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Causal Models of Reading Disability: A Twin Study

Published online by Cambridge University Press:  21 February 2012

Rolando D. Tiu Jr. ,
Sally J. Wadsworth ,
Richard K. Olson  and
John C. DeFries
Rolando D. Tiu Jr.*
Affiliation:
University of Colorado, [email protected]
Sally J. Wadsworth
Affiliation:
University of Colorado, USA
Richard K. Olson
Affiliation:
University of Colorado, USA
John C. DeFries
Affiliation:
University of Colorado, USA
*
*Address for correspondence: R. D. Tiu, Institute for Behavioral Genetics, University of Colorado, 1480 30th St., Boulder, CO 80309-0447, USA.

Abstract

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The genetic and environmental relationships among measures of phoneme awareness, naming speed, Intelligence Quotient (IQ), and reading performance were investigated in 623 identical and fraternal twin pairs tested in the Colorado Learning Disabilities Research Center. A Cholesky decomposition analysis of these measures provided evidence supporting the double deficit hypothesis that difficulties in phonological processing and naming speed both contribute to reading disability. Additionally, the model revealed marginally significant genetic and significant non-shared environmental relationships between IQ and reading independent of naming speed and phoneme awareness. Thus a more complete causal model of reading disability should include IQ as well as measures of phonological processing and naming speed.

Type
Articles
Information
Twin Research and Human Genetics , Volume 7 , Issue 3 , 01 June 2004 , pp. 275 - 283
Copyright
Copyright © Cambridge University Press 2004