The relationship between IQ and reading disabilities in English-speaking Canadian and Spanish children

This study was designed to examine the role of intelligence (IQ) in the definition of reading disabilities (RD) in languages with different orthographic systems. A sample of 94 Spanish children and 157 English-speaking Canadian children with RD was classified into four groups on the basis of IQ scores from the Wechsler Intelligence Scale for Children-Revised (< 80; 81-90; 91-109; 110-140). We examined the reading and spelling skills of Canadian and Spanish children as a function of Full Scale, Verbal, and Performance IQ scores. Significant differences between the languages were found when reading performance was analyzed as a function of Verbal IQ scores, in that there were some differences between the groups of Canadian children with RD but not between the groups of Spanish children. The Canadian children with Verbal IQ scores < 80 demonstrated relatively lower performance in reading and spelling skills than the Canadian groups with higher IQ scores. There were differences in reading tasks as a function of Performance IQ in English but not in Spanish. The differences in the role of IQ as a function of orthographic systems may relate to the greater significance of visual-orthographic as opposed to phonological processing in English.     

The validity of discrepancy-based definitions of reading disabilities.

This study addressed the validity of distinguishing children with reading disabilities according to the presence or absence of discrepancies between intelligence test scores and academic achievement. Three definitions of reading disability were used to provide criteria for five groups of children who (a) met a discrepancy-based definition uncorrected for the correlation of IQ and achievement; (b) met a discrepancy-based definition correcting for the correlation of IQ and achievement; (c) met a low achievement definition with no IQ discrepancy; (d) met criteria a and b; and (e) met none of the criteria and had no reading disability. Comparison of these five groups on a set of 10 neuropsychological tests corrected for correlations with IQ showed that group differences were small and accounted for little of the variability among groups. These results question the validity of segregating children with reading deficiencies according to discrepancies with IQ scores.     

Reading disabilities and the effects of colored filters

The efficacy of a controversial treatment, using colored filters to remediate reading disabilities, was measured empirically, with colored overlays placed over reading material on white paper. Irlen's (1983) method is to prescribe specific tinted filters as lenses that she claims filter specific light frequencies and remove a range of perceptual disorders that adversely affect reading and related learning performance. Irlen calls this condition "scotopic sensitivity" and claims it is a significant factor in a high percentage of people with learning disabilities. Ninety-two children with significant reading disabilities were classified as either scotopic or nonscotopic using the Irlen Differential Perceptual Schedule, and were randomly assigned to one of six treatment groups using colored or clear overlays. Reading performance (rate, accuracy, and comprehension) as measured by the Neale Analysis of Reading Ability (Neale, 1987) and the Formal Reading Inventory (Wiederholt, 1986) improved significantly when the scotopic children read with the preferred colored overlay filter compared to clear or different-colored overlay filters. Nonscotopic children showed no change.     

Diagnosis and treatment of reading disabilities based on the component model of reading: an alternative to the discrepancy model of LD

Currently, learning disabilities (LD) are diagnosed on the basis of the discrepancy between students' IQ and reading achievement scores. Students diagnosed with LD often receive remedial instruction in resource rooms. The available evidence suggests that the educational policy based on this discrepancy model has not yielded satisfactory results. This has led researchers to try other paradigms, such as the component model and response to intervention, for dealing with children with reading disabilities. The component model of reading (CMR) described in the present article identifies the reading component that is the source of reading difficulty and targets instruction at that component. Study 1 describes the CMR and reports on its validity. Study 2 describes the successful outcome of a 7-year CMR-based reading instruction program. Compared to the discrepancy model, the CMR has demonstrated several advantages.     

Comparisons of cutoff and regression-based definitions of reading disabilities

This study addressed the issue of specificity in reading disability by comparing two approaches to defining and selecting children with reading disabilities. One approach defined reading disability according to cutoff scores representing appropriate levels of intelligence and reading deficiency, whereas the other approach adjusted these scores for their intercorrelation through regression procedures. Results revealed clear differences in which children were identified as reading disabled according to the two definitions. However, differences in neuropsychological performance between children whose reading scores were discrepant or not discrepant with IQ were small and nonspecific for both definitions. The results of this study show that children identified as reading disabled vary according to the definition employed; at this point, there is little evidence suggesting any specificity of reading disability according to definition.     

