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

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.

Cross-linguistic transfer in bilinguals reading in two alphabetic orthographies: The grain size accommodation hypothesis

“…In other words, do cross-linguistic variations also affect auditory phonology and visual attention span skills? Both phonological decoding and whole-word reading strategies require the contribution of auditory and visual processes (Zoubrinetzky, Bielle, & Valdois, 2014), but via different grain size: The latter strategy particularly taxes the system's sensitivity to small auditory and visual grains (single-element units), whereas the former would rely on larger grains (multi-element chunks). Consequently, it is reasonable to assume that optimal grain sizes for auditory phonological processing and visual attention span also vary as a function of orthographic depth.…”

Visual attention span deficits and assessing causality in developmental dyslexia

“…http://dx.doi. org/10.1038/nrn3836-c1 (2015)) 2 , Lobier and Valdois bring together 12 of their studies to argue that a visual attention (VA) span deficit meets the criteria that are required to demonstrate causality in developmental dyslexia [3][4][5][6][7][8][9][10][11][12][13][14] . Unfortunately, all of the studies that were discussed used letters to assess VA span; thus, the demonstrated deficit only affects letters and is causally ambiguous , as the individuals with dyslexia and control individuals that were studied differed dramatically in their experience of recoding letters to sound.…”

“…Lobier and Valdois report an RL match study with 10-year-old children with dyslexia and 7-year-old typically developing children 7 . The VA span deficit (in letter report) was significant, but the younger children were markedly poorer at identifying single letters, which were the stimuli used in the VA span task.…”

“…The VA span deficit (in letter report) was significant, but the younger children were markedly poorer at identifying single letters, which were the stimuli used in the VA span task. Consequently, this difference in identification accuracy could have caused the VA span difference 7 . Furthermore, the individuals with VA span dyslexia showed markedly worse pseudoword reading than those with 'phonological' dyslexia, indicating that they have very severely reduced experience in phonological recoding.…”

Teorias da Dislexia: Sustentação com Base nas Alterações Perceptuais Auditivas

“…This way, we could hypothesize that voiceless/voiced interchanges are a manifestation of alteration in auditory temporal processing. This hypothesis is strengthened by evidence that this kind of misspelling is more frequent in oralized deaf and dyslexic individuals (Zoubrinetzky et al, 2014), for whom the alteration in auditory temporal processing is well documented.…”