Handedness can be more interesting than you might think. Being right- or left-handed can indicate genetic variation and can be related to how you understand language. Knowing this, and to support the lefty minority worldwide, the Left Handers Club in the UK declared a day for lefties: today.
Only one out of ten people is left-handed. Handedness is not always just about writing; brushing your teeth, striking a match and throwing a ball also matter. Even for Neanderthals the 1/10 ratio might have been the case, as fossils from 500,000 years ago suggest.
What makes you a lefty?
There are different ideas on why right-handedness is nine times more common than left-handedness. Studies show that handedness is affected both by the environment in which we grow up and by our genes.
For example, identical twins (with identical genes) have a higher likelihood of having the same handedness compared to fraternal twins (with 50% overlap in genetic code). These genetic effects can already be observed in the uterus. Fetuses that suck their left thumb often turn out left-handed, and the ones that suck their right thumb become right-handed.
What is the advantage of having a preferred hand for all tasks? It gives that particular hand precision in doing a particular task, of course. But it also affects brain function. The left side of your body is controlled by the right side of your brain and vice versa; the nerves in your body cross over in the brain. So if you master a task with your left hand, the right side of your brain becomes the master of controlling that task.
Most of both lefties and righties have the language areas, which help them produce and understand language, on the left side of their brains. Only in some lefties these language areas are flipped to the right side of the brain. This has lead brain researchers to wonder whether the genes for language and handedness overlap.
Advantage or disadvantage?
Many cultures see left-handedness as evil or weak. That’s why kids at school used to be – and sometimes still are – forced to write with their right hand. The science, however, paints a different picture. Although there are studies that linked left-handedness to schizophrenia and depression, there is also evidence showing that lefties are generally smarter and more creative.
You can imagine that there is still is quite some debate in the scientific world about these findings. What we do know, is that being a lefty – a minority – gives you a clear advantage in sports like boxing or fencing. Happy Left Handers Day!
Participate in research on the genetics of left-handedness at the Max Planck Institute in Nijmegen
Article on left-handedness in twins
Article on asymmetry of language areas in the brain
Website Left Handers Day
This blog was written by Tulya Kavaklioglu and can also be read in Dutch. Tulya is a PhD student at the Max Planck Institute for Psycholingustics and works on brain and behavioral asymmetries. She herself is right-handed but makes attempts of painting or drawing with her left hand every now and then, fails each time and calls it ‘modern art’.
Edited and translated by Lieneke.