Learning Disabilities and IQ Tests: Diagnostic Practices
under the Microscope

The field of “learning disabilities” (LD) was officially born on April 6, 1963 when Samuel Kirk, then an American professor of special education, suggested this term to describe apparently normal children “who have disorders in development of language, speech, reading, and associated communication skills.” Since then, millions of children have been diagnosed as learning disabled.

Today, in the USA, whenever a child is formally classified as learning disabled, he becomes the financial responsibility of the state. These children, who are provided with educational programs under federal law, are in most states distinguished from other children with learning problems on two grounds. First, the basis of their scholastic problems is presumed to be due to some neurological dysfunction. The LD category excludes children who have learning problems as a result of visual, hearing or motor handicaps, of mental retardation, of emotional disturbance, or of environmental, cultural or economic disadvantage. Second, to be diagnosed as learning disabled there must be a discrepancy between a child’s potential and his achievement. Stated differently, there is a discrepancy between a child’s expected school achievement and his real school achievement. Miles states that a person is dyslexic provided that there is a discrepancy between his intellectual level (potential) and his performance at reading and spelling (achievement) and that this discrepancy is accompanied by some other supporting “signs,” like problems with left and right, poor sense of time, putting letters and figures the wrong way around, unusual difficulty in remembering mathematical tables, putting letters in the wrong order, et cetera.

Needless to say, this diagnostic practice has been debated, disputed and criticized. Apart from the fact that a neurological dysfunction has never been proved, it is impossible to prove that the environment has played no role in the creation of a learning disability. Also consider that, if discovering discrepancies between potential and achievement is an acceptable and valid method of diagnosing disabilities, then there must be hundreds, maybe even thousands of other disabilities that we poor human beings may suffer from. They have so far gone undiscovered, simply because we have not yet compared the relevant potentials and achievements. For example, if one calculated from a person's physique, age, weight and height that he should be able to run the 100 meters in 11 seconds and the stop watch shows that he can only do so in 14 seconds, then that person must have a running disability. Now, of course the idea of a running disability is ridiculous, but isn't a learning disability then equally ridiculous? Why can't we use the same method to diagnose other disabilities?

Another matter in dispute is how big the discrepancy must be before one can refer to a child as learning disabled. The following event illustrates the untenability of the whole idea: A few years ago New York adopted a 50 percent discrepancy formula as a criterion for identification. A 50 percent discrepancy means that a child achieves only half as well as one would expect from him when considering his potential. Following the adoption of the 50 percent discrepancy criterion, the number of pupils identified as learning disabled dropped from 28,000 to 12,167, thus miraculously “curing” almost 16,000 children of their “disability.” A further implication of this new regulation was that a child of normal intelligence had to spend two years at school before a one-year discrepancy (50 percent) could be calculated and the child could receive treatment.

IQ: The Most Important Criteria of Potential

The most important criterion to determine a child’s potential (expected achievement) is his IQ score. The aim of the IQ test, supposedly, is to measure the intelligence of a child. It is, however, beyond comprehension why IQ should play such a predominant role. It has been demonstrated clearly by numerous studies how unreliable IQ test scores can be. The scores may vary by as much as 15 points from one test to another, while emotional tension, anxiety, and unfamiliarity with the testing process can greatly affect test performance. In addition, Gould described the biasing effect that tester attitudes, qualifications, and instructions can have on testing. In one study, ninety-nine school psychologists independently scored an IQ test from identical records, and came up with IQ's ranging from 63 to 117 for the same person. In another study, Ysseldyke et al. examined the extent to which professionals were able to differentiate learning-disabled students from ordinary low achievers by examining patterns of scores on psychometric measures. Subjects were 65 school psychologists, 38 special-education teachers, and a “naive” group of 21 university students enrolled in programs unrelated to education or psychology. Provided with forms containing information on 41 test or subtest scores (including the WISC-R IQ test) of nine school-identified LD students and nine non-LD students, judges were instructed to indicate which students they believed were learning disabled and which were non-learning disabled. The school psychologists and special-education teachers were able to differentiate between LD students and low achievers with only 50 percent accuracy. The naive judges, who had never had more than an introductory course in education or psychology, evidenced a 75 percent hit rate!

