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Developmental dyslexia: Related to specific or general deficits?
Abstract
The present study was designed to examine the question of whether developmental dyslexia in 12-year-old students at the beginning
of secondary education in the Netherlands is confined to problems in the domain of reading and spelling or also is related
to difficulties in other areas. In particular, hypotheses derived from theories on phonological processing, rapid automatized
naming, working memory, and automatization of skills were tested. To overcome the definition and selection problems of many
previous studies, we included in our study all students in the first year of secondary special education in a Dutch school
district. Participants were classified as either dyslexic, garden-variety, or hyperlexic poor readers, according to the degree
of discrepancy between their word recognition and listening comprehension scores. In addition, groups of normal readers were
formed, matching the poor readers in either reading age or chronological age. A large test battery was administered to each
student, including phonological, naming, working memory, speed of processing, and motor tests. The findings indicate that
dyslexia is associated with deficits in (1) phonological recoding, word recognition (both in their native Dutch and in English
as a second language), and spelling skills; and (2) naming speed for letters and digits. Dyslexia was not associated with
deficits in other areas. The results suggest that developmental dyslexia, at the age of 12, might be (or might have become)
a difficulty rather isolated from deficiencies in other cognitive and motor skills.
... However, again, this theory does not account for the highly specific difficulties in children with dyslexia. In addition, while some children with dyslexia experience motor impairments, some studies have reported motor problems in only a subgroup of children with dyslexia (Ramus et al., 2003) or not at all ( van Daal & van der Leij, 1999). Furthermore, there is evidence to suggest motor/cerebellar impairments in dyslexia are result of comorbidity with ADHD (Raberger & Wimmer, 2003;Rochelle & Talcott, 2006). ...
Dyslexia is a developmental disorder characterised by difficulties in the accurate and fluent decoding of printed words. The dominant theory of dyslexia argues that reading failures are caused by a phonological processing deficit, resulting in impaired phoneme awareness and problems learning letter-sound correspondences. In recent years researchers have proposed a novel theory of dyslexia. This theory, based on neuroimaging studies of Dutch children, suggests that problems learning to read arise from a specific deficit establishing automatic associations between letters and speech-sounds. Whilst many agree that letter-sound knowledge plays an important role in learning to read, the crucial aspect of this hypothesis concerns children’s ability to retrieve and apply this knowledge rapidly during reading. This thesis is one of the first studies to use behavioural measures to assess the contribution of automatic letter-sound integration in the reading performance of English-speaking children. A behavioural priming paradigm was used to measure automatic letter-sound integration. In this task, the participant is presented with a visual letter prime, followed by an auditory speech-sound target. The effect of the letter prime upon the processing of the speech-sound is examined in a number of studies, including a large cross-sectional study of typically developing children and a study involving children with dyslexia. Contrary to the hypothesis that dyslexia reflects a deficit in automatic letter-sound integration, the results from this research indicate that both dyslexic and typically developing children show automatic activation of speech-sounds from printed letters. Furthermore, the extent to which letters and speech-sounds are automatically integrated does not appear to predict variation in children’s reading performance. Rather, baseline performance on this task (simply deciding if a sound is speech or not) is predictive of reading performance, which is argued to provide further evidence of the importance of phonological skills for the development of decoding.
... Τα ευρήματά μας συμφωνούν με αυτά άλλων ερευνητών που διαπίστωσαν ότι οι φτωχοί αναγνώστες έχουν από την προσχολική ηλικία χαμηλό- τερες επιδόσεις σε σχέση με τους τυπικούς στην φωνολογική επίγνωση (Snowling, 2000), στην ταχύτητα κατονομασίας εικόνων (Van Daal, 1999), στις δοκιμασίες φωνολογικής μνήμης (Gathercole, 1998• Plaza et al., 2002, στην ακουστική επεξεργασία (Talcott, 2002), στις δοκιμασίες προφορικού λόγου (Larrivee & Catts, 1999) και στις κινητικές δοκιμασίες (Stoodley et al., 2005). Επιπρόσθετα, τα αποτελέσματά μας συνάδουν με σύγχρονα ευρήματα και απόψεις που υποστηρίζουν ότι η δυσλεξία και γενικότερα οι αναγνωστικές δυσκολίες δεν μπορούν να ερμηνευτούν με βάση ένα μεμονωμένο έλλειμμα (Βλάχος, 2010· Heim et al., 2008. ...
