Brain series #2 - Dominant hand or dominant brain

The human brain is divided into 2 halves (hemispheres) that consist of 100 billion neurons and 100 trillion connections. Within each half, there are specific regions that control particular functions of the body. Although the brain has 2 halves and both the hemispheres look very much alike, their functions are completely different and do not work independently of each other. To elaborate and explain if a person has a dominant brain or a dominant hand, let’s first learn about theories and studies by scientists.

Sperry’s Nobel Prize winning left and right brain theory :

The right and left brain theory is that people are either right-brained or left-brained, meaning that one side of their brain is dominant. This theory is based on the fact that the brain’s two hemispheres function differently. This first came to light in the 1960s due to the research of Psychobiologist and Nobel Prize winner Roger W. Sperry.

According to Sperry’s research, the left brain is connected to – logic, sequencing, linear thinking, mathematics, facts, thinking in words. The left brain is more verbal, analytical, and orderly than the right brain. It’s sometimes called the digital brain. It’s better at things like reading, writing, and computations. Whereas the right brain is also connected to – imagination, holistic thinking, intuition, arts, rhythm, nonverbal cues, feelings visualization, daydreaming. The right brain is artistic or creative. It is more visual and intuitive and is sometimes referred to as the analog brain. It has a more creative and less organized way of thinking.

Ambidexterity by cultural biases :

Cultural biases against left-handers have existed throughout history. In the Middle Ages, the devil was believed to be a lefty. In many countries, the percentage of left-handers is much smaller than in the West because it is believed that left-handers were more prone to mental disorders and pressured students to switch hands. Studies show that non-right-handed students are much more likely to struggle in school and have ADHD symptoms. That may be particularly true for those who are mixed-handed or ambidextrous. One study found that children who switch hands back and forth are about twice as likely to have dyslexia. Researchers don’t know exactly why. But they suspect that having an inconsistent dominant hand may be a bigger problem than consistent left-handedness. People who were left handed but were taught to use right hand are more likely to be ambidextrous and have mixed personalities. Whereas people who switch hands often in absence of ambidexterity are more likely to have ADHD.

Ambidextrous people exist because of 2 main reasons – one reason being the joy of learning to become ambidextrous and the second reason being forced change of handedness. An epitome of ambidexterity due to cultural bias is me. I was a left handed child but was taught to perform tasks, eat from my right hand in childhood. Since my left hand was dominant earlier, I still can work with it as neatly as I can with my right hand. Except for good writing, my left hand functions as efficiently as my right hand.

Is left/right handedness in the genes ? :

Now if you are wondering if you were born lefty or righty, let me tell you something interesting. Babies start to move their arms around 9-10 weeks. By the second trimester, the babies show a clear preference for sucking one thumb over the other. So handedness is probably hardwired before birth. Still, one likely won’t get a good sense of their child’s dominant hand until age 2 or 3. Many children continue to switch hands for different tasks during early childhood. Scientists have known that handedness is partly shaped by genes. But it wasn’t until 2019 that they identified differences in parts of the DNA of left- and right-handed people. The study, which also analyzed brain scans of 9,000 subjects, found that in lefties, the parts of the right and left sides of the brain that process language work in better tandem.

So…a dominant hand or a dominant brain ? :

A team of neuroscientists set out to test if humans have a dominant hand or a brain and after a 2 year analysis, they found no proof that the left and right brain theory is correct. Magnetic resonance imaging of 1,000 people revealed that the human brain doesn’t actually favor one side over the other. The networks on one side aren’t generally stronger than the networks on the other side.

The two hemispheres are tied together by bundles of nerve fibers, creating an information highway. Although the two sides function differently, they work together and complement each other. You don’t use only one side of your brain at a time. Whether you’re performing a logical or creative function, you’re receiving input from both sides of your brain. For instance, if you are talking to a person, your right brain will give you an idea of how a person is talking to you, whereas the left brain helps in understanding the language. In the case of math, the left brain handles mathematical equations, but the right brain helps out with comparisons and rough estimates.

Concluding the left and right brain theory, it is not completely known yet if the brain hemispheres control you, decide your personality or your hand dominance. But it is well known that whether you’re working out a complicated algebraic equation or painting an abstract work of art, both sides of your brain are actively participating and providing input.

A person’s personality, choices or IQ isn’t based on the left and right brain function but certain areas of your brain do have specialities that vary from person to person. Being a lefty is rare due to cultural biases and other genetic factors but this doesn’t mean that as lefty people are rarely seen, they are smarter than the right handed or even vice versa. Because you are not truly left-brained or right-brained, but you can play to your strengths and continue broadening your mental horizons. Thus, you have a dominant brain that works based on the complete brain and not just the right or left hemisphere. A normal, healthy brain is capable of lifelong learning and boundless creativity, irrespective of the person being left handed or right handed !

- Rachna Jadhav

@theresilientresearcher