Rapid processing of letters,digits and symbols: what purely visual‐attentional deficit in developmental dyslexia?

Visual‐attentional theories of dyslexia predict deficits for dyslexic children not only for the perception of letter strings but also for non‐alphanumeric symbol strings. This prediction was tested in a two‐alternative forced‐choice paradigm with letters, digits, and symbols. Children with dyslexia showed significant deficits for letter and digit strings but not for symbol strings. This finding is difficult to explain for visual‐attentional theories of dyslexia which postulate identical deficits for letters, digits and symbols. Moreover, dyslexics showed normal W‐shaped serial position functions for letter and digit strings, which suggests that their deficit is not due to an abnormally small attentional window. Finally, the size of the deficit was identical for letters and digits, which suggests that poor letter perception is not just a consequence of the lack of reading. Together then, our results show that symbols that map onto phonological codes are impaired (i.e. letters and digits), whereas symbols that do not map onto phonological codes are not impaired. This dissociation suggests that impaired symbol‐sound mapping rather than impaired visual‐attentional processing is the key to understanding dyslexia.     

Naming fluency in dyslexic and nondyslexic readers: Differential effects of visual crowding in foveal,parafoveal, and peripheral vision

Reading fluency is often indexed by performance on rapid automatized naming (RAN) tasks, which are known to reflect speed of access to lexical codes. We used eye tracking to investigate visual influences on naming fluency. Specifically, we examined how visual crowding affects fluency in a RAN-letters task on an item-by-item basis, by systematically manipulating the interletter spacing of items, such that upcoming letters in the array were viewed in the fovea, parafovea, or periphery relative to a given fixated letter. All lexical information was kept constant. Nondyslexic readers’ gaze durations were longer in foveal than in parafoveal and peripheral trials, indicating that visual crowding slows processing even for fluent readers. Dyslexics’ gaze durations were longer in foveal and parafoveal trials than in peripheral trials. Our results suggest that for dyslexic readers, influences of crowding on naming speed extend to a broader visual span (to parafoveal vision) than that for nondyslexic readers, but do not extend as far as peripheral vision. The findings extend previous research by elucidating the different visual spans within which crowding operates for dyslexic and nondyslexic readers in an online fluency task.     

Elucidating the component processes involved in dyslexic and non-dyslexic reading fluency: An eye-tracking study

The relationship between rapid automatized naming (RAN) and reading fluency is well documented (see Wolf, M. & Bowers, P.G. (1999). The double-deficit hypothesis for the developmental dyslexias. Journal of Educational Psychology, 91(3), 415–438, for a review), but little is known about which component processes are important in RAN, and why developmental dyslexics show longer latencies on these tasks. Researchers disagree as to whether these delays are caused by impaired phonological processing or whether extra-phonological processes also play a role (e.g., Clarke, P., Hulme, C., & Snowling, M. (2005). Individual differences in RAN and reading: A response timing analysis. Journal of Research in Reading, 28(2), 73–86; Wolf, M., Bowers, P.G., & Biddle, K. (2000). Naming-speed processes, timing, and reading: A conceptual review. Journal of learning disabilities, 33(4), 387–407). We conducted an eye-tracking study that manipulated phonological and visual information (as representative of extra-phonological processes) in RAN. Results from linear mixed (LME) effects analyses showed that both phonological and visual processes influence naming-speed for both dyslexic and non-dyslexic groups, but the influence on dyslexic readers is greater. Moreover, dyslexic readers’ difficulties in these domains primarily emerge in a measure that explicitly includes the production phase of naming. This study elucidates processes underpinning RAN performance in non-dyslexic readers and pinpoints areas of difficulty for dyslexic readers. We discuss these findings with reference to phonological and extra-phonological hypotheses of naming-speed deficits.     

发展性阅读障碍者的快速命名缺陷

快速命名任务是一种需要命名多个高熟悉项目的认知任务,尤其适合用来对成因复杂的发展性阅读障碍进行研究。许多研究者使用不同类型的快速命名任务发现,发展性阅读障碍者的快速命名缺陷在眼动过程表现为中央凹和副中央凹的加工困难,在认知过程中表现为抑制能力较差等。未来的研究中应该注意到快速命名缺陷的复杂性,采用多种方法相结合的方式来探究快速命名缺陷的本质,从而建立系统性的假说。     

Naming problems do not reflect a second independent core deficit in dyslexia: Double deficits explored

The double deficit hypothesis states that naming speed problems represent a second core deficit in dyslexia independent from a phonological deficit. The current study investigated the main assumptions of this hypothesis in a large sample of well-diagnosed dyslexics. The three main findings were that (a) naming speed was consistently related only to reading speed; (b) phonological processing speed and naming speed loaded on the same factor, and this factor contributed strongly to reading speed; and (c) although general processing speed was involved in speeded naming of visual items, it did not explain the relationship between naming speed and reading speed. The results do not provide support for the existence of a second independent core naming deficit in dyslexia and indicate that speeded naming tasks are mainly phonological processing speed tasks with an important addition: fast cross-modal matching of visual symbols and phonological codes.     

