New Insights on Developmental Dyslexia Subtypes: Heterogeneity of Mixed Reading Profiles

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Abstract

We examined whether classifications based on reading performance are relevant to identify cognitively homogeneous subgroups of dyslexic children. Each of the 71 dyslexic participants was selected to have a mixed reading profile, i.e. poor irregular word and pseudo-word reading performance (accuracy and speed). Despite their homogeneous reading profile, the participants were found to split into four distinct cognitive subgroups, characterized by a single phonological disorder, a single visual attention span disorder, a double deficit or none of these disorders. The two subgroups characterized by single and contrasted cognitive disorders were found to exhibit a very similar reading pattern but more contrasted spelling performance (quantitative analysis). A qualitative analysis of the error types produced in reading and spelling provided some cues about the participants' underlying cognitive deficit. The overall findings disqualify subtyping based on reading profiles as a classification method to identify cognitively homogeneous subgroups of dyslexic children. They rather show an opaque relationship between the cognitive underpinnings of developmental dyslexia and their behavioral manifestations in reading and spelling. Future neuroimaging and genetic studies should take this issue into account since synthesizing over cognitively heterogeneous children would entail potential pitfalls.

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Most cited references 37

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Developmental dyslexia: the visual attention span deficit hypothesis.

Marie-Line Bosse, Marie Tainturier, Sylviane Valdois (2007)

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.

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Specific reading disability (dyslexia): what have we learned in the past four decades?

Frank Vellutino, Paul Scanlon, Sarah J. Fletcher … (2003)

We summarize some of the most important findings from research evaluating the hypothesized causes of specific reading disability ('dyslexia') over the past four decades. After outlining components of reading ability, we discuss manifest causes of reading difficulties, in terms of deficiencies in component reading skills that might lead to such difficulties. The evidence suggests that inadequate facility in word identification due, in most cases, to more basic deficits in alphabetic coding is the basic cause of difficulties in learning to read. We next discuss hypothesized deficiencies in reading-related cognitive abilities as underlying causes of deficiencies in component reading skills. The evidence in these areas suggests that, in most cases, phonological skills deficiencies associated with phonological coding deficits are the probable causes of the disorder rather than visual, semantic, or syntactic deficits, although reading difficulties in some children may be associated with general language deficits. Hypothesized deficits in general learning abilities (e.g., attention, association learning, cross-modal transfer etc.) and low-level sensory deficits have weak validity as causal factors in specific reading disability. These inferences are, by and large, supported by research evaluating the biological foundations of dyslexia. Finally, evidence is presented in support of the idea that many poor readers are impaired because of inadequate instruction or other experiential factors. This does not mean that biological factors are not relevant, because the brain and environment interact to produce the neural networks that support reading acquisition. We conclude with a discussion of the clinical implications of the research findings, focusing on the need for enhanced instruction.

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Phonological recoding and orthographic learning: A direct test of the self-teaching hypothesis.

D L Share (1999)

According to the self-teaching hypothesis (Share, 1995), word-specific orthographic representations are acquired primarily as a result of the self-teaching opportunities provided by the phonological recoding of novel letter strings. This hypothesis was tested by asking normal second graders to read aloud short texts containing embedded pseudoword targets. Three days later, target spellings were correctly identified more often, named more quickly, and spelled more accurately than alternate homophonic spellings. Experiment 2 examined whether this rapid orthographic learning can be attributed to mere visual exposure to target strings. It was found that viewing the target letter strings under conditions designed to minimize phonological processing significantly attenuated orthographic learning. Experiment 3 went on to show that this reduced orthographic learning was not attributable to alternative nonphonological factors (brief exposure durations or decontextualized presentation). The results of a fourth experiment suggested that the contribution of pure visual exposure to orthographic learning is marginal. It was concluded that phonological recoding is critical to the acquisition of word-specific orthographic representations as proposed by the self-teaching hypothesis. Copyright 1999 Academic Press.

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Author and article information

Contributors

Evelyn Kroesbergen: Role: Editor

Journal

Journal ID (nlm-ta): PLoS One

Journal ID (iso-abbrev): PLoS ONE

Journal ID (publisher-id): plos

Journal ID (pmc): plosone

Title: PLoS ONE

Publisher: Public Library of Science (San Francisco, USA )

ISSN (Electronic): 1932-6203

Publication date Collection: 2014

Publication date (Electronic): 11 June 2014

Volume: 9

Issue: 6

Electronic Location Identifier: e99337

Affiliations

[1 ]Centre Référent de Diagnostic des Troubles du Langage et des Apprentissages, Pôle Couple-Enfant, Centre Hospitalier Universitaire, Grenoble, France

[2 ]Laboratoire de Psychologie et NeuroCognition, CNRS, UMR 5105, Université Grenoble Alpes, Grenoble, France

Utrecht University, Netherlands

Author notes

* E-mail: rachel.zoubri@ 123456gmail.com

Competing Interests: The authors have declared that no competing interests exist.

Conceived and designed the experiments: RZ FB SV. Performed the experiments: RZ FB. Analyzed the data: RZ FB SV. Contributed reagents/materials/analysis tools: RZ FB SV. Wrote the paper: RZ FB SV.

Article

Publisher ID: PONE-D-14-00286

DOI: 10.1371/journal.pone.0099337

PMC ID: 4053380

PubMed ID: 24918441

SO-VID: 419396bc-b6b7-427c-8832-d652baca608f

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This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

History

Date received : 5 January 2014

Date accepted : 14 May 2014

Page count

Pages: 15

Funding

This work was supported by ANR Blanc ORTHOLEARN: ANR-12-BSH2-0013-01. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

New Insights on Developmental Dyslexia Subtypes: Heterogeneity of Mixed Reading Profiles

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Most cited references 37

Developmental dyslexia: the visual attention span deficit hypothesis.

Specific reading disability (dyslexia): what have we learned in the past four decades?

Phonological recoding and orthographic learning: A direct test of the self-teaching hypothesis.

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