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Why Do People Have Dominant Hands?

X-ray of the hand.
Man's palms.
A model of a human hand.
Left-handed people don't necessarily process language in their brain's right hemisphere.
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  • Written By: Kris Roudebush
  • Edited By: Bronwyn Harris
  • Last Modified Date: 02 November 2014
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Although there is no consensus why people have dominant hands, there seems to be no shortage of theories regarding how handedness comes about. There are four recognized types of handedness.

The majority of the world's population is right handed. The next most common is left handedness, which as much as 10% of the population is thought to be. Mixed handedness is when some individuals will use their right hand for one activity, like writing, and their left for tennis. Finally, there is ambidexterity, which is very rare. Being truly ambidextrous means that both hands are used equally for all activities. The flip side of ambidexterity is ambilevous or ambisinister in which an individual is equally poor when using either hand.

One theory that is just starting to flesh itself out says that dominant hands is a result of both hands working together. This is called bilateral coordination. It's a process in which both hands are working together to accomplish a task. What you have is a worker hand, thought of traditionally as the dominant hand, that will perform the fine motor task. Your non-dominant hand is thought of as the helper hand and performs gross motor skills, like stabilizing an object.

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When talking about dominant hands, the most commonly accepted theory 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 is not entirely true, which makes this theory flawed.

In 2007, scientists looking for a left handedness gene found LRRTM1. This gene gives some credibility to the thought that having dominant hands might be genetic. This theory is also just being tested for validity because the gene carries other traits as well. However there is still only about a 1 in 4 chance of having a left handed child if both parents are left handed.

Having dominant hands might not seem like such an important thing when you're writing a check for the groceries, but the implications go pretty deep. Scientists believe that there is a relationship between learning and handedness. Finding answers to dominant hands could unlock seemingly unrelated issues like dyslexia and stuttering.

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anon350261
Post 11

"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.

anon350257
Post 10

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 whilst young to be competent at both, I reckon. We need to use our brains and bodies more effectively!

anon350245
Post 9

@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.

anon350232
Post 8

@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.

anon350210
Post 7

I'm mixed handed too, except opposite of anon316175. I write with my left and everything else left. Interesting.

anon350207
Post 6

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.

anon316175
Post 4

I'm mixed handed. I write with my right and do everything else with my left.

anon286987
Post 3

I am a righty but when I tumble I twist in my full left and I don't know why.

famnfriends
Post 2

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 todays school system.

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