Are you a leftie or righty?

In today’s “did you know?”, we’re exploring the science of handedness. Watch the video or read below to find out more:

Why are you right or left handed?

Researchers believe that our handedness (tendency to be right or left-handed) is determined in the womb. The majority of humans are right-handed (a whopping 85-90%) and this makes sense– our right hand is controlled by the left hemisphere of the brain which is responsible for speech and writing. The right hemisphere of the brain controls the left hand and is associated with creativity and imagination. Does this mean left-handed people are more creative than right-handed? It’s possible. Let’s dive into the science of handedness a bit more:

The Science

Scientists at the Universities of Oxford, St Andrews, Bristol and the Max Plank Institute in Nijmegen, the Netherlands have researched how handedness and our genetic code align. Their research revealed that a specific network of genes are likely associated with determining whether someone will be right- or left-handed. This determination happens in the womb before a baby is even born. Scientists have isolated the gene PCSK6, a gene “intimately involved in turning a spherical ball of equally oriented cells into an embryo that has discernible left and right sides.” According to an article in Time,

These influences also appear to determine handedness, or relative dexterity, at a level greater than would occur by mere chance.

Researchers do offer caution that genes may only be one component of dexterity. The role of behavior and training may also contribute to which hand a child prefers, another example of the fascinating combination of nature and nurture.

The Brain

Our brains are designed in an asymmetrical manner meaning that the right and left sides are responsible for different things. Just like you may be responsible for dishes and your partner is responsible for taking out the trash, the right hemisphere of the brain controls most emotional functions and the left hemisphere manages many thinking and intellectual skills.

We learned above that the use of the left hand is managed by the right side of the brain, the moods and emotional side. One study found that lefties may be more prone to depression and negative emotions since this side of their brain is activated more regularly.

Another study furthered this idea of our handedness and brain being interconnected. Researchers asked a group of right-handed participants to clench their right fist before memorizing a group of words. Remember, movement of the right hand signals the left side of the brain to ‘turn on’. These participants performed significantly better in recalling the memorized words than their counter-parts, a group of right-handers who clenched their left fists before memorization.

Dr. Daniel Geschwind, professor of psychiatry, neurology and human genetics at the University of California, Los Angeles says that while the majority of right-handers process language in the left-hemisphere, lefties have an equal distribution of this skill across their brains. This lack of asymmetry leads to more random and less specified skills. This wide distribution has a health benefit– if a left-handed person has a stroke on the left side of the brain (the language processing side), they tend to recover more quickly since their language processing skills are dispersed across the brain. There is a disadvantage, however. “Having more distributed language abilities probably makes the system more complicated, so it may increase the susceptibility to developmental [abnormalities] and neurodevelopmental disorders,” says Geschwind.

This begs a chicken or the egg type of question. Is the brain’s tendency toward asymmetry based on handedness or does the layout of the brain veer someone toward a preference? Geschwind believes this all may happen together: “Left-handedness is a marker for how the brain is organized in a more symmetric than less symmetric way.”

Caveman Hands

Right-hand majority isn’t a trending topic. As humans, we’ve been using our right-hand as the dominant choice for over 500,000 years. And interestingly, this fact is determined by caveman teeth.

Dental records of our hunting and gathering ancestors were studied by researchers at the University of Kansas. They found that when our great, great, great- (and on and on) grandfathers processed animal hides, they would hold one side of the carcass in their hand and the other in their mouth. Scientists reviewed the wear and tear on fossilized caveman teeth to determine the dominant hand used.

According to researcher David Frayer, Ph.D, “All you need to have is a single tooth, and you can tell if our assumptions are right — if the individual is right- or left-handed.” They found that similarly to today, most of the records showed a dominant right hand.

And how about other species? Research has found that other mammals, including gorillas and chimpanzees exhibit the use of a dominant hand. David P. Carey, a neuropsychologist at Bangor University in the United Kingdom says that even dogs have a preferred paw. “Your dog is one-pawed,” said Carey. “If you force a dog to reach for a toy through an aperture, it will tend over many trials to use one paw over the other.”

