As a left handed person and psychology graduate, this is a post I’ve wanted to write for a while because there’s actually a lot I don’t know about how being left handed affects the brain. Me and my dad are both left handed, but at opposite ends of the spectrum – he writes with his left hand (but that’s about it) whereas for me, even picking up something with my right hand feels weird and requires conscious effort. So if being left handed is genetic, why this difference?
Another reason I wanted to find out more information is that I actually quite like being left handed, despite the obvious irritation of everything from scissors to tin openers to computer keyboards being biased to the right-hander (and don’t even get me started on trying to write in anything other than biro). And there might even be some benefits to being a leftie, with theories that it’s linked to creativity, sports, or being good at playing an instrument. Here’s what we know:
About 10% of the population are left handed, although as you can see from the comparison between me and my dad, the degree of left handedness can vary. Men are also more likely to be left handed than women (e.g. Papadatou-Pastou et al, 2008). Scientists still aren’t sure of the exact cause of being left handed, although they are sure there is some genetic component – studies have shown that you are more likely to be left handed if one of your parents is (e.g. McManus & Brydon, 1991b).
Handedness has also been thought to relate closely to language functions in the brain. As you may remember if you read this post, in most people, language functions are lateralised to the left hemisphere (see below). As each hemisphere controls the opposite side of the body, there is thought to be a relationship between hand dominance and language, with right- handers having right side preference due to language functions located in the dominant left hemisphere.
However, in left-handers this relationship is not so clean cut – only about 30% are thought to have their language dominance in their right hemisphere. I actually participated in an fMRI experiment at uni which tested my handedness and language location in the brain, which found that even though I’m left handed, my language functions are normally lateralised in the left hemisphere. So opposite language lateralisation in the brain can’t be the only reason people are left handed, the process is way more complex, and still not something science fully understands.
Several studies have identified a link between being left handed and creativity. For example, Newland (1981) asked almost 100 right handed, and 100 left handed people to complete a test on creative thinking. The results showed that left handed participants scored more highly on all 4 sub-tests, suggesting they have greater creativity. Another study by Coren (1995) found that left-handers have better divergent thinking skills than right-handers – in other words, they are better at exploratory thinking to find solutions and create ideas. Being better at divergent thinking could explain why left handed people are more creative, and thought to be better at logic.
There is a lot of anecdotal evidence which suggests left-handers are smarter, or better at politics e.g. Mensa reported that 20% of its members are left handed (which is double what you’d expect, at 10% of the population). However, unfortunately, I can’t seem to find any actual experiments comparing IQ that back this up! Studies have shown however that professional orchestras have a higher proportion of left-handers, and that during school, a high proportion of children who excel at maths are left-handed.
Annoyingly, there don’t seem to be answers to all my questions about left handedness, and there is still a way to go to establish the genetic basis and to understand how the brain is organised in left handed individuals. Regardless, I hope you found this post interesting and let me know in the comments if there’s anything else you’d like me to feature on this blog.