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Visual-temporal processing in reading-disabled and normal twins

Visual-temporal processing in reading-disabled and normal twins Percent contrast thresholds for the detection of 1 or 8 cycle/degree sinusoidalgratings flickering in counter-phase at 1 or 10Hz were evaluated in 356 8–19 year old twinsand their school-age siblings. 107 of the twinshad a school history of reading disability.Subjects adjusted contrast levels to thresholdfrom above and below in a total of 32 trialsover about 12 minutes. Internal reliability foreach of the 4 stimulus conditions was 0.8, andeach stimulus condition was similarlycorrelated at 0.2–0.3 with several measuresof reading and phonological processing,suggesting modest relations with readingdeficits for both parvocellular (sustained) andmagnocellular (transient) visual processes. Thevariance in the word-reading measure that wasrelated to visual contrast thresholds waslargely shared with full-scale IQ, although IQand reading each also accounted for small(1%) but statistically significant amounts ofadditional independent variance in contrastthresholds. Word reading and nonword readingalso accounted for largely overlapping variancein contrast thresholds, but with a small (1%)amount of independent variance for nonwordreading. A behavioral-genetic analysis of themonozygotic and dizygotic twin correlationsindicated no significant genetic influence onindividual differences in contrast-thresholdlevels. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Reading and Writing Springer Journals

Visual-temporal processing in reading-disabled and normal twins

Olson, Richard; Datta, Helen
Reading and Writing , Volume 15 (2) – Oct 13, 2004
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References (49)

Publisher
Springer Journals
Copyright
Copyright © 2002 by Kluwer Academic Publishers
Subject
Linguistics; Language and Literature; Psycholinguistics; Education, general; Neurology; Literacy
ISSN
0922-4777
eISSN
1573-0905
DOI
10.1023/A:1013872422108
Publisher site
See Article on Publisher Site

Abstract

Percent contrast thresholds for the detection of 1 or 8 cycle/degree sinusoidalgratings flickering in counter-phase at 1 or 10Hz were evaluated in 356 8–19 year old twinsand their school-age siblings. 107 of the twinshad a school history of reading disability.Subjects adjusted contrast levels to thresholdfrom above and below in a total of 32 trialsover about 12 minutes. Internal reliability foreach of the 4 stimulus conditions was 0.8, andeach stimulus condition was similarlycorrelated at 0.2–0.3 with several measuresof reading and phonological processing,suggesting modest relations with readingdeficits for both parvocellular (sustained) andmagnocellular (transient) visual processes. Thevariance in the word-reading measure that wasrelated to visual contrast thresholds waslargely shared with full-scale IQ, although IQand reading each also accounted for small(1%) but statistically significant amounts ofadditional independent variance in contrastthresholds. Word reading and nonword readingalso accounted for largely overlapping variancein contrast thresholds, but with a small (1%)amount of independent variance for nonwordreading. A behavioral-genetic analysis of themonozygotic and dizygotic twin correlationsindicated no significant genetic influence onindividual differences in contrast-thresholdlevels.

Journal

Reading and Writing – Springer Journals

Published: Oct 13, 2004

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