In the United States and Canada, the terms learning disability, learning disabilities, and learning disorders (LD) refer to a group of disorders that affect a broad range of academic and functional skills including the ability to speak, listen, read, write, spell, reason and organize information.
A learning disability is not indicative of low intelligence. Indeed, research indicates that some people with learning disabilities may have average or above-average intelligence. Causes of learning disabilities include a deficit in the brain that affects the processing of information.
Types of learning disabilities
Learning disabilities can be categorized either by the type of information processing that is affected or by the specific difficulties caused by a processing deficit.
Information processing deficits
Learning disabilities fall into broad categories based on the four stages of information processing used in learning: input, integration, storage, and output.
This is the information perceived through the senses, such as visual and auditory perception. Difficulties with visual perception can cause problems with recognizing the shape, position and size of items seen. There can be problems with sequencing, which can relate to deficits with processing time intervals or temporal perception. Difficulties with auditory perception can make it difficult to screen out competing sounds in order to focus on one of them, such as the sound of the teacher’s voice. Some children appear to be unable to process tactile input. For example, they may seem insensitive to pain or dislike being touched.
This is the stage during which perceived input is interpreted, categorized, placed in a sequence, or related to previous learning. Students with problems in these areas may be unable to tell a story in the correct sequence, unable to memorize sequences of information such as the days of the week, able to understand a new concept but be unable to generalize it to other areas of learning, or able to learn facts but be unable to put the facts together to see the “big picture.” A poor vocabulary may contribute to problems with comprehension.
Problems with memory can occur with short-term or working memory, or with long-term memory. Most memory difficulties occur in the area of short-term memory, which can make it difficult to learn new material without many more repetitions than is usual. Difficulties with visual memory can impede learning to spell.
Information comes out of the brain either through words, that is, language output, or through muscle activity, such as gesturing, writing or drawing. Difficulties with language output can create problems with spoken language, for example, answering a question on demand, in which one must retrieve information from storage, organize our thoughts, and put the thoughts into words before we speak. It can also cause trouble with written language for the same reasons. Difficulties with motor abilities can cause problems with gross and fine motor skills. People with gross motor difficulties may be clumsy, that is, they may be prone to stumbling, falling, or bumping into things. They may also have trouble running, climbing, or learning to ride a bicycle. People with fine motor difficulties may have trouble buttoning shirts, tying shoelaces, or with handwriting.
Specific learning disabilities
Deficits in any area of information processing can manifest in a variety of specific learning disabilities. It is possible for an individual to have more than one of these difficulties. This is referred to as comorbidity or co-occurrence of learning disabilities.
The most common learning disability. Of all students with specific learning disabilities, 70%-80% have deficits in reading. The term “dyslexia” is often used as a synonym for reading disability; however, many researchers assert that there are different types of reading disabilities, of which dyslexia is one. A reading disability can affect any part of the reading process, including difficulty with accurate and/or fluent word recognition, word decoding, reading rate, prosody (oral reading with expression), and reading comprehension. Before the term “dyslexia” came to prominence, this learning disability used to be known as “word blindness.”
Common indicators of reading disability include difficulty with phonemic awareness — the ability to break up words into their component sounds, and difficulty with matching letter combinations to specific sounds (sound-symbol correspondence).
Impaired written language ability may include impairments in handwriting, spelling, organization of ideas, and composition. The term “dysgraphia” is often used as an overarching term for all disorders of written expression. Others, such as the International Dyslexia Association, use the term “dysgraphia” exclusively to refer to difficulties with handwriting.
Sometimes called dyscalculia, a math disability can cause such difficulties as learning math concepts (such as quantity, place value, and time), difficulty memorizing math facts, difficulty organizing numbers, and understanding how problems are organized on the page. Dyscalculics are often referred to as having poor “number sense”.
Nonverbal learning disability
Nonverbal learning disabilities often manifest in motor clumsiness, poor visual-spatial skills, problematic social relationships, difficulty with math, and poor organizational skills. These individuals often have specific strengths in the verbal domains, including early speech, large vocabulary, early reading and spelling skills, excellent rote-memory and auditory retention, and eloquent self-expression.
Sometimes called motor planning, dyspraxia refers to a variety of difficulties with motor skills. Dyspraxia can cause difficulty with single step tasks such as combing hair or waving goodbye, multi-step tasks like brushing teeth or getting dressed, or with establishing spatial relationships such as being able to accurately position one object in relation to another.
Disorders of speaking and listening
Difficulties that often co-occur with learning disabilities include difficulty with memory, social skills and executive functions (such as organizational skills and time management).
