Handedness in the NAS/NRC twin study

Area of Science:

• Human genetics
• Neuroscience
• Behavioral science

Background:

• Hand preference, or handedness, is a complex trait.
• Twin studies are crucial for understanding the interplay of genetic and environmental factors in human traits.

Purpose of the Study:

• To investigate the genetic and environmental influences on handedness.
• To determine if zygosity (identical vs. fraternal twins) affects handedness concordance.

Main Methods:

• A large-scale survey of hand preference was administered to 973 dizygotic (fraternal) and 1158 monozygotic (identical) male twin pairs.
• Laterality was assessed based on both direction and consistency of handedness.

Main Results:

• Significant pairwise concordance for handedness was observed in the total twin group.
• Concordance was significant for both consistency and directional factors of handedness.
• No significant differences in concordance were found between dizygotic and monozygotic twin pairs.

Conclusions:

• While handedness shows familial resemblance, this study indicates that zygosity does not significantly differentiate the degree of this resemblance.
• The findings suggest that genetic factors alone may not fully explain the observed patterns of handedness, highlighting potential environmental influences.