The external validity of age- versus IQ-discrepancy definitions of reading disability: lessons from a twin study.

Recent research has raised the question of whether age- and IQ-discrepancy forms of reading disability (RD) are distinguishable in terms of either their underlying linguistic deficit or their response to treatment, thus threatening the external validity of the traditional distinction between specific reading retardation and reading backwardness. The present study pursued the external validity of this distinction in three domains: (a) genetic etiology, (b) sex ratio and clinical correlates, and (c) neuropsychological profiles. Each of these domains was explored in the RD (n = 640) and control (n = 436) twins participating in the Colorado Reading Project (514 males, 562 females, with an overall mean age of 12.42 years). Little evidence for external validity was found in terms of the clinical correlates of attention deficit-hyperactivity disorder (ADHD), immune disorders, or handedness. Most importantly, there was no evidence of differential genetic etiology of the two phenotypes in this sample, in that deficits in both phenotypes were similarly heritable (h2g = .40 and .46 for age and IQ phenotypes, respectively) and the genetic correlation between them was high (rG = .88 to .96). However, the genetic and neuropsychological profile analyses did suggest that age- and IQ-discrepancy definitions of RD may relate differentially to component reading processes, such as phonological awareness and orthographic coding.     

Investigation of the Relationship of Attention Deficit Hyperactivity Disorder to the EKN1 Gene on Chromosome 15q21

Recently a gene, termed EKN1, has been identified because of a chromosomal breakpoint that occurred in this gene. This chromosomal breakpoint was found in 4 family members that had specific reading disabilities (RDs), indicating that disruption of this gene may be contributing to the risk of developing RDs. This gene was further supported as contributing to RD by association studies. Because of the evidence from twin studies for shared genetic factors contributing to RD and attention deficit hyperactivity disorder (ADHD), particularly inattention symptoms, we investigated the relationship of DNA markers in this gene to ADHD and ADHD symptoms in a sample of 186 nuclear families (probands, their parents, and affected siblings) collected through a proband with ADHD. We used 6 polymorphic DNA markers located across the gene, including the 2 markers previously reported to be associated with RD in a Finnish sample and a marker associated with RD in a sample of families collected in Toronto. We found a trend for association for several markers to the ADHD phenotype analyzed as a categorical trait using the transmission disequilibrium test and significant evidence for biased transmission of the haplotypes containing these markers, χ²(3) = 9.312, p =. 025. Using quantitative analysis, we observed evidence for association of one of the haplotypes to the inattention and hyperactive/impulsive symptom dimensions as reported by parents and to the inattention symptoms as reported by teachers, as well as a trend for association with the reading phenotypes of word identification and decoding. The results provide preliminary support for the role of the EKN1 chromosomal region in ADHD, suggesting that this region may contribute to ADHD symptoms in addition to RD.     

Slower implicit categorical learning in adult poor readers

We investigated the relationship between reading and explicit and implicit categorical learning by comparing university students with poor reading to students with normal reading abilities on two categorical learning tasks. One categorical learning task involved sorting simple geometric shapes into two groups according to a unidimensional rule. The sorting rule was easily stated by the participants, consistent with explicit learning, and all participants attained criterion levels of performance. The second task involved the integration of features on different dimensions with a more complex rule that could not be described by participants, even though most could attain criterion levels of performance consistent with implicit learning. Poor readers performed as well as those without reading problems in explicit learning but not in implicit learning. Implicit learning was correlated with word reading, phonological decoding, and orthographic skill, independent of verbal ability. We consider the role of implicit learning in reading, and how a deficit could impair phonological and orthographic representation and processing.     

Separating genuine cases of reading disability from reading deficits caused by predominantly inattentive ADHD behavior

Conventional methods of differentiating reading disability (RD) caused by deficits in decoding skills or comprehension from poor reading performance caused by inconsistent attention associated with attention-deficit/hyperactivity disorder (ADHD) have produced equivocal results. This study presents a model of differential diagnosis of attentional problems and RD that differs from these conventional approaches. The new diagnostic procedure uses intraindividual differences seen in the performance of at-risk learners on tasks related to reading that vary in their sensitivity to the sustained attention required for successful performance. The hypothesis is that children with inconsistent attention would perform more poorly on tests that require sustained attention, such as listening comprehension, than on tests that are more tolerant of inattention, such as reading comprehension. Such differences would not be seen in the test scores of children who have only RD, because their performance is determined more by the difficulty level of the reading tests than by the degree of sensitivity of the task to attention. The validity of this new model was evaluated by determining the capability of the differences seen in the scores of tests that differ in their sensitivity to sustained attention to predict the degree of inconsistency in sustained attention as measured by a continuous performance test. The data obtained from 39 children who are at risk for RD suggest that this is a viable model.     