Famous Lefties

Lefties or ‘southpaws’ may be in the minority, but there are several famous ones you may have heard of. President Obama, anyone? Yep, he’s a leftie. Several past Presidents made the list as well:

  • Bill Clinton
  • George H.W. Bush
  • Gerald Ford
  • Harry S. Truman
  • James A. Garfield

Some of your favorite musicians and actors may be the elusive leftie too. Here’s a few we found:

  • Kurt Cobain
  • Judy Garland
  • Jimi Hendrix
  • Paul McCartney
  • Tim Allen
  • Carol Burnett
  • Robert DeNiro
  • Nicole Kidman

And check out this awesome infographic on left-handers (click to expand):

What You May Not Know About Left-Handers

P.S. Less than 1% of the population is ambidextrous. If you’re in this super special club, you get a big virtual high-five from me!

8 replies on “Why Are You Right or Left Handed?”

  1. RAMONA M.

    My son had a bit of a hard time learning to write, I am not sure if he possessed the want to use his left hand. My husband and I and entire family is right handed, I have 1 aunt that was I taught him to wright with his right hand, it just seemed correct. He also needed some speech therapy. he could speak words without opening his lips. YES he did. Nowadays I see him using either hand to do things, hangs clothes from the opposite side of the rod, used the hanger like a lefty, also uses his left hand with the can opener etc. I believe he is ambidextrous. My fault I did not pick up on the lefthanded when he was a baby. I am ambidextrous myself.

  2. Elissa

    I am an 80s baby and also a lefty so thank goodness no forced right handedness in school! When I was 6 I broke my left arm and was in a class and had no choice but to do things right handed. As an adult I am left handed still but golf and bat right handed lol

    1. Rhonda C

      I am a lefty for writing, crocheting, and holding my eating utensil, but I use my right hand to cut food, so I don’t have to switch hands to eat a steak. I also wash dishes, shoot my handgun, and wipe things down with my right hand. What is it called when you can do many things with each hand but you are not ambidextrous?

  3. bonnie kaufman

    My aunt also was forced to be right handed and developed stuttering. I am also a lefty. As a child my mom enrolled me in ballet classes and she was told I would never be a dancer. My husband is a lefty, so was his dad, my grandson, my son in law. So we all Sat on the same side of the dinner table. Viva lefties!

  4. S

    In our family from our grand father’s side the next generation to us all the kids are left handed…even the 2 babies that is the grand children of my uncle who are now right handed …they actually we’re left handed tendency by birth but now are right handed…

  5. JoAnn White

    Very interesting. I’m left handed.I am creative, too. I’m a seamstress and was a professional beader in a bridal shop. I am slightly ambidextrous, too. I can only cut fabric with my right hand. Scissors won’t work if I use my left hand. I’m not sure you have ever heard of this occurance. In the first grade there was only 1 other child who was left handed. We were being taught writing skills, etc. Whenever we used our left hand to write, draw, color, we were told to use our right hand. Our hand was smacked with a ruler when we disobeyed! (This was in 1956!) We began to studder, and I’m sure we acted out. When my Mother realized what was going on, she first talked with the other mom, and they went to the school. They were not happy with this. It was school policy to retrain left handedness to right. It would make our life easier. Anyway, the two of us were left alone. We learned to adapt. We quit studdering Our lives went back to our normal. I thought this might interest you.
    JoAnn White

    1. Lynn Story

      Wow, I went through that stuff. I went to Catholic school from K to 3rd grade. I was made to use my R hand and got scolded by the nuns when I did not. Could not cut paper, again they got upset and made me use my right hand. It made me cry because using my R hand was so difficult. Guess what, I was strong and made it and am still a leftie and glad of it 😊

    2. Christine Conrad

      I resonate with the story. I was ‘forced’ to adjust and use my ‘right hand’ until in the forth grade I had a ‘left-handed’ teacher. The end to ‘forced’ right-handedness was life changing.

      I explore the tools designed for right-handedness and am reminded how I have to adjust often just to achieve the correct outcomes from those tools.

      I remember being given a ‘left-handed pencil’ one time. I was holding this pencil in my dominate left hand. It read: ‘This is a LEFT-HANDED pencil’. It took a moment to understand how it was different..the lettering was readable. It was not upside down!

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