Matthew effects in children with learning disabilities: Development of reading,IQ, and psychosocial problems from grade 2 to grade 8

Reading achievement, IQ, and behavior problems were assessed in second and eighth grade for a longitudinal sample of 57 children. Changes in these scores over time were compared for children with no learning disabilities versus children with math or reading disabilities (research-identified and/or school-identified). A widening of the group difference in IQ was seen between the math disabled and nondisabled groups, but otherwise the gaps between groups remained unchanged or narrowed over the six-year interval, indicating that hypothesized negative consequences of initial academic difficulties (“Matthew effects”) did not occur for most of the children with learning disabilities. Elevated rates of behavior problems were seen only for the group with math disabilities, suggesting that the type of learning disability needs to be taken into account in research on the association between academic and psychosocial problems.     

Cognitive Constraints on the Simple View of Reading: A Longitudinal Study in Children With Intellectual Disabilities

The present article aimed to explore how the development of reading comprehension is affected when its cognitive basis is compromised. The simple view of reading was adopted as the theoretical framework. The study followed 76 children with mild intellectual disabilities (average IQ = 60.38, age 121 months) across a period of 3 years. The children were assessed for level of reading comprehension (outcome variable) and its precursors decoding and listening comprehension, in addition to linguistic skills (foundational literacy skills, rapid naming, phonological short-term memory, verbal working memory, vocabulary, and grammar) and non-linguistic skills (nonverbal reasoning and temporal processing). Reading comprehension was predicted by decoding and listening comprehension but also by foundational literacy skills and nonverbal reasoning. It is concluded that intellectual disabilities can affect the development of reading comprehension indirectly via linguistic skills but also directly via nonlinguistic nonverbal reasoning ability.     

Do the effects of computer-assisted practice differ for children with reading disabilities with and without IQ-achievement discrepancy?

This study was designed to assess whether the effects of computer-assisted practice on visual word recognition differed for children with reading disabilities (RD) with or without aptitude-achievement discrepancy. A sample of 73 Spanish children with low reading performance was selected using the discrepancy method, based on a standard score comparison (i.e., the difference between IQ and achievement standard scores). The sample was classified into three groups: (1) a group of 14 children with dyslexia (age M = 103.85 months; SD = 8.45) who received computer-based reading practice; (2) a group of 31 "garden-variety" (GV) poor readers (age M = 107.06 months; SD = 6.75) who received the same type of instruction; and (3) a group of 28 children with low reading performance (age M = 103.33 months; SD = 9.04) who did not receive computer-assisted practice. Children were pre- and posttested in word recognition, reading comprehension, phonological awareness, and visual and phonological tasks. The results indicated that both computer-assisted intervention groups showed improved word recognition compared to the control group. Nevertheless, children with dyslexia had more difficulties than GV poor readers during computer-based word reading under conditions that required extensive phonological computation, because their performance was more affected by low-frequency words and long words. In conclusion, we did not find empirical evidence in favor of the IQ-achievement discrepancy definition of reading disability, because IQ did not differentially predict treatment outcomes.     

The relative roles of IQ and cognitive processes in reading disability

The purpose of the present study was to explore the relative roles of IQ and cognitive processes in reading performance. A sample of 443 Spanish children (264 male, 179 female) ranging in age from 7 to 13 years were classified into four groups according to IQ scores (<80, 80–90, 90–110, >110) and reading disabled (RD) and normally achieving readers (NR) were compared. The findings indicate that IQ scores were not related to the differences between children with RD and NR. We found that reading‐related cognitive deficits do differentiate between RD and NR children. Therefore, IQ scores do not make a significant contribution to our understanding of reading disability.     

Patterns of Performance of Chinese-American Students with Learning Disabilities: A pilot study

This pilot study examines the pattern of performances of 55 Chinese-American students with limited English proficiency (LEP) who were classified as learning disabled. The results indicate that the students in this study fell behind academically. The analysis reveals that the general pattern of performances of LEP Chinese-American students with learning disabilities is similar to that of English-speaking peers with learning disabilities. Although their full-scale IQ fell into the low average range, there was a significant discrepancy between verbal IQ and performance IQ. Their deficits in phonetic skills were related to the changed family situation, to the unique linguistic features of Chinese language, and to the instructional approaches at school. Based on the findings of this pilot study more appropriate assessments and better application of theory are needed for these students.     

