Current Directions in Dyslexia Research

Dirk J. Bakker, Kees P. van den Bos, David L. Share, Linda S. Siegel, Dirk J. Bakker, Kees P. van den Bos, David L. Share, Linda S. Siegel

• Publisher: Garland Science
• Year: 2020
• ISBN:
  9781000142549
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Engineering General
• Index: Technology & Engineering

This book covers research on biopsychological aspects of dyslexia reflects on psycholinguistic aspects of dyslexia offers reflections on dyslexia treatment research in general. It points out that in some dyslexics it is not sufficient to treat word identification difficulties alone.

Part I

Definition and Subtyping of Dyslexia

1Are Discrepancy-Based Definitions of Dyslexia Empirically Defensible?

Keith E. Stanovich

ABSTRACT

Most definitions of dyslexia involve the assessment of a discrepancy between reading ability and measured intelligence. These discrepancy definitions carry the implicit assumption that the reading difficulties of the dyslexic stem from problems different from those characterizing the poor reader without IQ discrepancy. An accumulating body of empirical evidence appears to contradict this assumption. The phenotypic performance profile that defines reading disability does not seem to differ for reading-disabled children with or without aptitude/achievement discrepancies. Degree of aptitude/achievement discrepancy is unrelated to the unique cognitive tradeoffs that are characteristic of the word identification performance of reading-disabled children. Genetic studies have indicated that IQ-discrepancy measurement does not identify a group of children with significantly different heritability values for core information processing deficits. Finally, there are as yet no indications that the neuroanatomical anomalies that are associated with reading disability are more characteristic of high-IQ than of low-IQ poor readers. These findings are extremely problematic for traditional conceptions of reading disability that rely on aptitude/achievement discrepancy to define a group of children whose reading problems are cognitively, physiologically, and etiologically distinctive.

INTRODUCTION

It is an affront to the field of reading disability research that the question “Does dyslexia exist?” can still be asked and debated. The reason that we are in the embarrassing position of debating such a seemingly basic question is that the field has repeatedly displayed a preference for terminology that connotes unverified theories about causation. The theory carried with the term “dyslexia” seems similarly to have gotten ahead of the evidence. Thus, unlike most discussions of the topic, we will begin our discussion at the beginning. Whether or not there is such a thing as “dyslexia”, there most certainly are children who read markedly below their peers on appropriately comprehensive and standardized tests. In this most prosaic sense, poor readers obviously exist. Controversy begins only when we address the question of whether, within this group of poor readers, there are groups of children who are “different”.

Terms like congenital word-blindness and dyslexia were coined to describe groups of children who were thought to be different from other poor readers in their etiology, neurological makeup, and cognitive characteristics. From the very beginning of research on reading disability, it was assumed that poor readers who were of high intelligence formed a cognitively and neurologically different group. Investigators who pioneered the study of the condition then known as congenital word-blindness were at pains to differentiate children with this condition from other poor readers. Hinshelwood (1917) stated clearly that he intended the term congenital word-blindness not for all poor readers but instead for those who were high functioning in other cognitive domains:

When I see it stated that congenital word-blindness may be combined with any amount of other mental defects from mere dullness to low-grade mental defects, imbecility or idiocy, I can understand how confusion has arisen from the loose application of the term congenital word-blindness to all conditions in which there is defective development of the visual memory center, quite independently of any consideration as to whether it is a strictly local defect or only a symptom of a general cerebral degeneration. It is a great injustice to the children affected with the pure type of congenital word-blindness, a strictly local affection, to be placed in the same category as others suffering from generalized cerebral defects, as the former can be successfully dealt with, while the latter are practically irremediable. (pp. 93–94).

Similarly, t...