Learning Disabilities
David Breiger Ph.D.
Jenise Jensen Ph.D.
Introduction and Background
Reports of individuals who acquired a sudden inability to read, write, or perform mathematical calculations after some type of neurological insult have been published since the 17th century. However, it was a description by Dr. W. Pringle Morgan in 1896 of a 14-year-old boy named Percy that led to the hypothesis that learning difficulties were due to a specific congenital or developmental disorder. Dr. Morgan’s report of Percy’s difficulty with learning to read, despite his overall normal intellect and intact visual and mental calculation skills, led another doctor, James Hinshelwood, MD, to conclude that this difficulty was due to problems with the visual memory system for words. The term “congenital word blindness” was coined in the early 1900s to describe this condition and represents the beginning of the research in the field of learning disabilities (LDs).
Later modifications to Hinshelwood’s theory resulted in the hypothesis that the inability to learn to read was due to problems with left-right orientation and strephosymbolia, or twisted word imagery, that was caused by a lack of cerebral dominance. Therefore, it was reasoned that deficits in the visual system resulted in seeing letters backwards (“b” for “d”) or transposing letters in words (“was” for “saw”). Until as recently as 30 years ago, this was one of the leading theories about the causes of developmental reading problems.
Another important point in the history of understanding childhood LDs was the 1918 flu pandemic. Many children who survived demonstrated attention, perceptual-motor, learning, and behavior problems despite having normal physical and neurological examinations. Because these difficulties could not be readily attributed to mental retardation or other forms of social or emotional disturbance, the term “minimal brain damage” was used to indicate that these learning and attention problems were due to some congenital factor intrinsic to the child. Further research and debate resulted in the term “minimal brain dysfunction” to reflect that a specific brain insult was not required to cause these problems. Attempts to identify neurological soft signs that might be diagnostic and predictive of which children would develop learning problems were also prominent throughout this period, to no avail.
It was not until the last 40 years that the official terms “learning disability” and “learning disorder” came into popular use. Dr. Samuel Kirk, a psychologist and special educator, first coined the term specific learning disability in 1963 to describe a group of children who had disorders of development in language, speech, reading, and associated communication skills that were not due to either sensory handicaps or mental retardation. The following chapter provides a summary of the current understanding of LDs, including their clinical features and course, prevalence, and etiological factors. Issues of assessment, identification, and treatment of LDs will also be discussed. The majority of this chapter will be primarily targeted at reading disabilities (RDs) as it has been the most researched, and hence is the best understood, of the LDs.
The Individuals with Disabilities Education Act (IDEA)
The term Learning Disorders is used in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR) to refer to a group of disorders that are characterized by learning problems resulting in an individual’s measured academic achievement falling substantially below the level expected given the person’s chronological age, educational level, and intellectual ability. The three primary LD diagnoses defined by the DSM-IV-TR are Reading Disorder, Mathematics Disorder, and Disorder of Written Language. The DSM-IV-TR also allows for the diagnosis of Learning Disorder Not Otherwise Specified (LD-NOS) to account for learning problems that do meet criteria for any specific LD.
The terms learning disorder and learning disability have largely been interchangeable in both the educational and psychiatric literature since the federal government officially adopted Kirk’s term “specific learning disability” in 1975 with the passage of Public Law 94-142. This federal law mandated schools to provide publicly funded special education and related services to students whose disabilities adversely affected their educational performance. PL 94-142 is currently named the Individuals with Disabilities Education Act (IDEA). The IDEA governs how states and public agencies provide early intervention, special education, and related services to more than 6.5 million eligible infants, toddlers, children, and adolescents with disabilities across the United States. Children from birth to 2 years of age with disabilities and their fam -ilies receive early intervention services under IDEA Part C. Children and adolescents (ages 3 to 21) receive special education and related services under IDEA Part B.
The IDEA defines the term “Specific Learning Disability” as: “A disorder in one or more of the basic psychological processes involved in understanding or in using language, spoken or written, that may manifest itself in an imperfect ability to listen, speak, read, write, spell, or to do mathematical calculations, including conditions such as perceptual disabilities, brain injury, minimal brain dysfunction, dyslexia, and developmental aphasia.” This term does not include a learning problem that is primarily the result of visual, hearing, or motor disabilities, of mental retardation, of emotional disturbance, or of environmental, cultural, or economic disadvantage.
