A Bayesian Probabilistic Framework for Identification of Individuals with Dyslexia.

Purpose: Bayesian-based models for diagnosis are common in medicine but have not been incorporated into identification models for dyslexia. The purpose of the present study was to evaluate Bayesian identification models that included a broader set of predictors and that capitalized on recent developments in modeling the prevalence of dyslexia. Method: Model-based meta-analysis was used to create a composite correlation matrix that included common predictors of dyslexia such as decoding, phonological awareness, oral language, but also included response to intervention (RTI) and family risk for dyslexia. Bayesian logistic regression models were used to predict poor reading comprehension, unexpectedly poor reading comprehension, poor decoding, and unexpectedly poor decoding, all at two levels of severity. Results: Most predictors made independent and substantial contributions to prediction, supporting models of dyslexia that rely on multiple rather than single indicators. RTI was the strongest predictor of poor reading comprehension and unexpectedly poor reading comprehension. Phonological awareness was the strongest predictor of poor decoding and unexpectedly poor decoding, followed closely by family risk. Conclusion: Bayesian-based models are a promising tool for implementing multiple-indicator models of identification. Ideas for improving prediction and implications for theory and practice are discussed.

Early Identification of Children with Dyslexia: Variables Differentially Predict Poor Reading Versus Unexpected Poor Reading.

Definitions of dyslexia typically make reference to unexpected poor reading, although how best to operationalize unexpected remains an issue. When operationally defined as reading below expectations based on level of oral language, cases of unexpected poor reading make up fewer than half of cases of poor reading, and cases of unexpected poor reading occur throughout the range of reading proficiency. An implication is that what optimally predicts poor reading may not optimally predict unexpected poor reading. The goal of the three presented studies was to test this implication empirically. In Study 1, a model-based meta-analysis, phonological awareness accounted for 40% of the variance in decoding but only 1% of the variance in decoding that was unexpected based on level of vocabulary. Conversely, unexpected phonological awareness accounted for 34% of the variance in unexpected decoding but only 1% of the variance in decoding. An analogous pattern of results occurred for reading comprehension. In Study 2, a study of 766 children in kindergarten, first grade, and second grade, latent variables were used to represent oral vocabulary, phonological awareness, and decoding. As was seen in Study 1, unexpected decoding was better predicted by unexpected phonological awareness than by phonological awareness. In Study 3, a longitudinal study of 1,025 children followed from preschool through grade 2, the pattern of results mirrored those of Studies 1 and 2. An important implication of these studies is that typical assessments may be better at identifying poor reading than they are at identifying unexpected poor reading or dyslexia.

Co-occurrence of Reading Disabilities and Math Disabilities: A Meta-Analysis.

Despite the importance of identifying individuals with reading disabilities, existing operational definitions of reading disability do not result in reliable identification. A large part of the problem arises from measurement error when a cut-point is imposed on a continuous distribution, especially for low base-rate conditions. One way to reduce measurement error is to include additional predictors in reading disability models. The present study examined co-occurring math disability as a possible additional criterion for predicting reading disability. Meta-analysis was used to examine the probability of individuals with reading disability also having a comorbid math disability. Possible moderators including age, severity of disability, and language were examined. The main result was an average weighted odds ratio of 2.12, 95% confidence interval [1.76, 2.55], indicating that students with a math disability are just over two times more likely to also have a reading disability than those without a math disability. Implications of the results are discussed.

Differential Co-Development of Vocabulary Knowledge and Reading Comprehension for Students with and without Learning Disabilities.

In this large-scale study of students from Title 1 schools (N = 14,773), we used multiple-group latent change score (LCS) modeling to investigate the developmental relations between vocabulary knowledge and reading comprehension in students with a school-identified learning disability (LD, n = 627) and typically developing students (n = 14,146). Students were tested for their vocabulary breadth and passage comprehension skills in Kindergarten through fourth grade. For typically developing students, there were bidirectional influences between their vocabulary knowledge and reading comprehension skills. There were no cross-lagged influences across constructs for students with an LD. We find evidence for a developmental delay, such that students with an LD had similar levels and gains in their vocabulary knowledge relative to typically developing students, but these students started much lower in their reading comprehension skills and did not catch up to their typically developing peers. We discuss the implications for children with learning disabilities and the development of their reading comprehension skills.

