Categorical and Dimensional Diagnoses of Dyslexia: Are They Compatible?

Luca Cilibrasi,Ianthi Tsimpli

doi:10.3389/fpsyg.2020.02171

Luca Cilibrasi, Ianthi Tsimpli

Open Access

https://doi.org/10.3389/fpsyg.2020.02171

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Abstract

Dyslexia is often assessed using categorical diagnoses, and subtypes of dyslexia are also recognized in a categorical fashion. Children may meet the criteria for dyslexia, and they may more specifically meet the criteria for a subtype of it, and thus get a diagnosis. This approach to diagnosis clashes with the actual distribution of reading performance in children (which is normal and continuous), and it has received criticism. This article offers a conceptual framework for conciliating these two positions. In short, the proposal is to use a set of multicomponent continuous assessments of reading, rather than thresholds. The proposal is explained using original data obtained from a sample of 30 children (age 7 to 11), tested in the United Kingdom. Using an assessment based on categorical-thresholds, only five children in our sample qualify for extra assistance, and only one may get a diagnosis of dyslexia, while with the mixed system proposed, a few additional children in the gray area would receive attention. This approach would not discard previous categorical approaches such as those distinguishing between surface and phonological dyslexia, but it would rather see these subtypes of dyslexia as the instance of a lower score on the continuum obtained on a single component of the multicomponent assessment.

Highlights

The National Institute of Neurological Disorders defines dyslexia as “a brain-based type of learning disability that impairs a person’s ability to read
The disorder varies from person to person, common characteristics among people with dyslexia are difficulties with phonological processing, spelling, and/or rapid visual-verbal responding”
The vast majority of assessments has a clinical aim, and for this reason, tests are designed to answer specific questions: does the child tested have dyslexia? Does the child qualify for assistance?

Summary

Introduction

The brains of children with dyslexia show peculiarities that can affect various regions, including for example the visual word form area (Dehaene and Cohen, 2011), Broca’s area (Paulesu et al, 2001), the magnocellular pathway (Stein, 2001) and the cerebellum (Nicolson et al, 2001). These patterns are not consistent across subjects (Kraft et al, 2016; Łuniewska et al, 2019), and behavioral tasks remain the most effective assessment available (Fletcher, 2009; Ramus et al, 2018). The transformation of text into sound is a complex process that involves various sub-skills, arguably phonological skills (Van Orden and Kloos, 2005), visual skills (Kulp and Schmidt, 1996), working memory (Siegel, 1994), and the coordination between them (Church et al, 2008)

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