The prevention and identification of reading disability

The Prevention and Identification of Reading Disability Patricia G. Mathes and Carolyn A. Denton There is abundant evidence that intervention for the prevention of reading disability is effective in dramatically reducing the prevalence of reading disability. This article explores the current state of knowledge regarding the causation and prevalence of reading disability, along with evidence that the incidence of this condition can be dramatically reduced through quality intervention. Specifically, we (1) explore what is known about the nature and causes of reading disability, (2) examine how reading disability can best be identified, and (3) estimate the percentage of children that have severe reading difficulties that indicate the true presence of a disability.

Copyright 2002, Elsevier Science (USA). All rights reserved.

ECENT RESEARCH indicates that early in,tervention in the primary grades is effective in preventing reading problems for most children, and that for those who continue to experience difficulty, the depth of the reading problem can be greatly reduced] This article explores the current state of knowledge regarding the causation and prevalence of reading disability, along with evidence that the incidence of this condition can be dramatically reduced through quality intervention. Specifically we: (1) explore what is known about the nature and causes of reading disability, (2) examine how reading disability can best be identified, and (3) estimate the percentage of children who have severe reading difficulties that indicate the true presence of a disability. There is abundant evidence that intervention for the prevention of reading disability is most effective when it is delivered to children very early (ie, kindergarten and first grade). That is before reading problems become intractable and complicated with issues of self-concept and learned helplesshess. 1"2 In the United States, if a student fails to learn to read adequately in first grade, there is about a 90% probability that that child will remain a poor reader by Grade 43,4 and about a 75% probability that he or she will be a poor reader in high school. 5

from state to state. Currently, children who conform to this definition qualify for special education services under the learning disabilities label, whereas children who do not conform do not qualify, even though they may experience serious difficulties in becoming competent readers. Although some low-achieving students who do not demonstrate the stipulated achievement-aptitude discrepancy may receive supplemental reading instruction in compensatory education or dyslexia programs, in many locations they receive no extra attention. The concept of unexpected underachievement has appeared in the literature since the middle of the 19 th century. The term "learning disability" (LD) first appeared in 1962, when Samuel Kirk 6 applied it to unexpected difficulties in the areas of language, learning, and communication. In 1969, the Learning Disabilities Act made special education services available to students with LD. 7 The category was reaffirmed with the passage of the Education for All Handicapped Children Act, Public Law No. 94-142, in 1975. 8 The concept of LD remains basically unchanged in the current authorization of the Individuals with Disabilities Education Act (IDEA). 9,m An estimated 90% of students identified as learning disabled are identified as having a reading disability. ~

TRADITIONAL UNDERSTANDING OF READING DISABILITY

VALIDITY OF THE DISCREPANCY MODEL

R

Traditionally, reading disability has been defined as unexpected underachievement characterized as a discrepancy between achievement and intellectual aptitude, despite adequate opportunity to learn and in the absence of sensory difficulties or cultural deprivation. This discrepancy is typically operationally defined in terms of a difference between a score on an IQ test and scores on a norm-referenced test of reading achievement. The specific discrepancy necessary to qualify varies

The problem with the current aptitude-achievement discrepancy model is that it lacks valid-

From the Department of Pediatrics, University of Texas, Houston Health Science Center, Houston, TX. Address reprint requests to Patricia G. Mathes, PhD, University of Texas-Houston, 7000 Fannin, UCT 2443, Houston, TX 77030. Copyright 2002, Elsevier Science (USA). All rights reserved 1071-9091/02/0903-0003535.00/0 do#lO. 1053/spen.2002.35498

Seminars in Pediatric Neurology, Vol 9, No 3 (September), 2002: pp 185-191

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ity. ~'12-15Thus, there is little basis for continuing to base qualifications for special services on current discrepancy models. 15-17 There is, at best, a questionable relationship between IQ and the way students respond to early reading intervention. Repeatedly, studies have found no relationship between IQ and intervention outcomes. 5'1s-22 One study found a small relationship of IQ with outcome on one of three outcome measures9 3 Beyond the fact that the current model lacks validity, it tends to favor students with higher IQs, as it is difficult for a student with a low average IQ to exhibit achievement scores low enough to produce the discrepancy. Furthermore, excluding cultural deprivation in the current definition of LD can result in the withholding of services to students from culturally different or impoverished backgrounds. However, there is no evidence that reading problems resulting from a lack of environmental stimulation and those caused by an assumed neurologic problem can in any way be discriminated. In fact, recent studies of brain activation patterns of children with serious reading problems from both affluent and impoverished environments evidence similar neurologic dysfunction suggesting that a reading problem is a reading problem, regardless of causation (ie, environmental or genetic). Furthermore, factors associated with inadequate instruction, emotional disturbance, and poverty may actually cause differences in neurologic and cognitive development that lead to severe learning difficulties, l The current definition of LD makes it all too likely that students experiencing difficulties stemming from these situations will be excluded from receiving services. Another problem with using a discrepancy model to identify reading disabilities is that it is very difficult to detect discrepancies early. Typically, children have to fall behind before the discrepancy is identified. Thus, the use of IQ-achievement discrepancy is inherently a "wait to fail" model. The problem with waiting until a child fails is that reading problems become intractable as children age. 3"4 CURRENT THINKING ABOUT READING DISABILITIES