How the Science of Reading Informs 21st-Century Education.

The science of reading should be informed by an evolving evidence base built upon the scientific method. Decades of basic research and randomized controlled trials of interventions and instructional routines have formed a substantial evidence base to guide best practices in reading instruction, reading intervention, and the early identification of at-risk readers. The recent resurfacing of questions about what constitutes the science of reading is leading to misinformation in the public space that may be viewed by educational stakeholders as merely differences of opinion among scientists. Our goals in this paper are to revisit the science of reading through an epistemological lens to clarify what constitutes evidence in the science of reading and to offer a critical evaluation of the evidence provided by the science of reading. To this end, we summarize those things that we believe have compelling evidence, promising evidence, or a lack of compelling evidence. We conclude with a discussion of areas of focus that we believe will advance the science of reading to meet the needs of all children in the 21st century.

The Reading Comprehension and Vocabulary Knowledge of Children with Poor Reading Comprehension despite Adequate Decoding: Evidence from a Regression-Based Matching Approach.

The present study examined the reading comprehension and receptive vocabulary skills of children with poor reading comprehension despite adequate decoding using a regression-based matching technique. Participants included five cohorts of children who were identified as typical readers (N = 70,493 - 75,553) or as children with specific reading comprehension difficulties (N = 480 - 8,717). Across cohorts, children with specific reading comprehension difficulties exhibited oral language difficulties based on a measure of vocabulary; however, the observed weakness in vocabulary was not as severe as their reading comprehension difficulties. Results from the regression-based matching technique suggested that the vocabulary weakness for these children is better characterized as a developmental delay rather than a developmental deficit. This outcome also emerged when more stringent criteria were used to identify subgroups of readers. Although children with poor reading comprehension despite adequate decoding have a weakness in at least one aspect of oral language, their oral language weakness does not account for the severity of their reading comprehension difficulties. Theoretical and practical implications are discussed.

Combining Old and New for Better Understanding and Predicting Dyslexia.

Despite decades of research, it has been difficult to achieve consensus on a definition of common learning disabilities such as dyslexia. This lack of consensus represents a fundamental problem for the field. Our approach to addressing this issue is to use model-based meta-analyses and Bayesian models with informative priors to combine the results of a large number of studies for the purpose of yielding a more stable and well-supported conceptualization of reading disability. A prerequisite to implementing these models is establishing informative priors for dyslexia. We illustrate a new approach for doing so based on the known distribution of the difference between correlated variables, and use this distribution to determine the proportion of poor readers whose poor reading is unexpected (i.e., likely to be due to dyslexia) as opposed to expected.

Using Meta-analytic Structural Equation Modeling to Study Developmental Change in Relations Between Language and Literacy.

The purpose of this review was to introduce readers of Child Development to the meta-analytic structural equation modeling (MASEM) technique. Provided are a background to the MASEM approach, a discussion of its utility in the study of child development, and an application of this technique in the study of reading comprehension (RC) development. MASEM uses a two-stage approach: first, it provides a composite correlation matrix across included variables, and second, it fits hypothesized a priori models. The provided MASEM application used a large sample (N = 1,205,581) of students (ages 3.5-46.225) from 155 studies to investigate the factor structure and relations among components of RC. The practical implications of using this technique to study development are discussed.

Examining the Etiology of Reading Disability as Conceptualized by the Hybrid Model.

A fairly recent definition of reading disability (RD) is that in the form of a hybrid model. The model views RD as a latent construct that is manifested through various observable unexpected impairments in reading related skills and through inadequate response to intervention. The current report evaluated this new conceptualization of RD from an etiological perspective. The sample consisted of 2737 twin pairs in first through fourth grade (Mage = 8.52) from the Florida Twin Project on Reading. Using twin analyses, results showed that a substantial proportion of genetic variance, a small proportion of shared environmental, and a small proportion of non-shared environmental variance was attributed to the RD factor. Findings suggest that the etiological architecture of RD closely mirrors the structure of the hybrid model of RD.

