In the past, scientists believed that a single gene was responsible for our handedness. Today we know that in addition to many different genes, the environment also has an influence on our dexterity.

Sebastian Ocklenburg from the Ruhr University Bochum investigates the handedness and cognitive asymmetries in humans and animals. On International Lefthanders Day we interviewed the biopsychologist about cats, kisses and Leonardo da Vinci.

10 left-handed musicians from Hendrix to Barenboim Rebel to the core Nirvana idol Kurt Cobain mostly played with his left hand — here on an inverted right-handed guitar. Once in a while he would pound Dave Grohl's right-handed drum kit. Cobain was a right-hander — and why he played guitar with the left is a mystery. The customized 1959 Martin D-18E guitar he played throughout the MTV Unplugged performance is being auctioned.

10 left-handed musicians from Hendrix to Barenboim The best left-handed guitarist Although his dad tried get him to switch, Jimi Hendrix strummed his guitar with his left hand. He was able to play the other way around, though — and ate and wrote with his right hand. He famously played a right-handed Fender Stratocaster flipped over and restrung. For Left-Handers' Day, DW presents other musicians who've made it big — despite being left-handed, or precisely because of it.

10 left-handed musicians from Hendrix to Barenboim Lord of heavy metal Black Sabbath guitarist Tony Iommi (left) gave heavy metal its riffs. Iommi always played left-handed, which is almost a miracle: He lost his ring and middle finger tips at the age of 17 in an industrial accident. He could have switched hands, but "decided to make do with what I had, and I made some plastic fingertips for myself. I just persevered with it," he told "Guitar World" in 2008.

10 left-handed musicians from Hendrix to Barenboim Sir Lefty Sir Paul McCartney is a virtuoso on almost any instrument. He plays most of them with his left hand — including his legendary Höfner 500/1 bass. One exception: He plays a right-handed drum kit. After the Beatles dissolved in 1970, McCartney continued solo and with his band Wings.

10 left-handed musicians from Hendrix to Barenboim The other lefty Beatle Ringo Starr is a lefty too, but plays his drums like a righty. Any drum set can easily be rearranged for left-handed play, simply by mirroring the arrangement of all the pieces. Starr's left-handed activities limited themselves, however, to off-stage.

10 left-handed musicians from Hendrix to Barenboim Drum legend and pop star Phil Collins plays drums, and everything else, left-handed. That means he has the hi-hat cymbal on his right — and played with his left hand — and kicks the bass with his left foot. The musician from London became famous with progressive rock band Genesis. When he was younger, the Beatles were among his idols: He saw lefties play from early on.

10 left-handed musicians from Hendrix to Barenboim Drums, tattoos, punk Blink-182 have done a lot to boost punk rock's image. Move over Sex Pistols, here comes the pop punk of the 90s. Travis Barker is the tattooed, flamboyant drummer, and he's a southpaw. One could say he's a non-conformist through and through — except that he plays a right-handed drum set.

10 left-handed musicians from Hendrix to Barenboim An inventive southpaw Elizabeth Cotten, an African-American blues singer, played in an unusual way: She simply took a right-handed guitar and turned it around — without reversing the strings. She is one of the few guitarists to have played the bass strings at the bottom with her fingers and stroke the melody with her thumb. Playing this way is therefore called "cotten picking."

10 left-handed musicians from Hendrix to Barenboim Comedy and music Charlie Chaplin fled London's poverty early and emigrated to the States. There he reached fame with his short movies, including "The Vagabond" in 1916. In it, he plays the violin with his left hand. Privately he also played violin and cello quite well, always bowing with his left. "Every spare moment away from the studio is devoted to this instrument," read a press release from 1917.

10 left-handed musicians from Hendrix to Barenboim Conductor with a cause Born in Buenos Aires, Daniel Barenboim learned piano from the masters of his day and is one of the world's most respected conductors. He is also founder of the West-Eastern Divan Orchestra, the only joint Israeli-Palestinian orchestra. Since 1992 he has been the director of the Berlin State Opera, where the left-hander picks up the baton with his right hand. Author: Christoph Trost



DW: About 85 to 90 percent of all people are right-handed. Does this preference for the right side also apply to other body parts or activities?

Sebastian Ocklenburg: Yes, there are many such asymmetries - even if the right side is not always preferred. A nice example is kissing. When kissing, everyone has to turn their head to one side. When you turn your head to the other side than the one you usually use for kissing, it feels very strange. Give it a try!

That's right. I always turn my head to the right. Luckily my boyfriend does, too, or we'd probably be in trouble. Are there other examples?

The feet. With football players, you can always see that most people clearly prefer a foot when they shoot at the goal. There are a few people, for example Lionel Messi, who can shoot equally well with both feet.

These players often have a big advantage. Beyond these motor asymmetries, there are also sensory asymmetries. For example, when people look through a telescope with their eyes, almost everyone uses just one particular eye. When people use their ears to listen at the door, almost everyone prefers to use one particular ear - even if they have the same hearing ability in both ears.

Prince William and Duchess Catherine like to turn their head to the right side - like 65 percent of all humans.

Are these preferences related to handedness - are left-handed people also left-footed?

Partly. The motor asymmetries are strongly related. If I am left-handed, I am usually also left-footed and prefer to kiss with the left side of my head turned in. However, this is independent of the sensory asymmetries in hearing or seeing. Although they are interrelated, they are independent of handedness.

Do we see the same asymmetries in animals?

Yes, it's also true of animals. For example, we have just submitted a study on the "laziness" of cats and dogs. In contrast to humans, however, the distribution here is more 50 to 50, so there are about the same number of left- and right-handed animals.

How do you test the 'pawedness' on animals?

Usually the animal is given a task in which it has to reach for food. Everyone can replay this at home with their own pet. Take an empty toilet roll, cover one side and put some food inside. The tube must be narrow enough that the animal cannot fit it's snout inside, but has to grab the food with its paw.

If you give your pet the roll ten times and it uses the same paw ten times to get the food, then you know that the animal is right- or left-pawed.

Cats and dogs prefer to use one specific paw.

Why do these preferences even exist? Why are some people left-handed and others right-handed?

The handedness has very little to do with our hands - the brain is decisive. In humans, it is divided into two halves, the right and the left side. Whether you are left-handed or right-handed depends on which half of the brain is particularly good at performing fine motor skills.

In right-handed people, that's the left side of the brain, in left-handed people, the right side. This lateral displacement is due to the nerve tracts crossing in the spinal cord. The left side of the brain always controls the right side of the body and vice versa.

Does this make the brains of right-handed and left-handed people function differently? Are left-handed people really smarter or more creative than right-handed people?

No, I'm afraid I have to disappoint you. In the 1970s there were a few small, poorly controlled studies that came to this conclusion. Since then, however, this has been refuted several times. Left-handed people are neither smarter nor more creative than right-handed people. Unfortunately, however, this result is much less interesting, which is why many people still refer to the studies from the 1970s.

And to a whole series of famous personalities who were allegedly all left-handed.

Yes, for example Leonardo da Vinci, who was also supposed to be left-handed. But if you look at the scientific literature on the subject, it becomes clear that this statement is based on a single portrait, on which da Vinci paints with his left hand. That he wears the right arm in a bandage on this portrait and paints with the right hand on other portraits is concealed.