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Cited by 716

The DOI matches its Crossref record; 2 of the 2 references it cites were found in a registry or an index.

Evidence That Dyslexia May Represent the Lower Tail of a Normal Distribution of Reading Ability

Open access
Shaywitz, Sally E., Escobar, Michael D., Shaywitz, Bennett A., Fletcher, Jack M., Makuch, Robert·1992·New England Journal of Medicine
DOI 10.1056/nejm199201163260301
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Abstract

BACKGROUND: Dyslexia is now widely believed to be a biologically based disorder that is distinct from other, less specific reading problems. According to this view, reading ability is considered to follow a bimodal distribution, with dyslexia as the lower mode. We hypothesized that, instead, reading ability follows a normal distribution, with dyslexia at the lower end of the continuum. METHODS AND RESULTS: We used data from the Connecticut Longitudinal Study, a sample survey of 414 Connecticut children who entered kindergarten in 1983 and were followed as a longitudinal cohort. Dyslexia was defined in terms of a discrepancy score, which represents the difference between actual reading achievement and achievement predicted on the basis of measures of intelligence. Data were available from intelligence tests administered in grades 1, 3, and 5 and achievement tests administered yearly in grades 1 through 6. For each child there were 108 possible discrepancy scores ([3 x 3 years] x [2 x 6 years]) based on combinations of the ability scores (full-scale, verbal, and performance IQ) in each of three years and two achievement scores (reading and mathematics) in each of six years. We demonstrated that each of the discrepancy scores followed a univariate normal distribution and that the interrelation of two different discrepancy scores followed a bivariate normal distribution. At most, only 9 of 108 discrepancy scores (8.3 percent) and 171 of 3402 pairs of discrepancy scores (5.0 percent) were significantly different (at the 5 percent level) from the expected scores--well within the expected values for data with univariate and bivariate normal distributions, respectively. We also examined the stability of dyslexia over time. The normal-distribution model predicted (and the data indicated) that only 7 of the 25 children (28 percent) classified as having dyslexia in grade 1 would also be classified as having dyslexia in grade 3. CONCLUSIONS: Reading difficulties, including dyslexia, occur as part of a continuum that also includes normal reading ability. Dyslexia is not an all-or-none phenomenon, but like hypertension, occurs in degrees. The variability inherent in the diagnosis of dyslexia can be both quantified and predicted with use of the normal-distribution model.

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Metadata

Authors
Shaywitz, S. E., Escobar, M. D., Shaywitz, B. A., Fletcher, J. M., & Makuch, R.
Venue
New England Journal of Medicine
Publisher
Massachusetts Medical Society
Published
1992-01-16
Volume
326
Issue
3
Pages
145-150
ISSN
  • 0028-4793 (ISSN-L)
  • 1533-4406
DOI
10.1056/nejm199201163260301
OpenAlex
W2317934904
Cited by
716
References
2
FWCI
40.78
Type
journal article
Language
en
Open access
bronze

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