Cerebellar tests differentiate between groups of poor readers with and without IQ discrepancy

A comprehensive test battery, including phonological, speed, motor and cerebellar tasks, was administered to the entire cohort of two schools for children with learning disabilities. Testing was undertaken blind without accessing the psychometric data on the children. Children were then allocated to a discrepancy group on the basis of their IQ, with the majority (n = 29) classified as nondiscrepant (IQ < 90) and a smaller set (n = 7), with IQ of at least 90, classified as discrepant (with dyslexia). Both groups showed significant deficits relative to age-matched controls on almost all the tests. On phonological, speed, and motor tasks, the nondiscrepant group were at least as severely impaired as the discrepant group. By contrast, on the cerebellar tests of postural stability and muscle tone, the nondiscrepant group performed significantly better than the children with dyslexia and close to the level of the controls. The findings indicate that cerebellar tests may prove a valuable method of differentiating between poor readers with and without IQ discrepancy. The findings are interpreted in terms of the cerebellar deficit hypothesis for dyslexia.     

Predicting the future achievement of second graders with reading disabilities: Contributions of phonemic awareness, verbal memory, rapid naming, and IQ

Concurrent and prospective correlations among reading, spelling, phonemic awareness, verbal memory, rapid serial naming, and IQ were examined in a longitudinal sample that was studied at Grade 2 and Grade 8. Substantial temporal stability of individual differences in all of these skills was seen over the six-year period between assessments. The strongest predictors of future reading and spelling outcomes were different for normally achieving second graders than for those who had been designated as having reading disabilities. For the former, Grade 2 literacy scores were the best predictors of later achievement. For the children with reading disabilities, however, prediction of most future reading and spelling skills was substantially improved by the inclusion of the cognitive-linguistic measures, particularly rapid naming.     

Adults with reading disabilities: converting a meta-analysis to practice

This article reviews the results of a meta-analysis of the experimental published literature that compares the academic, cognitive, and behavioral performance of adults with reading disabilities (RD) with average achieving adult readers. The meta-analysis shows that deficits independent of the classification measures emerged for adults with RD on measures of vocabulary, math, spelling, and specific cognitive process related to naming speed, phonological processing, and verbal memory. The results also showed that adults with high verbal IQs (scores > 100) but low word recognition standard scores (< 90) yielded greater deficits related to their average reading counterparts when compared to studies that included adults with RD with verbal IQ and reading scores in the same low range. Implications of the findings related to assessment and intervention are discussed.     

The role of IQ in a component model of reading

The purpose of this study was to test the role of visual processing speed and IQ in a model of reading. This study investigated whether the processes involved in reading differ between a group of children with and a group without reading disability. These two groups of children completed tests of reading comprehension, listening comprehension, decoding, processing speed, and intelligence. The results indicated that processing speed explains a significant amount of variance in reading comprehension over that accounted for by the simple view of reading. Also, IQ accounts for a significant amount of variance in reading over that accounted for by the simple view of reading and processing speed. Path analyses indicated that the effect of IQ on reading is partially mediated by decoding in the children with reading disability. The results point to the importance of the role of IQ in predicting reading comprehension.     

Relation between Kaufman Brief Intelligence Test and WISC-III scores of children with RD

Concurrent validity of the Kaufman Brief Intelligence Test (K-BIT) with the Wechsler Intelligence Scale for Children-Third Edition (WISC-III) was evaluated, as well as the K-BIT's accuracy as a predictor of WISC-III scores, in a sample of young children with reading disabilities. The two measures were administered to 65 children from Atlanta, Boston, and Toronto who ranged from 6-5 to 7-11 years of age at testing. Correlations between the verbal, nonverbal, and composite scales of the K-BIT and WISC-III were .60, .48, and .63, respectively. Mean K-BIT scores ranged from 1.2 to 5.0 points higher than the corresponding WISC-III scores. Standard errors of estimation ranged from 10.0 to 12.3 points. In individual cases, K-BIT scores can underestimate or overestimate WISC-III scores by as much as 25 points. Results suggest caution against using the K-BIT exclusively for placement and diagnostic purposes with young children with reading disabilities if IQ scores are required.     

Differential genetic etiology of reading disability as a function of IQ

To test the hypothesis that the genetic etiology of reading disability differs as a function of IQ, composite reading performance data from 223 pairs of identical twins and 169 pairs of same-gender fraternal twins in which at least one member of each pair was classified with reading disability were subjected to multiple regression analysis (DeFries & Fulker, 1985, 1988). In the total sample, heritability of the group deficit in reading performance (h(g)2) was .58 (+/- .08). However, when the basic regression model was fitted separately to data from twin pairs with average Wechsler (1974, 1981) full scale IQ scores below 100 or 100 and above, resulting estimates of h(g)2 were .43 and .72, respectively, a significant difference (p < or = .03, one-tailed). The results of fitting extended regression models to reading performance and continuous IQ data provide evidence that the genetic etiology of reading disability differs as a linear function of IQ (p < or = .007, one-tailed). These results suggest that IQ is relevant for the diagnosis of reading disability and that environmental influences may be more salient as a cause of reading difficulties in children with lower IQ scores.     

