Statistical learning and dyslexia: a systematic review

The existing literature on developmental dyslexia (hereafter: dyslexia) often focuses on isolating cognitive skills which differ across dyslexic and control participants. Among potential correlates, previous research has studied group differences between dyslexic and control participants in performance on statistical learning tasks. A statistical learning deficit has been proposed to be a potential cause and/or a marker effect for early detection of dyslexia. It is therefore of practical importance to evaluate the evidence for a group difference. From a theoretical perspective, such a group difference would provide information about the causal chain from statistical learning to reading acquisition. We provide a systematic review of the literature on such a group difference. We conclude that there is insufficient high-quality data to draw conclusions about the presence or absence of an effect.     

Gender ratio and cognitive profiles in dyslexia: a cross-national study

The purpose of this study was to analyze possible gender-related differences in the prevalence of dyslexia. A cross-national comparison of Spain and Guatemala was conducted. Both countries speak the same language but have a different standard of living and educational level. A second purpose of this study was to analyze the cognitive profile of Guatemalan and Spanish males and females children with dyslexia. The log-linear analysis indicated that the number of dyslexics detected was different across the countries but there were no differences as a function of gender. Similarly, there were no significant or meaningful differences between dyslexic males and females in the cognitive processes involved in reading. Therefore, gender differences do not appear to be characteristic of developmental dyslexia.     

Computerised screening for dyslexia in adults

Identifying dyslexia in adulthood presents particular challenges because of complicating factors such as acquisition of compensatory strategies, differing degrees of intervention and the problem of distinguishing dyslexic adults from those whose literacy difficulties have non‐cognitive causes. One of the implications is that conventional literacy measures, per se, do not provide a satisfactory basis for screening for dyslexia in adulthood as some dyslexic adults have above‐average literacy skills and some non‐dyslexic adults have very poor literacy skills. This study examined an alternative approach to dyslexia screening, using three tests that depend heavily on phonological processing, lexical access and working memory, but which are not conventional measures of literacy. Using these tests, which are computer delivered, 70 dyslexic adults from three different types of educational institution were compared with 69 non‐dyslexic adults from the same institutions. The results showed that the dyslexic and non‐dyslexic groups were significantly different on all three computer‐based tests, with an average effect size of 1.55. Adaptive versions of these tests were then created to reduce overall administration time for the suite to about 15 minutes. Analysis showed that the combined scaled scores from the adaptive versions of the three tests significantly discriminated the dyslexic from the non‐dyslexic group with an increased effect size of 2.07 and with a sensitivity rate of 90.6% and a specificity rate of 90.0%. It was concluded that this approach is a valid and useful method of identifying dyslexia in adulthood, which, given the ease of administration to large numbers of adults, has noted advantages for education and employment.     

Dyslexia in Greek higher education: a study of incidence, policy and provision

Dyslexia is defined as a disability that primarily affects reading and writing. Internationally, the number of dyslexic students entering higher education is on the rise. It is estimated that students with dyslexia represent a small but significant minority. Many English-speaking countries have developed support services and teaching practices to accommodate dyslexic students' educational needs. In Greece, research on dyslexia is very limited. The purpose of this study is to define the incidence of dyslexia among the Greek student population and to examine dyslexic students' age, gender and major field of study. Data were collected from a total of 406 departments at all Greek public institutions of higher education (n = 32). The existing practices for identifying and provisions for supporting dyslexic students were also examined. The incidence of dyslexia in Greek higher education was estimated to be 0.16%, which is far below the estimated incidence in the general population. Interesting results were yielded regarding the variability of higher education institutions' responses to dyslexia. In almost all Greek institutions, provision takes place in the form of oral examinations and generic counseling. technological education institutions (TEIs) seem to be more aware of the educational needs of dyslexic students, possibly because they have three times more dyslexic students than higher education institutions (HEIs). All Greek universities deal with the needs of dyslexic students on an individual basis, making provision reactive rather than proactive. The results of the present study are discussed in the light of inclusive education and equality of opportunity for students who learn in a different way but do not differ from their counterparts in terms of intelligence or general abilities.     