IDEA was reauthorized in 2004. A number of noteworthy changes were incorporated including the following: alignment of IDEA with “No Child Left Behind”; emphasis on “Adequate Yearly Progress” (AYP); a mandate that Individual Education Plans (IEPs) must have measurable goals; increased certification standards for Special Education teachers; and requirement that parents receive quarterly reports on goal attainment. In addition, children who are homeless and disabled need to be identified, evaluated if necessary, and provided with IEPs.
Although IDEA provides a federal definition of specific LDs, states and local school districts have flexibility in how they identify which students meet criteria for special education services. The majority of school districts have traditionally used a discrepancy model to identify students with learning problems substantial enough to qualify for special education services under the classification of Specific Learning Disability. This formula requires a statistically significant difference of at least 1.5 to 2 standard deviations between assessed academic achievement and cognitive ability in order to qualify for special education. This type of identification system relies on categorical definitions of LD. However, there is also a debate that LDs, like many other medical and psychological disorders, may actually fall on a continuum and that a dimensional or spectrum model may be more appropriate. This type of identification system would allow children who would have otherwise been characterized as “poor readers,” but not learning disabled, to receive needed services. For example, a student whose overall cognitive ability was measured in the “low average” range (standard score of 85) and single word reading skills were in the “below average” range (standard score of 70) would not necessarily be identified as LD and receive services. This is because the student’s reading ability, while low, is often interpreted as being commensurate with his or her inherent ability using the traditional discrepancy model.
The latest revisions of the IDEA beginning in 2004 included an alternative to using the achievement-aptitude discrepancy formula to identify children with an LD. The revision prohibited requiring a severe discrepancy (while still allowing the use of the information) and allowed school districts to use Response to Intervention (RTI) as part of the evaluation process. RTI is the practice of providing high-quality instruction and interventions matched to student need, monitoring progress frequently to make decisions about changes in instruction or goals, and applying child response data to important educational decisions.
The implementation of RTI can be described as follows:
Students are provided “effective instruction” by their teacher(s).
Students’ progress is frequently monitored.
Students who do not make progress then receive either different instruction or more of the same instruction.
Progress continues to be monitored.
Students who continue to not make progress either qualify for special education, or qualify for a special education evaluation.
Conceptually, RTI holds great promise for improving educational experience for children with LDs. However, effective implementation of RTI is fraught with difficulties. Readers interested in the strengths and weaknesses of RTI can find more information in the Suggested Readings section at the end of the chapter.
Reading Disability
Clinical Features
A reading disability (RD), also known as dyslexia, is characterized by the presence of deficits in an individual’s reading achievement despite having average intelligence and educational opportunities. However, considerable research has demonstrated that single word reading (decoding) is not strongly related to global measures of intellectual functioning. Current diagnostic criteria in the DSM-IV-TR as well as the achievement-aptitude model do not reflect the overwhelming consensus of researchers in the field of dyslexia. Research in the past 20 years has demonstrated that dyslexia is related to deficits in processing the basic sounds that make up language, a skill that is referred to as phonological awareness. Specifically, these children demonstrate an isolated weakness with phonological processing that results in difficulty with decoding or being able to “sound out” words, although higher order cognitive skills of thinking, reasoning, and understanding abstract concepts are intact and possibly advanced.
In order to become an effective reader, a child must first be able to hear and identify the individual sounds in a spoken word. These are called phonemes and are the basic building blocks of language. For example, the word “mat” is comprised of three phonemes: “mmm,” “aah,” and “tuh.” Phonological processing allows one to identify, understand, store, and retrieve each of these sounds so that they can be put together to form a word or morpheme. This process occurs automatically in spoken language through a process called coarticulation where individual phonemes are rapidly compressed or blended together to produce speech that is understandable and not taxing on the memory system. Hence, the spoken word “mat” is perceived as one single sound, rather than the three separate phonemes that it actually contains.
In reading and writing, these individual phonemes are mapped onto letters that share the same structural sound properties. For example, the letter “B” makes the /b/or “buh” sound. This process is termed the alphabetic principle. Reading requires that an individual be able to decode words by simultaneously segmenting each letter into its representative sound, retain these sounds in memory, and then blend them together to form a word. Effective reading also requires that an individual become fluent in this skill so that attentional and cognitive resources
can be used for the purpose of recalling previous words and sentences in a paragraph in order to obtain meaning.
can be used for the purpose of recalling previous words and sentences in a paragraph in order to obtain meaning.
