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.     

Semantic dementia without surface dyslexia in Spanish: unimpaired reading with impaired semantics

Surface dyslexia has been attributed to an overreliance on the sub-lexical route for reading. Typically, surface dyslexic patients commit regularisation errors when reading irregular words. Also, semantic dementia has often been associated with surface dyslexia, leading to some explanations of the reading impairment that stress the role of semantics in irregular word reading. Nevertheless, some patients have been reported with unimpaired ability to read irregular words, even though they show severe comprehension impairment. We present the case of M.B., the first Spanish-speaking semantic dementia patient to be reported who shows unimpaired reading of non-words, regular words, and - most strikingly - irregular loan words. M.B. has severely impaired comprehension of the same words he reads correctly (whether regular or irregular). We argue that M.B.'s pattern of performance shows that irregular words can be correctly read even with impaired semantic knowledge corresponding to those words.     

SD-squared: on the association between semantic dementia and surface dyslexia

Within the connectionist triangle model of reading aloud, interaction between semantic and phonological representations occurs for all words but is particularly important for correct pronunciation of lower frequency exception words. This framework therefore predicts that (a) semantic dementia, which compromises semantic knowledge, should be accompanied by surface dyslexia, a frequency-modulated deficit in exception word reading, and (b) there should be a significant relationship between the severity of semantic degradation and the severity of surface dyslexia. The authors evaluated these claims with reference to 100 observations of reading data from 51 cases of semantic dementia. Surface dyslexia was rampant, and a simple composite semantic measure accounted for half of the variance in low-frequency exception word reading. Although in 3 cases initial testing revealed a moderate semantic impairment but normal exception word reading, all of these became surface dyslexic as their semantic knowledge deteriorated further. The connectionist account attributes such cases to premorbid individual variation in semantic reliance for accurate exception word reading. These results provide a striking demonstration of the association between semantic dementia and surface dyslexia, a phenomenon that the authors have dubbed SD-squared.     

New evidence for morphological errors in deep dyslexia

Morphological errors in reading aloud (e.g., sexist-->sexy) are a central feature of the symptom-complex known as deep dyslexia, and have historically been viewed as evidence that representations at some level of the reading system are morphologically structured. However, it has been proposed (Funnell, 1987) that morphological errors in deep dyslexia are not morphological in nature but are actually a type of visual error that arises when a target word that cannot be read aloud (by virtue of its low imageability and/or frequency) is modified to form a visually similar word that can be read aloud (by virtue of its higher imageability and/or frequency). In the work reported here, the deep dyslexic patient DE read aloud lists of genuinely suffixed words (e.g., killer), pseudosuffixed words (e.g., corner), and words with non-morphological embeddings (e.g., cornea). Results revealed that the morphological status of a word had a significant influence on the production of stem errors (i.e., errors that include the stem or pseudostem of the target): genuinely suffixed words yielded more stem errors than pseudosuffixed words or words with non-morphological embeddings. This effect of morphological status could not be attributed to the relative levels of target and stem imageability and/or frequency. We argue that this pattern of data indicates that apparent morphological errors in deep dyslexic reading are genuinely morphological, and discuss the implications of these errors for theories of deep dyslexia.     

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.     

Stimulus-specific neglect in a deep dyslexic patient

We report a patient (B.V.) who appears to suffer from two dyslexic disorders. First, B.V. showed a severe impairment in reading aloud nonwords (e.g., reading TREST as TREE), in addition to making several semantic errors when reading aloud words (e.g., reading ILL as SICK) and in picture naming (e.g., responding KNIFE to a picture of a FORK). These results suggest that B.V. suffers from deep dyslexia. Second, B.V. showed an impairment in reading the final letters of both words and nonwords (e.g., reading SHOWN as SHORT and reading PROGE as PROOF). Thus, it appears that B.V. also suffers from neglect dyslexia. We discuss how these two forms of dyslexia could be interacting to account for B.V.'s pattern of errors in reading aloud words and nonwords and in picture naming.     

