Why do people like to hold things with their right hand but hold babies with their left hand?

Close your eyes and imagine that you are holding a 40-centimeter-high vase worth 200,000 yuan. This is a magpie-peony famille rose vase from the Qing Dynasty. Please imagine its exquisite painting skills and moist glaze while actually holding the vase with one hand. Then open your eyes and see if you are using your left hand or your right hand.

Next, close your eyes and imagine holding a 2-month-old baby. He is looking at you with eyes wide open, and you are holding his head and body with one hand. Which hand do you use this time?

In reality, most people would choose to hold a vase with their right hand and a baby with their left hand . Both of these objects are precious and fragile, so why do people unconsciously hold them with different hands?

Magpie peony famille rose vase and baby from the Jiaqing period of the Qing Dynasty | bid.yahoo / Tuchong Creative

I like to use my right hand to hold anything.

The only exception is holding a baby?

Ninety percent of people are right-handed. When holding an object with one hand, it sounds natural to choose the right hand, which is stronger and more flexible.

But when it comes to holding a baby, about 69% of people choose to use their left hand. This preference can be seen in various cultures and historical periods , such as prehistoric mother and child statues, current tutorials on how to hold a baby, photos of Princess Kate of the United Kingdom after giving birth, and the daily posture of the author of this article's reference [1]. Not only that, when holding a doll or imagining holding a baby, most people still choose the left hand. There are even studies that observe that chimpanzees and gorillas prefer to hold their infants on the left side.

Top left: Statue of mother and child in Mexico before the Commonwealth of Nations; Top right: Tutorial on holding a baby; Bottom left: Princess Kate holding the little prince standing at the door of the hospital after giving birth; Bottom right: Professor Audrey van der Meer, who studies the left-hand preference for holding babies | metmuseum / wikihow / Kensington Palace / Elin Iversen, NTNU

However, people's preference for holding the left side is only so obvious when holding a baby under 12 weeks old. As the child grows older and gains weight, many people will switch to holding with the more powerful right hand.

A study asked 300 college students to repeat the test similar to the one at the beginning of the article. The result was that when they imagined holding an expensive vase, 81% of them chose to hold it with their right hand; when they imagined holding an old shoe box that was worthless, 64% of them still chose their right hand; only when they imagined holding a baby, most people (66%) chose to use their left hand.

Among the various combinations of choices, the choice of object on the right and baby on the left was the most common (47.2%) , especially among right-handed people and women . The opposite choice, that is, object on the left and baby on the right, was very rare (5%).

Most subsequent studies have also yielded similar results, proving that "holding babies in the left hand and holding objects in the right hand" is a common phenomenon. In addition to considering which hand is more useful, there must be other reasons that drive people to hold babies on the left side.

Left holding baby

Because the heart is located on the left?

The first attempt to explain the preference for left-hand holding was the heartbeat hypothesis proposed by American psychologist Lee Salk in 1960.

Salk believes that most people hold their babies on their left side because the human heart is located slightly to the left of the chest. When babies are held on their left side, they are more likely to hear their parents' heartbeats and thus calm down, which makes it easier for parents to comfort their babies, so they prefer the left side.

However, the sound of the heartbeat is not only audible on the left side. Of the two heartbeats, one is heard most clearly on the left chest and the other is loudest in the middle of the chest. In addition, researchers have found that mothers with congenital left-right organ reversal (heart on the right) are also accustomed to holding their babies on the left side.

Therefore, the heartbeat hypothesis cannot fully explain why people prefer to hold their babies on their left side.

Hold on the left

Is it easier to spot when your baby is uncomfortable?

After that, two mainstream hypotheses emerged. One of them is that the right cerebral hemisphere dominates emotional processing, and parents hold their babies on the left side, so the information received by the left side of the body is projected to the right hemisphere, which is more conducive to emotional communication.

According to this hypothesis, people subconsciously hold their babies on their left side, mainly to make the babies appear in their left visual field. Since the optic nerves that transmit visual information cross left and right, the image of the left visual field will be projected to the right cerebral hemisphere. Of the two cerebral hemispheres, the right side has an advantage in emotional processing , especially in recognizing negative emotions, such as recognizing angry, scared, sad or crying baby faces.

Therefore, when the baby is held in the left hand position, parents can detect the child's discomfort with less effort.

The blue on the left side of the visual field is reflected in the inner side of the left eye and the outer side of the right eye. Since the information received by the outer side of both eyes directly enters the ipsilateral brain, the information received by the inner side of both eyes crosses and enters the contralateral brain. The blue information on the left side is transmitted to the right hemisphere | getbodysmart

In studies comparing the two visual fields, subjects were more accurate in identifying the emotions in baby faces when the images appeared in the left visual field than in the right visual field, especially among right-handed people, further supporting the above hypothesis.

