Why do most mothers hold babies on their left sides? Science says it promotes maternal bonding and helps with social processing for the baby.
Favoring one side over the other when holding your child is common. Research indicates that 70 to 85% of women and girls show a preference to hold infants and/or dolls to the left sides of their bodies. Additionally, preschool girls have also demonstrated the bias toward the left.
And while now that you’re thinking about it, you realize you probably favor your left side, but never knew why. Scientists for years have wondered the same thing, and various theories have cropped up through the years as to why–including ones related to a mother’s hand-use preference, child placement in relation to a mother’s heart, left-breast sensitivity and others.
A recent study published in Nature Ecology & Evolution now shows the reasoning to be more related to complex brain recognition, and innately wired. Turns out that when a baby is held on the left side of her body, the right side of her brain, which is responsible for language and the interpretation of emotional signals and cues lights up, activating her brain to process the touch and more finely bond with her baby.
This positioning on the left side and interpretation of touch and personal cues of the right side of the brain is called lateralisation, and it may mean that holding your child on your left side allows you to fully monitor the needs and cues of your child by purposely and subconsciously guiding sensory information to the right side of your brain.
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What researchers find interesting is that humans are not the only creatures on the planet that lateralisation is unique to–in fact, many mammals have left-side bias as well. Researchers examined various mammalian species, including reindeer, walruses, kangaroos and whales, and found that these species’ mothers also kept their babies to the left. More, when babies were given the option of sides to stay on with regard to their mothers, they also chose to stay to the lefts of their mothers. This observation gives researchers reason to believe that this may be an innate and evolved ability of mammalian mothers.
And far be it from us to make an implications about mothers and fathers, but researchers did find that the left-side bias is not matched in the male gender. They found that fathers still tended to hold their children on their left sides (though not as consistently) but that men who were not fathers had absolutely no bias toward either side.
Photo Credit:Valentina Yachichurova/flickr