Learning Disabilities -- very good paper


Early Warning Systeme

Since the 1976–77 school year, when Congress first required public schools to count the number of children with learning disabilities (Learning Disability (LD)), the share of school-age children labeled Learning Disability (LD) has risen from 1.8 percent to 5.2 percent. Learning disabilities now account for more than half of all students enrolled in special-education programs, up from 22 percent a quarter century ago. In the past decade alone, the number of students aged 6–21 identified as learning disabled under the Individuals with Disabilities Education Act (IDEA) has increased 38 percent. The largest jump, of 44 percent, has been seen among adolescents aged 12–17—a significant yet poorly understood increase. Private and postsecondary schools have experienced similar increases.

The steadily growing number of students identified as Learning Disability (LD) invites public skepticism. Most scientific experts, however, agree that 5 percent, and likely more, of our school population suffer severe difficulties with language and other skills. Even so, the disproportionate rise in the incidence of Learning Disability (LD), especially among adolescents, does raise questions about the methods of identifying and treating learning disabilities.

What explains the rise of Learning Disability (LD)? Is it the result of positive developments, such as improved identification methods? Or is the definition of Learning Disability (LD) too general and ambiguous to catch younger students before they fail? Are some students identified as Learning Disability (LD) simply the victims of poor teaching? Put another way, does the education profession adequately prepare teachers to address differences among children?

We propose that the rise in the incidence of Learning Disability (LD) is largely the result of three factors. First, remediation is rarely effective after 2nd grade. Second, measurement practices today work against identifying Learning Disability (LD) children before 2nd grade. Third, federal policy and the sociology of public education itself allow ineffective policies to continue unchecked.

The best mainstream research—studies that reflect the consensus of experts in such fields as child development, education, and neuroscience—shows that most longstanding difficulties in defining and treating Learning Disability (LD) stem from inaccurate assumptions about their causes and characteristics. Moreover, the data now justify very early identification and prevention programs for children at risk for Learning Disability (LD). This is nowhere more true than with reading disabilities, which are by far the most common and most troublesome of these disorders, constituting 80 percent of all students with Learning Disability (LD). Fortunately, reading disability is also the best understood and most effectively corrected learning disability. If children receive effective instruction early and intensively, they can make large gains in general academic achievement.

Early intervention can greatly reduce the number of older children who are identified as Learning Disability (LD). Without early identification, children typically require intensive, long-term special-education programs, which have meager results. Early intervention allows ineffective remedial programs to be replaced with effective prevention while providing older students who continue to need services with enhanced instruction so they can return to the educational mainstream.

The Rise of Learning Disability (LD)

The term learning disability traditionally refers to unexpected underachievement in adequate educational settings. Students with Learning Disability (LD) do not listen, speak, read, write, or compute as well as their “potential”—usually as measured by IQ—suggests they should. Historically, neurobiological factors—put crudely, glitches in the brain—were blamed.

Conditions resembling unexpected underachievement are found in medical and psychological literature beginning in the mid-19th century, where they are described variously as word blindness, dyslexia, dysgraphia, and dyscalculia. In 1962 Samuel Kirk, a psychologist at the University of Illinois, coined the term learning disabilities, which quickly entered professional and popular parlance. Like his more medically oriented predecessors, Kirk focused on unanticipated learning problems in a seemingly capable child. He defined Learning Disability (LD) as “a retardation, disorder, or delayed development in one or more of the processes of speech, language, reading, spelling, writing, or arithmetic resulting from a possible cerebral dysfunction and not from mental retardation, sensory deprivation, or cultural or instructional factors.” Kirk posited Learning Disability (LD) as an amalgam of disabilities, all grouped under a single label, just as the federal definition of Learning Disability (LD) has ever since. This was an intellectually bold move—but it was at best half right, and today we labor under its adverse consequences.

The term learning disability gained rapid acceptance among parents and professionals in the 1960s and ’70s. Rhetorically it exuded optimism. It did not stigmatize children; it imputed no shortage of intelligence, no emotional disturbance, no troubled home life, no bad schools. It almost presumed cultural and environmental advantage. Pragmatically it spoke to a real problem: before the 1960s, underachieving children couldn’t receive special education unless they were mentally deficient, emotionally disturbed, or physically handicapped. Professional and parental advocacy soon led to the 1969 Learning Disabilities Act, followed by the 1975 Education for All Handicapped Children Act (renamed the Individuals with Disabilities Education Act in 1990).