Word identification and reading disorders in the Spanish language

In this study, a reading-level-match design was used to test the hypothesis that children with reading disability (RD) are characterized by poor phonological skills, and that a developmental lag, as opposed to a specific deficit, will be found in transparent orthographies. Spanish has a transparent orthography and thus children with RD should not show severe difficulties in the use of the phonological route, as in the English language. A sample of 118 participants was selected and organized into three different groups: 40 with RD, 38 normal readers matched in age with the former, and 40 younger normal readers at the same reading level as those with RD. Two experiments were conducted to investigate the effects of lexicality, word frequency, word length, and positional frequency of syllables on lexical decision making and word-naming performance. While the participants were performing the naming task, we recorded what they read to subsequently analyze the form as well as the frequency of naming errors. The present study provides evidence for a deficit in phonological processing in a transparent orthography, particularly in nonword reading, because there were differences between the reading-level-matched groups.     

The etiological relationship between reading disability and phonological disorder

The present study investigated the etiological relationship between two disorders: dyslexia or reading disability (RD) and phonological disorder (PD). These disorders manifest at different ages and have typically been studied by researchers in different disciplines. However, a growing body of evidence suggests that the disorders overlap at symptomatic, cognitive, and etiological levels of analysis. In previous studies, each disorder has been found to be heritable, and there is also evidence that RD and PD run together in families, but no studies to date have documented whether there is a shared genetic influence between the two disorders. The present study examined this question in a sample of RD and non-RD twins. Subjects with a history of PD were identified and the etiological relation between the two disorders was examined. Results indicated that in the present sample, RD and PD are each heritable on their own. Further, even when correcting for RD, the two disorders were found to be coheritable, indicating that the finding of cofamiliality of RD and PD is at least partially driven by genetic influences. The implications of these results for the conceptualization, identification, and treatment of these two disorders are discussed.     

The Literacy Skills of English Language Learners in Canada

The purpose of this article is to review published studies of the English literacy of children in Canada who are English language learners (ELLs) with the goal of understanding the reading development of ELLs and characteristics of reading disabilities (RD) in this population. Phonological processing, syntactic awareness, and working memory of ELLs with and without RD were compared to that of native English‐speaking (L1) students with and without RD. Our review found that ELLs with RD experienced reading difficulties similar to those of L1 students with RD. On the basis of the evidence, ELLs are not at greater risk for RD than their native English‐speaking peers. We propose that the diagnosis of a reading disability can be made in a similar manner in both ELL and L1 students.     

Reading Disabilities Among Hebrew-speaking Children in Upper Elementary Grades: The Role of Phonological and Nonphonological Language Skills

The purpose of the present study was to examine the contribution of phonological and nonphonological language skills to reading among Hebrew-speaking children with and without reading disabilities (RD) aged 10–13. We expected that the performance of children with RD would be significantly poorer in all of the language processes compared with those of chronological age-matched children with no RD. Also, we expected that nonphonological language skills would contribute unique variance to reading level. The results showed that the most marked predictor for all reading measures was the phonological awareness measure. However, nonphonological language skills also showed a significant contribution to variance in accuracy and rate of reading real words but not to variance in pseudoword reading. The discussion highlights how investigating different orthographic systems can deepen our understanding of the role of the different language processes at play in reading. Our results further stress the importance of using multi-componential reading measures (i.e., pseudowords, real words and reading rate) when analyzing the relationship between reading and language skills.     

A comparative analysis of cognitive profiles: Monozygotic and dizygotic reading-disabled twins

Previous twin studies have provided evidence for genetic influences on reading disability (RD) or normal reading ability. The existence of subtypes of RD — each with its characteristic cognitive profile — has been suggested. Whether the etiology of the particular subtypes is genetic is uncertain. The present study examined within-pair comparisons of cognitive profiles (with respect to composites of general reading, symbol processing speed and sequential memory) in RD and control twins. Twin profile analysis were applied to these cognitive composites on 120 pairs of RD and control twins. Results showed a greater monozygotic (MZ) than dizygotic (DZ) resemblance in profiles indicating that individual differences in the patterning of cognitive abilities related to reading are genetically influenced.     

