There has long been a link between left-handedness and talent. Da Vinci was left-handed, as was Mark Twain, Mozart, Marie Curie, Nikola Tesla and Aristotle. It’s no different now – former US President Barack Obama is also left-handed, as are Bill Gates and Lionel Messi.
But is left-handedness really more likely to be a genius? Let’s take a hard look at the latest evidence, including our new research on handedness and math ability.
It is estimated that between 10% and 13.5% of the population is not right-handed, some of them can use either hand, and most are left-handed.
Handedness is a manifestation of brain function and is therefore associated with cognition. Left-handers, on average, have a more developed right hemisphere, which is specialized in processing spatial reasoning and mental representations of rotating objects.
Also, the corpus callosum, the bundle of nerve cells that connects the two brain hemispheres, is generally larger in lefties. This suggests that some left-handers have stronger connections between the two hemispheres and thus better information processing capabilities. But it’s still not clear why. One theory is that living in a world designed for right-handers forces left-handers to use both hands, thereby enhancing connectivity. This opens up the possibility that by training ourselves to use both hands, we can all enhance connectivity.
These uniquenesses may be why lefties seem to have an advantage in certain trades and arts. For example, musicians, creative artists, architects, and chess players are more likely to be left-handed. Needless to say, efficient information processing and better spatial skills are crucial in all of these activities.
Handedness and Mathematics
But what about the link between left-handedness and math skills? Not surprisingly, the role of handedness in mathematics has long been a hot topic of research. More than 30 years ago, a major study suggested that left-handedness may indicate precocious math maturity. The study found that the proportion of mathematically gifted students who were left-handed was much greater than that of the general population.
However, the idea that left-handedness is a predictor of higher intelligence has recently been challenged. Some researchers claim that being left-handed is not associated with any advantage in cognitive skills, and may instead have an adverse effect on general cognitive function, and therefore on academic performance.
For example, one study found that left-handed children performed slightly worse on a battery of developmental tests. In addition, a recent review found that left-handedness appears to be disproportionately high among people with intellectual disabilities. Another, larger study found that in a sample of children ages 5 to 14, left-handers appeared to have poorer math skills.
design experiments carefully
Interestingly, each of these past studies measured handedness and categorized participants differently, and some studies simply asked participants what their handedness was. And, most importantly, the methods they used to measure mathematical ability varied from simple arithmetic to complex problem solving. These differences in experimental design may be responsible for the confounding observations.
In order to get more accurate and reliable results, we decided to conduct a whole series of experiments involving more than 2300 students (primary and secondary). The experiments varied in the type and difficulty of the math tasks.
To ensure comparability, we used the same questionnaire, the Edinberg Dominance Questionnaire, to assess handedness in all experiments. The questionnaire asks which hand people prefer to use for writing, drawing, throwing, brushing teeth and other things. The questionnaire assesses how much people prefer their right-handedness versus their left-handedness, using a relative scale rather than an absolute classification as left-handed or right-handed. This property allows us to build more reliable and powerful statistical models.
The results, published in Frontiers Science, showed that left-handers in the sample performed better on tasks involving difficult problem-solving, such as associating mathematical functions with a given data set. This pattern of outcomes was particularly pronounced among male adolescents. In contrast, when the task was not so demanding, such as performing simple calculations, there was no difference between left-handed and right-handed. We also found that extreme right-handedness—those who said they preferred their right hand for everything on the handedness test—performed worse across all experiments than moderately left-handed and right-handed people.
Lefties, on average, seem to have an advantage in solving demanding math tasks, at least in elementary and middle school. Additionally, being extremely right-handed may indicate a mathematical disadvantage. Taken together, these findings suggest that handedness, as a measure of connectivity between the brain hemispheres, somehow affects cognition.
Even so, handedness is only an indirect expression of brain function. For example, only one-third of people with a more developed right hemisphere of the brain are left-handed. So many right-handed people will also have a brain structure similar to that of left-handers. So we need to be careful about understanding people’s handedness—whether it’s a sign of genius or a sign of cognitive impairment.