Reversing letters and reading transformed text in dyslexia: A reassessment

The visual deficit hypothesis of development dyslexia has largely been abandoned because many of the phenomena that initially motivated it could not be replicated under controlled experimental conditions, while phonological processing deficits were found to provide a better explanation for the replicable phenomena. Nevertheless, many teachers and special educators continue to subscribe to the hypothesis that deficits of visual perception are a major cause of reading failure in dyslexia. As part of a larger family study, we reexamined the questions (1) whether probands and affected relatives in dyslexia families reverse easily confused letters more frequently under experimental conditions than normal readers from the same families, and (2) whether they show unusual facility in reading geometrically transformed text. The findings indicated that young dyslexia students reverse easily confused letters more often than normal readers. Reading group differences of letter reversal were significant in children from 7–10 years but not thereafter; and virtually no subject reversed letters when spelling whole words. Furthermore, dyslexic persons in every age group from 7–60 years actually took longer than normal readers to decode geometrically transformed text; and the time to decode transformed texts increased progressively with age after adolescence in both dyslexic persons and normal readers. Thus, reading group differences in decoding easily confused letters and reading geometrically transformed text do not support the visual deficit hypothesis and probably do not help to clarify the etiology of developmental dyslexia.     

Do dyslexic and other poor readers differ in reading-related cognitive skills?

The rationale for the study was that if dyslexic and garden-variety poor readers differ in reading-related cognitive skills, there is justification for believing dyslexia to be a distinct entity. Subjects were 110 children aged 6 to 10 years, divided into groups of dyslexic poor readers varying in verbal IQ, garden-variety poor readers, and good readers. Findings suggest that there are valid grounds for believing that dyslexia is a separate entity from garden-variety poor reading, and that it is found among children at all verbal IQ levels. Poor phonological awareness and nonword reading, in relation to normal readers, were shared by dyslexic and garden-variety poor readers. Deficits unique to dyslexic poor readers were problems in both automatic visual recognition and phonological recoding of graphic stimuli. The study supports the phonological-core variable-difference model of Stanovich (1988) in that both dyslexic and garden-variety poor readers showed phonological processing deficits, but they were more extensive in dyslexics.     

How Does Parental Reading Influence Children’s Reading? A Study of Cognitive Mediation

Cognitive processes underlying a behavioural outcome (like reading ability) and the impact of familial risk (e.g., for dyslexia) have been studied in isolation. We present a novel design, linking the two avenues. How do familial influences impact on children’s cognitive skills, which subsequently underlie reading development? Participants from the Familial Influences on Literacy Abilities (FIOLA) Project included 373 children and their parents. We considered three causal routes from parental reading and children’s putative cognitive endophenotypes to children’s reading. Path analyses showed that half of parental effects on children’s reading bypassed and half operated through children’s cognitive underpinnings. Spousal correlation was small but significant. Findings do not support a strong hypothesis of cognitive endophenotypes with full mediation. Furthermore, we discuss the use of parental skills as a proxy for offspring’s liability. Finally, familial reading difficulties are not fully accounted for by known cognitive skills, which has implications for dyslexia diagnosis.     

Visual stress in adults with and without dyslexia

The relationship between dyslexia and visual stress (sometimes known as Meares‐Irlen syndrome) is uncertain. While some theorists have hypothesised an aetiological link between the two conditions, mediated by the magnocellular visual system, at the present time the predominant theories of dyslexia and visual stress see them as distinct, unrelated conditions, a view that has received some support from studies with children. Studies of visual stress in adults are rare, yet recent reports of a high incidence of this phenomenon amongst university students with diagnosed dyslexia call for further investigation of the issue. This study sought to clarify the relationship between visual stress and dyslexia by comparing the reading performance of dyslexic and non‐dyslexic adults with, and without, colour. Degree of susceptibility to visual stress was determined by means of a symptom rating scale. Optimal colour was determined using an Intuitive Colorimeter, which was also employed to assess reading speed under the two experimental conditions. Only the dyslexic students with high visual stress showed significant gains in reading speed when using optimal colour. The use of response to treatment (rather than symptomatology) as a diagnostic criterion for visual stress is questioned, especially when applied to adults, as this may give misleading findings. On the basis of reported symptomatology, students who experience high levels of visual stress are more likely to show improvements in reading rate with optimal colour if they also have dyslexia than if they do not have dyslexia. Although not establishing an aetiological link, these findings imply an interaction between the two conditions with major implications for theory, diagnosis and treatment.     