Word associations in deep dyslexia

Deep dyslexia is an acquired reading disorder resulting in the production of semantic errors during oral reading and an inability to read aloud nonwords. Several researchers have postulated that patients with deep dyslexia have both phonological and semantic access impairments but the data supporting these claims are not convincing. In fact, the hallmark feature of deep dyslexia--the semantic errors--strongly implies that these patients can access semantic information from printed words. We test the integrity of the semantic system in two such patients through auditory and visual word association tasks. The data support the notion that semantics remains intact and that the disorder and associated errors arise through a selection impairment related to failure of inhibitory connections in the phonological lexicon.     

Acquired dyslexia in Spanish: a review and some observations on a new case of deep dyslexia

Readers and writers of Spanish use an orthography that is highly transparent. It has been proposed that readers of Spanish can rely on grapheme-phoneme correspondences, alone, to access meaning or phonology from print. In recent years, a number of case studies have yielded evidence inconsistent with this idea. We review these studies with particular focus on those that report evidence for reading based on direct lexical mappings between print, orthographic representations, and meaning or phonology. We report a new case of acquired literacy impairment in Spanish, MJ, who presents a pattern of preserved abilities and deficits symptomatic of deep dyslexia. The patient is unable to read nonwords, but can read a substantial number of words. Her reading is characterized by the production of semantic, visual, and derivational errors. We argue that MJ has a deficit in her lexical selection ability, common to both her reading and her naming problems. We propose that MJ, and the other cases we review, demonstrate that lexical reading is adopted by skilled readers even in a transparent language.     

When does a deep dyslexic make a semantic error? The roles of age-of-acquisition, concreteness, and frequency

Semantic reading errors are the central and defining feature of deep dyslexia. This study compared the words the deep dyslexic patient LW read correctly with those she omitted and those to which she produced semantic errors in terms of their concreteness, age-of-acquisition, frequency, and length. Semantic errors were made to less concrete, later-acquired, and shorter words than were read correctly; there was no reliable effect of word frequency. More importantly, the actual semantic errors produced were later-acquired than the stimulus words, but they were not more concrete or reliably more frequent. These results implicate age-of-acquisition in the process that produces semantic errors. It is proposed that concreteness determines the specificity of the semantic system to activate a set of candidate responses and that age-of-acquisition biases the ease with which certain words can be selected from this set to be produced as reading responses.     

发展性阅读障碍儿童阅读中的眼跳定位缺陷：基于新词学习的实验证据

通过与生理年龄匹配儿童比较新词重复学习中眼跳定位模式变化的异同, 探讨发展性阅读障碍儿童在新词学习中的眼跳定位是否存在缺陷。以发展性阅读障碍儿童和生理年龄匹配儿童为被试, 采用重复学习新词范式, 结果发现：(1)与生理年龄匹配组相比, 发展性阅读障碍儿童跳入新词的眼跳距离较短、首次注视落点位置更靠近词首; (2)生理年龄匹配组儿童利用学习次数调节新词眼跳定位模式的能力高于发展性阅读障碍儿童, 即随着新词学习次数的增加, 生理年龄匹配组儿童跳入和跳出新词的眼跳距离随之增长, 首次注视落点位置更靠近词中心; 相比之下, 发展性阅读障碍儿童仅在跳出新词的眼跳距离上有所增长, 但增加幅度也显著小于生理年龄匹配组。结果表明, 发展性阅读障碍儿童在新词学习中的眼跳定位, 及利用学习次数对眼跳定位的调节上均表现出一定缺陷。     

Impaired oral reading in two atypical dyslexics: a comparison with a computational lexical-analogy model

