More left-handed men are born during the winter (10.5% of those born in winter months are left handed versus 8.2% of those born in non-winter months)

Overall, 7.5 percent of women and 8.8 percent of men were left-handed. “We were surprised to see that this imbalance was caused by more left-handed men being born specifically during November, December, and January. On a monthly average, 8.2 percent of left-handed men were born during the period February to October. During November to January, this number rose to 10.5 percent,” according to Ulrich Tran, lead author of the study.