The core weakness of dyslexia lies in developing an awareness that spoken and written words are made up of phonemes. Hence, children with reading problems have difficulty recognizing that words are made up of much smaller segments representing individual sounds. These problems are then compounded further by the process of reading, which requires that a child learn that these sounds are tied to squiggly lines on paper called letters. Finally, a child must then understand that when these letters are put together to form words, they represent the same number and sequence of sounds that are heard in a spoken word. Children must first develop phonemic awareness in order to become effective readers and learn how to decode and decipher words into their representative phonemes.
Although children with dyslexia can be taught phonological awareness skills, many continue to have difficulty with the automatization of this process that allows them to read fluently, or in a quick, smooth, and accurate manner. Effective readers are able to identify individual words with a little to no effort, and thus, are able to devote the majority of their cognitive resources to comprehension. Poor fluency can have an immense effect on comprehension when an individual is pressured by time or has a large volume of written material to understand and integrate. This is because so much energy must be dedicated to decoding text with few reserves left over for understanding critical pieces of information, recalling previously read material, and drawing inferences from prior knowledge. It is also important to note that because higher order cognitive skills are intact in dyslexic individuals, comprehension can be largely unaffected when they are allowed to read at their own pace or they are able to use visual cues to help them derive meaning from the text.
Many dyslexic individuals also have considerable difficulties with rote memorization and rapid word retrieval which is also thought to be related to poorly developed phonemic awareness. This is often the most frustrating paradox of dyslexia since the inability to quickly find the correct word is often misinterpreted as the person being slow or below average intellectually when the converse is actually true. Many individuals with dyslexia have been shown to have strong receptive vocabulary, grammar and syntactic skills, but have difficulty retrieving words on demand due to the inability to use the phonemic properties of the word to assist with quick and easy access from long-term memory. In fact, sound-based slips of the tongue often are not indicative of poor understanding of the word’s meaning, but rather of confusion regarding the word’s sounds (e.g., saying the word “intrepid” for “interrupted”). This is also one of the more persisting symptoms of dyslexia, as adults who develop adequate reading skills will continue to demonstrate difficulties with rapid and fluent word retrieval and will have speech characterized by long pauses, fillers (“um”), and nonspecific language (“that thing”).
Epidemiology
RD is the most common form of LD, accounting for 50% to 80% of all diagnosed LDs. Prevalence in the DSM-IV-TR is estimated at 3% to 10% of the population with a ratio of males to females of 3 to 4:1. However, other studies suggest that the prevalence rate is actually closer to 17% to 20% with a much more equal rate between boys and girls. The lower prevalence rate and bias toward males cited in previous studies are likely due to the manner in which subjects were identified for these studies. The majority of these samples relied on children who were clinic-referred or already qualified for special education services. Because boys are more likely to display disruptive behavior in the classroom when confronted with academic challenges, whereas girls tend to display quietly inattentive behavior, boys are more often referred for evaluation. In fact, longitudinal studies that have obtained a representative sample of all young children entering school have found that the rate of RD is much higher than previously indicated, as well as much more equal between females and males. It is also interesting that
recent research has begun to question a previously held notion that dyslexia only occurs in individuals who speak alphabetic languages, and not in individuals who speak logographic languages such as Chinese.
recent research has begun to question a previously held notion that dyslexia only occurs in individuals who speak alphabetic languages, and not in individuals who speak logographic languages such as Chinese.
Clinical Course
Previous theories about LDs posited that they represented a developmental lag that could be outgrown or effectively treated with a short-term “booster” of intervention that would allow a child to catch up. It is now understood that LDs can be persistent over time, although the manner in which the specific symptom is exhibited can vary. In fact, nearly 75% of children classified as RD in the third grade continue to demonstrate reading problems in the ninth grade. Specifically, adults who were identified as having an RD as children often continue to demonstrate difficulties with decoding unfamiliar words, spelling, and fluency. Reading can continue to be frustrating for adolescents and adults whose comprehension often depends upon a laborious, time-consuming process of relatively slowed word retrieval. This is especially true for those bright individuals whose academic or vocational ambitions require a considerable amount of reading.
