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Psychology Basics Learning Disorders TYPE OF PSYCHOLOGY: Psychopathology FIELDS OF STUDY: Child and adolescent disorders Learning disorders (LD) comprise the disorders usually first diagnosed in infancy, childhood, or adolescence. Because the condition affects the academic progress of approximately 5 percent of all public school students in the United States, it has attracted the attention of clinicians, educators, and researchers from varied disciplines. Substantial progress has been made in the assessment and diagnosis of learning disorders but questions regarding etiology, course, and treatment of the disorder continue to challenge investigators. KEY CONCEPTS ∙ disorder of written expression ∙ dyslexia ∙ learning disabilities ∙ learning disorder not otherwise specified ∙ mathematics disorder ∙ phonological processing ∙ reading disorder Learning disorders (LD) is a general term for clinical conditions that meet three diagnostic criteria: An individual's achievement in an academic domain (such as reading) is substantially below that expected given his or her age, schooling, and level of intelligence; the learning disturbance interferes significantly with academic achievement or activities of daily living that require specific academic skills; and if a sensory deficit (such as blindness or deafness) is present, the learning difficulties are in excess of those usually associated with it. The American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders: DSM-IV-TR (rev. 4th ed., 2000) specifies four subcategories of learning disorders: Reading Disorder, Mathematics Disorder, Disorder of Written Expression, and Learning Disorder Not Otherwise Specified (NOS). The criteria for the first three specific learning disorders are the same except for the academic domain affected by the disorder. The fourth subcategory is reserved for disorders involving learning the academic skills that do not meet the criteria for any specific learning disorder. Included are problems in all three academic domains (reading, mathematics, written expression) that together significantly interfere with academic achievement even though academic achievement as measured on standardized tests does not fall substantially below what is expected given the individual's chronological age, intelligence quotient (IQ), or age-appropriate education. A variety of statistical approaches are used to produce an operational definition of "substantially below" academic achievement. Despite some controversy about its appropriateness, the most frequently used approach defines "substantially below" as a discrepancy between achievement and IQ of more than two standard deviations (SD). In cases where an individual's performance on an IQ test may have been compromised by an associated disorder in linguistic or information processing, an associated mental disorder, a general medical condition, or the individual's ethnic or cultural background, a smaller discrepancy (between one and two SDs) may be acceptable. Differential diagnosis involves differentiating learning disorders from normal variations in academic achievement, scholastic difficulties due to lack of opportunity, poor teaching, or cultural factors, and learning difficulties associated with a sensory deficit. In cases of pervasive developmental disorder or mild mental retardation, an additional diagnosis of learning disorder is given if the individual's academic achievement is substantially below the expected level given the individual's schooling and intelligence.
PREVALENCE Prevalence rates for learning disorders vary, depending on the definitions and methods of determining the achievement-intelligence discrepancy. According to the American Psychiatric Association, estimates range from 2 to 10 percent for the general population, and 5 percent for public school students in the United States. The prevalence rate for each specific learning disorder is more difficult to establish because many studies simply report the total number of learning disorders without separating them according to subcategory. Reading disorder is the most common, found in 4 percent of school-age children in the United States. Approximately four out of five cases of LD have Reading Disorder alone or in combination with Mathematics Disorder and/or Disorder of Written Expression. About 1 percent of schoolage children have Mathematics Disorder, one out of five cases of LD. Disorder of Written Expression alone is rare, it is usually associated with Reading Disorder. Studies based on referrals to school psychologists or clinics reported that more males than females manifested a learning disorder. However, studies employing careful diagnostic assessment and strict application of the criteria have found more equal rates for males and females. LD often coexists with another disorder, usually language disorders, communication disorders, attention-deficit hyperactivity disorder (ADHD), and/or conduct disorder. ETIOLOGY There is strong empirical support for a genetic basis of Reading Disorder or dyslexia from behavior genetic studies. John C. DeFries and his colleagues indicate that heredity can account for as much as 60 percent of the variance in Reading Disorders or dyslexia. As for the exact mode of genetic transmission, Lon R. Cardon and his collaborators, in two behavior genetic studies, identified chromosome 6 as a possible quantitative trait locus for a predisposition to develop Reading Disorder. The possibility that transmission occurs through a subtle brain dysfunction rather than autosomal dominance has been explored by Bruce Pennington and others. The neurophysiological basis of Reading Disorders has been explored in studies of central nervous dysfunction or faulty development of cerebral dominance. The hypothesized role of central nervous dysfunction has been difficult to verify despite observations that many children with learning disorders had a history of prenatal and perinatal complications, neurological soft signs, and electroencephalograph abnormalities. In 1925, neurologist Samuel T. Orton hypothesized that Reading Disorder or dyslexia results from failure to establish hemispheric dominance between the two halves of the brain. Research has yielded inconsistent support for Orton's hypothesis and its reformulation, the progressive lateralization hypothesis. However, autopsy findings of cellular abnormalities in the left hemisphere of dyslexics that were confirmed in brain imaging studies of live human subjects have reinvigorated researchers. These new directions are pursued in studies using sophisticated brain imaging technology. Genetic and neurophysiological factors do not directly cause problems in learning the academic