Visual rapid naming and phonological abilities: different subtypes in dyslexic children

One implication of the double-deficit hypothesis for dyslexia is that there should be subtypes of dyslexic readers that exhibit rapid naming deficits with or without concomitant phonological processing problems. In the current study, we investigated the validity of this hypothesis for Portuguese orthography, which is more consistent than English orthography, by exploring different cognitive profiles in a sample of dyslexic children. In particular, we were interested in identifying readers characterized by a pure rapid automatized naming deficit. We also examined whether rapid naming and phonological awareness independently account for individual differences in reading performance. We characterized the performance of dyslexic readers and a control group of normal readers matched for age on reading, visual rapid naming and phonological processing tasks. Our results suggest that there is a subgroup of dyslexic readers with intact phonological processing capacity (in terms of both accuracy and speed measures) but poor rapid naming skills. We also provide evidence for an independent association between rapid naming and reading competence in the dyslexic sample, when the effect of phonological skills was controlled. Altogether, the results are more consistent with the view that rapid naming problems in dyslexia represent a second core deficit rather than an exclusive phonological explanation for the rapid naming deficits. Furthermore, additional non-phonological processes, which subserve rapid naming performance, contribute independently to reading development.     

Phonological recoding,rapid automatized naming,and orthographic knowledge

Phonological recoding, orthographic knowledge, and rapid automatized naming (RAN) are three major contributors to word identification. However, the interrelations between these components remain somewhat unclear. The current analyses focus on how phonological recoding and alphanumeric versus non-alphanumeric RAN contribute to different components of orthographic knowledge (word specific vs. general). Results indicate that alphanumeric and non-alphanumeric RAN contribute to orthographic knowledge components differently. Alphanumeric RAN relates more to word-specific orthographic knowledge, whereas non-alphanumeric RAN relates more to general orthographic knowledge. Furthermore, phonological recoding is more closely related to word-specific orthographic knowledge than to general orthographic knowledge.     

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.     

What does rapid automatized naming measure? A new RAN task compared to naming and lexical decision

The present research investigated the relationship between Rapid Automatized Naming (RAN) performance, letter-string reading measures of sight vocabulary (SV) and phonetic decoding (PD), and lexical decision. Criterion-based naming rates were obtained from three types of RAN tasks: digits, letters, and letter sounds. Latency measures were obtained from the naming of regular words, exception words, nonwords and pseudohomophones; as well as button press and verbal lexical decision tasks. Regression analyses supported the hypotheses that RAN-Letters latency reflects SV processing in that its variance is uniquely accounted for by exception word naming latency and button press lexical decision latency, and that RAN-Letter Sounds latency best reflects PD processing in that its variance is uniquely accounted for by pseudohomophone and nonword naming latency. Findings are discussed in light of what the RAN tasks are measuring, implications involving visual word recognition models of reading, and the utility of the new RAN-Letter Sounds task with respect to diagnostic and remediation applications.     

Rapid serial naming: relations between different stimuli and neuropsychological factors

We report two studies on rapid serial naming (RSN). Study 1 addressed the relations among RSN tasks comprising different stimuli. Separate components for RSN of alphanumeric and non-alphanumeric stimuli, as well as for tasks in which the stimuli alternated between categories were identified. In Study 2, phonological skills, processing speed, motor dexterity, and verbal fluency were found to explain RSN performance. The studies indicate: (1) that RSN tasks vary in their properties according to the stimuli used and according to the way the tasks are arranged, and (2) that RSN tasks are multi-componented.     

