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Handedness in Twins: Joint Analysis of Data From 35 Samples

Published online by Cambridge University Press:  21 February 2012

Sarah E. Medland ,
David L. Duffy ,
Margaret J. Wright ,
Gina M. Geffen  and
Nicholas G. Martin
Sarah E. Medland*
Affiliation:
Queensland Institute of Medical Research, Brisbane, Australia; Cognitive Psychophysiology Laboratory, University of Queensland, Australia. [email protected]
David L. Duffy
Affiliation:
Queensland Institute of Medical Research, Brisbane, Australia.
Margaret J. Wright
Affiliation:
Queensland Institute of Medical Research, Brisbane, Australia.
Gina M. Geffen
Affiliation:
Cognitive Psychophysiology Laboratory, University of Queensland, Australia.
Nicholas G. Martin
Affiliation:
Queensland Institute of Medical Research, Brisbane, Australia.
*
*Address for correspondence: Sarah Medland, Queensland Institute of Medical Research, PO Royal Brisbane Hospital, Brisbane 4029, Australia.

Abstract

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Simultaneous analysis of handedness data from 35 samples of twins (with a combined sample size of 21,127 twin pairs) found a small but significant additive genetic effect accounting for 25.47% of the variance (95% confidence interval [CI] 15.69–29.51%). No common environmental influences were detected (C = 0.00; 95% CI 0.00–7.67%), with the majority of the variance, 74.53%, explained by factors unique to the individual (95% CI 70.49–78.67%). No significant heterogeneity was observed within studies that used similar methods to assess handedness, or across studies that used different methods. At an individual level the majority of studies had insufficient power to reject a purely unique environmental model due to insufficient power to detect familial aggregation. This lack of power is seldom mentioned within studies, and has contributed to the misconception that twin studies of handedness are not informative.

Type
Articles
Information
Twin Research and Human Genetics , Volume 9 , Issue 1 , 01 February 2006 , pp. 46 - 53
Copyright
Copyright © Cambridge University Press 2006