The most widely accepted deﬁnition of a learning disability in the United States has for decades been based on language that appears in federal law. It ﬁrst appeared in 1975 when Congress passed Public Law 94-142, the Education for All Handicapped Children Act. To require a free public education for children with learning disabilities, the law had to deﬁne them ﬁrst, which it did in this way:
The term “speciﬁc learning disability” means a disorder in one or more of the basic psychological processes involved in understanding or in using language, spoken or written, which may manifest itself in imperfect ability to listen, speak, read, write, spell, or to do mathematical calculations. . . . The term does not include children who have learning disabilities, which are primarily the result of visual, hearing, or motor handicaps, of mental retardation, or emotional disturbance, or of environmental, cultural, or economic disadvantage. (U.S. Department of Education, 1977, p. 65, 083)
The deﬁnition was reﬁned further in the 1990 revision of the law, the Individuals with Disabilities Education Act (IDEA). IDEA clariﬁes and codiﬁes an additional element of the deﬁnition: to be diagnosed with a learning disability, a student must demonstrate a severe discrepancy between general ability (usually deﬁned as intelligence) and speciﬁc achievement in one or more of seven academic areas: oral expression, listening comprehension, written expression, basic reading skill, reading comprehension, mathematics calculation, or mathematics reasoning.
The discrepancy requirement has resulted in a mandate for how children are to be tested for a learning disability. The assessment battery always includes a standard individual intelligence test, such as the WISC-III, and an individual achievement test. The individual achievement test is given one-on-one, unlike the usual school-based standardized achievement test administered in a group setting. This allows for much more diagnostic information to be collected regarding the kinds of errors being made, rather than simply knowing which items were wrong. A severe discrepancy is deﬁned statistically as a difference of one standard deviation or more between the two scores, which in practice means a difference between the two scores of at least 15 points. What this means is that a child with a learning disability is performing at a lower level than would be expected based on his or her general intellectual ability.
This is not a rare problem. Between 4 and 5 percent of all U.S. schoolchildren are diagnosed with a learning disability. Boys are more likely to be diagnosed with learning disabilities than girls, by a ratio of about three to two.
Most learning disabilities belong to one of two broad categories: verbal or nonverbal. People with verbal learning disabilities, unsurprisingly, have difﬁculty with words. The most common form of verbal learning disability is dyslexia, which results in trouble recognizing or processing letters and the sounds they make. This causes people with dyslexia to have a great deal of difﬁculty with tasks that involve reading and writing. A common myth about dyslexia is that it causes people to reverse letters and numbers or to see them backwards, but those reversals are actually a normal part of language development, and are just as common in children without dyslexia. Though there are numerous forms of dyslexia, most people with dyslexia have special trouble recognizing phonemes (basic speech sounds) in print; for example, making the connection between the “ch” sound and the letter pair that produces it. Dyslexia used to be blamed on everything from laziness to innate stupidity to poor vision, but it is now fairly widely acknowledged to be a neurological problem with a probable genetic cause, as it clearly runs in families. This is supported by PET scan studies (see Brain Imaging Techniques) that have shown that different parts of the brain are active when people with dyslexia read compared to people without dyslexia.
Dyslexia is not the only kind of verbal learning disability. Whereas dyslexia is a disorder that primarily affects ability to read, dysgraphia refers to learning disabilities that primarily affect writing ability. Like dyslexia, dysgraphia is now widely acknowledged to be a neurological disorder with a probable genetic component.
The nonverbal learning disabilities include all school problems ﬁtting the federal deﬁnition that do not primarily involve verbal skills. Within that category, mathematical learning disabilities are often referred to as dyscalcula. Dyscalcula involves problems with learning fundamentals of math and one or more of the basic numerical skills. This may involve a variety of neurological underpinnings because mathematical skills depend on both the obvious (accurate visual processing and motor skills) and the not so obvious (memory, language comprehension, planning skills). Dyscalcula is often ﬁrst diagnosed when a teacher notices the child transposing numbers, forgetting simple shape names, or apparently failing to understand simple spoken instructions. Although it doesn’t ﬁt the deﬁnition of a speciﬁc learning disability, as it doesn’t impact a particular skill area, attention-deﬁcit/hyperactivity disorder (ADHD) is also frequently categorized by state laws as a learning disability.
The federal deﬁnition of a learning disability is now widely perceived among educational and psychological professionals as a failure, and other approaches are becoming increasingly popular. The main reason for this disenchantment with the discrepancy deﬁnition is the simple observation that great numbers of children who exhibit serious learning difﬁculties in school and who would certainly beneﬁt from the services offered to those with learning disabilities cannot meet the discrepancy criterion. This occurs because a learning disability can easily have an adverse effect on both the achievement measures and the intelligence tests to which they are to be compared. Consider children with a nonverbal learning disability. There is no reason to expect that such children would consistently perform well on the nonverbal portions of the IQ test, yet if they perform poorly both on those and on the nonverbal measures of the achievement test, they will be judged not to have a learning disability by virtue of having performed poorly on both.
As a result of dissatisfaction with the federal deﬁnition, many psychologists and educators have begun to promote a new deﬁnition. It is the result of meetings by the National Joint Committee on Learning Disabilities (NJCLD), made up of representatives from eight national organizations interested in learning disabilities. The new deﬁnition is similar to the federal deﬁnition, but it differs in several important ways: it removes the severe discrepancy requirement, it acknowledges that a person may have a learning disability and other handicapping conditions, and it speciﬁes that learning disabilities may continue into adulthood.
- National Joint Committee on Learning Disabilities. “A Position Paper of the National Trust Committee on Learning Disabilities.” Journal of Learning Disabilities, 21 (1988): 53–55;
- U. S. Department of Education. “Deﬁnition and Criteria for Deﬁning Students as Learning Disabled.” Federal Register, 42(250) (1977): 65083.