Alphanumeric category effects: Evidence against the sufficiency of a localization explanation

The Hatfield Polytechnic, Hatfield, Herts ALIO 9AB, England The experiment utilized a serial choice reaction time (RT) paradigm in which only one alphanumeric stimulus was presented per trial, and the target set consisted of a single identified item. The categorical relationship between the target and nontarget items was varied as a property of blocks of trials. Target and nontarget RTs were smaller when the specified target item (e.g., the number 6) was categorically distinct from the nontargets (e.g., letters) than when it was from the same category (e.g., digits). The processing of catch-trial stimuli (items from the alternate category to the nontargets) and homographie category-ambiguous items was inhibited only in the former, between-category, condition. The results are contrasted with those obtained in visual search tasks. They suggest that a “locational-cue” explanation of alphanumeric category effects is inadequate.     

Rate variables and automatized naming in developmental dyslexia

The rate variable in rapid automatized naming (RAN) was investigated in 50 adolescent and 40 adult students with developmental dyslexia, in matched normal controls, and in learning-disabled students without reading difficulties. Visual stimuli depicting familiar colors and common objects were presented in isolation at three film speeds and three exposure times. Film speed and exposure time contributed as independent variables to error rate; and dyslexic subjects of both age groups made significantly more naming errors than controls. Dyslexic subjects also responded with longer naming latencies than controls when the same RAN stimuli were presented in a continuous sequential mode as a matrix of rows and columns. Naming latencies in the sequential presentation were highly correlated with naming errors in the film version. The implications of reduced naming rates for nongraphological stimuli in developmental dyslexia are discussed.     

Dyslexic and nondyslexic reading fluency: Rapid automatized naming and the importance of continuous lists

Rapid automatized naming (RAN; Denckla & Rudel, 1976) tasks are consistent predictors of fluency that also discriminate between dyslexic and nondyslexic reading groups. The component processes of RAN that are responsible for its relationship with reading ability remain underspecified, however. We report a study on dyslexic and nondyslexic adult groups that experimentally manipulated RAN formats to elucidate how different components of RAN differentially influence dyslexic and nondyslexic performance. The dyslexic group showed a pervasive deficit in rapid access of individually presented items. Additionally, they showed a significant impairment when multiple items were presented, whereas nondyslexic readers showed marginal facilitation for this format. We discuss the implications of these findings with respect to reading-group differences in reading fluency.     

Cerebral dominance assessed by object- and color-naming latencies: sex and familial sinistrality effects.

Two vocal RT experiments were conducted. The first required the naming of five lateralized drawings of common objects; the second of five hues of equal brightness and saturation. Tachistoscopic exposure time was 100 msec. Both tasks yielded faster RT to stimuli channeled directly to the left hemisphere, demonstrating that the left hemisphere superiority for naming letters or digits obtained in previous tachistoscopic studies was not dependent on the use of alphanumeric stimuli. Interesting sex differences in object-naming and familial sinistrality differences in color-naming were obtained. Compared with other behavioral tasks for assessing language laterality, color-naming seems highly recommended in terms of freedom from spatial-confounding, good percentage agreement with clinical estimates of the frequency of left hemisphere language dominance in right handers, and sensitivity to familial sinistrality influences.     

Multiple stimulus presentation yields larger deficits in children with developmental dyslexia: A study with reading and RAN-type tasks

In this study, we examined the effect of multiple versus single stimulus presentation in typically developing readers and children with developmental dyslexia. The tasks involved either reading single words or arrays of words or naming single or multiple colors and digits (rapid automatized naming or RAN). To be able to compare these sets of conditions, we recorded total response times (i.e., the time between stimulus onset and the end of the participant’s vocal response) in all cases. The study included 43 typically developing readers and 25 children with dyslexia.

Results indicate that typically developing readers have a clear advantage with multiple over single items on both RAN and reading tasks. The children with dyslexia showed a moderate advantage for multiple stimuli in naming colors and digits but presented the opposite pattern in reading.

With regard to reading, the disproportionate impairment of the children with dyslexia in dealing with multiple arrays suggests difficulty in integrating the multiple subcomponents of the reading task over and above the basic nuclear deficit in decoding words. Regarding the RAN tasks, results confirm that the requirement of integrating multiple subcomponents may be critical in mediating the predictive value of these measures on reading.     

Visual and name coding in dyslexic children

Summary Four experiments are reported which were designed to test for differences between dyslexic and non-dyslexic subjects at a number of visual information processing functions. It is argued that the older dyslexic child's reading problems cannot be ascribed to slowness of visual code production, to the limited capacity of the system, or to an extra rapid rate of decay. The results are compatible with the theory that, as a group, the dyslexic children tested show a slowness or inadequacy at a non-visual, name or linguistic coding level. It is suggested that this deficiency does not lie in the area of articulatory encoding but at an earlier stage where phonological or lexical codes are produced from visual stimuli.     