Familial history of reading difficulty is associated with diffused bilateral brain activation during reading and greater association with visual attention abilities

Reading difficulty (RD; or dyslexia) is a heritable condition characterized by slow, inaccurate reading accompanied by executive dysfunction, specifically with respect to visual attention. The current study was designed to examine the effect of familial history of RD on the relationship between reading and visual attention abilities in children with RD using a functional MRI reading task. Seventy-one children with RD participated in the study. Based on parental reports of the existence of RD in one or both of each child’s parents, children with RD were divided into two groups: (1) those with a familial history of RD and (2) those without a familial history of RD. Reading and visual attention measures were collected from all participants. Functional MRI data during word reading was acquired in 30 participants of the entire cohort. Children with or without a familial history of RD demonstrated below-average reading and visual attention scores, with greater interaction between these measures in the group with a familial history of RD. Greater bilateral and diffused activation during word reading also were found in this group. We suggest that a familial history of RD is related to greater association between lower reading abilities and visual attention abilities. Parental history of RD therefore may be an important preschool screener (before reading age) to prompt early intervention focused on executive functions and reading-related skills.     

The Co-occurrence of Reading Disorder and ADHD: Epidemiology, Treatment, Psychosocial Impact, and Economic Burden

The co-occurrence of reading disorder (RD) and attention-deficit/hyperactivity disorder (ADHD) has received increasing attention. This review summarizes the epidemiology, treatment strategies, psychosocial impact, and economic burden associated with the co-occurrence of these conditions. Common genetic and neuropsychological deficits may partially explain the high degree of overlap between RD and ADHD. Children who face the additive problems of both disorders are at greater risk for academic failure, psychosocial consequences, and poor long-term outcomes that persist into adulthood. However, few studies have evaluated interventions targeted to this patient population, underscoring the importance of identifying effective multimodal treatments that address the neuropsychological deficits of RD and ADHD through carefully planned clinical research.     

Phonological Awareness and Rapid Naming Skills of Children with Reading Disabilities and Children with Reading Disabilities Who Are At Risk for Mathematics Difficulties

Limited research has examined the skills of children with a reading disability (RD) and children with RD and a mathematics disability (MD). Even less research has examined the phonological awareness (PA) and rapid automatized naming (RAN) skills in these two groups of children and how these skills relate to reading and math achievement. Additionally, various classification criteria are frequently implemented to classify children with MD. The purpose of this study, therefore, was to examine the PA and RAN skills in children who met different criteria for RD only and children with RD who are at risk for mathematics difficulties (MDR). Participants were 114 second‐ or third‐grade students with RD from public elementary schools in three large metropolitan areas. Students were classified as at risk for mathematics difficulties utilizing a 25th‐percentile cutoff and a 15th‐percentile cutoff as assessed by the KeyMath‐Revised Test ( Connolly, 1988 ). A series of PA and RAN measures were administered along with a range of reading and mathematics measures. Hierarchical regression analyses indicated that children with RD only evidenced a different pattern of results compared to children with RD + MDR. Additionally, using a more stringent criterion to classify children at risk for mathematics difficulties resulted in a differential pattern of results when compared to a less stringent classification criterion.     

The Effectiveness of Visual Perception,Intelligence and Reading Understanding in Predicting Reading Achievement in Junior High School Children

Abstract

The purpose of this study was to assess the role that certain selected variables have in predicting reading achievement. Three hundred forty-seven students were administered the Minnesota Percepto-Diagnostic Test (MPD), the California Test of Mental Maturity (CTMM), Science Research Associates-Reading for Understanding (RFU) and the California Achievement Test (CAT). The last test was used as the criterion variable. All intercorrelations between the criterion and predictor variables were significant beyond the P = .05 level of confidence. Partial correlations deviated very little from the original or zero-order correlations. A regression equation was derived for the present sample. A multiple correlation of .874 was found when the three predictor variables were combined. It was established that 76 per cent of the criterion variations was attributable to the relation of criterion to predictors. It was concluded that in initial screening for weakness in reading achievement the present tests would be of considerable value for the appropriate diagnosis and action for students deficient in this area.     

ADHD and reading disability in male adults: is there a connection?

