Special twin environments, genetic influences and their effects on the handedness of twins and their siblings

Sarah E. Medland*, Margaret J. Wright, Gina M. Geffen, David A. Hay, Florence Levy, Nicholas G. Martin, David L. Duffy

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

31 Citations (Scopus)

Abstract

It has been suggested that twinning may influence handedness through the effects of birth order, intra-uterine crowding and mirror imaging. The influence of these effects on handedness (for writing and throwing) was examined in 3657 Monozygotic (MZ) and 3762 Dizygotic (DZ) twin pairs (born 1893-1992). Maximum likelihood analyses revealed no effects of birth order on the incidence of left-handedness. Twins were no more likely to be left-handed than their singleton siblings (n = 1757), and there were no differences between the DZ co-twin and sibling-twin covariances, suggesting that neither intra-uterine crowding nor the experience of being a twin affects handedness. There was no evidence of mirror imaging; the co-twin correlations of monochorionic and dichorionic MZ twins did not differ. Univariate genetic analyses revealed common environmental factors to be the most parsimonious explanation of familial aggregation for the writing-hand measure, while additive genetic influences provided a better interpretation of the throwing hand data.

Original languageEnglish
Pages (from-to)119-130
Number of pages12
JournalTwin Research
Volume6
Issue number2
DOIs
Publication statusPublished - Apr 2003
Externally publishedYes

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