Duration of breastfeeding determines a child being a righty or lefty, researchers have found. As per the University of Washington’s study, the prevalence of left-handedness is lower among breastfed infants. The study, conducted with 62,129 mother-child pairs, indicates that infants that are breastfed for over nine months are more likely to be a righty and those bottle-fed are probably mostly lefty. This is because the region of the brain that controls handedness localises to one side of the brain. And breastfeeding optimises this process towards becoming right or left-handed, the researchers say.

Handedness, whether it is right or left, is set early in foetal life and at least partially determined by genetics, says the author of the study Philippe Hujoel, professor at the University of Washington. ‘We think breastfeeding optimises the process the brain undergoes when solidifying handedness. That is important because it provides an independent line of evidence that breastfeeding may need to last six to nine months.’

The journal Laterality: Asymmetries of Body, Brain and Cognition published these findings. The study shows that babies that are breastfed for one month had a 9 per cent lower chance of being non-right-handed, while one to six months showed a decrease of 15 per cent and more than six months had a 22 per cent lower chance of non-right-handed. Hujoel adds that the study does not imply that breastfeeding leads to right-handedness.

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