Many children with RD exhibit a reluctance to attend school, moodiness, self-derogatory comments about their ability, and disruptive behavior due to boredom, frustration, and/or shame. In fact, school dropout rates for children and adolescents with LD are estimated to be as high as nearly 40%, resulting in major problems with employment as adults. Other profound lifelong psychosocial correlates of dyslexia include self-perceptions of lower intellectual ability, more generalized psychological distress, and less social mobility.
The term Matthew effects has been used to characterize the accumulated disadvantage of not being able to fluently read. Third grade has been identified as the turning point in school where instruction models switch from “learning to read” to “reading to learn.” Unfortunately, if children have not learned adequate decoding and fluency skills by this age, the achievement gap between them and their peers in all academic areas begins to widen. Longitudinal studies of children who did not receive early and intense intervention have demonstrated that these students continue to lag behind their peers throughout high school in many academic areas, but especially in those areas that require a great deal of reading.
Etiology and Pathogenesis
RD has been shown to be both familial and genetic with a nearly 80% concordance rate reported in monozygotic (MZ) twins in comparison to less than 50% concordance rate in dizygotic (DZ) twins and other siblings. Furthermore, if one family member is affected, the rates for other members are much higher than that in the general population. For example, the rates of reading problems in children of dyslexic parents have been found to be as high as 30% to 60%. Parents of children with RD are also more likely to have reading problems (25% to 60%), with a higher risk for fathers (46%) than mothers (33%). Finally, linkage studies suggest a major role for chromosomes 6 and 15, with additional potential markers on chromosomes 1 and 2.
Structural and functional neuroimaging studies have demonstrated differences in brain structure and activation for children and adults with RD compared to matched normal controls. Structural studies have revealed possible differences in the left-hemispheric regions that support language in individuals with RD, most notably in the areas of the planum temporale, insular cortex, and corpus callosum. The most consistent findings have demonstrated that skilled readers generally demonstrate an asymmetry of the planum temporale favoring the left side, whereas individuals with dyslexia demonstrate a lack of, or reversed, asymmetry.
Functional neuroimaging studies have also supported left-hemispheric differences between individuals with and without RD, notably in the basal temporal, temporoparietal, and inferior frontal regions. Specifically, increased activation in the angular gyrus, Wernicke’s area, and basal temporal areas within the left temporoparietal region has been shown on word-recognition tasks
in skilled readers. In contrast, adults and children with RD exhibit increased activation in the anterior portions of the brain, as well as a reversed pattern of hemispheric activation in the right temporoparietal region, on these tasks.
in skilled readers. In contrast, adults and children with RD exhibit increased activation in the anterior portions of the brain, as well as a reversed pattern of hemispheric activation in the right temporoparietal region, on these tasks.
TABLE 17-1 Differential Diagnoses for All Learning Disabilities | |
|---|---|
|
Although there is strong evidence that RD is a genetic and neurobiological disorder, the effect of the environment cannot be ignored. Parents who have reading problems often have fewer books in the home and are less likely to read to their children or to model reading as a preferred and rewarding activity. Furthermore, it is becoming clearer what the effect of inadequate instruction has on brain development. Neuroimaging studies suggest that intervention aimed directly at addressing the core phonological deficit of RD produces changes in brain activation that more closely resemble nondisabled readers. Recent work has also demonstrated neural plasticity in typically developing readers in response to reading interventions. For these reasons, it is clear that both neurobiological and environmental factors interact to produce the phenotype that is currently defined as dyslexia.
Differential Diagnoses and Common Comorbidities
The most common differential diagnoses for all LDs are summarized in Table 17-1. These include ruling out sensory problems related to vision or hearing difficulties and mental retardation. The DSM-IV-TR and special education definitions also specify that inadequate educational opportunities, poor motivation, and significant emotional problems must be ruled out as well. However, it is important to note that the mere presence of these factors does not rule out the diagnosis of LD. Instead, their presence can contribute to and interact with a comorbid learning disability, making a differential diagnosis quite difficult. Finally, methods of assessment and interpretation of testing results should be sensitive to an individual’s ethnic or cultural background, as well as a child’s current proficiency in developing a second language, to avoid possibly mislabeling a child as LD or mentally retarded.