Evidence of a highly specific relationship between rapid automatic naming of digits and text-reading speed

This paper explores the specificity of the relationship between rapid automatic naming and reading fluency. Reading accuracy, rate, and fluency was measured among a sample of 67 children, the majority of whom were very poor readers. Regression analyses revealed that phonological processing tasks predicted reading accuracy and comprehension whereas rapid digit (but not picture) naming predicted reading accuracy and rate. After further controlling reading accuracy, digit naming was still a significant predictor of reading rate. This suggests that rapid alphanumeric naming is a highly specific predictor of reading rate and that rapid digit naming and phonological processing are distinct contributors to different aspects of reading in poor readers.     

Learning to read facilitates the retrieval of phonological representations in rapid automatized naming: Evidence from unschooled illiterate,ex‐illiterate,and schooled literate adults

Rapid automatized naming (RAN) of visual items is a powerful predictor of reading skills. However, the direction and locus of the association between RAN and reading is still largely unclear. Here, we investigated whether literacy acquisition directly bolsters RAN efficiency for objects, adopting a strong methodological design, by testing three groups of adults matched in age and socioeconomic variables, who differed only in literacy/schooling: unschooled illiterate and ex‐illiterate, and schooled literate adults. To investigate in a fine‐grained manner whether and how literacy facilitates lexical retrieval, we orthogonally manipulated the word‐form frequency (high vs. low) and phonological neighborhood density (dense vs. spare) of the objects' names. We observed that literacy experience enhances the automaticity with which visual stimuli (e.g., objects) can be retrieved and named: relative to readers (ex‐illiterate and literate), illiterate adults performed worse on RAN. Crucially, the group difference was exacerbated and significant only for those items that were of low frequency and from sparse neighborhoods. These results thus suggest that, regardless of schooling and age at which literacy was acquired, learning to read facilitates the access to and retrieval of phonological representations, especially of difficult lexical items.     

Speed of phonological and orthographic processing as factors in dyslexia: electrophysiological evidence

The author investigated the hypothesis that speed of processing in the phonological and orthographic systems is one of the underlying variables of word-reading effectiveness. Speed of processing was assessed using measures of behavioral reaction time and electrophysiological latencies during phonological and orthographic task performance. Participants were 20 dyslexic and 20 normal-reading, male college students. An electrophysiological component complex (N1-P2-N2), as well as 2 other components (P3 and N4), was identified in both groups on each of the experimental tasks. Significant group differences were obtained only on the phonological tasks. Speed of processing during phonological judgment tasks was significantly prolonged among the dyslexic readers compared with the controls as reflected by P2, P3, and N4 latencies and reaction time. Between-task comparisons revealed significantly prolonged P2, P3, and N4 latencies on phonological compared with orthographic tasks in both dyslexic and normal readers, indicating that phonological classification of words may demand more time than orthographic classification. However, the gap score between speed of processing on the phonological and orthographic tasks was larger among the dyslexic readers and was observed mainly in P3 latency and reaction time. The highest correlation between word-reading accuracy score and the experimental measures was obtained in the dyslexic group with P3 latency gap score and in the control group with P2 latency gap score. The author proposes that slow phonological processing may cause "asynchrony" between the processing speeds within and between phonological and orthographic systems and may lead to a lack of efficient integration among the various subprocesses activated in reading, may slow down reading rate, and may impair word-reading effectiveness.     

The cognitive profile and multiple-deficit hypothesis in Chinese developmental dyslexia

The present study was conducted to examine the cognitive profile and multiple-deficit hypothesis in Chinese developmental dyslexia. Thirty Chinese dyslexic children in Hong Kong were compared with 30 average readers of the same chronological age (CA controls) and 30 average readers of the same reading level (RL controls) in a number of rapid naming, visual, phonological, and orthographic tasks. Chinese dyslexic children performed significantly worse than the CA controls but similarly to the RL controls on most of the cognitive tasks. The rapid naming deficit was found to be the most dominant type of cognitive deficit in Chinese dyslexic children. Over half of the dyslexic children exhibited deficits in 3 or more cognitive areas, and there was a significant association between the number of cognitive deficits and the degree of reading and spelling impairment. The present findings support the multiple-deficit hypothesis in Chinese developmental dyslexia.