Moreover, most studies support that the left side of a person's face is usually more expressive than the right side , and the emotions expressed are more easily recognized by others. When holding a baby on the left side, parents are more likely to see the baby's left face, and babies also see the left side of their parents more often. This also helps parents recognize their children's emotions and may help children develop the ability to recognize facial emotions.

In addition to visual information, there may also be differences when auditory signals are input from the left and right sides. Some studies have shown that the left ear is more capable of distinguishing emotions in speech . This may be because after the sound is transmitted to the left ear, the information is mainly transmitted to the right cerebral hemisphere for processing, and this side also has an advantage in processing the emotions of sound.

Explaining the left-hug preference by the right hemisphere dominating emotional processing is one of the most popular hypotheses at present, but it has also been questioned by some studies and no definite and consistent detailed conclusions have been reached yet.

Holding your baby on his left side may help with emotional communication | giphy

Hold with left hand

Maybe it's just to free up my right hand for better use.

The third hypothesis is the most direct, proposing a preference for left-handed holding only because 90% of people are right-handed, and left-handed holding can free up the flexible and powerful right hand to do other things. After all, taking care of a child is not just about holding the baby, but also about feeding and caring for the baby , as well as feeding and taking care of yourself.

James E. Huheey was the first to explain infant holding preference from the perspective of handedness in 1977. A recent study analyzing infant holding preferences of nearly 15,000 people showed that 74% of right-handed people preferred to hold their babies on the left side, while only 61% of left-handed people preferred to hold their babies on the left side.

Another study set up a more complex task, requiring subjects to put a pacifier in the mouth of a doll while holding it. According to their usual hand habits, 765 subjects were divided into right-handed, ambidextrous (both left and right hands can be used flexibly) and left-handed. The proportions of these three groups holding the doll in their left arm were 79.1%, 66.1% and 39.3% respectively. In other words, the more people are used to using their right hand, the more likely they are to use their left hand when holding the doll . The researchers believe that this result shows that handedness is the main determinant of the preference for holding babies.

Seeing the above data, some people may ask, since they have to choose their non-dominant hand to hold the baby, why do right-handed people hold the baby with their left hand in nearly 80% of cases, while left-handed people only choose their right hand in about 60% of cases? Researchers believe that this may be due to the influence of the environment. Most public facilities, equipment and tools are designed for right-handed people, such as keyboards, musical instruments and cameras, so left-handed people are forced to learn to use their right hand more flexibly.

In addition, the fact that women prefer to hold babies on their left side more than men can also be partially explained by the handedness theory, because there are more left-handed men than women. In addition, men usually play with dolls less and have less experience holding babies, which may also be part of the reason.

So, the question is, when people hold their furry children with one hand, do they use the hand they hold the child or the hand they hold the object? A very preliminary small study analyzed photos of people holding dogs and found that most women held their dogs on the left side, while men had no preference.

Next time you pick up something with one hand, pay attention to which hand you subconsciously use and what you are holding. Perhaps interesting new scientific knowledge lies in your unthinking actions.

References

[1]van der Meer ALH. Handedness as a major determinant of lateral bias in human functional cradling. Infancy. 2023 Dec 15.

[2]Almerigi JB, Carbary TJ, Harris LJ. Most adults show opposite-side biases in the imagined holding of infants and objects. Brain Cogn. 2002;48(2-3):258-63.[3]Gianluca Malatesta, Daniele Marzoli, Luca Tommasi. Keep a Left Profile, Baby! The Left-Cradling Bias Is Associated with a Preference for Left-Facing Profiles of Human Babies. Symmetry. 2020;12(6):911.

[4]Packheiser J, Schmitz J, Berretz G, Papadatou-Pastou M, Ocklenburg S. Handedness and sex effects on lateral biases in human cradling: Three meta-analyses. Neurosci Biobehav Rev. 2019;104:30-42.

[5]Vauclair J. Maternal cradling bias: A marker of the nature of the mother-infant relationship. Infant Behav Dev. 2022;66:101680.

[6]Lindell A. Lateralization of the expression of facial emotion in humans. Prog Brain Res. 2018;238:249-270.

[7]Alzahrani AD, Almuhammadi MA. Left ear advantages in detecting emotional tones using dichotic listening task in an Arabic sample. Laterality. 2013;18(6):730-47.

[8]van der Meer A, Husby A. Handedness as a major determinant of functional cradling bias. Laterality. 2006;11(3):263-76.

[9]Malatesta G, Marzoli D, Rapino M, Tommasi L. The left-cradling bias and its relationship with empathy and depression. Sci Rep. 2019;9(1):6141.

[10]Abel EL. Human left-sided cradling preferences for dogs. Psychol Rep. 2010;107(1):336-8.

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Source: Guokr (ID: Guokr42)

Author: Dai Tianyi

Editor: Wang Mengru

Proofread by Xu Lailinlin

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