The aim of this longitudinal study was to examine whether specific skills developed during preschool years could predict the reading performance in children with low reading abilities in the first and second grade of primary school. In this longitudinal study 287 children (146 boys and 141 girls) participated, of whom we separated as children with low reading performance those that had a score 1.5 standard deviation below the average performance in total reading ability. 21 children (7.3% of the original sample) met the above criterion in the 1st grade and 22 children (7,6% of the original sample) in the 2nd grade. At the kindergarten, the phonological awareness (syllable segmentation, recognition of common initial phoneme, deletion of syllable and phoneme), the rapid automatized naming (RAN), the phonological short-term memory (digit span and repetition of nonwords), the auditory processing (discrimination of sets of sounds), the motor development (static balance, eye-movement co-ordination, coping shape) and the oral language (receptive and expressive vocabulary) were evaluated. Reading performance (accuracy, fluency and text comprehension) was evaluated in the 1st and 2nd grade of primary school. The results showed that phonological awareness and rapid automatized naming (RAN) predicted the low (total) reading performance in 1st grade, while phonological awareness was also the only predictor of reading accuracy and fluency. In the 2nd grade, the tests of motor development predict the low (total) reading performance, the rapid automatized naming predict reading accuracy and fluency and the coping shape predict text comprehension. Our results suggest that the utilization of such early evidence in the implementation of intervention programs during preschool and first school years could contribute to the prevention of possible problems in the reading performance of primary school children.
... Many studies have reported that individuals with dyslexia perform more poorly on pseudoword repetition than control participants (e.g. Brady, Poggie, & Rapala, 1989;Brady, Shankweiler, & Mann, 1983;Hulme & Snowling, 1992;Kamhi & Catts, 1986;Snowling, 1981;Snowling, Goulandris, Bowlby, & Howell, 1986;Van Bon & Van Der Pijl, 1997;Van Daal & van der Leij, 1999), compatible with the notion that a phonological core deficit provides a causal explanation for dyslexia. But note that Reis and Castro-Caldas (1997) found that illiterates also performed much worse than literates on pseudoword repetition (replicated in Castro-Caldas, Petersson, Reis, Stone-Elander, & Ingvar, 1998). ...
2017): Distinguishing cause from effect – many deficits associated with developmental dyslexia may be a consequence of reduced and suboptimal reading experience, Language, Cognition and Neuroscience, ABSTRACT The cause of developmental dyslexia is still unknown despite decades of intense research. Many causal explanations have been proposed, based on the range of impairments displayed by affected individuals. Here we draw attention to the fact that many of these impairments are also shown by illiterate individuals who have not received any or very little reading instruction. We suggest that this fact may not be coincidental and that the performance differences of both illiterates and individuals with dyslexia compared to literate controls are, to a substantial extent, secondary consequences of either reduced or suboptimal reading experience or a combination of both. The search for the primary causes of reading impairments will make progress if the consequences of quantitative and qualitative differences in reading experience are better taken into account and not mistaken for the causes of reading disorders. We close by providing four recommendations for future research. ARTICLE HISTORY
The study explores the role of phonotactics in word recognition processes. Its specific aim is to observe the influence of phonotactic probability and word frequency on reading in children with dyslexia. It is envisaged as a study employing a natural reading environment, as close to the common reading of a text in a book as possible. The approach taken in this study is based on the argumentation that implicit learning plays an important role in language acquisition. In this study, we observed directly the influence of phonotactic probability and word frequency on reading in children with dyslexia. The rationale behind this is that the phonotactic rules of a language are subject to implicit learning.
