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Lookup NU author(s): Dr Gareth RichardsORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
Reared-apart twin studies are a powerful means for identifying the relative contributions of heredity and environment to variation in human physical and behavioural traits. One such characteristic is handedness, for which it has long been noted that approximately 20% of twin pairs are comprised of one right-handed cotwin and one left-handed cotwin. Reared-together twin studies suggest a slightly greater concordance in monozygotic (MZT) than dizygotic (DZT) twins, implying that genetics influences hand preference. We report here two studies of handedness in reared-apart twins. Study 1 synthesizes the available data and estimates that at least N = 560 same-sex reared-apart twin pairs (for which zygosity is known with reasonable confidence) have been identified. Of these, handedness data are available for both members of n = 415 pairs. We observed similar levels of concordance/discordance for reared-apart monozygotic (MZA) and dizygotic (DZA) twins. However, although direction of handedness (right or left) has frequently been examined, strength of handedness (strong or weak) has not. Study 2 examined strength of hand preference and relative hand skill, as well as right- and left-hand speed, information available for participants in the Minnesota Study of Twins Reared Apart (MISTRA). We provide evidence of heritability for right-hand and left-hand speed. We also found hand preference strength was more alike than chance in DZA, but not MZA, twins. Findings are discussed in relation to genetic and environmental influences on human handedness.
Author(s): Richards G, Segal NL
Publication type: Article
Publication status: Published
Journal: Neuropsychologia
Year: 2023
Volume: 184
Print publication date: 06/06/2023
Online publication date: 12/04/2023
Acceptance date: 20/02/2023
Date deposited: 02/05/2023
ISSN (print): 0028-3932
ISSN (electronic): 1873-3514
Publisher: Elsevier
URL: https://doi.org/10.1016/j.neuropsychologia.2023.108523
DOI: 10.1016/j.neuropsychologia.2023.108523
Data Access Statement: The datasets generated and/or analyzed during the current study are not publicly available due to limited ethics approval for the wider Minnesota Study of Twins Reared Apart (MISTRA) and to the specifc consent provided by the participants. They may be available from the second author on reasonable request and pending approval of any future analyses by the MISTRA. SASS syntax and R code used to run analyses for Study 2 are publicly available on the Open Science Framework https://osf.io/e4ysv/
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