In this study, we introduce a new analytic strategy for comparing the cognitive profiles of children developing reading skills at different rates: a regression-based logic that is analogous to the reading-level match design, but one without some of the methodological problems of that design. It provides a unique method for examining whether the reading subskill profiles of poor readers with aptitude/achievement discrepancy differ from those without discrepancy. Children were compared on a varied set of phonological, orthographic, memory, and language processing tasks. The results indicated that cognitive differences between these 2 groups of poor readers all reside outside of the word recognition module. The results generally support the phonological-core variable-difference model of reading disability and demonstrate that degree of aptitude/ achievement discrepancy is unrelated to the unique cognitive tradeoffs that are characteristic of the word recognition performance of children with reading disabilities.

Working memory has been proposed as an important component of reading and arithmetic skills. The development of working memory was studied in normally achieving and subtypes of learning disabled children. The performance of reading disabled (RD), arithmetic disabled (ARITHD), and attentional deficit disordered (ADD) children, age 7-13, was compared to normal achievers (NA) on 2 working memory tasks, 1 involving sentences and the other involving counting. There was a significant growth of working memory as a function of age. In addition, the RD children had significantly lower scores on both tasks. The ARITHD children had significantly lower scores only on the Working Memory--Counting task, and the ADD group had scores similar to the normally achieving children except at the youngest age level in the Working Memory--Sentences task. Thus, a reading disability appears to involve a generalized deficit in working memory. Children with an arithmetic disability do not have a generalized language deficit but have a specific working memory deficit in relation to processing numerical information. As children with ADD did not have deficits in these tasks, working memory may not have significant attentional components. An important component of the development of reading and computational arithmetic skills appears to be the growth of working memory for language and numerical information.

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Using regression-based procedures introduced by A. Castles and M. Coltheart (1993), the authors identified 17 phonological and 15 surface dyslexics from a sample of 68 readingdisabled 3rd-grade children by comparing them to chronological-age (CA) controls on exception word and pseudoword reading. However, when Ihe dyslexic subtypes were defined by reference to reading-level (RL) controls, 17 phonological dyslexics were defined but only 1 surface dyslexic. When the CA-defined subtypes were compared to RL controls, the phonological dyslexics displayed superior exception word reading but displayed deficits in pseudoword naming, phonological sensitivity, working memory, and syntactic processing. The surface dyslexics, in contrast, displayed a cognitive profile remarkably similar to that of the RL controls.There is considerable face validity to the idea that reading disabled individuals differ among themselves in the way that they have become poor readers and in the cognitive underpinnings of their disability. Yet the field has made very little progress toward defining separable groups of disabled readers. For example, the idea that separate subgroups of poor readers could be defined based on aptitudeachievement discrepancies has not proven fruitful for the reading disabilities field (

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.