Most definitions of Learning Disability (LD) have at least four elements in common. The four elements posit Learning Disability (LD) as: 1) heterogeneous; 2) intrinsic or neurobiological; 3) marked by a significant discrepancy between learning potential (measured intelligence) and academic performance (measured skills in reading, writing, mathematics, and oral language); and 4) not caused by cultural, educational, environmental, or economic factors or by other disabilities (such as mental deficiency, visual or hearing impairments, or emotional disturbance).

The tenacity of these elements in definitions of Learning Disability (LD) has grounded our public policies and pedagogy in outdated science and flawed understandings of the nature of these disabilities. Their validity is rarely scrutinized, and the results of these occasional examinations are typically ignored. We suspect this impasse owes not to the evidence as much as to professional and political inertia.

New Definitions

In federal legislation, Learning Disability (LD) is not a single disability but a category of special education composed of disabilities in any one or more of seven skill domains: listening, speaking, basic reading (decoding and word recognition), reading comprehension, writing, arithmetic calculation, and mathematics reasoning. These disabilities can be accompanied by emotional, social, and behavioral disorders, including attention deficits, but they cannot, in the federal definition, be the primary cause of the learning disabilities.

If the current policy definition of Learning Disability (LD) creates a deliberately wide net, with seven possible disabilities, it also invites sloppy science. The definition tells us only what Learning Disability (LD) is not. This has provoked recent calls for changing the various domain-specific categories to reflect evidence-based research and to specify criteria for identifying the attributes of different learning disabilities. This recommendation is based on the observation that generic definitions, while useful for political, advocacy, and compliance purposes, get in the way of good practice in identifying and teaching students with Learning Disability (LD) and conducting research. To date this recommendation has made little headway in entrenched special-education communities; it failed to find its way into the 1997 reauthorization of IDEA. Until this bold but elementary initiative is undertaken, the assessment and instruction of children with Learning Disability (LD) will remain unreliable.


New evidence on neurobiological causes. The study of learning disabilities was founded on the assumption that neurobiological factors were the basis of the problems with learning. Neurobiological dysfunction was inferred from what was known about the linguistic, cognitive, academic, and behavioral characteristics of adults with brain injuries, as well as from evidence that reading problems run in families. Until recently, explanations of Learning Disability (LD) continued to favor neurobiological (or intrinsic) rather than environmental (or extrinsic) causes.

New, objective ways to assess putative brain dysfunction have led to extraordinary breakthroughs, especially in the area of reading. A sizable body of evidence indicates that poor readers exhibit disruption primarily, but not exclusively, in the neural circuitry of the brain’s left hemisphere, the part that serves language. Investigations using post-mortem brain specimens and magnetic resonance imaging (MRI) suggest subtle structural differences in several brain regions between reading-disabled (RD) and nonimpaired readers. More significant is the converging evidence from studies based on functional brain imaging that reveals the activity of the brain while someone reads. These studies indicate a pattern of brain organization in poor readers that differs from that seen in nonimpaired readers, with less activity in regions of the left hemisphere that are associated with proficient reading.

Functional brain imaging, conducted while a child reads words, is also being used to show how intensive teaching can influence the brain’s reading circuitry (see Figure 1). Imaging occurs before and after intervention, during which children significantly improve in reading ability. It appears that after intervention, brain activation patterns shift to the normative profile seen in nonimpaired readers. This finding, if it can be replicated, appears to show that the neural systems supporting reading develop during interaction with the environment, including instruction.

Figure 1–Neural systems supporting reading may not be fixed, but develop if challenged. Shown is an image of a 10-year-old with severe reading disabilities before and after 60 hours of intensive instruction, during which the child rose into the average range in word-reading ability. The “before” image captures a brain exhibiting the standard activity pattern of children with reading disabilities. The “after” image shows increased activity in the left hemisphere, a pattern common to nonimpaired readers.

Genetic studies of the reading disabled reinforce this interaction perspective. Reading problems have long been known to recur across family generations; an offspring of a parent with RD is eight times more likely to have a reading disability. Studies of twins strongly support the genetic link to Learning Disability (LD), pointing to regions on chromosomes 1, 2, 6, and 15. However, genetic factors explain only about half of the variation in reading development; environmental factors account for the other half.

This finding suggests that what is inherited is a susceptibility to RD that the environment can trigger. For example, parents who read poorly may be less likely to read to their children. In such cases, high-quality reading instruction in school is critical, as confirmed by recent studies of identical and fraternal twins. Scientists at the University of Colorado led by psychologist Richard K. Olson have explored the relationship between IQ levels and genetic and environmental influences on RD. They found that genetic influences tend to be more important for children with RD who exhibit relatively high IQ scores, while environmental influences tend to be more important for children with RD who possess relatively low IQ scores. The researchers argued strongly against excluding such relatively low IQ children from intervention simply because there wasn’t a great discrepancy between IQ and achievement. It is a grim fact that the traditional requirement of a discrepancy winds up excluding children who most need help.

