Home > iDEAL Focus > Features > Scientists don’t know cause of left-handedness
Scientists don’t know cause of left-handedness
By Tan Weiyun

THERE’S no doubt the world is designed for right-handed people. As the minority — about one in 10 — left-handers haven’t had a fair shake over the centuries and have historically been regarded as inferior to the right-handed.

But lefties can stand up with their heads and, of course, hands high as August 13 is the International Left-handers Day.

Left-handers have often faced discrimination in a world designed for right-handers. As well as inconvenience, left-handed people have been considered unlucky, or worse, evil, by the right-handed majority.

Discrimination toward left-handed people is built directly into the language. The word “left” in English comes from the Anglo-Saxon word “lyft,” which means weak or broken.

In many Islamic countries, people are not allowed to eat with their left hand because it’s considered “unclean” since it is used for cleaning the body after defecation.

International Left-handers Day is designed to increase public awareness about the advantages and disadvantages of being left-handed. According to statistics, lefties are estimated to comprise 10 to 12 percent of the world’s population. Another survey shows that two-thirds of lefties are males.

Being left-handed can be troublesome for many.

“My father would slap me on the hand each time I used my left hand to write or use chopsticks when I was small,” says lefty Huang Mengli, a 28-year-old flight attendant who now uses both hands.

Like Huang, many Chinese lefties were forced to switch from the left to the right by their parents. Due to the importance of stroke order, developed by and for right-handed people, children are required to use their right hands to write legible Chinese characters.

If not, they might be considered less desirable and even abnormal. When they grow up, they become “recessive lefties.”

The left-handed Yu Yue, 32, is luckier than Huang because her father is also a lefty and she was encouraged to use both hands.

“It was a little difficult learning to write,” she says. But now she can write skillfully with both hands.

Of course, being a lefty leads to other considerations. When eating with others, sitting on the left side of the table is advised “otherwise our chopsticks fight,” Yu says, smiling.

Left-handers have long known that most products are designed for the right-handed, but Yu says she is happy to see there are more things tailor-made for southpaws these days including watches, rulers, scissors, computer mouses and some musical instruments.

She works in administration at Hengyuanxiang, a cashmere wool producer and supplier based in Shanghai, and is a member of the company’s left-handers club, which caught the media’s attention several years ago.

In 2007, the company advertised some job vacancies and one of the requirements was that applicants must be lefties, which earned applause from the lefty group but also criticism that it was discriminatory toward right-handed people.

Financier Yao Bo, 28, is a proud lefty and is quick to highlight studies that suggest lefties are more creative.

“There is significant scientific research showing that lefties have a broader imagination, stronger memories for details, better sense of space and a more unique creativity,” he says.

Yao established Zuo Li Shou Zuo Pie Zi, a club for left-handers in 2009 in Hangzhou, capital city of Zhejiang Province. The club now has more than 5,000 members from around the country including Beijing, Shanghai, Tianjin, Shenzhen (Guangdong Province) and Changsha (Hunan Province).

Throughout history, many great politicians, artists, entrepreneurs, philosophers, athletes and writers have been lefties. Leonardo da Vinci, Michelangelo, Isaac Newton, Marie Curie, Gandhi and Charles Darwin were all southpaws. John McEnroe, Brad Pitt, Bill Gates, Julia Roberts, Paul McCartney, Celine Dion and Rafael Nadal are also lefties.

Seven American presidents were or are left-handed, including Barack Obama and Bill Clinton. Former Chinese Premier Wen Jiabao uses his left hand to play basketball and ping pong.

In sports, lefties are often difficult to deal with. Left-handed pitchers in baseball make things difficult for batters because they can put different spins on the ball. In tennis, left-handed players also cause trouble as they create angles others are not used to dealing with.

The human brain has two hemispheres and each is responsible for different tasks. The right hemisphere controls the left side of the body while the left generally controls the right side. The left hemisphere can process abstract, logical information such as languages and numbers for analysis and judgment. The right side processes figurative information including sounds, images, smells and more to do creative things.

Scientists still don’t know why some people are left-handed although there is no shortage of theories, says Tu Rongsheng, a professor from the School of Psychology and Cognitive Science at East China Normal University.

One popular theory is that hand orientation might develop before birth, most commonly determined by observing a fetus and which hand it predominantly holds close to the mouth.

Another explanation is that exposure to higher rates of testosterone before birth can lead to a left-handed child. This is the Geschwind theory. It’s named after Norman Geschwind, the neurologist who proposed it.

It suggests the fetal brain’s development is shaped by variations in testosterone levels during pregnancy. Testosterone suppresses the growth of the left cerebral hemisphere, meaning more neurons migrate to the right hemisphere, which controls the left side of the body.

Research by Australian scientists suggest malnutrition, toxins and pressure while in the uterus may cause left-handedness. Researchers from Graylands Hospital in Perth examined the maternal health records of more than 1,000 high school students’ mothers in Belgrade and found that women who smoked often during pregnancy were more likely to give birth to lefty babies than those who didn’t.

In addition, left-handed babies were discovered to have lower Apgar scores, a simple method to assess the health of newborn children immediately after birth in appearance, pulse, grimace, activity and respiration.

“However, the real cause of left-handedness is still a mystery,” Tu says. “But it is important to develop a balance between the two hemispheres of the brain.”

Most lefties are proud of being left-handed since it sets them apart from others and can be a friendly conversation starter.

Yao is no different. He says he often comes up with new ideas, thinks wider and has more accurate intuition in many things than the right-handed.

“To tell you a secret, I can correctly guess 80 percent of the top five stocks with gains everyday,” he says.

Leave a comment
Customer Service: (86-21) 52920164