Why Do We Have Left-Handed & Right-Handed People?

Which hand do you use to write? You might have noticed that everybody has a dominant hand. But do you know how a dominant hand becomes ‘dominant’? let us find out about the mysteries of right-handedness and left-handedness.

When writing, some people use their right hand, while some use their left hand. Are you wondering how many people are right-handed and how many are left-handed and why? If both the parents are left-handed, then there is a 50% chance that the child will be a left-hander. If any one parent is a left-hander, then there is a 17% chance that the child will be a left-hander. Even if both the parents are right-handed, there is still a 2% chance that the child will be left-handed. It is said that in Japan, 8 out of 9 people are right-handed. It means that a larger number of people are right-handed. That’s why scissors, can openers, door knobs and such are usually designed for the convenience of right-handed people. But why are there a lesser number of left-handed people? There are many theories on that.

One theory is that in the olden days when humans started using tools, they used their right hand more frequently and thus right-handedness got established. As the human heart is on the right side yet another theory says that in the olden days’ people used to cover their heart with their left hand and hunt or fight with their right. But none of these are facts.

By the way, do you know at which stage we get to know if a person is right or left-handed? In a one-year-old baby, hand domination is yet to be determined. We usually get an idea when the child is about 2-3 years old. At this time, the hands in which the child holds the spoon or starts drawing usually determine the domination. This is the time when the nerve network connects to the brain. Finally, at about 4-5 years of age, it gets decided if the person will be right-handed or left-handed. But what is the difference between a right-handed person and a left-handed person? There is a difference in the way the brain functions in a right-handed and a left-handed person.

Let us take a look at how the brain functions. The human brain is divided into two parts like this. The left brain is on the left side. It is good in languages, logic, math, etc., and is called the ‘language brain’. The right brain is on the right side. It is good in estimating shapes, music, drawing, etc. and is called the ‘arts brain’. The nerves that come out of the left side of the brain are connected to the right side of the body and those on the right are connected to the left side of the body. In other words, those who are left-handed use the right side of the brain more and those who are right-handed use the left side of their brain more. The way the right and left brain performs in right and left-handed people are slightly different.

It is not that the human brain is exactly divided into left and right. The left and right brains are assigned to complement each other. Both the sides of the brain are connected with a thick bundle of nerve fibres called corpus callosum and they exchange information. For instance, the message of sound that enters through the right ear enters into the right side of the brain. The Broca and Wernicke that control language function are situated on the left side and hence the handling of language is smooth. However, if a sound enters through the left ear, it will be transmitted to the right brain to the right brain and through the corpus callosum, it will enter the left brain to be acted upon. The sound information mostly enters left-handed people through their left ear. That is why they have more opportunities to use both sides of their brains and the corpus callosum is thicker. Rarely, however, do the right and left brains function differently and some people can be both right and left-handed simultaneously.

Recent studies show that 95% of right-handed people and 70% of left-handed people have their speech centres on the left side of their brain. However, it is only a matter of predominance. Even in those brains where there is no speech centre, there is a certain amount of speech ability. Further, it is not just hands that are left or right side dominant. Using the right and left hands equally means that you are using your right and left sides of the brain equally. This enables the corpus callosum to be trained well and the information that is received by the brain is handled with perfect balance.

Amongst sports stars and artists, there are many left-handed people. Maybe they have a better balance between both sides of their brains. This shows there is a good balance between the right and left brain. The current society has a majority of right-handed people. However, it seems like it is better to use both hands together. Those who use their left brains more are right-handed and those who use their right brains more are left-handed.