Influence of increased letter spacing and font type on the reading ability of dyslexic children

Recent research studies have shown that increased letter spacing has a positive effect on the reading ability of dyslexic individuals. This study aims to investigate the effect of spacing on the readability of different fonts for children with and without dyslexia. Results did not support the hypothesis of better performance among children with dyslexia when reading text in Dyslexie than in other fonts. They, however, revealed that only spacing plays a role in enhancing dyslexic individuals’ reading performance because Dyslexie and the Times New Roman interspaced font have no difference. Furthermore, the negative effect of the unfriendly fonts Times New Roman Italic and Curlz MT was eliminated through increased interletter spacing.     

A decade of research with dyslexic college students: A summary of findings

The major findings of several research projects that investigated dyslexic college students are summarized in this paper. Consistent findings of these investigations led to the following conclusions. 1) Developmental dyslexia is a syndrome made up of the following four symptoms: slow rate of reading, error-prone oral reading, poor written spelling, and grammatically incorrect writing; 2) all these symptoms could be traced to a poor mastery of the grapheme-phoneme relational rules; 3) developmental dyslexia can be found in subjects who appear to have adequate oral language skills; 4) ex-dyslexics who appear to be “poor spellers but good readers” have subtle reading deficits; and 5) the 20 dyslexic subjects investigated appear to constitute a homogeneous group which raises questions regarding dyslexia subtypes.     

发展性阅读障碍亚类型的研究

发展性阅读障碍是关系人类健康和发展的重要课题。多年来研究者试图寻找这个群体中发生困难的真正原因,希望从根本上解决阅读落后问题和消除阅读障碍。但是研究者发现阅读障碍群体内部具有很大的变异性。文章在简介了当今具有代表性的两种流派对阅读障碍原因的解释和相应的研究证据后,着重阐述了阅读障碍的亚类型的发展历史、研究者对亚类型的划分以及不同亚类型在语言技能上、一般感知能力和生理机制方面的差异,并且阐述了亚类型研究对阅读障碍早期预测的作用,为根本消除阅读障碍提供了新的视角。     

What can spelling errors tell us about the causes and treatment of dyslexia?

Until recently the majority of research undertaken into dyslexia focused on English‐speaking dyslexics, who tend to make significantly more phonological than visual errors. This led to a major assumption about the possible cause of dyslexia being a lack of phonological awareness. According to the phonological deficit theory, the level of phonological consistency of a language determines not only the reading speed but also the amount and types of reading and spelling errors made by dyslexic people. This theory has been seriously challenged by the results of a number of studies in more phonologically consistent languages, such as Greek, Italian and Japanese, where morphology seemed to play a more crucial role than the phonological structure of a language per se. The 116 dyslexic people who took part in this experiment were matched on age, sex, IQ and psycho‐educational performance. A total of 58 US English‐speaking dyslexic people were compared to 58 Greek dyslexic people. Both groups met the diagnostic criteria. Results demonstrated that Greek dyslexics were found to make significantly fewer phonological errors (11.0%) than the US dyslexics (85.5%, p < .000), but comparatively more visual (66.8% to US 14.0%, P < .000) and grammatical errors (22.2% to US 0.1%, p < .000) than their English‐speaking counterparts. These data showed highly significant quantitative and qualitative spelling differences. Greek dyslexics could be accurately differentiated from the US English dyslexics based on the three types of spelling errors.     

Dyslexia and oral reading errors

Thomson was the first of very few researchers to have studied oral reading errors as a means of addressing the question: Are dyslexic readers different to other readers? Using the Neale Analysis of Reading Ability and Goodman's taxonomy of oral reading errors, Thomson concluded that dyslexic readers are different, but he found that they do not resemble beginning readers. Thomson's study and his use of miscue analysis is re‐evaluated, both in relation to the educational and political climate of the time – which was hostile to the concept of dyslexia – and in the light of research and social developments since then. The study of oral reading still has value today, both for the teacher and the researcher, provided its limitations as a technique are fully appreciated.     

