More left-handed men born during winter
New research suggests that a hormonal mechanism may be responsible for more left-handed men being born during the months of November, December and January.
Scientists at the Faculty of Psychology, University of Vienna analyzed data of nearly 13,000 adults from Austria and Germany. They used two independent samples, which allowed them to test whether the findings could be replicated within the same study.
The researchers determined that 7.5 percent of women and 8.8 percent of men are left-handed, but were surprised to see that the difference was caused by more left-handed men being born during November, December and January.
The findings, published in the journal Cortex, suggest that the reason for more left-handed men being born during certain months may be the amount of daylight during those months. Researchers said that amount of daylight may be linked to testosterone levels, which could make a seasonality effect plausible. They added, however, that evidence is indirect and inconsistent and that more studies are needed in order to determine a clear connection.