Based on 378 studies, 541 independent samples, and over 34,000 participants, the current meta-analysis aimed to explore the associations between cognition and reading difficulties (RD). Results showed that compared with age-matched typically developing (TD) peers, RD showed deficits across processing speed, short-term memory, attention, working memory, inhibition, switching, visuospatial skills, and updating (gs = −.72 to −.48), with more individual differences on inhibition, processing speed, switching, attention, visuospatial skills, and short-term memory (ln SDR = .03 to .17). The cognitive deficits among those with RD were more severe with age, with lower reading and IQ scores, and on verbal cognitive tasks. Individual differences in cognitive skills among those with RD were larger with age, as well as on comprehensive/nonverbal IQ identification or reading comprehension identification. Comorbidity did not affect the cognitive profile of RD strongly. Meta-analytic structural equation modeling showed phonological processing and language comprehension explained over 70% of the variance between RD and TD across cognitive skills, yet executive function and visuospatial skills contributed uniquely to RD. These findings highlight a domain-specific cognitive path to RD. That is, cognitive deficits may lead to insufficient language development, causing RD indirectly. However, the association between cognitive deficits and RD is not unidirectional or static. Across development, insufficient accumulation of language skills among those with RD also affects cognitive development, especially in the verbal domain. Without high-quality, sustained instruction, mutual associations between cognitive deficits and RD, forming a vicious circle, may be one major reason for persistent reading struggles among individuals with RD.
Deficits in phonological information processing in upper elementary students with specific learning disabilities in reading or spelling may increase, decrease, or remain stable over time. The authors examined the development of phonological processing longitudinally in 209 students (109 with learning disabilities and 100 typically achieving; n = 127 boys) in Germany, from grade 3 to grade 5 (ages 8–11; mean age at recruitment = 8 years 6.78 months, SD = 5.39 months). Latent change score models revealed that the development of rapid automatized naming was best described as a decreasing deficit, whereas a persistent deficit in phonological awareness was observed. Differences between students with and without learning disabilities regarding the phonological loop increased over time. Further, there were no developmental differences as a function of reading versus spelling deficits. Theoretical and practical implications are discussed.
Purpose: This paper presents the findings of a systematic literature review regarding
the role of phonological memory in reading acquisition and early onset of dyslexia.
Method: Searching multiple bibliographic databases (PUBMED, HEAL-LINK/Annals of
Dyslexia, SCOPUS, SCHOLAR), 254 published studies were identified as potentially
relevant with 12 meeting the inclusion criteria. Eight of them refer to the role of
phonological memory in reading ability and 4 in dyslexia. Results: The findings of the
review highlight: (i) the limited range of conducted research regarding the association
of phonological memory and reading ability in general and dyslexia in particular
among preschool children, (ii) the significant heterogeneity of tools and tasks
implemented and (iii) the shared conclusion by the vast majority of the studies
suggesting that phonological memory affects reading ability and is an onset predictor of
dyslexia. Conclusions: As a general conclusion, it was found that a common goal of all
studies was to evaluate the contribution of phonological memory to reading ability.
However, significant heterogeneity was found in tools and tasks (to a lesser extent) they
used in their studies. Also, no clear conclusion emerged on the role of phonological
memory in the acquisition of reading skill. More specifically, some studies have found a correlation between phonological memory and reading ability and some other non-correlation.
In this study the differential relationships of phonological awareness and rapid naming (serial and dis-crete) with reading accuracy and speed were examined. Participants were 52 Dutch second grade children. Measures of phonological awareness, serial rapid naming (objects and digits) and discrete rapid digit naming were administered. Also, various aspects of reading ability were measured: reading accuracy and speed for words and nonwords, and text reading fluency. The results indicated that second grade Dutch children were not fully accurate readers. A clear dissociation was found between phonological awareness and serial rapid naming, the former being mainly related to reading accuracy and the latter to reading speed. However, both were related to text reading fluency. A dissociation was also observed between serial and discrete rapid digit naming. The latter was particularly associated with word reading speed. The implications for the interpretation of cross-linguistic studies on the correlates of reading are discussed.
