Handedness in twins: a meta-analysis

Area of Science:

• Human genetics
• Developmental neuroscience
• Behavioral genetics

Background:

• Handedness, the preference for using one hand over the other, is a complex human trait.
• Previous research on the heritability of handedness has yielded inconsistent results.
• The role of genetic and environmental factors in determining handedness remains an active area of investigation.

Purpose of the Study:

• To investigate the incidence of left-handedness in twins compared to singletons.
• To explore differences in left-handedness frequency between monozygotic (identical) and dizygotic (fraternal) twins.
• To examine concordance rates for hand preference in twin pairs to understand genetic contributions.

Main Methods:

• Conducted the largest meta-analysis to date, combining data from twin and singleton studies.
• Analyzed incidence rates of left-handedness across different birth types (twins vs. singletons).
• Compared left-handedness frequencies between monozygotic and dizygotic twins and assessed concordance for hand preference.

Main Results:

• A higher incidence of left-handedness was observed in twins compared to singletons.
• No significant difference in left-handedness frequency was found between monozygotic and dizygotic twins.
• Identical twins exhibited higher concordance for hand preference than fraternal twins, suggesting a genetic component.

Conclusions:

• The findings support a genetic model for handedness, particularly evident in the higher concordance rates among identical twins.
• The increased prevalence of left-handedness in twins warrants further investigation into potential prenatal or perinatal environmental factors.
• This meta-analysis provides robust evidence contributing to the understanding of handedness etiology.