Types of Reading Disability The most widely recognized and researched reading disability is associated with difficulty with

reading single words. This type of difficulty is the most pervasive characteristic of dyslexia. 24 These single-word reading problems are thought to be based on an underlying phonological processing core deficit. 25"26 Both children and adults with dyslexia experience great difficulty in applying the alphabetic principle to decode words quickly and efficiently. The result is that decoding is labored, fluency is poor, and comprehension is negatively impacted. 27,2s A less common and less researched reading disability is associated with poor language comprehension. Although much less frequent than decoding difficulty, this disability affects some persons who have normal phonological processing skills, but demonstrate difficulty in formulating main ideas, summaries, and inferences. This difficulty is demonstrated when listening to, as well as reading text. 2s A third group of students who experience great difficulty in learning to read are those who experience both decoding problems and language comprehension problems. Given the strong correlation between oral language development and socioeconomic level, 29 it is likely that many children from impoverished families would experience difficulties with both phonological processing and language comprehension. Currently, little research has been conducted with these students. However, we would argue that students in the last category have the greatest needs and most severe reading disabilities.

Genetic and Environmental Influences It is clear that there are some individuals who have a genetic predisposition to experience reading difficulties. Reading has been linked to sites on chromosomes 1, 2, 6, 15, - 6 , and 15 replicated, although there is no evidence for genes that are specifically responsible for reading ability or disability. Likewise, only 50% of the variability in reading skill is explained by genetic factors. 3~ Thus, the genetic penetrance for reading disability is low. Furthermore, children with no genetic predisposition for reading problems, but who are being raised in environments with little early literacy stimulation, will present with reading problems that are equivalent to the child with a genetic predisposition. Thus, it is now clear that a child's environment, both at home and in school, plays a primary role in determining whether a particular

READING DISABILITY

child will evidence reading problems, regardless of the genetic predisposition of that child. 3~ The importance of environment can be seen in recent work being conducted at the University of Texas--Houston Medical School using Magnetic Source Imaging (MSI) brain imaging technology to examine the brain activation patterns of very young children as they learn to read. 31 This group has imaged the brains of children at the end of kindergarten who are either at-risk or not at-risk for developing phonologically based reading problems. What has been found is that even at this early age, difference in brain activation patterns are apparent. When asked to read simple words, children who are not at risk for reading problems evidence organized activation in the temporoparietal areas of the left hemisphere. In children at risk for reading disability, temporoparietal areas of the left hemispheres, including the posterior third of the superior and middle temporal gyri and the angular and supramarginal gyri, fail to become engaged while reading. These children also evidence marked increase in activation in the homotopic areas of the tight hemisphere. 3l'32 Likewise, identical brain activation patterns are observed with older children who have been identified as dyslexic compared with children with no reading difficulties. 33,34 Even so, the impact that the environment can have in (1) creating differences in patterns of brain functioning, and (2) preventing or overcoming these differences cannot be overlooked. The University of Texas--Houston group have demonstrated that the brain activation patterns of older children identified with dyslexia can be normalized through quality instruction. 31 For further detail about brain activation profiles of children with reading problems, see Papanicolaou elsewhere in this issue. EARLY IDENTIFICATION

One of the most exciting developments in reading over the past 20 years is a dramatic growth in our understanding of which skills predict later reading problems associated with a phonologic processing core deficit. Today, we can confidently predict which children are most at-risk for developing dyslexia as young as the middle of kindergarten. 35 Thus, there is no reason to wait for a child to fail and then evaluate a discrepancy between achievement and IQ to determine whether he or

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If progress is inadequate, move to next level.

Level 1 : Primary Intervention Enhanced general education classroom instruction. Level 2: Secondary Intervention Child receives more intense intervention in general education, presumably in small groups. Level 3: Tertiary Child placed in special education: Intervention increases in intensity and duration.