The Comprehension Problems of Children with Poor Reading Comprehension despite Adequate Decoding: A Meta-Analysis.

The purpose of this meta-analysis was to examine the comprehension problems of children who have a specific reading comprehension deficit (SCD), which is characterized by poor reading comprehension despite adequate decoding. The meta-analysis included 86 studies of children with SCD who were assessed in reading comprehension and oral language (vocabulary, listening comprehension, storytelling ability, and semantic and syntactic knowledge). Results indicated that children with SCD had deficits in oral language (d = -0.78, 95% CI [-0.89, -0.68], but these deficits were not as severe as their deficit in reading comprehension (d = -2.78, 95% CI [-3.01, -2.54]). When compared to reading comprehension age-matched normal readers, the oral language skills of the two groups were comparable (d = 0.32, 95% CI [-0.49, 1.14]), which suggests that the oral language weaknesses of children with SCD represent a developmental delay rather than developmental deviance. Theoretical and practical implications of these findings are discussed.

Genome-Wide Polygenic Scores Predict Reading Performance Throughout the School Years.

It is now possible to create individual-specific genetic scores, called genome-wide polygenic scores (GPS). We used a GPS for years of education (EduYears) to predict reading performance assessed at UK National Curriculum Key Stages 1 (age 7), 2 (age 12) and 3 (age 14) and on reading tests administered at ages 7 and 12 in a UK sample of 5,825 unrelated individuals. EduYears GPS accounts for up to 5% of the variance in reading performance at age 14. GPS predictions remained significant after accounting for general cognitive ability and family socioeconomic status. Reading performance of children in the lowest and highest 12.5% of the EduYears GPS distribution differed by a mean growth in reading ability of approximately two school years. It seems certain that polygenic scores will be used to predict strengths and weaknesses in education.

Using Simulations to Investigate the Longitudinal Stability of Alternative Schemes for Classifying and Identifying Children with Reading Disabilities.

The present study employed data simulation techniques to investigate the one-year stability of alternative classification schemes for identifying children with reading disabilities. Classification schemes investigated include low performance, unexpected low performance, dual-discrepancy, and a rudimentary form of constellation model of reading disabilities that included multiple criteria. Data from Spencer et al. (2014) were used to construct a growth model of reading development. The parameters estimated from this model were then used to construct three simulated datasets wherein the growth parameters were manipulated in one of three ways: A stable-growth pattern, a mastery learning pattern and a fan-spread pattern. Results indicated that overall the constellation model provided the most stable classifications across all conditions of the simulation, and that classification schemes were most stable in the fan-spread condition, and were the least stable under the mastery learning growth pattern. These results also demonstrate the utility of data simulations in reading research.

Developmental relations between vocabulary knowledge and reading comprehension: a latent change score modeling study.

The present study followed a sample of first-grade (N = 316, Mage = 7.05 at first test) through fourth-grade students to evaluate dynamic developmental relations between vocabulary knowledge and reading comprehension. Using latent change score modeling, competing models were fit to the repeated measurements of vocabulary knowledge and reading comprehension to test for the presence of leading and lagging influences. Univariate models indicated growth in vocabulary knowledge, and reading comprehension was determined by two parts: constant yearly change and change proportional to the previous level of the variable. Bivariate models indicated previous levels of vocabulary knowledge acted as leading indicators of reading comprehension growth, but the reverse relation was not found. Implications for theories of developmental relations between vocabulary and reading comprehension are discussed.

Text (Oral) Reading Fluency as a Construct in Reading Development: An Investigation of its Mediating Role for Children from Grades 1 to 4.

In the present study we investigated a developmentally changing role of text reading fluency in mediating the relations of word reading fluency and listening comprehension to reading comprehension. We addressed this question by using longitudinal data from Grades 1 to 4, and employing structural equation models. Results showed that the role of text reading fluency changes over time as children's reading proficiency develops. In the beginning phase of reading development (Grade 1), text reading fluency was not independently related to reading comprehension over and above word reading fluency and listening comprehension. In Grades 2 to 4, however, text reading fluency completely mediated the relation between word reading fluency and reading comprehension whereas it partially mediated the relation between listening comprehension and reading comprehension. These results suggest that text reading fluency is a dissociable construct that plays a developmentally changing role in reading acquisition.

