Discrepancy Model: Early Attempt at LD Identification
In 1965, Bateman provided a suggested method for identifying learning disabilities that called for a discrepancy between students’ estimated general intellectual potential and their actual academic performance. The use of intelligence tests that yield an overall intelligence score, or Intelligence Quotient (IQ), have traditionally been used to measure general intellectual ability. Meanwhile, achievement tests have served as the primary measure of academic performance. The discrepancy model differentiated people with a suspected learning disability from generally low functioning individuals by comparing IQ scores to achievement. The demonstration of poor achievement and low IQ is expected, while poor achievement and high IQ is unexpected. The unexpected nature of a discrepancy was what served as a signal for a learning disability.
In 1977, the United States Department of Education established federal guidelines for identifying students with learning disabilities, and set parameters through a definition that incorporated Bateman’s suggested use of a discrepancy. The federal government outlined procedures for identifying a learning disability, in which the discrepancy model was suggested as a potential method. However, the federal guidelines never established how much of a discrepancy was needed to justify a learning disability. Individual states adopted the federal definition in one form or another and proposed formulas of their own for determining whether a discrepancy was significant enough to warrant classification of a learning disability.
Problems with the Discrepancy Method
Considering a practical perspective, the discrepancy method for identifying a learning disability proved to be problematic over the years because there was little consensus regarding what constituted a significant discrepancy. States and school districts within states set different discrepancy criteria. This lack of agreement implies that a student can gain or lose a learning disability classification by moving from one state to another, or even from one school district to another within a state. This lack of consensus is problematic because the status of a student’s special education placement becomes subject to where he or she lives, and fragments the objective study of learning disabilities.
A number of RTI proponents have directed attention to research that has accumulated over the years suggesting that the discrepancy method does not accurately identify specific learning disabilities. A logical criticism of the discrepancy model exists in the method’s inability to provide any insight into the underlying cognitive processes that lie at the core of a specific learning disability. The most that can be said about using the discrepancy method in search of a learning disability classification is that a student who exhibits academic underachievement, but does not exhibit low overall cognitive ability, cannot attribute the learning deficiency to general low functioning. However, the specific cognitive domain(s) that are central to defining a specific learning disability remain unknown. Furthermore, there is no specific information to guide highly individualized intervention at the special education level. With these criticisms in mind, IDEA 2004 specifically stipulates that a state cannot impose the use of a discrepancy in determining a specific learning disability.
What is the disability?
When cognitive processing is not identified there can be no sure understanding of what underlies poor academic performance.
A specific learning disability cannot be substantiated under IDEA 2004 when an underlying cognitive processing deficit is not identified. Furthermore, special education remediation efforts are limited because of the lack of information to guide highly targeted and individualized design.
- Mercer, C. D. (1997). Students with learning disabilities (5th ed.). Upper Saddle River, NJ: Merrill.
- VanDerHeyden, A., M., & Burns, M., K. (2010). Essentials of response to intervention. Hoboken, NJ: Wiley.