Relationship between PPVT and WISC-R in children with reading disabilities

The Peabody Picture Vocabulary Test (PPVT), Form A was compared to the Wechsler Intelligence Scale for Children-Revised (WISC-R) in two samples of children with reading disabilities. One group of 14 children, referred to a university clinic, were administered the WISC-R, followed by the PPVT. The second group of 38 children from a private learning disability center were administered the PPVT first, followed by the WISC-R. In the combined sample, the PPVT IQ (X̄ = 109.2) was significantly higher than the WISC-R Verbal IQ (X̄ = 98.9), Performance IQ (X̄ = 97.0), and Full Scale IQ (X̄ = 97.5). Similarly, the PPVT IQ was significantly higher than the WISC-R Full Scale in both samples separately, regardless of which test was administered first. In one case, the PPVT IQ was 50 points higher than the WISC-R IQ. Correlations between the PPVT and WISC-R Verbal, Performance, and Full Scale IQs were significant (rs = .56, .29, and .50, respectively). The results suggest that the two tests do not provide interchangeable IQs for a population of reading disabled children.     

Can reading disabilities be diagnosed without using intelligence tests?

Unlike conventional procedures, which use IQ in making diagnostic and eligibility decisions regarding learning disabilities, this demonstration study used listening comprehension and other reading-related tasks to make a differential diagnosis of reading disabilities. Tests of listening and reading comprehension were administered to 180 children from Grades 3 through 8. A regression equation was then derived to predict reading comprehension from listening comprehension. The regression equation was applied to the listening comprehension scores of seven children from Grades 3 to 8 who had reading difficulties, and their reading comprehension was predicted. Based on the discrepancy between their actual reading comprehension and the predicted reading comprehension, their reading difficulty was attributed to one of the following three factors: (a) poor decoding, (b) poor comprehension, or (c) a combination of poor decoding and poor comprehension. The validity of these diagnostic decisions was assessed by testing independently these children's word-decoding skill and reading speed. The results suggest that this diagnostic procedure has potential utility.     

Evidence for unexpected weaknesses in learning in children with attention-deficit/hyperactivity disorder without reading disabilities

This study examined the mechanisms underlying verbal learning in children with and without attention-deficit/hyperactivity disorder (ADHD), none of whom had reading disabilities. Children with ADHD were compared to typically developing children on both process and product scores from the California Verbal Learning Test for Children. The findings indicated that children with ADHD initially learned the same number of words as controls but showed weaknesses recalling the words after delays, suggesting that children with ADHD are less efficient learners. Regardless of ADHD status, boys and girls performed differently. Boys used semantic clustering less frequently and recalled fewer words from the middle region of the list than girls; girls also outperformed boys in terms of overall performance, despite lower verbal IQ scores. These findings show that children with ADHD can exhibit unexpected weaknesses in learning even without a formal learning disability. Gender differences in verbal learning are also illustrated.     

The locus of so-called IQ test results in reading disabilities

It would appear the question of relevance of IQ in the assessment and remediation of children with RD is not quite the relevant question to ask, if only traditional intelligence tests are the focus. From the psychoeducational point of view of refining diagnosis, and from the administrative perspective of accountability, it would be helpful to accept a threshold of something like an IQ of 85 as the lower bound in defining learning or reading disabilities. A discrepancy from this threshold as derived from regression analysis or other more refined analyses and taking into account varying reliabilities, intercorrelations, and standard errors of measurement of different measuring instruments may constitute a learning or reading disability. How discrepant the aptitude-achievement should be to constitute a "significant" difference is a function of, among other factors, the material and human resources available to any particular school system. Leong (1987) has made suggestions for essentially a two-stage assessment leading to more refined diagnosis with the use of well-standardized group tests and teachers' estimates for the first stage (assessment) and more refined individual tests to diagnose those showing discrepant aptitude-learning performance in the border-zone. The rationale is that all those children requiring special services are so served and those in the uncertainty region must be carefully diagnosed so as to minimize so-called "misfits" in accordance with signal detection principles. It should be noted that the diagnosis of learning or reading disabilities can never be exact, even with the use of reliable and valid test instruments, and the "fuzzy set" approach should apply to the process (Horvath, Kass, & Ferrell, 1980).(ABSTRACT TRUNCATED AT 250 WORDS)