Linda S. Siegel, professor in the Department of Educational Psychology and Special Education at the University of British Columbia in Vancouver, Canada, proposes that we abandon the IQ test in the analysis of the LD child. According to most definitions — although they are not conclusive — intelligence is made up of the skills of logical reasoning, problem solving, critical thinking, and adaptation. This scenario seems reasonable, until one examines the content of IQ tests. The definition of intelligence, as it is operationalized in all IQ tests, includes virtually no skills that can be identified in terms of the most widely accepted definitions of intelligence. To support her statement, Siegel gives a detailed analysis of the subtests of the Wechsler Intelligence Scale for Children-Revised (WISC-R). The WISC, or Wechsler Intelligence Scale for Children, is one of the most widely used tests for assessing the potential of learning-disabled students between the ages of six and sixteen. This IQ test is composed of Verbal and Performance sections, and is nearly always used in LD diagnosis. In each subtest of the Verbal scale, performance is in varying degrees dependent on specific knowledge, vocabulary, expressive language and memory skills, while in the Performance scale, visual-spatial abilities, fine motor coordination, perceptual skills, and in some subtests speed, are essential for scoring. As Siegel rightly points out, IQ tests measure, for the most part, what a person has learned, not what he or she is capable of doing in the future (his potential).

There is an additional problem in the use of IQ tests with individuals with learning disabilities. According to Siegel it is a paradox that IQ scores are required of people with LD because most of these persons have deficiencies in one or more of the component skills that are part of these IQ tests — memory, language, fine motor skills, et cetera. The effect is that they may end up having a lower IQ score than a person who does not have such problems, even though they may both have identical (or better) reasoning and problem-solving skills. The lower IQ score, therefore, may be a result of the learning disability, and IQ scores may therefore underestimate the real intelligence of the individual with a learning disability.

Another assumption of the discrepancy definition is that the IQ score should predict reading, so that if you have a low IQ score you should be a poor reader and that poor reading is an expected consequence of low IQ. However, there are individuals who have low IQ scores and are good readers.

It makes one shudder to think that far-reaching decisions are sometimes made about children, and that such decisions are often based solely on test scores.

References:

• Anastasi, A. (ed.), Testing Problems in Perspective (Washington DC: American Council on Education, 1966).

• Du Preez, J. J., & Steenkamp, W. L., Spesifieke Leergestremdhede: 'n Neurologiese Perspektief (2nd ed.), (Durban: Butterworth, 1986).

• Epps, S., Ysseldyke, J. E., & McGue, M., “'I know one when I see one' — Differentiating LD and non-LD students,” Learning Disability Quarterly, 1984, vol. 7.

• Gould, S. J., The Mismeasure of Man (New York: W. W. Norton, 1981).

• Kavale, K. A., “Status of the field: Trends and issues in learning disabilities,” in K. A. Kavale (ed.), Learning Disabilities: State of the Art and Practice (Boston: College-Hill Press, 1988).

• Miles, T. R., Understanding Dyslexia (London: Hodder and Stoughton, 1978).

• Sattler, J., Assessment of Children's Intelligences and Special Abilities (Boston: Allyn & Bacon, 1982).

• Siegel, L. S., “IQ is irrelevant to the definition of learning disabilities,” Journal of Learning Disabilities, 1989, vol. 22(8).

• Siegel, L. S., “Issues in the definition and diagnosis of learning disabilities; A perspective on Guckenberger v. Boston University,” Journal of Learning Disabilities, 1 July 1999, vol. 32.

• Siegel, L. S., & Metsala, E., “An alternative to the food processor approach to subtypes of learning disabilities,” in N. N. Singh & I. L. Beale (eds.), Learning Disabilities: Nature, Theory, and Treatment (New York: Springer-Verlag, 1992).