The present study examined the comorbidity between attention-deficit/hyperactivity disorder (ADHD) and reading disability (RD) in male adults. Participants were 120 men, of whom 24 were classified as having ADHD. The basis for the diagnosis was two self-report scales validated by interviews and background data. An extensive battery was used to assess phonological abilities and various aspects of reading skills. No differences were obtained between adults with and without ADHD on measures of either phonological processing skills or word decoding, indicating a low comorbidity with RD. This finding was valid even when different criteria were used to diagnose RD. However, the two groups differed in reading comprehension, with individuals with ADHD performing poorly in tests of reading comprehension. These results are compatible with the view that reading comprehension involves many of the higher cognitive control functions assumed to be impaired in ADHD. However, these attentional control functions are not critical to word recognition, which is determined by a more encapsulated phonological processing module. The pattern of associations between ADHD and RD observed in the present study is explained with reference to the differential attentional demands of the two aspects of reading.     

Accuracy and Fluency in List and Context Reading of Skilled and RD Groups: Absolute and Relative Performance Levels

The purpose of this study was to examine (1) the performance levels and the magnitude of performance difference between students with reading disabilities (RD) and skilled readers when reading a typical classroom text; (2) the hypothesis that students with RD have specific difficulty using context in such a way that reading fluency is affected; and (3) whether RD subtypes may be differentiated according to performance on contextual and context‐free reading tasks. Two groups of fourth graders (85 skilled readers and 24 students with RD) completed a standardized test of reading comprehension, read aloud a folktale, and read aloud the folktale's words in a randomly sequenced list. Performance was scored as correct rate and percentage correct. Based on the number of words per idea unit in the passage, we also estimated the rate at which reader groups encountered and processed text ideas. Compared to the RD group, skilled readers read three times more correct words per minute in context, and showed higher accuracy and rates on all measures. Both context and isolated word‐reading rates were highly sensitive to impairment. We found no evidence for RD subtypes based on these measures. Results illustrate differences in reading levels between the two groups, the temporal advantage skilled readers have in linking text ideas, how word reading differs as a function of task format and performance dimension, and how limited word‐identification skills (not comprehension) produce contextual reading difficulties for students with RD.     

A Critical Analysis of Siegel's Case for Revision of the Learning Disability Construct

In this paper I analyse Siegel's revisionist conceptualization of the learning disability concept. Siegel has attempted to demonstrate that the construct of learning disabilities is flawed because of its long‐term linkage with the variable of intelligence. The discrepancy formulation is the particular focus of her criticism. She has denigrated the use of IQ tests in LD diagnosis and argued that intelligence and reading measure many of the same abilities and therefore any difference between these two functions is confounded; that IQ is not a valid measure of reading potential in children with LD and normal populations; and that logical analysis and empirical research demonstrate that the concept of intelligence is redundant in any conception of learning disabilities. I present arguments against each of these propositions and several other matters raised in her paper. I propose two basic approaches to learning disabilities and give expression to these in two theoretical models, a simple categorical model (designated as Model C) and the underachievement model (Model D). I show that Siegel's interpretation is based on a weak version of Model C, but that this model fails to elucidate the essential meaning of the learning disability construct. I show that Model D is the more appropriate alternative. I contend that the application of standard regression procedures inherent in Model D would lead to a more appropriate definition of LD and that more stringent standards for the underachievement criterion would offset many of the problems that Siegel has highlighted in her paper.     

The Deficit Profiles of Chinese Children with Reading Difficulties: a Meta-analysis

The current meta-analysis synthesized findings from profiling research on Chinese children with reading difficulties (RD). We reviewed a total of 81 studies published between 1964 and May 2015, representing a total of 9735 Chinese children. There are 982 effect sizes for the comparison between children with RD and age-matched typically developing (A-TD) children and 152 effect sizes for the comparison between children with RD and reading-level-matched typically developing (R-TD) children on multiple linguistic and cognitive skills. Results showed that compared to A-TD children, children with RD have severe deficits in morphological awareness, orthographic knowledge, phonological awareness, rapid naming, working memory, and visual skills and moderate deficits in short-term memory and motor skills. Compared to R-TD children, children with RD only have moderate deficits in rapid naming and mild deficits in orthographic knowledge. Moderation analyses for the comparison between RD and A-TD children revealed that children with more severe RD show more severe deficits in morphological awareness, phonological awareness, rapid naming, and visual skills. However, neither location (Mainland vs. Hong Kong) nor type of reading screening (character recognition vs. character recognition combined with reading comprehension) emerged as a moderator of the deficit profiles. These findings indicate that Chinese children with RD have deficits on a wide range of cognitive and linguistic skills. Deficits in rapid naming and orthographic knowledge may be potential causal factors for RD in Chinese based on existing evidence. Implications for the diagnosis and instructions of Chinese children with RD were discussed.     

