Left out

Being left-handed is more than a quirk. Research reveals it impacts not only how we use our bodies, but also how our minds are wired.

Theoretically, the chances of being left- or right-handed are 50-50, but the actual number of left-handed people is far less than 50 per cent. Although left-handers are in the minority, it is a phenomenon that persists and it impacts not only the body, but also the mind.

In a binary world of handedness, there are only two ways for things to go: left or right. Based on that binary nature, you might expect a shared outcome with equal numbers of left- and right-handed people in the world. You would be wrong.

Today, only around 10 per cent of people around the world are left-handed. There is a slight difference between the sexes, with about 12 per cent of men and eight per cent of women being left-handed, but the overwhelming preference for being right-handed is global. It is tempting to think that this might arise from a capitalist culture wanting a uniform market for its products. It is far more economical to only make right-handed golf club sets. It is not just a matter of convenience either, related to things like handwriting.

Some suggest that right-handedness is convenient when it comes to writing left to right, to avoid smudging for instance, but right-handedness is also dominant in countries where the language is written right to left. The evidence is that hand preference is deeper than cultural, more than convenient, and begins even before the marketers get their hands on your eyeballs.

It seems that hand-preference begins in the womb.

In the journal Scientific Reports, researchers from the University of Padua published the results of their work that involved them analysing which hand a foetus brought to their mouth or eyes more frequently and then coming back to the children at age eight and nine to see which was their dominant hand. They found that by the 18th week of gestation, the hand that was judged to be dominant could accurately predict hand-dominance almost 100 per cent of the time. Other research has suggested that hand-preference exists as early as week 13 in the womb and can be seen in thumb sucking activity.

Researchers from Ruhr-University Bochum have suggested, in a paper in the journal eLife, that since hand preference is exhibited before the motor cortex in the brain connects to the spinal cord, that it is an aspect of the spinal cord that determines handedness.

It might just be that an asymmetry in the genetic activity of the spinal cord even before it connects to the brain is what determines whether you will be left- or right-handed. This intrauterine determinism means you have no real choice about your preferred hand, which raises the question, what are the implications of leftand right-handedness? The answer is that those effects are both physical and psychological.

To the bone

Before we get to the more well-known claims about creativity and right-brain dominance, let’s look at the physical effects of hand dominance. We will start with an examination of a surprising place, a shipwreck that took place almost 500 years ago.

The Mary Rose was the pride of King Henry VIII’s fleet and it was sunk in a battle with French ships in the Solent River in 1545. The ship was excavated in the 20th century and not only were many artefacts intact, but the crew’s skeletal remains were also in surprisingly good condition. Just as in our times, right-handedness would have been more dominant among the crew but perhaps even more so because left-handedness was associated with witchcraft and, therefore, strongly discouraged. Assuming a massive preponderance of right-handers among the crew, the researchers analysed the skeletal remains and found that, for instance, there were more age-related changes in the right collarbones of the crew than in the left collarbones. This is presumably due to the right-handedness of the crew.

A lifetime of using one hand over another will impact how your skeleton changes over a lifetime.

There will be other symmetrical physical effects arising from handedness too. This kind of use-related effect is what might be predicted, but digging into how handedness relates to psychology and mental abilities becomes a little more complex.

Calculating creativity for left-handed people

A perennial claim about left-handers is that they are more creative. This argument is often supported by the fact that Leonardo da Vinci was left-handed. So were Mark Twain, Mozart, Marie Curie, Nicola Tesla and Aristotle. This list is impressive, but while I don’t want to rain on left-handers’ parades, there are some right-handers who have been quite creative too. Ernest Hemingway was right-handed, so is Steven Spielberg, as were Virginia Woolf and philosopher Simone Weil.

The point is that assembling lists like these does not really prove anything, other than what the compiler of the list wants to believe.

There is a more compelling biological argument linking left-handedness to creativity based on the premise that the left side of the body is governed by the right hemisphere of the brain, which is the more “creative” side, as opposed to the “analytical” left hemisphere. It’s a nice logic, but it’s not that simple.

It is true that the left side of the brain controls the right side of the body and vice versa. It is also true that the two brain hemispheres do have specialities.

For instance, language is processed more in the left hemisphere, while facial recognition takes place more on the right. However, the left and right hemispheres in your brain do not operate in isolation.

There is a band of nerve tissue known as the corpus callosum that connects them. Arising out of this complicated physiology is an equally nuanced reality.

Saying that left-handers are right-brained is just an oversimplification. Researchers from Washington University have confirmed that the vast majority of right-handers depend on the left-brain hemisphere for language processing. However, as pointed out by researchers from Bangor University, UK, in the journal Frontiers in Psychology, about 70 per cent of left-handers also depend on the left hemisphere when it comes to language. While there are laterality differences when it comes to brain hemisphere use, it is simply not accurate to say left-handers are entirely right-brained. It is true, however, that left-handers do tend to have a more developed right hemisphere and their corpus callosum is larger, suggesting more communication between the two hemispheres. This tells us that the theoretical underpinning of the “creative leftie” is not totally solid, but how does it play out in real life?

Cornell University, USA, researchers sought an answer to this question by going through more than 1000 scientific papers on the topic dating back more than 100 years. Papers that did not report their data in a standardised fashion were weeded out but, still, what remained was a meta-analysis of more than a century’s worth of research. We know that “divergent thinking” is supported by the brain’s right hemisphere and is the ability to explore many possible solutions to a problem and make unexpected connections.

Divergent thinking is the essence of creativity.

The analysis found that across these 100 years of research, handedness made no real difference in terms of divergent thinking and creativity.

If that leaves you lefties a little dispirited, then take heart, because researchers from England’s University of Liverpool found that you have another cerebral superpower. Through conducting studies on more than 2300 primary and high school students, they found that left-handers are much better at solving difficult mathematical problems. For easier arithmetic calculations, right-handers did just as well, but when the mathematical pressure was on, the left-handers excelled.

There are also other, more mundane ways that your handedness influences how you interact with your world.

On the other hand

You probably think of yourself as mistress of your domain, or perhaps captain of your soul. Most of us do, in one way or another, think that we consciously determine what we do in this life. In reality, however, your handedness might influence the decisions that you make.

Publishing their findings in the journal Psychological Science, researchers conducted a series of experiments and found that when participants were asked which of two products to buy, or which of two alien creatures looked more trustworthy, people overwhelmingly chose the product or alien that appeared on the side of their preferred hand. Given the predominance of right-handers in the world, that’s why advertisers prefer to have their ads on the right-hand page. These kinds of handedness-based preferences have been demonstrated in children as young as five years old.

The theory goes that people like things better when they are easier to perceive and interact with. Left-handers interact more easily with things that are on their left. At least some of your decisions in life come down to what is easiest and most fluent, and that is often determined by your dominant hand.