Fig 1. The three-tiered model for preventing reading disability.

she qualifies for special services. Instead, we can identify risk for reading failure early, provide highquality intervention before failure has occurred, and in most cases normalize reading ability. Early literacy skills that have been demonstrated to accurately predict risk in young children include: (1) phonemic awareness or the ability to hear the individual phonemes (sounds) within words (ie, cat = / c / / a / / t O , (2) knowledge of letter names and sounds, and (3) speed of lexical retrieval measured through the rapid naming of objects, colors, digits, or letters. 35"36 CHANGING CRITERIA FOR IDENTIFYING READING DISABILITY

Given that we now know how to prevent most reading disabilities from occurring, there is movement to change the way in which reading disabilities are identified. Rather than focus on whether a child has an IQ-achievement discrepancy, current proposals recommend that determination of reading disabilities be made based on an examination of response to quality intervention. ~'37"38 This response to treatment would be determined using ongoing, frequent measures of word recognition, fluency, vocabulary and comprehension, as well as subskills that correlate strongly with reading development. 15 Current proposals recommend a three-tiered model of reading intervention as shown in Figure 1. On the first tier, classroom-level general education instruction is improved. Children who still experience difficulty after receiving quality classroom-level instruction move into more intense interventions, presumably delivered within general education in small groups (Tier 2). In the threetiered intervention model, only after these two levels of intervention have failed would a child be considered reading disabled, requiting tertiary intervention. Tertiary intervention is typically de-

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scribed as having greater intensity and duration than secondary intervention. Presumably, at this point special education services would be provided. 38,39

Under this three-tiered model, there would be provisions for (1) early identification of children at-risk for reading failure followed by, (2) carefully designed intense early reading instruction incorporating an emphasis on systematic, explicit instruction in alphabetic reading skills balanced with meaningful experiences with authentic texts and writing, and (3) continued support beyond the initial acquisition of reading skill to ensure continued academic growth into the upper grades. 4~ Thus, all students who are identified as at-risk for possible reading problems would be provided with intervention within general education. Only children who did not make adequate progress would be considered for a reading disabilities label. However, this label would not be based on IQ-achievement discrepancies, but rather on inadequate response to intervention. 37'38"4~ QUALITY OF INTERVENTION

The success of the three-tier model hinges on ensuring that instruction at each of the three levels is of high quality. As a result, it would unify general, special, and compensatory education services into one supple unit and require that all teachers involved in the process are provided ongoing staff development and mentoring in the critical content of effective reading instruction. This critical content includes provisions for emergent readers to develop phonological awareness, letter-knowledge, and concepts of print. For beginning readers, this instruction ensures acquisition of accurate and quick word recognition skills, increasing the speed and ease of reading connected text, providing extensive engagement with decodable text, and strategies for enhancing the deep processing of text. Most crucial among these critical components is the inclusion of systematic instruction in phonological recoding (ie, soundingout words) as a word recognition strategy. Phonological recoding appears to account for individual differences in word recognition in both children and adults. 42 Beyond phonological and alphabetic knowledge, children must be able to read connected text with relative ease if the meaning of that text is to be accessed and the development of mature comprehension strategies are to pros-

per. 14,43,44 Early literacy instruction that integrates alphabetic knowledge into the actual act of reading meaningful text has been shown to enhance both fluency and comprehension. 45'46 Clearly, readers must recognize words fluently to comprehend text, but fluency alone is not sufficient for achieving deeper levels of understanding. 2"47 Competent comprehenders are strategic; they typically follow a generalizable plan when approaching texts. 47'48 For children who do not develop strategies independently, they must be taught to do SO. 47 REDUCING THE INCIDENCE OF READING DISABILITY

We have stated that the incidence of reading disability can be dramatically reduced through quality instruction. The question still remains as to just how much the prevalence of reading disabilities can be reduced. Research suggests that primary classroom level of intervention is adequate to reduce substantially the large numbers of struggling readers. For example, Foorman et a119 found that classroom-level explicit instruction in phonological awareness and the alphabetic principle, along with opportunities to apply skills in reading and writing, brought most students in Grades 1 and 2 in eight high-poverty schools to national averages. Table 1 presents the findings of several studies that illustrate the power of solid classroom-level instruction in the prevention of reading problems. In total, these studies demonstrate that nationally, if core classroom instruction conformed to empirically proven best practice, only about 6% or less of children should be expected to experience reading problems requiring secondary intervention. The prevalence of reading difficulty can be further reduced through secondary, small group intervention. There are many examples of successful secondary-level interventions. Torgesen et a149 identified children in kindergarten who had poor phonological awareness, that is, they had difficulty blending and segmenting sounds in speech. By second grade, secondary intervention brought 75% of these children to grade-level reading. Vellutino et al 5~ identified middle-class children with very low word recognition skills at the beginning of Grade 1. After one semester of intervention, 70% were reading at grade level. After two semesters, over 90% were at grade level. Table 2 presents examples of the effect of secondary intervention on the numbers of children who can be expected to

