Shallow or deep? The impact of orthographic depth on visual processing impairments in developmental dyslexia

Serena Provazza,Barbara Carretti,Anne-Marie Adams,David Giofrè,Lorena Montesano,Daniel Roberts

doi:10.1007/s11881-021-00249-7

Abstract

The extent to which impaired visual and phonological mechanisms may contribute to the manifestation of developmental dyslexia across orthographies of varying depth has yet to be fully established. By adopting a cross-linguistic approach, the current study aimed to explore the nature of visual and phonological processing in developmental dyslexic readers of shallow (Italian) and deep (English) orthographies, and specifically the characterisation of visual processing deficits in relation to orthographic depth. To achieve this aim, we administered a battery of non-reading visual and phonological tasks. Developmental dyslexics performed worse than typically developing readers on all visual and phonological tasks. Critically, readers of the shallow orthography were disproportionately impaired on visual processing tasks. Our results suggest that the impaired reading and associated deficits observed in developmental dyslexia are anchored by dual impairments to visual and phonological mechanisms that underpin reading, with the magnitude of the visual deficit varying according to orthographic depth.

Highlights

Developmental dyslexia (DD) is a neurodevelopmental disorder and the most common specific learning disability, affecting ~ 15% of people globally (American Psychiatric Association., 2013)
Most importantly, to explore the extent to which non-reading visual deficits are observed in DD readers of shallow (Italian) and deep (English) orthographies
All DD participants presented with a deficit in processing visual stimuli, aligning with previous findings (Gabay et al, 2017b; Giofrè et al, 2019a; Jozranjbar et al, 2020; Provazza et al, 2019b; Sigurdardottir et al, 2018; Sigurdardottir et al, 2015; Vogel et al, 2014)

Summary

Introduction

Developmental dyslexia (DD) is a neurodevelopmental disorder and the most common specific learning disability, affecting ~ 15% of people globally (American Psychiatric Association., 2013) It is characterised by an unexpected inability to achieve fluent, accurate. The commonly accepted explanation for reading impairments in DD is a deficit in phonological processing (see Elliot & Grigorenko, 2014, for a review; Snowling, 1981, 1995; Stanovich, 1988; Stanovich & Siegel, 1994; Swan & Goswami, 1997; Vellutino et al, 2004). In developmental terms, this deficit is considered to affect the acquisition of phonological decoding skills (i.e. grapheme to phoneme conversion), which prevents construction of the orthographic lexicon, impacting fluent, whole-word recognition. A phonological deficit typically encompasses impaired phonological awareness, verbal short-term/ working memory, and/or letter knowledge, three of the most widely studied measures of phonological skills in developmental reading disorders (Hulme & Snowling, 2013; MelbyLervåg et al, 2012; Snowling & Melby-Lervåg, 2016)

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Conclusion