IQ Is Irrelevant to the Definition of Learning Disabilities

Abstract

The purpose of this article was to examine the logic and the empirical data supporting the proposition that intelligence tests are not necessary for the definition of a learning disability. Four assumptions of the use of IQ test scores in the definition of learning disabilities were examined. These assumptions were (a) IQ tests measure intelligence; (b) intelligence and achievement are independent, and the presence of a learning disability will not affect IQ scores; (c) IQ scores predict reading, and children with low IQ scores should be poor readers; and (d) reading disabled children with different IQ scores have different cognitive processes and information skills. It was argued that IQ scores measure factual knowledge, expressive language abilities, and short-term memory, among other skills, and that because children with learning disabilities have deficits in these areas, their scores may be spuriously low. It was also shown that some children with low IQ scores can be good readers, indicating that low IQ scores do not necessarily result in poor reading. Empirical evidence was presented that poor readers at a variety of IQ levels show similar reading, spelling, language, and memory deficits. On logical and empirical grounds, IQ test scores are not necessary for the definition of learning disabilities.

Co-Morbidity in Mathematical Learning Disabilities: Rule or Exception?

“…The contrast (VIQ>PIQ), in one fourth was reported. Therefore we do agree with Mazzocoo and Mayers (2003) and Siegel (1989) that the discrepancy-criterion is not sensitive enough, especially in girls, to identify all children with mathematical learning disabilities.…”

“…In the debate about the usefulness of IQ-measurement in the assessment of learning disabilities, Siegel (1989) pointed out that the discrepancy model has lead to a great number of children with learning disabilities that are not detected. In line with those findings, Mazzocco and Myers (2003) more recently stated that the criterion is not sensitive enough to identify all children with mathematical disabilities.…”

Specific reading disability (dyslexia): what have we learned in the past four decades?

“…Altogether, the evidence supporting the use of IQachievement discrepancy classifications models is quite limited Hoskyn & Swanson, 2000;Lyon et al, 2001Lyon et al, , 2002Stuebing et al, 2002;Vellutino et al, 2000; see also Share et al, 1989;Siegel, 1988Siegel, , 1989. Thus, it is apparent that a child may need little more than average or even low average intelligence to learn to decipher print.…”

The Double-Deficit Hypothesis

“…Wolf et al (2002) stated that the fact that some studies do not find a relationship between naming speed and reading might be due to a greater number of nondiscrepant readers in the dyslexia sample; Wolf et al hypothesized that the greater the number of nondiscrepant participants with dyslexia in the sample, the less predictive naming speed will be-thus suggesting that an ability-achievement discrepancy is a necessary requisite for the viability of the double-deficit hypothesis. However, a large body of research has called into question the validity and utility of IQ scores in the definition and analysis of dyslexia (e.g., Fletcher, 1992;Siegel, 1989Siegel, , 1992Siegel, , 1999Stanovich & Siegel, 1998;Vellutino et al, 1996;Vellutino, Scanlon, & Lyon, 2000), and current conceptualizations of dyslexia do not include the requirement of an ability-achievement discrepancy (e.g., Lyon et al, 2001). Thus, to lend empirical support to the hypothesis, it is first necessary to demonstrate that discrepant readers do in fact have dyslexia.…”