READING DISABILITY

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Table 1. Impact of High-Quality Classroom Level Instruction on the Percentage of Children Who Require Secondary Reading Services Defined as Reading Below the 30 th Percentile After Intervention

Study Foorman et al (1998) Mathes et al (2001) AIIor et al (2002) Mathes et al (in press)

Hours of Instruction 174 35 35-55 35

Reading %tile for Initial Identification of Risk Status

% of Lowest Readers ReadingBelow 30th %tile After Intervention

% of Students Reading Below 30th %tile After Intervention Extrapolated to the Total Population

Classroom

18

30%

5.4%

Classroom (peer tutoring) Classroom

25

28%

7%

25

27%

7%

25

18%

5%

Student/Teacher Ratio

(peer tutoring) Classroom (peer tutoring)

have severe reading difficulties requiring tertiary (special education) services. In examining this table, it is important to note the teacher-to-child ratio and the number of hours of instruction since it is likely that the numbers of students who remain poor readers is related to both the duration and intensity of the intervention. Intensity is increased as the number of students in a group decreases. In sum, the evidence suggests that if high-quality secondary instruction was regularly provided in our public schools, only 2% or less of children would require tertiary intervention.

validated in research projects can be "scaled up" to be implemented well across many school contexts .5 Presently, research has focused on classroomlevel and secondary-level intervention that impacts most students. What is much less clear is the content of tertiary instruction. Little has been done to follow-up and provide additional services to the few children who have made poor progress in secondary intervention models. Thus, we presently have little guidance as to what will be required to promote adequate progress among this small set of impaired readers. 27 There is some evidence that specific interventions reduce the numbers of children who would still qualify for tertiary to less than .5 percent. 52'53 Although not empirically tested, it would seem logical to assume that these most powerful interventions would be the most appropriate for children with the greatest need. Likewise, the bulk of research on the prevention of reading difficulties has focused on the most common type of reading problems, those associated with phonological processing problems. Much less is known about how to appropriately intervene

LINGERING QUESTIONS Although we have substantial research evidence as to effective models of reading intervention at the primary (classroom) and secondary levels, we do not as yet know whether a three-tiered reading intervention model can be consistently implemented to identify students in need of more intense special services. Further research is necessary to validate this model as practical and accurate. A primary question focuses on how such a model based on instructional practices that have been

Table 2. Impact of High-Quality Secondary Level Instruction on the Percentage of Children Who Require Tertiary Reading Services Defined as Reading Below the 30 th Percentile After Intervention

Study

Hours of Instruction

Felton (1993) Vellutino et al (1996) Torgesen et al (1999) Torgesen et al (in press) Torgesen et al (2002) Denton & Mathes (2002) ~ Denton & Mathes (2002) a

340 35-65 88 92 80 80 80

Reading %tile for Student/Teacher initial Identification Ratio of Risk Status 1:8 1:1 1:1 1:3 1:3 1:3 1:3

16 15 12 18 18 18 18

a Denton & Mathes (2002) report findings on two different interventions.

% of Lowest Readers ReadingBelow 30th %tile After Intervention

% of Students Reading Below 30th %tile After Intervention Extrapolated to the Total Population

24% 30% 23% 8% 4% 3% 12%

3.8% 4.5% 2.8% 1.4% .7% .5% 2.2%

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with students who experience language comprehension problems. 28 CONCLUSION

Our understanding of reading disability is evolving. It is clear that many students Struggle to develop reading competence. Although most of these students exhibit common characteristics related to difficulties in processing the sounds of language, we have yet to satisfactorily answer the question, "When is a reading difficulty a serious reading disability?" The current practice of identifying reading disability according to a discrepancy

between IQ and achievement scores, although relatively easy to implement, has the potential to under-identify many students who need special services. A more useful way to identify reading disability may be through the evaluation of a student's response to well-implemented, quality intervention. However, much remains to be learned regarding the implementation of this type of identification system. Even so, what is clear from repeated studies is that the need to label any child as reading disabled can be largely eradicated through high-quality instruction provided early in a child's school career.

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