Developmental Relations between Reading and Writing at the Word, Sentence and Text Levels: A Latent Change Score Analysis.

Relations between reading and writing have been studied extensively but the less is known about the developmental nature of their interrelations. This study applied latent change score modeling to investigate longitudinal relations between reading and writing skills at the word, sentence and text levels. Latent change score models were used to compare unidirectional pathways (reading-to-writing and writing-to-reading) and bidirectional pathways in a test of nested models. Participants included 316 boys and girls who were assessed annually in grades 1 through 4. Measures of reading included pseudo-word decoding, sentence reading efficiency, oral reading fluency and passage comprehension. Measures of writing included spelling, a sentence combining task and writing prompts. Findings suggest that a reading-to-writing model better described the data for the word and text levels of language, but a bidirectional model best fit the data at the sentence level.

Text Comprehension Mediates Morphological Awareness, Syntactic Processing, and Working Memory in Predicting Chinese Written Composition Performance.

The goal of the present study was to test opposing views about four issues concerning predictors of individual differences in Chinese written composition: (a) Whether morphological awareness, syntactic processing, and working memory represent distinct and measureable constructs in Chinese or are just manifestations of general language ability; (b) whether they are important predictors of Chinese written composition, and if so, the relative magnitudes and independence of their predictive relations; (c) whether observed predictive relations are mediated by text comprehension; and (d) whether these relations vary or are developmentally invariant across three years of writing development. Based on analyses of the performance of students in grades 4 (n = 246), 5 (n = 242) and 6 (n = 261), the results supported morphological awareness, syntactic processing, and working memory as distinct yet correlated abilities that made independent contributions to predicting Chinese written composition, with working memory as the strongest predictor. However, predictive relations were mediated by text comprehension. The final model accounted for approximately 75 percent of the variance in Chinese written composition. The results were largely developmentally invariant across the three grades from which participants were drawn.

To Wait in Tier 1 or Intervene Immediately: A Randomized Experiment Examining First Grade Response to Intervention (RTI) in Reading.

This randomized controlled experiment compared the efficacy of two Response to Intervention (RTI) models - Typical RTI and Dynamic RTI - and included 34 first-grade classrooms (n = 522 students) across 10 socio-economically and culturally diverse schools. Typical RTI was designed to follow the two-stage RTI decision rules that wait to assess response to Tier 1 in many districts, whereas Dynamic RTI provided Tier 2 or Tier 3 interventions immediately according to students' initial screening results. Interventions were identical across conditions except for when intervention began. Reading assessments included letter-sound, word, and passage reading, and teacher-reported severity of reading difficulties. An intent-to-treat analysis using multi-level modeling indicated an overall effect favoring the Dynamic RTI condition (d = .36); growth curve analyses demonstrated that students in Dynamic RTI showed an immediate score advantage, and effects accumulated across the year. Analyses of standard score outcomes confirmed that students in the Dynamic condition who received Tier 2 and Tier 3 ended the study with significantly higher reading performance than students in the Typical condition. Implications for RTI implementation practice and for future research are discussed.

"Waiting to Fail" Redux: Understanding Inadequate Response to Intervention.

This introduction to the special issue provides an overview of the promise, but also the ongoing challenges, related to Response to Intervention (RTI) as a means of both prevention and identification of reading disabilities. We conclude by describing the articles in this special issue and considering their implications for future research.

Incorporating RTI in a Hybrid Model of Reading Disability.

The present study seeks to evaluate a hybrid model of identification that incorporates response-to-intervention (RTI) as a one of the key symptoms of reading disability. The one-year stability of alternative operational definitions of reading disability was examined in a large scale sample of students who were followed longitudinally from first to second grade. The results confirmed previous findings of limited stability for single-criterion based operational definitions of reading disability. However, substantially greater stability was obtained for a hybrid model of reading disability that incorporates RTI with other common symptoms of reading disability.