classifier–noun phrases (“one-classifier–rope”) in three blocked picture naming experiments. In Experiment 1, we observed larger semantic category interference with phrases than with nouns, suggesting comparable semantic categorical effects on classifier and noun selection. In Experiments 2 and 3, items with similar shapes produced an interference effect when they were named with classifier–noun phrases, but not with bare nouns. This indicates that object shape modulates classifier (but not noun) selection. We conclude that object shape properties can by themselves influence word selection processes just as semantic relationships (captured by semantic category) do. The factors operating during word selection may be more diverse than has been previously thought.     

Word association and the acquisition of reading

Two studies relating reading ability to word association responses were carried out. The first involved early readers and matched control children from pre-first-grade classes. There were 29 early readers and 29 nonreading controls matched for age, sex, and IQ. The early readers were found to give significantly more paradigmatic, or same-form-class, responses than the controls. The second study related reading ability, mental age, and word association responses in developmentally delayed teen-agers and young adults, and pre-first-grade children who varied in reading ability. With partial correlation reading ability was found to be related to paradigmatic responding, while mental age was not significantly related. These results indicate that reading acquisition may change word association responses in children through a reorganizing process in the lexicon.The authors would like to thank the Halifax and Dartmouth School Boards for their cooperation. We would also like to thank Paul Cable of Special Education, and the principals and teachers: Beth Conrad, Karen Duerdan, Elaine Fram, Peter Montgomery, Wayne Serebrin, and Bill Schipilow. Their help was greatly appreciated. An earlier version of study 1 was presented at the American Psychological Association meeting in Los Angeles, August 1981.