Nonsense passage reading as a diagnostic aid in the study of adult familial dyslexia

We examined Nonsense-Passage oral reading in adults, using data derived from new and previously published studies (Finucci et al 1976, Gross-Glenn et al 1985). Time-scores and error-frequency data are presented for five samples of non-dyslexic readers with a minimum of a high-school education and no childhood history of dyslexia (N=127). Considerable uniformity is demonstrated across these samples, and reading performance of non-dyslexic individuals contrasts sharply with that observed in four samples of adult familial dyslexics. Both affected and compensated-affected dyslexic subjects read the passages significantly more slowly and with more errors than did nondyslexic readers. Results are discussed in relation to the cognitive and neural processes that may underlie this specific reading difficulty in dyslexics. We have found Nonsense-Passage reading to be especially useful in family studies of inherited dyslexia as a means of quantifying oral reading deficits in adults who have learned to compensate for their children reading difficulties.     

Lexical and sub-lexical effects on accuracy, reaction time and response duration: impaired and typical word and pseudoword reading in a transparent orthography

In an opaque orthography like English, phonological coding errors are a prominent feature of dyslexia. In a transparent orthography like Spanish, reading difficulties are characterized by slower reading speed rather than reduced accuracy. In previous research, the reading speed deficit was revealed by asking children to read lists of words. However, speed in list reading sums the time required to prepare an utterance, reaction time (RT), with the time required to say it, response duration (RD). Thus, the dyslexic speed deficit in transparent orthographies could be driven by slow RTs, by slow RDs, or both. The distinction is especially important if developmental readers rely on phonological coding to achieve lexical access because the whole word would have to be encoded before it could be identified. However, while the factors that affect reading RT have been extensively investigated, no attention has been paid to RD. We studied the performance of typically developing and dyslexic Spanish children in an oral reading task. We analysed the impact of word frequency and length on reading accuracy, RT, and RD. We found that accuracy, RT, and RD were affected by word frequency and length for both control and dyslexic readers. We also observed interactions between effects of reader group—dyslexic, typically developing (TD) younger or TD older readers—and effects of lexicality, frequency, and word length. Our results show that children are capable of reading aloud using lexical and sub-lexical coding processes in a transparent orthography.     

Questioning the benefits that coloured overlays can have for reading in students with and without dyslexia

Visual stress (the experience of visual distortions and discomfort during prolonged reading) is frequently identified and alleviated with coloured overlays or lenses. Previous studies have associated visual stress with dyslexia and as a consequence, coloured overlays are widely distributed to children and adults with reading difficulty. However, this practice remains controversial. We investigated whether overlays have advantageous and reliable benefits for reading in undergraduate students with and without dyslexia. Both groups read jumbled text faster with a coloured overlay than without. The dyslexic group did not show greater gains than controls, despite reporting significantly more symptoms of visual stress. However, coloured overlays did not improve reading rate or comprehension of connected text. The improvement in reading speed with an overlay was not reliable and was significantly reduced at retesting for dyslexic students. These results question the value of coloured overlays as a tool for identifying visual stress and as a form of remediation for the reading difficulties associated with dyslexia.     

Multivariate predictive model for dyslexia diagnosis

Dyslexia is a specific disorder of language development that mainly affects reading. Etiological researches have led to multiple hypotheses which induced various diagnosis methods and rehabilitation treatments so that many different tests are used by practitioners to identify dyslexia symptoms. Our purpose is to determine a subset of the most efficient ones by integrating them into a multivariate predictive model. A set of screening tasks that are the most commonly used and representative of the different cognitive aspects of dyslexia was proposed to 78 children from elementary school (mean age = 9 years ± 7 months) exempt from identified reading difficulties and to 35 dyslexic children attending a specialized consultation for dyslexia. We proposed a multi-step procedure: within each category, we first selected the most representative tasks using principal component analysis and then we implemented logistic regression models on the preselected variables. Spelling and reading tasks were considered separately. The model with the best predictive performance includes eight variables from four categories of tasks and classifies correctly 94% of the children. The sensitivity (91%) and the specificity (95%) are both high. Forty minutes are necessary to complete the test.     

