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IQ Scores Do Not Differentiate between Difficult-to-Remedial and Readily Remediated Poor Readers: More Evidence against the IQ Achievement Discrepancy Definition of Reading Disability

Frank Vellutino, Donna Scanlon, and G. Reid Lyon


In this paper, we discuss research bearing on the traditional use of the IQ-achievement discrepancy to define specific reading disability. We initially review the evidence presented by Rutter and Yule (1975) in support of this practice, and then discuss results from subsequent studies which question the reliability of Rutter and Yule's findings. We also discuss results from more recent studies demonstrating that the IQ-achievement discrepancy does not reliably distinguish these groups. We highlight results from a study we have recently completed, in which it was found that IQ scores did not differentiate between poor readers who were difficult to remediate. In view of the convergent evidence against the use of IQ scores to define specific reading disability, we suggest that the IQ-achievement discrepancy definition of this disorder be discarded.

* Journal of Learning Disabilities, 73(3-4), pp. 81-103.

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