A computational model of reading was developed based upon the notion that the structural relationship between orthography and phonology is of greater importance than the dimension of semantics for the reading aloud of single words. Degradation of this model successfully simulated the reading performance of two patients with atypical acquired dyslexia. The first patient CAV, studied and described in the literature by Warrington in 1981, presented with unusual concrete word dyslexia, i.e., he had a category-specific reading deficit for concrete words compared with abstract words. The second patient BG is a phonological dyslexic who, although displaying a strong concreteness effect (concrete words read better than abstract words), was able to read functors individually perfectly well, a pattern that is rarely if ever seen. The computational model was used to generate a set of words for which it was predicted that BG would show no concreteness effect. The results of BG's reading of these words were consistent with this prediction, thereby providing greater support for the validity of the model. It is concluded that a computational approach that attempts not only to reproduce the core symptoms of the major varieties of acquired dyslexia but also to simulate clinical data from specific patients has much to contribute to the understanding of cognitive deficits and to the design of effective rehabilitation strategies.     

Word recognition in a phonemic dyslexic patient

The systems underlying word recognition were investigated in a single case study of a patient (K.F.) with an acquired dyslexia. His reading performance was related to parts of speech, word frequency and word concreteness, and his reading errors were analysed. There was a very striking difference between his ability to read concrete and abstract words. Furthermore visual errors, which could not be attributed to a deficit at a peripheral level, predominated; phonemic errors did not occur. It is argued that these findings support a dual encoding model of word recognition, the present case illustrating the impairment of the phonemic route, a direct graphemic-semantic route being relatively spared. These findings and interpretation are for the most part consistent with Marshall and Newcombe's (1973) studies of acquired dyslexia. The present findings are discussed in terms of more general theories of word recognition.     

Frequency effects with visual words and syllables in a dyslexic reader

The present study investigated the nature of the inhibitory syllable frequency effect, recently reported for normal readers, in a German-speaking dyslexic patient. The reading impairment was characterized as a severe deficit in naming single letters or words in the presence of spared lexical processing of visual word forms. Three visual lexical decision experiments were conducted with the dyslexic patient, an unimpaired control person matched to the patient and a control group: Experiment 1 manipulated the frequency of words and word-initial syllables and demonstrated systematic effects of both factors in normal readers and in the dyslexic patient. The syllable frequency effect was replicated in a second experiment with a more strictly controlled stimulus set. Experiment 3 confirmed the patient's deficit in activating phonological forms from written words by demonstrating that a pseudohomophone effect as observed in the unimpaired control participants was absent in the dyslexic patient.     

Whole-word phonological representations of disyllabic words in the Chinese lexicon: data from acquired dyslexia

This study addresses the issue of the existence of whole-word phonological representations of disyllabic and multisyllabic words in the Chinese mental lexicon. A Cantonese brain-injured dyslexic individual with semantic deficits, YKM, was assessed on his abilities to read aloud and to comprehend disyllabic words containing homographic heterophonous characters, the pronunciation of which can only be disambiguated in word context. Superior performance on reading to comprehension was found. YKM could produce the target phonological forms without understanding the words. The dissociation is taken as evidence for whole-word representations for these words at the phonological level. The claim is consistent with previous account for discrepancy of the frequencies of tonal errors between reading aloud and object naming in Cantonese reported of another case study of similar deficits. Theoretical arguments for whole-word form representations for all multisyllabic Chinese words are also discussed.     

The Nature of the Automatization Deficit in Chinese Children with Dyslexia

Clarifying whether automatization deficits constitute the primary causes or symptoms of developmental dyslexia, we focused on three critical issues of the dyslexic automatization deficit, namely universality, domain specificity, and severity. Thirty Chinese dyslexic children (mean age 10 years and 5 months), 30 chronological-age-, and 30 reading-level-matched children were tested in 4 areas of automaticity: motor, visual search, Stroop facilitation effects, and automatic word recognition. The results showed that the dyslexic children performed significantly worse than the CA-controls but not the RL-controls in all the tasks except for Stroop congruent-color words, on which they performed worse than children in both control groups. The deficits reflect a lag in reading experiences rather than a persistent cognitive deficit.     

