Examination of the double-deficit hypothesis with adolescents and young adults with dyslexia

Evaluation of the multiple-deficit hypothesis among dyslexic Arabic-speaking children

This study examined the multiple-deficit hypothesis among Arabic-speaking elementary school students. A total of 90 students, divided into three main groups based on their performance on an Arabic word-reading task: dyslexic (n = 30), regular age-matched (n = 30), and 3rd-grade regular students, who were matched to the dyslexic group in regard to their reading proficiency level (n = 30). Participants underwent a nine-domain Arabic reading experiment that measured accuracy and fluency to evaluate general reading proficiency. The performance of Arabic dyslexic students was significantly worse than age-matched controls, but similar to young matched controls based on the reading level of each cognitive task. Moreover, dyslexic students showed deficits in three or more cognitive functions, depending on severity. This study adds to the limited empirical research on the double-deficit hypothesis and its extension to the multiple-domain model among young Arabic students.

The Use of Cognitive Tests in the Assessment of Dyslexia

In this literature review, we address the use of cognitive tests, including intelligence tests, in the assessment and diagnosis of dyslexia, from both historic and present-day perspectives. We discuss the role of cognitive tests in the operationalization of the concepts of specificity and unexpectedness, two constructs considered essential to the characterization of dyslexia since the publication of early case reports in the late nineteenth century. We review the advantages and disadvantages of several approaches to specific learning disabilities' identification that are used in schools. We also discuss contemporary debates around the use of standardized cognitive testing in dyslexia evaluations, in particular, the arguments of those who favor an approach to diagnosis based on prior history and the results of a comprehensive evaluation and those who favor an approach based on an individual's response to intervention. We attempt to explain both perspectives by examining clinical observations and research findings. We then provide an argument for how cognitive tests can contribute to an accurate and informed diagnosis of dyslexia.

Predicting dyslexia in Arabic-speaking children: Developing instruments and estimating their psychometric indices

Dyslexia is a reading disability that is characterized by when an individual has trouble in rapid and accurate word decoding. This study developed, piloted and assessed the validity and reliability of three instruments: Rapid Automatized Scale (RANS), Arabic Reading Ability Scale (ARAS) and Phonological Awareness Scale (PAS), on a sample of 700 students (aged 8-9 years). Four groups (n = 30) were formed based on the participants' results of the three instruments; Double Deficit (DD), Rapid Automatized Naming Deficit (RAND), Phonological Awareness Deficit (PAD) and No Deficit groups. Content validities of the instruments were supported using published reports; though educational experts further revised RANS. It found a significant inverse correlation between the PA test score and RAN (mistakes and time) score (r = -.44; p < .001), and a significant positive correlation between RAN mistakes and RAN time (r = .47; p < .001). Acceptable internal reliability of the RANS was demonstrated by a Cronbach's alpha test coefficient of α = .85 (>.70; acceptable). High inter-rater reliability tests were observed for the three instruments (r ≥ .86, p < .001). The three instruments can predict reading difficulties and dyslexia in Arabic-speaking populations.

From Schools to Scans: A Neuroeducational Approach to Comorbid Math and Reading Disabilities

We bridge two analogous concepts of comorbidity, dyslexia-dyscalculia and reading-mathematical disabilities, in neuroscience and education, respectively. We assessed the cognitive profiles of 360 individuals (mean age 25.79 ± 13.65) with disability in reading alone (RD group), mathematics alone (MD group) and both (comorbidity: MDRD group), with tests widely used in both psychoeducational and neuropsychological batteries. As expected, the MDRD group exhibited reading deficits like those shown by the RD group. The former group also exhibited deficits in quantitative reasoning like those shown by the MD group. However, other deficits related to verbal working memory and semantic memory were exclusive to the MDRD group. These findings were independent of gender, age, or socioeconomic and demographic factors. Through a systematic exhaustive review of clinical neuroimaging literature, we mapped the resulting cognitive profiles to correspondingly plausible neuroanatomical substrates of dyslexia and dyscalculia. In our resulting "probing" model, the complex set of domain-specific and domain-general impairments shown in the comorbidity of reading and mathematical disabilities are hypothesized as being related to atypical development of the left angular gyrus. The present neuroeducational approach bridges a long-standing transdisciplinary divide and contributes a step further toward improved early prediction, teaching and interventions for children and adults with combined reading and math disabilities.