Phonological awareness,verbal working memory and the acquisition of literacy

This paper describes a 2-year longitudinal study of 76 initially prereading children. The study examined the relationships between phonological awareness (measured by tests of onset and rime, phonemic segmentation and phoneme deletion), verbal working memory and the development of reading and spelling. Factor analyses showed that the verbal working memory tests which were administered loaded on two distinct but highly related factors, the first of which,simple repetition, involved the repetition of verbal items exactly as spoken by the experimenter, whereas the second,backwards repetition, involved repetition of items in reverse order. Factor analyses also showed that, whist the phonological awareness variables consistently loaded on the backwards repetition factor at the beginning and end of Grade 1, by Grade 2 the phonological awareness variables loaded on a separate factor which also included sentence repetition. Results of multiple regression analyses, with reading and spelling as a compound criterion variable, indicated that phonological awareness consistently predicted later reading and spelling even when both simple and backwards repetition were controlled. In contrast, verbal working memory did not consistently predict reading and spelling across testing times. Whilst there was some indication that verbal working memory, especially backwards repetition, measured during Grade 1 did predict reading and spelling in Grade 2, these effects were no longer evident when all three phonological variables were controlled. Nevertheless, with 4 individual reading and 2 individual spelling measures as the criterion variables, it was shown that phonological awareness was not quite such a consistent predictor of reading and spelling: it was most highly related to reading pseudowords and spelling real words; but it was not so highly related to spelling pseudowords, apparently because the processing demands of the task for the young children in the study were extremely high. Given the importance of verbal working memory for the completion of phonological awareness, reading and spelling tasks, in particular for spelling pseudowords, the findings are interpreted as providing some support for a theoretical position which posits that both phonological awareness and verbal working memory contribute to the early stages of literacy acquisition. Whilst the findings suggest some support for a general underlying phonological ability, there is also evidence that, as children learn to read and write, verbal working memory and phonological awareness become more differentiated.     

Gender bias in IQ-discrepancy and post-discrepancy definitions of reading disability

The present study investigated the hypothesis that the higher prevalence of reading disability (RD) often observed among boys is partly an artifact of gender bias in the prediction of reading from IQ. The relevant regression statistics derived from a sample of more than 900 children revealed a statistically significant intercept bias. Predicted reading scores for boys were systematically overestimated, thereby inflating IQ-reading discrepancies; the converse was found for girls. When defined separately for girls and boys, severe underachievement in reading was found to be equally prevalent in both genders and, furthermore, was associated with qualitatively and quantitatively similar patterns of deficits. Because the bias arose from general differences between boys and girls in reading score distributions (a lower mean and greater variance for boys) rather than from differences in IQ scores, gender bias poses a potential threat not only to traditional IQ-discrepancy definitions but also to post-discrepancy definitions that are based solely on reading score cutoffs. Future classification criteria for RD need to take heed of the possibility that when the distributions of reading scores for boys and girls are not identical, performance cutoffs designating low achievement that are based on data pooled from both genders are likely to result in the overidentification of boys with RD and the underidentification of girls with RD.     

Mixed Mode Latent Class Analysis: An Examination of Fit Index Performance for Classification

This Monte Carlo study examines the performance of fit indices commonly used by applied researchers interested in finite mixture modeling for the purposes of classification. Conditions for the simulation study were selected to reflect conditions found in applied educational and psychological research. The factors included in the investigation were metric level of indicators, sample size, and class prevalence. All models contained a combination of categorical and continuous indicators. All categorical indicators were dichotomous, and continuous indicators were normally distributed. The fit indices examined were Akaike’s information criterion, Bayesian information criterion (BIC), sample size-adjusted Bayesian information criterion (SSBIC), integrated classification likelihood criterion with Bayesian-type approximation, and Lo–Mendell–Rubin likelihood ratio test. Overall, SSBIC tended to identify the correct solution with higher frequency than other indices. BIC tended to identify the correct solution with higher frequency than the other indices in models with more continuous than categorical indicators, or when rare classes were absent.