Handedness is not the only asymmetry in our bodies. Whether hugging, kissing or eavesdropping, we usually prefer one side of the body to the other. And animals do the same.
It used to be 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 the dexterity of our hands.
Sebastian Ocklenburg from the Ruhr University Bochum researches handedness and cognitive asymmetries in humans and animals. On the occasion of the international left-handed day, we interviewed the biopsychologist about cats, kisses and Leonardo da Vinci.
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. If you turn your head to the other side than the one you usually use for kissing, it feels very strange. Try it out!
Vote. I always turn my head to the right. My friend fortunately also, otherwise we would probably have problems. Are there other examples?
The feet. With soccer players, you can always see that most of them clearly prefer one foot when they shoot at the goal. There are a few, for example Lionel Messi, who can shoot equally well with both feet.
These players then 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 all of them use only one eye to do so. If they listen with the ear at the door also almost all prefer to use a particular ear – even if they have equal hearing in both ears.
Like 65 percent of the population, Prince William and Duchess Kate prefer the head tilt to the right side when kissing.
If these preferences are related to handedness, then left-handed people are also left-footed people?
Partly, partly. The motor asymmetries are strongly connected. If I am left-handed, I am usually left-footed and prefer to kiss with the left side of my head turned in. But this is independent from sensory asymmetries in hearing or seeing. They are interrelated, but independent of handedness.
Are there such asymmetries also with animals?
Yes, this is also the case with animals. For example, we have just submitted a study that deals with the ‘pottiness’ of cats and dogs. In contrast to humans, however, the distribution here is more 50 to 50, i.e. there are about the same number of left- and right-pawed animals.
How is ‘pawiness’ tested in animals?
Most of the time, the animal is given a task that requires it to reach for food. Anyone can play this at home with his own pet. Take an empty toilet paper roll and tape up one side and fill in some lining. But the tube has to be so narrow that the animal can’t get in with its snout, but has to reach for the food with its paw.
If you hold out the roll to your pet ten times and it uses the same paw ten times to reach the food, then you know that the animal is right- or left-footed.
Cats and dogs are among the animals that each prefer a paw.
Why do these preferences exist at all? Why are some people left-handed and others right-handed?
Handedness has very little to do with our hands per se, it’s the brain that matters. The human brain is divided into two halves, the right and the left side. Whether you’re left- or right-handed depends on which of the brain hemispheres is particularly good at performing fine motor tasks.
With right-handers it is the left hemisphere of the brain, with left-handers it is the right hemisphere. This side shift is because the neural pathways cross in the spinal cord. The left side of the brain always controls the right side of the body and vice versa.
Do the brains of right-handed and left-handed people function differently as a result?? Are left-handed people actually smarter or more creative than right-handed people??
No, I’m sorry to disappoint you there. In the 70’s there were a few small, poorly controlled studies that came to this conclusion. But since then this has been disproved several times. Left-handed people are neither more intelligent nor more creative than right-handed people. Unfortunately, however, this result is much less interesting, which is why the studies from the 70s are still referred to.
And to a whole host of famous people who were supposedly all left-handed.
Yes, for example Leonardo da Vinci, who is said to have been 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 in which da Vinci paints with his left hand. But the fact that he wears his right arm in a bandage on this portrait and paints with his right hand on other portraits is concealed.
Professor Sebastian Ocklenburg teaches biopsychology at the Ruhr University Bochum. He specializes in hemispheric asymmetries in humans and other animals, handedness, and cognitive genetics, among other things.
The interview was conducted by Sophia Wagner.
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Paul McCartney
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