Phonological-Orthographic Deficits in Developmental Dyslexia in Three Spanish-English Bilingual Students

Introduction The purpose of this study is to present three case studies of developmental dyslexia in dual-language learners (DLLs) and our assessment process. We identify how phonological and orthographic deficits influence reading outcomes. We review the literature on theoretical models of bilingualism and reading models of developmental dyslexia to guide the assessment process through a multicomponential approach. We point out differences in the manifestation of dyslexia in more and less transparent writing systems. We suggest that reading instruction in Spanish can afford benefits to English-Spanish DLLs with developmental dyslexia. Method The study included three participants, two in fifth grade (10.3-11.7 years) and one in college (18.7 years). The assessment battery included reading nonwords and sight words (Test of Word Reading Efficiency); reading accuracy, fluency, and comprehension (Gray Oral Reading Tests-Fourth Edition); phonological awareness subtests (Comprehensive Test of Phonological Processing); and rapid automatized naming tests. A language and reading history interview was elicited from the mothers. In addition, we analyzed the participants' phonemic and word errors in reading. Results Our three participants showed core phonological deficits, with decreased performance in decoding nonwords and low accuracy in reading aloud. In spite of their reading and writing deficits, reading comprehension was within average levels for the three participants in this study. Conclusions We show the importance of assessing reading processes in students with a history of reading and writing problems. Our findings are based on three single case studies and are not generalizable. Our aim is to stimulate questions and research on dyslexia and the particular needs of DLLs.

Investigating the double-deficit hypothesis of developmental dyslexia in an orthography of intermediate depth

The present study aimed to investigate the double-deficit hypothesis (DDH) in an orthography of intermediate depth. Eighty-five European Portuguese-speaking children with developmental dyslexia, aged 7 to 12, were tested on measures of phonological awareness (PA), naming speed (NS), reading, and spelling. The results indicated that PA and NS were not significantly correlated, and that NS predicts reading fluency (but not reading accuracy and spelling) beyond what is accounted for by PA. Although the majority of the children with developmental dyslexia have double deficit (62.4%), some children have a single phonological deficit (24.7%) or a single NS deficit (8.2%). Children with a double deficit were not more impaired in reading fluency, reading accuracy, and spelling than both single-deficit subtypes. In conclusion, the findings of the present study are partially consistent with the DDH and provide evidence for the multifactorial model of developmental dyslexia. Implications of the DDH for an orthography of intermediate depth are emphasized.

The effect of phonological awareness on rapid automatized naming

Background: Phonological awareness (PA) is a fundamental predictor of reading disability. However, researches on reading have indicated that PA assessment alone is not sufficient to prevent reading problems. Rapid automatized naming (RAN) has been suggested as another influential factor in reading deficits independent of PA. This study investigated the impact of phonological awareness on rapid automatized naming.

Methods: This was a randomized clinical trial study in which 62 Persian monolingual first graders were recruited from 3 schools using convenience sampling. Inclusion criteria were lack of deficits with sensory-motor skills and knowledge of the Persian alphabets. Measures of PA and RAN were utilized. The participants were randomly assigned into either the intervention or the control group. The intervention group was divided into small groups of 4-6 children who received thirty 40-minute training sessions in PA. T test, Mann-Whitney, and Wilcoxon tests were used for data analysis.

Results: The results revealed that the RAN time was significantly reduced (p≤0.001), with a significant increase in PA scores (p≤0.001). In addition, there was a significant inverse relationship between some of the measures of the phonological awareness subtests and rapid automatized naming (eg, phonemic blending & RAN (numbers): ρ=-0.52 with p≤0.001).

Conclusion: The findings showed that in the initial assessment, PA and RAN had a significant relationship, but RAN could be significantly improved by PA training.

Training RAN or reading? A telerehabilitation study on developmental dyslexia

Rehabilitation procedures recommended for developmental dyslexia (DD) are still not fully defined, and only few studies directly compare different types of training. This study compared a training (Reading Trainer) working on the reading impairment with one (Run the RAN) working on the rapid automatized naming (RAN) impairment, one of the main cognitive deficits associated with DD. Two groups of DD children (N = 45) equivalent for age, sex, full IQ, and reading speed were trained either by Reading Trainer (n = 21) or by Run the RAN (n = 24); both trainings required an intensive home exercise, lasting 3 months. Both trainings showed significant improvements in reading speed and accuracy of passages and words. Bypassing the use of alphanumeric stimuli, but empowering the cognitive processes underlying reading, training RAN may be a valid tool in children with reading difficulties opening new perspectives for children with severe impairments or, even, at risk of reading difficulties.

Deficient Response to Altered Auditory Feedback in Dyslexia

Although dyslexia is characterized by a deficit in phonological representations, the nature of this deficit is debated. Previously, it was shown that adults with dyslexia respond differently to online manipulations of auditory feedback. In the present study, we found that individual differences in reading and reading-related skills within a group of 30 children (10-13 years old) with dyslexia were associated with the response to altered feedback. The fractional anisotropy of the arcuate fasciculus/superior longitudinal fasciculus was not directly related to the response to altered feedback. This study corroborates that speech perception-production communication is important for phonological representations and reading.

Genetic and environmental risk factors for developmental dyslexia in children: systematic review of the last decade

Despite advances in the characterization of developmental dyslexia (DD), several questions regarding the interplay between DD-susceptibility genes and environmental risk factors remain open. This systematic review aimed at answering the following questions: What has been the impact of new resources on the knowledge about DD? Which questions remain open? What is the investigative agenda for the short term? Forty-six studies were analyzed. Despite the growing literature on DD candidate genes, most studies have not been replicated. We found large effects on causative genes and smaller environmental contributions, involving maternal smoking during pregnancy, SES and the DYX1C1-1259C/G marker. Implications are discussed.