Growing up in the southern Kazakh village of Temirlan, Dina got used to a series of daily corrections.

She'd pick up a fork with her left hand. Someone would move it to her right. At school she'd work on a lesson holding a pencil in her left hand. Her teachers, worried, would urge her to switch to the "normal" side.

"I was also trying to write with my right hand, but it didn't work," she says. "I was the only one in my school who was left-handed. So it was a hard time because everyone was calling me a lefty. 'Solaqay' -- that's in Kazakh. It literally means a person who writes with their left hand, but at that time it did have some negative connotations."

Dina is one of an estimated 900 million people worldwide who are "sinistral," or predisposed to using their left hand, rather than their right, for writing and most manual functions.

Natural-born left-handers are believed to make up as much as 13 percent of the human population.

But as the world marks International Left-Handers Day on August 13, some say the real number is in fact far higher, and that many lefties have been forced to switch hands because of unfounded fears that left-handers were somehow disabled, odd, or simply unlucky.

Language Bias

The stigma was especially widespread in the former Soviet Union, where pedagogical trends stressed qualities like conformity, discipline, and uniform penmanship.

"It was simply a lack of knowledge that played a role," says Gennady Chichkanov, a Moscow-based clinical psychologist. "It's simpler when a child writes with his right hand. So it's easier to put something in his right hand and say, 'Write.' That's how it was in the Soviet Union."

But some say everything from language to religion has added to the longstanding cultural preference for right over left.

In many languages, of course, the word for "right" is not only used to designate a direction but to signify correctness, truthfulness. By contrast, the word "left" in languages such as Russian is often used to connote something fake or of poor quality.

By extension, it is traditionally the right arm that is used in hand-on-heart pledges, military salutes, and making the sign of the cross. In Islam, standard etiquette dictates that a person must enter a house or mosque right foot first, but use their left foot to enter a lavatory.

With such traditions in mind it might seem reasonable to encourage left-handed children to switch to the right.

Science, however, provides its own compelling argument for leaving left-handers alone. The brain, after all, is divided into two hemispheres, each with its own distinct function and each directing the motor functions of the body's opposite side.

In short, the left side of the brain – the hemisphere responsible for language, math, and rational thought – controls the right side of the body. The right side of the brain – more commonly associated with creative, emotional impulses – controls the body's left side.

Accomplished Lefties

Forcing a child to switch the hand he or she writes with can cause considerable chaos as the brain struggles to establish new communication paths with the body.

Adding to the confusion is the fact that people also have a dominant eye and a dominant foot in addition to a dominant hand. According to Chichkanov, tampering with the formula can have devastating consequences on a child's ability to learn.

"If a lefty writes with his right hand it's bad, because we're changing the hand but not the leading eye or the leading foot," he says. "So a child who has had his hand changed is more prone to distraction; he absorbs information more poorly. As a result, he can become more irritable. That kind of process simply doesn't improve his chances of success at school."

Any lingering doubts about left-handers is easily dispelled by a look at some of the world's most accomplished people. Famous lefties include Leonardo da Vinci, Albert Einstein, Aleksandr Pushkin, Paul McCartney, Barack Obama, and Martina Navratilova.

There is even speculation that Russian President Vladimir Putin is a closet lefty. Although the Russian leader writes with his right hand, he also wears his watch on his right hand -- suggesting it is in fact his dormant side -- and he has been seen making the sign of the cross with his left.