Learning disabilities now account for more than half of all students enrolled in special-education programs.

Discrepancy between ability and achievement. Not surprisingly, the discrepancy criterion has proved contentious. This criterion was federally recommended in the wake of the 1975 Education for All Handicapped Children Act, which called for “objectively and accurately” distinguishing the child with learning disabilities from children with other academic deficiencies.

The use of a discrepancy between aptitude and achievement to “objectively determine” the presence of Learning Disability (LD) probably seemed reasonable at the time. Long before severe discrepancy became synonymous with Learning Disability (LD), practitioners puzzled over the inability of some children of average and superior intelligence to master academic concepts. The discrepancy metric also reflected the common but incorrect view that IQ scores were robust predictors of an individual’s ability to learn. Despite the admonition of Edward L. Thorndike and others that IQ scores primarily estimate current cognitive functioning and not learning potential, in 1977 policymakers recommended using the scores inappropriately, as they have ever since.

These false assumptions about IQ and learning potential lead to unreliable formulas for discerning discrepancies themselves. As has been widely documented, the formulas are so fraught with psychometric, statistical, and conceptual problems that they are often useless. The discrepancy metric may even harm more children than it helps, as when the formulas used by different states deprive some students of special education following a family’s move from one state to another. Even worse, the entire measurement practice interferes with the early identification of Learning Disability (LD). Children must fall below a predicted level of performance before becoming eligible for special education. Yet such underperformance cannot be measured reliably until a child reaches about nine years of age, or the 3rd grade. However, epidemiological data show that most children who read poorly at age nine or younger read poorly as adults. The IQ/achievement-discrepancy method creates a “wait-to-fail” model: we wait until they fail.

The term learning disability traditionally refers to unexpected underachievement in adequate educational settings, usually measured as a discrepancy between IQ and achievement.

Another flaw in using the discrepancy concept is the inequitable education that results. No converging evidence shows an intrinsic “processing” difference among students who are weak in reading, whether they exhibit a discrepancy or not. Likewise, no evidence shows a difference in the effect of intensive instruction. The discrepancy requirement ultimately denies special services to garden-variety poor readers. This inequitable pattern recurs in reading disability:
Some children who achieve average scores on tests of word recognition read connected text with difficulty. Their slow reading impairs their comprehension. These readers clearly require special instruction, yet they do not receive it because reading fluency is rarely assessed. By contrast, if a slow-reading student has a high IQ, a weak word-reading score may secure him special-education services. Broadly speaking, the discrepancy formulation focuses attention on IQ and not on the reading process, irrationally favoring some individuals while allowing many deserving students to drift further and further from the education they need.

Excluding environment and other disabilities. As noted, Learning Disability (LD) by definition cannot stem from certain conditions that commonly impede learning: mental deficiency; emotional disturbance; visual or hearing impairments; inadequate teaching; and cultural, social, or economic disadvantages. This rubric makes for disastrous policy as well. First, it adds little conceptual clarity and actually constrains our understanding of learning disabilities. As the noted neuropsychiatrist Sir Michael Rutter of the University of London argues, this approach to definition suggests that if all the ordinary causes of the disorder can be excluded, the unknown—LD—can then be invoked. Second, some excluded conditions are known to impair cognitive and linguistic skills and actually lead to academic difficulties identified as Learning Disability (LD).

An important example, too little scrutinized, is exclusion based on a student’s instructional history, no matter how incompetent. It was once thought that children who profit from instruction do not have a biologically based learning disability. However, as we have seen, brain-imaging studies of reading indicate otherwise: Instruction appears to establish the neural networks that support reading. No child is born a reader; all children in literate societies must be taught how to read.

No data exist to support the hypothesis that differences in the brain make some children respond less to intervention than other children do. The data, however, do indicate that the environment—including instruction, nutrition, prenatal and postnatal care, and parental drug abuse—influences neural development for better or worse. Children thus affected need the best instruction at the earliest possible time, but current federal definitions of Learning Disability (LD) preclude such a basic, sensible policy. Studies show that programs like Head Start, which are designed to prepare children for school, do a poor job of getting children ready to read. The largest federal study to date found that, on average, children left Head Start knowing only one letter of the alphabet, and that many teachers were discouraged from teaching the alphabet. Yet alphabetic knowledge in kindergarten is the single best predictor of reading success.