Differentiating between difficult-to-remediate and readily remediated poor readers: more evidence against the IQ-achievement discrepancy definition of reading disability.

In this article 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 that have questioned the reliability of their findings. We also discuss results from more recent studies demonstrating that the IQ-achievement discrepancy does not reliably distinguish poor from normal readers, whereas language-based measures do reliably distinguish these groups. We highlight results from a study we recently completed, in which it was found that IQ scores did not differentiate between poor readers who were found to be readily remediated and 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.

Normal reading despite limited eye movements.

Many investigators have demonstrated that poor readers exhibit abnormal eye movements during reading. An association between defective vergence, accommodation, and poor reading skills has also been noted by some investigators. Children who are poor readers have been subjected to therapeutic interventions on the basis of the assumption that improving their eye movements, as part of a multifaceted program of "vision therapy," will yield commensurate improvement in reading performance. This approach has been controversial, and other authors have expressed opposing views. We report the ophthalmologic and reading assessments of two children with Möbius' syndrome who were average to above-average readers despite essentially absent horizontal eye movements.

Semantic and phonological coding in poor and normal readers.

Three studies were conducted evaluating semantic and phonological coding deficits as alternative explanations of reading disability. In the first study, poor and normal readers in second and sixth grade were compared on various tests evaluating semantic development as well as on tests evaluating rapid naming and pseudoword decoding as independent measures of phonological coding ability. In a second study, the same subjects were given verbal memory and visual-verbal learning tasks using high and low meaning words as verbal stimuli and Chinese ideographs as visual stimuli. On the semantic tasks, poor readers performed below the level of the normal readers only at the sixth grade level, but, on the rapid naming and pseudoword learning tasks, they performed below the normal readers at the second as well as at the sixth grade level. On both the verbal memory and visual-verbal learning tasks, performance in poor readers approximated that of normal readers when the word stimuli were high in meaning but not when they were low in meaning. These patterns were essentially replicated in a third study that used some of the same semantic and phonological measures used in the first experiment, and verbal memory and visual-verbal learning tasks that employed word lists and visual stimuli (novel alphabetic characters) that more closely approximated those used in learning to read. It was concluded that semantic coding deficits are an unlikely cause of reading difficulties in most poor readers at the beginning stages of reading skills acquisition, but accrue as a consequence of prolonged reading difficulties in older readers. It was also concluded that phonological coding deficits are a probable cause of reading difficulties in most poor readers.

Free recall of concrete and abstract words in poor and normal readers.

The present study compared poor and normal readers in second and sixth grade on free recall of concrete and abstract words. On the basis of the assumption that memory for abstract words relies more heavily upon linguistic coding ability than does memory for concrete words, it was expected that poor readers would have much greater difficulty on recall of abstract words than would normal readers, but would more closely approximate the normal readers on recall of concrete words. The hypothesis was confirmed at the second-grade level but not at the sixth-grade level, wherein the magnitude of group differences on concrete words was comparable to that on abstract words. Post hoc analyses of intrusion errors suggested that the linguistic coding hypothesis may be a viable explanation of reader group differences on memory tasks only at lower age levels.