Why Do People Have Dominant Hands?
There isn’t usually a consensus in the medical or research community when it comes to understanding why most people have a dominant hand. One of the more popular theories assumes that the brain engages in something of a division of labor, assigning dominance to one hand over the other in order to promote efficiency; this is usually consistent with the idea of each of the brain’s hemispheres controlling a different sort of data and information processing. Another theory posits that dominance is really a matter of perspective, and that the hand best at fine motor skills may actually depend on the gross motor and “helper” qualities of the other in order to fully function. Some researchers are also exploring whether dominance is simply a matter of genetics. What most scholars do agree on, though, is that the brain signals that lead to dominance, no matter why they happen, seem to be related to learning and information processing generally. Understanding dominance may help uncover things like why people have learning disabilities.
Understanding Handedness Generally
When people talk about dominance in hands, they’re usually referring to what is known more casually as “handedness,” or the idea that most people have one hand that is used to do things like write or grab for objects more instinctively than the other. The majority of humans are “right handed,” which means that their right hand is dominant and the one they use for the majority of daily tasks.
The next most common is left handedness, which as much as 10% of the population is thought to be. Then come the alternatives. Mixed handedness is when some individuals will use their right hand for one activity, like writing, but their left for another, like holding scissors or hitting a tennis ball. Finally, there is ambidexterity, which is usually acknowledged as very rare. Being truly ambidextrous means that both hands are used equally for all activities. The flip side of ambidexterity is ambilevous or ambisinister qualities, which cause a person to be equally poor when using either hand.
Division of Labor
The most commonly accepted theory explaining dominance is division of labor. This refers to the hemispheres of the brain and how information is processed and divided between the hemispheres and fine motor skills in the hands, eyes, feet, and ears. It's generally known that speaking and communication activities in right handed people are performed in the left hemisphere of the brain. The major argument against this theory holds that what's true of right handed people should be opposite for left handed people. In other words, left-handed people should process language in the right hemisphere of their brain. That isn’t usually the case, which makes this theory flawed, at least from a technical perspective.
Bilateral Coordination Theory
Another suggestion is that dominance happens as a result of both hands working together. This is called bilateral coordination. On this theory the dominant hand is a “worker hand” that performs most of the fine motor skills required to get through a day. The non-dominant hand is thought of as the “helper hand” and performs gross motor skills like stabilizing objects.
In 2007, scientists looking for a left handedness gene found a marker later named LRRTM1. This gene gives some credibility to the thought that handedness might be genetic. The genetic predisposition theory is also being tested for validity because the gene carries other traits as well. Even sill, the connection isn’t apparent. Only about a 1 in 4 babies born to two left handed parents are also left handed. The gene may be recessive, as is the case with the gene determining light eyes, but not enough is known at this point to say for sure.
Dominance when it comes to hand use might not seem like such an important thing when doing ordinary tasks like writing a check for the groceries, but the implications may go pretty deep. Scientists increasingly believe that there is a relationship between learning and handedness. Finding answers to dominant hands could unlock seemingly unrelated issues like dyslexia and stuttering.
"Finding answers to dominant hands could unlock seemingly unrelated issues like dyslexia and stuttering."
Why? This only generates a desire for a longer article. I appreciate the content here already, but this last statement just poses more questions.
"I am a righty but when I tumble I twist in my full left and I don't know why."
If I'm reading this correctly, are you landing on your left side first? If so, that is because your brain is trying to protect your dominant side. I had that issue when riding a motorcycle that I had a harder time leaning to the right than on the left because of it.
I'm right handed for almost everything. But when i play play cricket or baseball, I bat left handed. I can also play guitar left or right handed, but I'm nowhere near as good with my left. "I stopped practicing,"
I've always thought. Why be really bad with one side of your body? We should train ourselves while young to be competent at both, I reckon. We need to use our brains and bodies more effectively!
@anon350207: Actually, I am a cellular neuroscientist and can confirm that language, at the very least, is processed almost exclusively in the left hemisphere of the brain in an area just above the Sylvian fissure. As well, there are very small variations in task processing between the left and right hemispheres which gave rise to the "right vs. left brain" myth.
As the article states though, this likely has nothing to do with dominant handedness.
@famnfriends: That happened to me when I was in school. I was a lefty (still am; I just write with my right hand, I paint with my left, though) and it was frowned upon.
I'm mixed handed too, except opposite of anon316175. I write with my left and everything else left. Interesting.
Actually a lot of new research shows that aspects like "language, creativity, spatial configuring" and the like, are not actually controlled by one side of the brain vs the other.
No one side of the brain controls any of these functions. Both hemispheres are used. So the idea that left handed people are more creative because their right side is dominant is complete fodder.
I'm mixed handed. I write with my right and do everything else with my left.
I am a righty but when I tumble I twist in my full left and I don't know why.
How interesting! When my brother, who is right-handed, was in school, the teachers would hit a child on the hand with a ruler if they started to write with the left hand. Can this hurt something in the brain and contribute to learning disabilities? If there is a connection between the brain and which hand you use, this is scary, I am glad we do not do that to our children in today's school system.
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