The cerebellar deficit hypothesis, proposed by Nicolson and Fawcett (1996; 1999), suggests that dyslexia, one of the most frequent specific learning disabilities, involves general impairment in the ability to perform skills automatically, which several studies have linked to the cerebellum. Disorders in cerebellar development may lead to impairments in reading and writing that are key features of dyslexia and other specific learning disabilities, which would be consistent with the presumed role of the cerebellum in language-related skills. The cerebellum has traditionally been considered as a motor area, so performance on motor and balance tasks may be a way to assess problems in cerebellar function associated with specific learning impairment. The aim of the present study was to determine whether there are differences in performance on balance and motor tasks (Yap and van der Leij, 1994; Ramus and colleagues, 2003) between students with specific learning disabilities (N=32) and typically developing students (N=32), as well as to determine whether performance in both groups correlates with reading skills. Students were in the fourth grade of elementary school in Zagreb, Croatia. Typically developing students achieved a significantly higher total score on balance and motor tasks than students with specific learning disabilities (Mann Whitney U test), supporting the cerebellar deficit hypothesis. In addition, performance on balance and motor tasks correlated significantly with performance on reading tasks (Spearman’s rank correlation). Further research is needed to clarify these correlations and why they occur.
This chapter focuses on specific language impairment and developmental dyslexia from a converging methodological/ developmental perspective under the rhetoric of language learning impairment (LLI). It proposes a multilevel approach, which aims to integrate molecular, cellular, macroscopic, and behavioral evidence. Current etiological models from psychological and biological domains are addressed. The chapter then talks about prospective studies beginning early in the life span and studies targeting remedial intervention. It then provides recommendations and future directions regarding basic research as well as remedial work in developmental language disorders. The chapter highlights that future studies need to address issues emanating from different subtypes of LLI, different modalities, different training methods, different tasks tapping various aspects of language/ literacy skills, and also whether the resulting neural plasticity is a transient or permanent phenomenon. It further points out that the impact of developmental disorders of language on society is substantive.
This paper is an interim report on a large-scale survey. The background to the authors' research into dyslexia is briefly outlined. Next comes an explication of the contrast between "anomaly" and "normal variation." Some details are then provided of a survey of 12,905 children, age ten, who were given a variety of educational and cognitive tests relevant to a diagnosis of dyslexia. It is shown that the resultant distributions of scores are incompatible with the hypothesis of normal variation. The counter-hypothesis, viz. that dyslexia involves some kind of anomaly, has, therefore, to that extent resisted refutation.
Current definitions of reading disability or dyslexia all involve the existence of a discrepancy between reading ability and measured intelligence. It is argued here that the use of intelligence as an aptitude benchmark in the definition of dyslexia conceals illogical assumptions about the concept of potential. The author suggests instead the use of a more educationally relevant aptitude measure, such as listening comprehension. However, all discrepancy definitions predicated on mismatches between aptitude and achievement are called into question by findings that the acquisition of literacy fosters the very cognitive skills that are assessed on aptitude measures. These findings undermine the logic of discrepancy measurement by weakening the distinction between aptitude and achievement. The author concludes that the validity of a severe discrepancy between aptitude and achievement as the defining feature of dyslexia has yet to be established to a degree that would justify differential educational classification or treatment. /// [French] Les définitions actuelles des troubles de lecture ou dyslexie postulent généralement des écarts entre le niveau d'aptitudes intellectuelles tel que mesuré par les tests standardisés et le niveau d'habiletés en