Auditory processing disorder
Difficulties processing auditory information include difficulty comprehending more than one task at a time and a relatively stronger ability to learn visually.
The presence of a learning disability is sometimes suspected by a child’s parents long before problems are seen at school. However, the issues typically become visible when a child begins having difficulty at school. Difficulty learning to read is often one of the first signs that a learning disability is present.
Learning disabilities are often identified by school psychologists, clinical psychologists, and neuropsychologists through a combination of intelligence testing, academic achievement testing, classroom performance, and social interaction and aptitude. Other areas of assessment may include perception, cognition, memory, attention, and language abilities. The resulting information is used to determine whether a child’s academic performance is commensurate with his or her cognitive ability. If a child’s cognitive ability is much higher than his or her academic performance, the student is often diagnosed with a learning disability. The DSM-IV and many school systems and government programs diagnose learning disabilities in this way.
Although the discrepancy model has dominated the school system for many years, there has been substantial criticism of this approach among researchers. Recent research has provided little evidence that a discrepancy between formally-measured IQ and achievement is a clear indicator of LD. Furthermore, diagnosing on the basis of a discrepancy does not predict the effectiveness of treatment. Low academic achievers who do not have a discrepancy with IQ (i.e. their IQ scores are also low) appear to benefit from treatment just as much as low academic achievers who do have a discrepancy with IQ (i.e. their IQ scores are higher).
Response to Intervention (RTI)
Much current research has focused on a treatment-oriented diagnostic process known as response to intervention (RTI). Researcher recommendations for implementing such a model include early screening for all students, placing those students who are having difficulty into research-based early intervention programs, rather than waiting until they meet diagnostic criterion. Their performance can be closely monitored to determine whether increasingly intense intervention results in adequate progress. Those who respond will not require further intervention. Those who do not respond adequately to regular classroom instruction (often called “Tier 1 instruction”) and a more intensive intervention (often called “Tier 2″ intervention) are considered “nonresponders.” These students can then be referred for further assistance through special education, in which case they are often identified with a learning disability. Some models of RTI include a third tier of intervention before a child is identified as having a learning disability.
A primary benefit of such a model is that it would not be necessary to wait for a child to be sufficiently far behind to qualify for assistance. This may enable more children to receive assistance before experiencing significant failure, which may in turn result in fewer children who need intensive and expensive special education services. In the United States, the 2004 reauthorization of the Individuals with Disabilities Education Act permitted states and school districts to use RTI as a method of identifying students with learning disabilities. RTI is now the primary means of identification of learning disabilities in Florida.
There are still concerns about the use of RTI, particularly in that it requires a strong intervention program before students can be identified with a learning disability. If students’ receive poor quality interventions, they can be judged non-responsive and thus as having a learning disability when the cause is really only poor instruction.
Many normed assessments can be used in evaluating skills in the primary academic domains: reading, not including word recognition, fluency, and comprehension; mathematics, including computation and problem solving; and written expression, including handwriting, spelling and composition.
The most commonly used comprehensive achievement tests include the Woodcock-Johnson III (WJ III), Weschler Individual Achievement Test II (WIAT II), the Wide Range Achievement Test III (WRAT III), and the Stanford Achievement Test-10th edition. These tests include measures of many academic domains that are reliable in identifying areas of difficulty.
In the reading domain, there are also specialized tests that can be used to obtain details about specific reading deficits. Assessments that measure multiple domains of reading include Gray’s Diagnostic Reading Tests-2nd edition (GDRT II) and the Stanford Diagnostic Reading Assessment. Assessments that measure reading subskills include the Gray Oral Reading Test IV – Fourth Edition (GORT IV), Gray Silent Reading Test, Comprehensive Test of Phonological Processing (CTOPP), Tests of Oral Reading and Comprehension Skills (TORCS), Test of Reading Comprehension 3 (TORC-3), Test of Word Reading Efficiency (TOWRE), and the Test of Reading Fluency.
Of course, assessment of learning disabilities requires the consideration of more than test scores. The purpose of assessment is to determine what is needed for intervention, which also requires consideration of contextual variables and whether there are comorbid disorders that must also be identified and treated, such as behavioral issues or language delays.
Some (adjustments, equipment and assistants) are designed to accommodate or help compensate for the disabilities while others (specialized instruction) are intended to make improvements in the weak areas. Practice is a particularly important component in developing competence, regardless of the starting point. Children who start out with a weakness in a basic skill, such as reading, may miss out on the necessary practice because of the need to catch up with their chronological age peers. Thus a small weakness can snowball into a larger problem