for special education services in the category of LD. The objectivity and appropriateness of the method suggested in the 1977 regulations have been questioned over the past 15 years.

The 1977 federal regulations established classification criteria that were not entirely consistent with the LD conceptual definition (see Appendix 6-B), which implied an underlying cognitive processing disorder as the core feature of the disability. The classification criteria had three broad components (see Regulation 540 in Appendix 6-A). The first was low achievement in one of seven areas. The second was “a severe discrepancy between achievement and intellectual ability” in one or more of the seven achievement areas. The third involved what are known as the exclusion criteria: LD could not be the result of inappropriate educational programming; visual, hearing, or motor impairment; mental retardation; emotional disturbance; or environmental, cultural, or economic disadvantage. These criteria could be summarized as defining LD as unexpected low achievement that cannot be explained by low ability, absence of an opportunity to learn, or other factors.

State requirements for determining eligibility generally apply the discrepancy and exclusion factors, although there are substantial variations. The most recent national survey of state criteria (Mercer et al., 1996) indicated that 94 percent of states mentioned a processing disorder in the conceptual definition, but processing factors were included in only 33 percent of the states’ classification criteria. Virtually all states applied the exclusion factors (98 percent), and all included the achievement areas of reading, writing, and math. Dissatisfaction with the achievement-ability severe discrepancy criterion has led to consideration of achievement-domain-specific criteria for eligibility (see Chapter 8 for a discussion of problems with the severe discrepancy method).

Domain-Specific Definitions

Federal law defines LD not as a single disability, but as a group of disabilities that are expressed in one or more skill domains. The disabilities are manifested in the areas of: (1) listening; (2) speaking; (3) basic reading (decoding and word recognition); (4) reading comprehension; (5) arithmetic calculation; (6) mathematics reasoning; and (7) written expression. The broadness of this definition encompasses a wide range of learning difficulties eligible for treatment. However, the complexity of each skill domain and the overlap between the domains compromise diagnostic precision. Diagnosis is further complicated by the fact that disabilities in these areas may be accompanied by other disorders, which are not the cause of the LD.

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