lecture. Le point de vue défendu dans cet article est que le fait d'utiliser l'intelligence comme critère dans la définition de la dyslexie repose sur des postulats non fondés quant au concept de potentiel intellectuel. L'auteur propose d'utiliser plutôt des critères académiques, tels que la compréhension verbale. Malgré tout, toutes hypothèses prédisant des écarts entre des types d'aptitudes et des habiletés interreliées sont sujettes à caution dans la mesure où des données de recherche montrent que le développement des habiletés écrites influence le développement des aptitudes cognitives qui sont mesurées par les tests standardisés. Ces données jettent un doute sur la logique qui sous-tend ces hypothèses quant à l'existence d'écarts entre aptitudes cognitives et habiletés en lecture en minimisant la distinction entre aptitudes et habiletés. L'auteur conclut que l'existence de différences importantes entre aptitudes cognitives et habiletés en lecture comme critère de définition de la dyslexie reste à démontrer si l'on veut justifier le bien fondé de classements et de traitements différents des enfants dyslexiques. /// [Spanish] Las definiciones actuales de dificultades de lectura o dislexia envuelven todas la existencia de una discrepancia entre habilidad de lectura e inteligencia medida. Se argumenta aquí que el uso de la inteligencia como una marca de aptitud en la definición de dislexia esconde razonamientos ilógicos acerca del concepto de potencial. El autor sugiere en cambio, el uso de una medida más relevante educativamente de medición de aptitudes, tal como la comprensión oral. Sin embargo, todas las definiciones de discrepancia predicadas en las uniones equivocadas entre aptitud y logro son cuestionadas por los hallazgos de que la adquisición de la lectura promueve las mismas habilidades cognitivas que se miden en las medidas de aptitud. Estos hallazgos minan la lógica de la medida de discrepancia al debilitar la distinción entre aptitud y logro. El autor concluye que la validez de una severa discrepancia entre aptitud y logro como la marca que define a la dislexia aún está por establecerse a un grado tal que justificara la clasificación educativa o el tratamiento diferencial. /// [German] In allen derzeitigen Definitionen über Lesestörung oder Legasthenie ist eine Diskrepanz zwischen Lesefähigkeit und gemessener Intelligenz vorhanden. An dieser Stelle wird argumentiert, daß die Verwendung des Faktors Intelligenz-als eine Eignungsbewertung bei der Definition von Legasthenie-die unlogische Annahme eines Potentialkonzepts verschleiert. Stattdessen schlägt der Verfasser vor, eine Eignungsmaßnahme anzuwenden, die stärker auf die Schulbildung anwendbar ist, wie z.B. das Hörverständnis. Alle Diskrepanzdefinitionen, die auf der Fehlanpassung zwischen Eignung und Leistung basieren, wurden durch die Feststellung in Frage gestellt, daß der Erwerb der Lesefähigkeit genau diejenigen kognitiven Fertigkeiten fördert, die anhand von Eignungsmaßnahmen festgelegt werden. Der Verfasser schließt daraus, daß die Gültigkeit einer wesentlichen Diskrepanz zwischen Eignung und Leistung als das definierende Merkmal für Legasthenie noch in gewissem Grade festgelegt werden muß, damit eine differentielle Bildungsklassifizierung oder Bildungsmaßnahme berechtigt wäre.
This study examined whether the characteristic reading speed impairment of German dyslexic children results from a general skill-automatization deficit sensu Nicolson and Fawcett (1990) or from more specific deficits in visual naming speed and phonological skills. The hypothesized skill-automatization deficit was assessed by balancing, peg moving, and visual search. Rapid "automatized" naming tasks served as measures of impaired visual naming speed, and the phonological deficit was assessed by speech perception, phonological sensitivity, and phonological memory tasks. Dyslexic German children and age-matched control children (all boys) were tested at the end of Grade 2 and as participants of a longitudinal study also at the beginning of Grade 1. No evidence for a skill-automatization deficit was found, as the dyslexic children did not differ at all on the balancing tasks and little on the other nonverbal skill tasks. However, the dyslexic children showed impaired visual naming speed and impaired phonological memory performance that were observed not only in Grade 2 but also before learning to read. Overall, the findings support the conclusion that, even in regular orthographies, difficulties in learning to read are due to a phonological deficit and not to a general skill-automatization deficit.