Babies who are bottle fed are more likely to be left-handed, according to a new study from the University of Washington.
Researchers looked at 60,000 mother-baby pairs to compare breastfed infants to those who are bottle fed. The results show less left-handed babies in the breastfeeding group. The findings suggest the way baby is fed is linked to the development of complex brain functions, which ultimately decide which side baby will lean towards when developing his dominant hand.
"We think breastfeeding optimizes the process the brain undergoes when solidifying handedness," says Philippe Hujoel, the study's author. "That's important because it provides an independent line of evidence that breastfeeding may need to last six to nine months."
That said, the study can’t determine whether breastfeeding directly leads to right-handed kids. As it points out, a child’s dominant hand is set early in fetal life and is at least partially determined by genetics.
With this in mind, the research sheds light on the point when the region of the brain that controls whether someone will be right- or left-handed confines to one side of the brain. These findings suggest breastfeeding may optimize this process towards becoming right- or left-handed.