Not long ago, I asked myself why people can be right-handed or left-handed. I wanted to delve into this a bit, and decided to share the results in the form of an article.
What were the most common questions that popped into my mind when considering this topic? The first and most important one sounded something like this: at what age do predispositions form in a person to become left-handed or right-handed? What exactly influences whether a person becomes left-handed/right-handed? Why are there more right-handed people? Can a person be effectively retrained in all aspects? Does having perfect control of both hands (right and left) give any advantage over classic right-handed/left-handed individuals?
Before attempting to answer these questions, I want to point out that about 85-90 percent of people are right-handed. There are also people who are equally good at using both hands. They are called ambidextrous. In general, when people discuss right-handedness and left-handedness, they often confuse two completely different concepts: left-handedness and leftism. Left-handedness refers to the dominance of the left hand in writing, daily life, and other activities. Leftism refers to left-sided asymmetry in paired organs (the dominance of the left side over the right side). In other words, a person’s leading side may not only be the left hand, but also the left foot, ear, or eye. Of course, we don’t notice this when walking normally. But as soon as you engage in sports, you immediately see the difference. Football players, for whom leftism is a life choice, kick the ball with their left foot (I’ve played against such people many times and have seen this), and even in high or long jump events, they push off with their left foot as well. Although I’ll use these terms as synonyms later in the article, it’s still important not to confuse them and to know the difference.
So, when does the habit of using the left hand as the primary one, rather than the right hand, form? Well, pretty much from birth. The main reason for all this is genetics. If at least one parent is left-handed, the likelihood that one of the children will also be left-handed increases significantly. If both parents are left-handed, the probability is even higher. Moreover, children of right-handed parents can also be born left-handed. This is also related to genes that were not expressed in the parents themselves. In other words, when a child is born left-handed, it is a genetic predisposition, but why it happens is a more complex question. Around the age of 4, it becomes clear whether a child is right-handed or left-handed. Before this age, it’s difficult to determine because children use both hands equally often and interchangeably. During my research, I also came across a study that suggested that in later marriages (40+), the likelihood of having a left-handed child is higher than in younger marriages. However, I’m not sure how reliable this information is.
The next question I wanted to explore was whether it’s possible to retrain someone from being right-handed to left-handed and vice versa. Here, we need to separate the two terms again. If we’re talking about left-handed people, it is possible to teach and train them to use their right hand as well as they use their left, but when it comes to true leftism (the left-sided asymmetry of paired organs in the brain), it is impossible to change the brain's asymmetry. Many people don’t see the point in retraining a left-handed person to be right-handed. There is no real need for this, especially for children, as it could cause additional stress. On the other hand, children absorb information from the world around them very quickly, so changing their leading hand or foot might not be too difficult.
Next, I became curious about who is smarter: left-handed or right-handed people? There was a lot of information on the internet, often contradictory. Many sources claim that left-handed people are more creative, while right-handed people are smarter. Whether that’s true or not, I think it’s entirely individual. This comparison seems especially absurd if we remember that the most common theory explaining left-handedness (the concept of one hemisphere being dominant) that originated in 1864 is now debunked and doesn’t hold up. Here’s what Wikipedia says about this theory:
This is the most widespread theory of the development of a dominant hand. The theory suggests that the same hemisphere of the brain controls both speech and motor centers, and that splitting the work between the two hemispheres would reduce efficiency. Additionally, if all functions were distributed across both hemispheres, the size of the brain and its energy consumption would increase, which is impossible. Since the majority of people have the left hemisphere controlling speech, right-handed people dominate. The theory also states that left-handed people would have the opposite (reversed) division of centers in their hemispheres. Finally, because other primates don’t have a speech center (at least not to the same extent as humans), it makes no sense that they would be predominantly right-handed, which is actually true.
Refutations:
The theory doesn’t explain why the left hemisphere always controls the speech center.
While 95% of right-handed people use the left side of the brain for speech, there’s no such dependency for left-handed people. Some use the right hemisphere for linguistic skills, others use the left hemisphere, and some use both.
The theory may explain some reasons for handedness, but it has too many flaws to explain all the reasons for left-handedness.
Finally, I wanted to examine the advantages in work, sports, and life between the two groups. In general, there are no significant advantages of one group over the other. However, in sports (as mentioned above), left-handed people do have a slight advantage. For example, in tennis, about 90% of players are right-handed, meaning that most people are used to playing against right-handed players (since there are more of them). So, for a right-handed player, facing a left-handed one can be more challenging, as they rarely play against left-handed opponents, whereas left-handed players often play against right-handed ones.
