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

In: Twin research and human genetics: the official journal of the International Society for Twin Studies (ISTS) and the Human Genetics Society of Australasia, Band 15, Heft 1, S. 116-119

Abstract

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).