间距和语义对阅读障碍儿童拥挤效应的影响

以14名阅读障碍儿童以及与其年龄和阅读水平相匹配的儿童为实验对象,考察了间距和语义对阅读障碍儿童拥挤效应的影响。结果发现阅读障碍儿童受拥挤效应的影响显著大于正常儿童,表明阅读障碍存在视觉加工缺陷;间距和语义均影响阅读障碍儿童的拥挤效应,表明影响阅读障碍儿童拥挤效应的因素既有刺激的低水平视觉特征,也有高水平语言信息;间距与阅读障碍儿童拥挤效应的关系呈U型。     

Picture Naming Deficits in Developmental Dyslexia: The Phonological Representations Hypothesis

The picture and word naming performance of developmental dyslexics was compared to the picture and word naming performance of non-dyslexic (“garden variety”) poor readers, reading age, and chronological age-matched controls. The stimulus list used for both tasks was systematically manipulated for word length and word frequency. In order to examine picture naming errors in more depth, an object name recognition test assessed each subject's vocabulary knowledge of those names which they were unable to spontaneously label in the picture naming task. Findings indicated that the dyslexic and the garden variety poor readers exhibited a picture naming deficit relative to both chronological and reading age-matched controls. Findings also indicated that both groups of impaired readers obtained superior scores in the word naming task than in the picture naming task, while both groups of controls showed no difference in performance across tasks. The dyslexics' picture naming errors, but not those of the garden variety poor readers, were particularly marked on polysyllabic and/or low frequency words, indicating a possible phonological basis to the picture naming deficit of the dyslexic children. These children also recognized significantly more unnamed target words than all comparison groups, suggesting a particular difficulty inretrievingthe phonological codes of known picture names rather than a vocabulary deficit. Results are discussed in terms of dyslexics' difficulty in encoding full segmental phonological representations of names in long-term memory and/or in processing these representations in order to generate required names on demand.     

Spanish developmental dyslexia: Prevalence, cognitive profile, and home literacy experiences

This study was designed to examine the prevalence, cognitive profile, and home literacy experiences in subtypes of Spanish developmental dyslexia. The subtyping procedure used comparison with chronological-age-matched and reading-level controls on reaction times and accuracy responses to high-frequency words and pseudowords. Using regression-based procedures, 8 phonological dyslexics and 16 surface dyslexics were identified from a sample of 35 dyslexic fourth graders by comparing them with chronological-age-matched controls on reaction times to high-frequency word and pseudoword reading. However, when the dyslexic subtypes were defined by reference to reading-level controls, 12 phonological dyslexics were defined but only 5 surface dyslexics were identified. Both dyslexic subtypes showed a deficit in phonological awareness, but children with surface dyslexia also showed a deficit in orthographical processing assessed by a homophone comprehension task. This deficit was associated with poor home literacy experiences, with the group of parents with children matched in reading age, in comparison with the group of parents with children with surface dyslexia, reporting more literacy home experiences.     

Deep dyslexia in childhood?

Deep dyslexia is an acquired reading disorder in which semantic substitutions (e.g., city read as town) are made in reading single isolated words. In this paper, evidence for deep dyslexic-type errors is presented from the word-recognition responses of six children, aged 7 years and 0 month to 8 years and 9 months, with severe reading disorders. These semantic substitutions occur in the absence of phonological skills. Therefore, it appears that there exists a small subset of developmental dyslexics who at the beginning of acquisition of reading skills are able to engage in semantic processing, but who show severe impairment of phonological processing. The existence of these reading errors indicate that the use of a phonological code is not necessary to extract meaning from the printed word.     

Further evidence on the effect of word imageability in dyslexia

Subjects with acquired dyslexia sometimes find abstract words more difficult to read than concrete words. Three dyslexic patients were found to show performance corrrelating with the imageability of the material, but not with its concreteness. This could not be explained in terms of lexical complexity; indeed, derived nouns were easier to read than simple nouns. These effects were reliable across the three subjects. It was suggested that they were naming imaginal representations of the referents of imageable nouns.