Left-handed people only represent about ten% of the world’s population, but a quick glance reveals that many key players are left-handed.
For example, three of the last six US presidents were lefties: George HW Bush, Bill Clinton, and Barack Obama. Additionally, an eclectic multitude of outliers that rocked the world in one way or another had the dominant left hand: Michelangelo, Leonardo DeVinci, Paul McCartney, David Bowie, Jimi Hendrix, James Baldwin, Nikola Tesla, Oprah Winfrey, Bill Gates and Steve Jobs, according to a Report 2019 and The New York Times.
It’s an impressive list, but what does the data say? Are left-handed people smarter than right-handed people?
Related: Why are people left-handed (or right-handed)?
To investigate this question, the researchers looked at the differences in math achievement between more than 2,300 right-handed and left-handed students aged 6 to 17 in Italy. While there was no difference looking at the easier math problems, left-handed students had a significant advantage over more difficult problems, such as associating a mathematical function with a data set, according to the 2017 study in the journal Borders, led by Giovanni Sala, Assistant Professor at the Institute for Comprehensive Medical Science at Fujita Health University in Japan.
But why would a person’s dominant hand have anything to do with mathematical ability? Left-handedness is associated with surprising differences in the architecture of the brain. A 1995 meta-analysis of 43 studies in the review Psychobiology determined that left-handed people have a significantly larger corpus callosum – the bundle of nerve fibers connecting the two hemispheres of the brain – than right-handed people.
“One possibility is that the stronger connection between the two hemispheres allows the [left-handed] about having stronger spatial abilities, and we know that spatial abilities are linked to mathematics because mathematics is often conceptualized in space, ”said Sala, who conducted his research at the University of Liverpool in the United States. UK
In some cases, it can depend on how a person becomes left-handed. “Left-handedness is a very complex trait, and left-handedness in particular can be an advantage or a disadvantage depending on the cause,” Sala told Live Science. Sometimes “awkwardness can be caused by some sort of brain too bad, when the right hemisphere has to take over because there is some kind of damage in the left hemisphere. ”
This type of damage could be caused by a hemispherical lesion that occurs before birth, according to a 1985 study in the journal Brain and cognition. If the lesions occur in the left hemisphere of the brain, it could cause the individual to primarily use the right half of their brain. Since the hemispheres of the brain are indexed (meaning the left hemisphere controls the right side of the body, and vice versa), a dominant right hemisphere can lead to left handedness. The study calls this a “pathological left-hander” and notes that it can lead to learning difficulties. In other words, being left-handed is sometimes associated with learning problems.
It’s complex, but Sala’s study paints a picture of left-handed people who are overrepresented both at the bottom and at the top of the cognitive spectrum. “Once you see that the subject is not intellectually challenged… then awkwardness appears to be a predictor of intellectual ability,” particularly mathematical ability, according to his study, Sala said. However, he cautions that his results are not the last word and that more studies need to be done.
Additionally, other data shows that right-handed people have a slight intellectual advantage over left-handed people. A 2017 study in the journal Neuroscience and Behavioral Reviews looked at 18 other studies that included data from over 20,400 people and found that right-handed people had negligibly higher IQs than left-handed people, on average. “The jury is still out on whether it is the degree of hand preference that is associated with intelligence and whether there is a relationship between relative manual skill and intelligence,” said wrote the authors in the study.
History of the left
Awkwardness has not always been viewed in such a positive light. In the 1936 pamphlet “The Prevention and Correction of Left-Handedness in Children”, by JW Conway, left-handedness was described as a “disease” as serious and problematic as rickets and pneumonia.
The prejudices against left-handers have deep roots and are ingrained in our very language. Being someone’s “right hand” is good, while having “two left feet” or receiving a “left-handed compliment” is bad. The word itself comes from Old English “lyft” which means weak or broken, while the word “right” is given the additional honors of meaning factually correct, morally justified or a “moral or legal right. ”
These slights are not unique to English either. The French word for left is “gauche”, which in English and French also means “awkward or tactless”, while “droit”, the French word for right, translates to “skillful”. Going back even further, the Roman word for left was “sinister,” while their word for right, or “dexter,” gives us the English word dexterity.
Even modern research recognizes some downsides to being leftist persuasion. It has been statistically associated with schizophrenia, dyslexia, and breast cancer, to only cite a few. (However, an association does not prove that one causes the other.)
But these prejudices only make even more impressive these many left-handers who have become historical and contemporary icons. Not bad for a bunch of supposedly left and sinister freaks, right?
Originally posted on Live Science.