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Multiple Regression Analysis of Reading Performance Data from Twin Pairs with Reading Difficulties and Nontwin Siblings: The Augmented Model

Published online by Cambridge University Press:  28 March 2012

Sally J. Wadsworth ,
Richard K. Olson ,
Erik G. Willcutt  and
John C. DeFries
Sally J. Wadsworth*
Affiliation:
1Institute for Behavioral Genetics, University of Colorado, Boulder, CO, USA
Richard K. Olson
Affiliation:
2Department of Psychology and Neuroscience, University of Colorado, Boulder, CO, USA
Erik G. Willcutt
Affiliation:
1Institute for Behavioral Genetics, University of Colorado, Boulder, CO, USA 2Department of Psychology and Neuroscience, University of Colorado, Boulder, CO, USA
John C. DeFries
Affiliation:
1Institute for Behavioral Genetics, University of Colorado, Boulder, CO, USA 2Department of Psychology and Neuroscience, University of Colorado, Boulder, CO, USA
*
Address for Correspondence: Sally J. Wadsworth, Institute for Behavioral Genetics, 447 UCB, University of Colorado, Boulder CO 80309, USA. E-mail: Sally.Wadsworth@Colorado.edu

Abstract

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The augmented multiple regression model for the analysis of data from selected twin pairs was extended to facilitate analyses of data from twin pairs and nontwin siblings. Fitting this extended model to data from both selected twin pairs and siblings yields direct estimates of heritability (h2) and the difference between environmental influences shared by members of twin pairs and those of sib or twin–sib pairs (i.e., c2(t) – c2 (s)). When this model was fitted to reading performance data from 293 monozygotic and 436 dizygotic pairs selected for reading difficulties, and 291 of their nontwin siblings, h2 = .48 ± .22, p = .03, and c2 (t) – c2 (s) = .22 ± .12, p = .06. Although the test for differential shared environmental influences is only marginally significant, the results of this analysis suggest that environmental influences on reading performance that are shared by members of twin pairs (.36) may be substantially greater than those for less contemporaneous twin–sibling pairs (.14).

Keywords

multiple regressiontwinssiblingsreadingheritabilityshared environment

Information

Type
Articles
Information
Twin Research and Human Genetics , Volume 15 , Issue 1: Special Section: The Intersection of Behavioral Genetics and Political Science , February 2012 , pp. 116 - 119
Copyright
Copyright © Cambridge University Press 2012