Why Most Parents Carry Babies on the Left Hip

dad holding baby on left side
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Chances are that when you carry your baby you prefer holding him or her on one side of your body. It's likely that that side is the left side, and research explains why.

According to a study in Development Science, up to 85 percent of women prefer to hold their babies on the left side of their bodies, cradling their little ones on their left hips. Even if the mother happened to be left-handed, statistically, she still held her baby on the left side.

Theories about why mothers and other caregivers prefer to hold their babies on the left side have ranged through the years. Some assumed that it was as simple as the fact that the majority of people are right-handed, so it would only make sense to carry babies on the left side, leaving their right hand open to carry on important tasks. And while that may be true to some extent, science supports the theory that there may be a little more to it than that.

A Theory for Left-Sided Biases

In scientific terms, the phrase for caregivers carrying their babies on the left hip is called "left-sided bias." That's just a fancy way to say that the parent prefers the left side. A study in Nature explained that the left-sided bias in mammals is actually because of the way the brain develops.

The study explored which side primate offspring approach their mothers from in nature, from normal interactions to situations when they are scared and hovering near their mothers.

Overwhelmingly, the researchers found that offspring approached their mothers on the left side.

When you apply this to humans, who are also primates, the same behavior is also often observed.

The Science Behind It

As it turns out, the reason for the left-side bias is that the right side of the brain gets signals from the left side of our bodies.

The right side of the brain is the side that is responsible for interpreting cues from our environment about how to navigate social situations, how to build relationships and bond, and how to recognize when our babies might be in distress, for example. The right side of the brain is also the "bonding" side of the brain, responsible for many of the paternal feelings of love we have for our kids.

Because our right side is only able to do its job by getting information from our left eye, it makes sense, then, that we would naturally be more likely to keep our babies on the left side. There are also different benefits of keeping the baby on the left, such as the fact that the baby is closer to mom's heartbeat, which may help regulate temperature and keep the baby calm. Overall, it makes sense to keep babies on the left. In short, it makes our job as a parent easier.

Of course, that doesn't mean all parents keep their babies and kids on the left side, but it's an interesting theory to consider.

Sources:

Bourne, V.J. & Brenda, K.  Brain lateralization and cradling bias. When left means right: an explanation of the left cradling bias in terms of right hemisphere specializations. Developmental Science 7,1:19–24. 2004.

Karenina, K., et al. Lateralization of mother–infant interactions in a diverse range of mammal speciesNature Ecology & Evolution. 2017.

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