If you’re wondering whether your baby will grow up to be right- or left-handed, the answer could be in the way infants are fed. New research has linked hand preference to whether or not babies are breastfed or bottle-fed.
The study, conducted by researchers at the University of Washington, found that bottle-fed babies are more likely to be left-handed. The study looked at data from about 60,000 infant and mom pairs and found that left-handedness was lower among breastfed babies than bottle-fed babies.
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“We think breastfeeding optimizes the process the brain undergoes when solidifying handedness,” said Philippe Hujoel, the study’s author, a professor at the UW’s School of Dentistry and adjunct professor of epidemiology at the School of Public Health. “That’s important because it provides an independent line of evidence that breastfeeding may need to last six to nine months.”
It’s important to note that the study does not show that breastfeeding leads to right-handedness, only that breastfeeding might optimize a process called brain lateralization, which determines when the region of the brain that controls handedness localizes to one side of the brain. Hand preference is set early in fetal life and is at least partially determined by genetics, Hujoel explained.