LDs, including RD, often occur in association with general medical conditions, such as very low birth weight, prematurity, lead poisoning, fetal alcohol syndrome, and fragile X syndrome. However, the presence of these disabilities does not necessarily indicate learning problems, and many individuals with LD do not have such a history.
The most common comorbidities with RD are primarily related to emotional and behavioral disturbances, as summarized in Table 17-2. Attention-Deficit/Hyperactivity Disorder (ADHD) is the most frequently reported comorbidity with RD in both epidemiological and clinical studies, regardless of whether individuals are selected for reading problems or for ADHD. Between 15% and 26% of individuals with dyslexia also meet criteria for ADHD, whereas 25% to 40% of individuals with ADHD have reading difficulties. Furthermore, the core deficits in language and phonological processing specific to dyslexia have been shown to be independent of a comorbid diagnosis of ADHD.
RD can also take a high toll on children’s psychological health. Emotional or physical symptoms (e.g., anxiety, depression, stomach aches, reluctance to go to school) are common in children and adolescents with RD, with studies indicating that 14% to 32% of RD children
experience depressive moods and feelings of lack of control and low self-efficacy. Twin studies have supported higher rates of all internalizing and externalizing disorders in individuals with RD. Gender differences have also been found with a stronger association toward externalizing symptoms for boys and internalizing symptoms for girls with reading difficulties.
experience depressive moods and feelings of lack of control and low self-efficacy. Twin studies have supported higher rates of all internalizing and externalizing disorders in individuals with RD. Gender differences have also been found with a stronger association toward externalizing symptoms for boys and internalizing symptoms for girls with reading difficulties.
TABLE 17-2 Common Comorbidities for All Learning Disabilities | |
|---|---|
|
Assessment
The essentials of assessment for RD are summarized in Table 17-3 and explicated here. Children with normal reading processes spontaneously begin to identify and segment the sounds or phonemes in words around the ages of 4 to 6 years. For example, children at these ages are particularly attuned to and take pleasure in rhymes and can begin to group words by their initial and ending sounds. This has been shown to be a critically important skill for learning to read and, hence, difficulties in this area can be very predictive markers for reading problems. Early assessment of dyslexia usually focuses on three areas that are related to phonological processing: (1) phonemic awareness or the ability to identify phonemes and manipulate words by removing and replacing sounds; (2) rapid automatic naming or the ability to quickly and efficiently retrieve phonologic information from long-term memory; and (3) phonologic working memory or the ability to temporarily store bits of verbal information.
The first area of assessment, phonemic awareness, can be measured in several ways, including sound comparison, segmentation, blending, and manipulation of phonemes in words. Sound comparison involves asking a child to decide which words are alike based on their initial, ending, or middle sounds. For example: “Which word begins with the same sound as pan: tub, pig, or can?” Segmentation can be measured by asking a child to either report how many sounds are in a word or to pronounce the sounds he hears. For example: “How many sounds are there in the word cat?” “Three” or “kuh” “aaa” “tuh.” Alternatively, asking a child what sounds “kuh” “aaa” and “tuh” makes requires him to blend these phonemes together to form a word. Finally, the most advanced phonemic awareness skill involves having a child add, move around, or delete sounds from one word in order to form another word. For example: “What word do you get if you take the/l/sound away from the word slide?” It is important to note that most children have mastered the majority of these skills by the end of first grade.
The second area, rapid automatic naming, is assessed by having a child name as quickly as he or she can an array of stimuli arranged in rows on a card. Because the purpose of the task is to assess how efficiently a child can retrieve information (rather than measure the child’s vocabulary), the stimuli used are usually very familiar items such as letters, numbers, colors, or objects. Finally, phonologic working memory is a critical skill when learning to read as sounding out a word is a complex process that requires decoding letters into their sounds, storing these sounds in memory while decoding the remaining letters of a word, and then blending these sounds to form a word. Assessment of phonologic working memory usually involves having a child repeat strings of random numbers, letters, or words. Table 17-4 lists several early warning signs for clinicians and parents to be aware of in children who may exhibit RD.
TABLE 17-3 Assessment Essentials for Reading Disorder | ||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ||||||||||||||||||||||||||||||||||||||||
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