skills. Rather, they affect development of neuropsychological, information-processing, linguistic, or communication abilities, producing difficulties or deficits that lead to learning problems. The most promising finding from research on process and ability deficits concerns phonological processing-the ability to use phonological information (the phonemes or speech sounds of one's language)-in processing oral and written language. Two types of phonological processing, phonological awareness and phonological memory (encoding or retrieval), have been studied extensively. Based on correlational and experimental data, there is an emerging consensus that a deficit in phonological processing is the basis of reading disorder in a majority of cases. ASSESSMENT Assessment refers to the gathering of information in order to attain a goal. Assessment tools vary with the goal. If the goal is to establish the diagnosis, assessment involves the individualized administration of standardized tests of academic achievement and intelligence that have norms for the child's age and, preferably, social class and ethnicity. To verify that the learning disturbance is interfering with a child's academic achievement or social functioning, information is collected from parents and teachers through interviews and standardized measures such as rating scales. Behavioral observations of the child may be used to supplement parent-teacher reports. If there is a visual, hearing, or other sensory impairment, it must be determined that the learning deficit is in excess of that usually associated with it. The child's developmental, medical, and educational histories and the family history are also obtained and used in establishing the differential diagnosis and clarifying etiology. If LD is present, then the next goal is a detailed description of the learning disorder to guide treatment. Tools will depend upon the specific type of learning disorder. For example, in the case of dyslexia, E. Wilcutt and Pennington suggest that the achievement test given to establish the achievement-intelligence discrepancy be supplemented by others such as the Gray Oral Reading Test (GORT-III), a timed measure of reading fluency as well as reading comprehension. Still another assessment goal is to identify the neuropsychological, linguistic, emotional, and behavioral correlates of the learning disorder and any associated disorders. A variety of measures exist for this purpose. Instrument selection should be guided by the clinician's hypotheses, based on what has been learned about the child and the disorder. Information about correlates and associated disorders is relevant to setting targets for intervention, understanding the etiology, and estimating the child's potential response to intervention and prognosis. In schools, identification of LD involves a multidisciplinary evaluation team including the classroom teacher, a psychologist, and a special education teacher or specialist in the child's academic skill deficit (such as reading). As needed, input may be sought from the child's pediatrician, a speech therapist, an audiologist, a language specialist, or a psychiatrist. A thorough assessment should provide a good description of the child's strengths as well as weaknesses that will be the basis of effective and comprehensive treatment plans for both the child and the family. In school settings, these are called, respectively, an Individual Educational Plan (IEP) and an Individual Family Service Plan (IFSP). TREATMENT Most children with LD require special education. Depending upon the disorder's severity, they may learn best in a one-to-one setting, small group, special class, or regular classroom plus resource room tutoring. Treatment of LD should address both the disorder and associated conditions or correlates. Furthermore, it should include assisting the family and school in becoming more facilitative contexts for development of the child with LD. Using neuropsychological training, psychoeducational methods, behavioral or cognitive-behavioral therapies, or cognitive instruction, singly or in combination, specific interventions have targeted the psychological process dysfunction or deficit assumed to underlie the specific learning disorder; a specific academic skill such as word attack; or an associated feature or correlate such as social skills. Process-oriented approaches that rose to prominence in the 1990's are linguistic models aimed at remediating deficits in phonological awareness and phonological memory, and cognitive models which teach specific cognitive strategies that enable the child to become a more efficient learner. Overall, treatment or intervention studies during the last two decades of the twentieth century and at the beginning of the twenty-first century are more theory-driven, built on prior research, and rigorous in methodology. Many studies have shown significant gains in target behaviors. Transfer of training, however, remains elusive. Generalization of learned skills and strategies is still the major challenge for future treatment research. As the twenty-first century begins, LD remains a persistent or chronic disorder. SOURCES FOR FURTHER STUDY American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders: DSM-IV-TR. Rev. 4th ed. Washington, D.C.: Author, 2000. Provides a more detailed description of the diagnostic criteria, associated features and disorders, and differential diagnosis. It also describes the course of the disorder and familial pattern, if any, for the specific learning disorders. Brown, F. R., III, H. L. Aylward, and B. K. Keogh, eds. Diagnosis and Management of Learning Disabilities. San Diego, Calif.: Singular Publishing Group, 1996. A multidisciplinary group of contributors provide a comprehensive yet detailed view of diagnosis, assessment, and treatment of learning problems. Because of its clarity and scope, this is recommended as an introductory text. Lyon, G. Reid. "Treatment of Learning Disabilities." In Treatment of Childhood Disorders, edited by E. J. Mash and L. C. Terdal. New York: Guilford, 1998. This chapter gives an excellent description of treatment models and reviews the research on their respective efficacies. Sternberg, R. J., and Louise Spear-Swerling, eds. Perspectives on Learning Disabilities. Boulder, Colo.: Westview Press, 1999. This sophisticated presentation and critique of biological, cognitive, and contextual approaches to learning disabilities is highly recommended for graduate students and professionals. Felicisima C. Serafica See AlsoAttention-Deficit Hyperactivity Disorder (ADHD); Brain Structure; Intelligence; Intelligence Tests; Language; Logic and Reasoning; Memory; Speech Disorders. |
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