Is there a thing called dyslexia?

A controversy whether developmental dyslexia is qualitatively different from other forms of reading disability has existed among reading specialists for many years because poor readers, regardless of the labels attached to them, resemble each other symptomatically (i.e., in reading achievement). For this reason, it is difficult to establish a priori criteria based on symptoms to identify dyslexia and compare it with other forms of reading disability. One possible solution to this impasse is to see if poor readers differ in the etiology of their reading disability and, if they do, then to see whether one group of poor readers fits the traditional definition of dyslexia. This strategy was adopted in the present study. In this paper, it was hypothesized that the etiology of dyslexia is different from that of other forms of reading disability because there is a difference in the components that malfunction in dyslexia and other forms of reading disability. Studies have shown that the two components that account for a large proportion of variance in reading are decoding and comprehension. Previous studies also indicate that dyslexic children are deficient in decoding skills but not necessarily in comprehension. In this study, reading-disabled children were divided into two groups on the basis of their listening comprehension. Children whose listening comprehension was at or above grade level were placed in one group; poor readers with below-grade-level listening comprehension were placed in the second group. Both groups, however, were matched for reading comprehension. The two groups and a control group of normal readers were administered a number of tasks that were designed to assess the efficiency of the components of reading. It was found that poor readers with normal listening comprehension were deficient in tasks that involved grapheme-phoneme conversion (Component I, decoding). When tested on tasks that minimized decoding requirements, their reading comprehension was comparable to that of normal readers. In contrast, the group with sub-average listening comprehension was poor in measures of reading comprehension, even when decoding requirements were minimal. With the exception of very few children, this group also had adequate decoding skills. Because poor readers with normal listening comprehension had average or above average IQ, they conform to the traditional definition of dyslexia. Poor readers with below average listening comprehension had below average IQ and could be considered as “general reading backward.” It was, therefore, concluded that the etiology of developmental dyslexia is different from that of general reading backwardness. In this paper, the termetiology refers to proximal causal factors such as decoding and comprehension and not to distal causal factors such as genetic and neurological characteristics.     

Dyslexia: stability of definition over a five year period

The results of longitudinal studies suggest that although dyslexic children improve their reading skills with time, they do not outgrow their disability (Spreen, 1982). This paper compares the development of reading and spelling in a group of dyslexics and non-dyslexics over a five-year period. In addition to addressing the issue of the relative rates of development of reading in the two groups, a central focus of the paper is the extent to which dyslexia can be said to represent a stable disability. How many of the children classified as dyslexic at age eight would be reclassified as dyslexic at age thirteen? Three distinct groups emerged: ‘stable',‘transient’ and ‘late emerging dyslexics'. The ‘stable’ dyslexics were children classified as dyslexic at both ages, the transient were those classified only at the younger age, and the ‘late emerging’ were those classified at age thirteen. Regression analysis was used as the technique of identification of the dyslexics.     

Learning to Read Bilingually Modulates the Manifestations of Dyslexia in Adults

According to the Grain Size Accommodation hypothesis (Lallier & Carreiras, 2017), learning to read in two languages differing in orthographic consistency leads to a cross-linguistic modulation of reading and spelling processes. Here, we test the prediction that bilingualism may influence the manifestations of dyslexia. We compared the deficits of English monolingual and early Welsh–English bilingual dyslexic adults on reading and spelling irregular English words and English-like pseudowords. As predicted, monolinguals were relatively more impaired in reading pseudowords than irregular words, whereas the opposite was true for bilinguals. Moreover, monolinguals showed stronger sublexical processing deficits than bilinguals and were poorer spellers overall. This study shows that early bilingual reading experience has long-lasting effects on the manifestations of dyslexia in adulthood. It demonstrates that learning to read in a consistent language like Welsh in addition to English gives bilingual dyslexic adults an advantage in English literacy tasks strongly relying on phonological processing.