Around 10% of people are left-handed, and we still don’t really know why.
In fact, humans are the only species on the planet that show handedness.
For a long time it was assumed that being left-handed was some kind of reflection of a deep disturbance in childhood.
Thankfully, we know better now — but not much better.
While the assumption has always been that handedness is genetic, the evidence is thin.
One thing we can say about righties and lefties, though, is that the differences can extend deep into the mind and brain.
1. The right-hand bias
Lefties live in a world of discrimination.
Everything is set up for righties.
That extends to the very concept of right and left in the brain.
Right is, after all, right and left is, well, it might as well be called wrong.
When tested, people are found to associate things on their right-hand-side with being good and things on their left with being…not quite right.
Tie a righties’ arm behind her back, though, and she soon changes her tune.
2. The leftie advantage in sports
Being a leftie is a decent advantage in sports — but only some sports.
Usually it’s the sports which involve less cooperation where being a leftie is advantage.
Baseball, boxing, hockey, fencing and table tennis are all sports where lefties are massively over-represented at the highest level.
In baseball, for example, over 50% of the best players are lefties.
When people have to work together in a sport — like football — then there’s much less advantage in being a leftie.
3. Right-handed, left-brained
Around 95% of people are left-brained.
Remember that the brain is cross-wired to the body.
So the left-hand-side of the brain controls the right-hand-side of the body.
Left-brained people also have their speech and language centres in the left-hand-side of their brains.
Not all lefties are wired the opposite way, though, with their language and speech centres in the right-hand-side of the brain.
Some lefties still have left-side dominant brains.
4. Recognising faces
The brains of lefties are probably different in all sorts of fascinating ways we don’t yet know about.
One thing we do know is that lefties use both halves of their brain to work out the difference between one person from another.
In contrast, righties process faces in the right-hand-side of the brain.
This is probably just the tip of the iceberg since lefties are routinely excluded from neuroimaging studies.
Because their brains are different, they screw up the results.
Sorry lefties, you’re too weird for science!
Talking of which…
5. Mental illness
Lefties have repeatedly been found to suffer higher incidence of mental illness.
They are disproportionately represented among patients suffering from psychosis and schizophrenia.
Careful, though, don’t discriminate: it doesn’t mean lefties are all mad — just that their risk is slightly higher.
6. Lefties born in winter?
One theory about why some people are lefties is that it comes down to hormones.
It turns out that men born in the winter are more likely to be left-handed.
The cause could be down to the way the seasons affect the hormones.
We do know that men are more likely to be lefties than women — so perhaps there’s something to the hormonal theory.
7. The ambidextrous advantage
People vary a lot in how right- or left-handed they are.
Some people are heavily handed: they do everything with their right, or their left, hand.
Other people can go either way.
The ambidextrous also tend to be better at maths, one study has found.
8. Righties earn more
Despite the popular view that lefties are more naturally talented, it’s righties who pull down 10-12% higher salaries, data from the US and the UK finds.
The higher wages amongst right-handers are probably due to the fact that they have, on average, greater cognitive skills than left-handers.
More on this here: Left-Handers or Right-Handers: Whose Brains Work Faster?
Embrace your brothers and sisters!
After all this talk of disunity in our species, let’s end on a universal note.
It turns out that lefties and righties are not all that different in the very thing that defines them.
Generally people can learn to use their non-dominant hand with almost as much precision as their dominant hand.
It just takes a bit of practice.
Typically there is only about a 10% difference between speed and accuracy with the dominant and non-dominant hand.