Terms such as learning disorder and learning disability often are used interchangeably, although the latter term is used more commonly. A major stride in the definition of learning disabilities came from the National Joint Committee for Learning Disabilities. The National Joint Committee for Learning Disabilities defined a learning disability as a generic term that refers to a heterogeneous group of disorders manifested by significant difficulties in the acquisition and use of listening, speaking, reading, writing, reasoning, or mathematical abilities. These disorders are intrinsic to the individual and presumed to be due to central nervous system dysfunction. Even though a learning disability may occur concomitantly with other handicapping conditions (e.g., sensory impairment, mental retardation, social and emotional disturbance) or environmental influences (e.g., cultural differences, insufficient/inappropriate instruction, psychogenic factors), it is not the direct result of those conditions or influences (Hammill et al. 1981, p. 336).
This definition went further than the earlier one contained in the Education for All Handicapped Children Act of 1975 (P.L. 94–142) by stipulating specifically that a learning disability must be presumed to be due to central nervous system dysfunction. Although this was implied in previous definitions, never before was it made explicit. Accordingly, the newer definition helps to resolve a good deal of confusion and ambiguity involving identification and differential diagnosis. Deficiencies in academic achievement can arise from a variety of factors, operating alone or in combination. To say that there is a learning disability, however, means that there must be a basis for inferring that some form of brain dysfunction is involved.
Diagnostic and Statistical Manual of Mental Disorders, 4th edition, Text Revision (DSM-IV-TR) identifies three types of learning disorders: (1) reading disorder, (2) mathematics disorder, and (3) disorder of written expression. In each disorder, the diagnosis depends on documentation that
- Achievement in the area, as assessed on an individually administered standardized test, falls substantially below expectations based on the person's age, measured intelligence, and education
- The deficiency significantly interferes with academic achievement or daily activities requiring the particular skill
- The skill deficiency exceeds what usually would be associated with any sensory deficit, if present
Inherent in these criteria are considerations pertaining to the severity, extent, and specificity of the observed deficit—whether it be in reading, mathematics, or written expression. The deficit must be nontrivial or substantial, although this is not defined further by DSM-IV-TR. It must affect relevant aspects of daily functioning. It also must be specific and not simply reflective of intellectual, sensory, or educational limitations.
The diagnostic category of learning disorder not otherwise specified refers to deficiencies in reading, mathematics, or written expression that interfere with academic achievement but do not meet criteria for a specific learning disorder. This is an ambiguous category that probably should not be viewed as representing a disorder. At best, it implies that a learning disorder is suspected but cannot be documented through ordinary ...