What determines a person’s handedness and can you make yourself ambidextrous?

Stan Megraw
23 January 2012

If asked whether we're right or left-handed, we'd likely answer by referring to the hand we use for writing. But writing is a special case of handedness. Many of us do not show such a strong preference for other tasks (e.g. opening a door).

And what if you play sports? You may write with your right hand, but swing a golf club left-handed. Does that mean you're ambidextrous?

To help define a person's handedness, behavioral scientists use questionnaires. From their studies, we know that most of us (90%) are right-handed. Very few people (1%) are ambidextrous.

Did You Know?
Handedness is also found in animals. Cockatoos, for instance, prefer to hold food with their left claw.

So why are there so many right-handed people?

Scientists have been studying handedness for decades and haven't yet found a clear answer. One simple explanation is that, when we were young, we mimicked our parents or were influenced by environmental factors (e.g. many gadgets are designed for right-handers). But this doesn't explain how society's handedness developed in the first place.

Did You Know?
Most fetuses show dominance for the right hand (thumb sucking) prior to birth. Handedness for different activities is usually established by the age of 2-3 years.

Although researchers are unsure of what causes handedness, they do know that there is a strong link with the brain.

Lateralization of the Brain

Our brain is divided into a left and right hemisphere. Lateralization refers to the fact that the two halves specialize in controlling different functions. In general, the left hemisphere is responsible for motor control of the right side of our body, and vice versa for the right hemisphere.

When we have a preference for one hand (e.g. eating with a spoon), the brain's hemisphere opposite to that hand tends to be more developed for that task. If we use our untrained hand for that same task, control of that action shifts to the other hemisphere. So over time, both sides of our brain can be trained for the same function.

Did You Know?
Pianists show less brain lateralization than guitarists. Non-musicians have more lateralization than either piano or guitar players.

For the majority of right-handers (97%), the left hemisphere is also specialized for communicating (e.g. gesturing, language and speech). Since motor control of our hands is contra lateral (opposite) to our brain's hemisphere, it seems logical that the majority of us use our right hand for writing. But this doesn't explain why many left-handed writers (68%) also have the same functions in the left hemisphere. Obviously other factors are involved.

Strong-handed and Mixed-handed?

Dr. Stephen Christman, a professor at the University of Toledo in Ohio, recommends we use the terms "strong-handed" and "mixed-handed" rather than left- or right-handed.

"Whether you write with your right or left hand is not really important," he recently told the Eagle-Tribune (North Andover, Mass). "What's important in handedness is the degree of handedness, the strength of your hand preference," he said.

There is some logic to Dr. Christman's proposal. Although ambidextrous people are rare, most of us don't exclusively use one hand over the other.

Mixed-handedness and Ambidexterity

The term "ambidextrous" implies that an individual is equally skilled in using either hand for all activities. Mixed-handedness however is less restrictive; the right hand is favored for some actions and the left for others. So if you're interested in being ambidextrous, perhaps a more realistic goal would be to become more mixed-handed and less strong-handed.

How successful you'll be in changing your handedness will depend on the type and complexity of the task. Activities that are likely to be more hand-specific and more difficult to change are those that need a lot of practice and skill (e.g. writing) or involve coordinating different muscle groups for quick, smooth motions (e.g. throwing a ball; swinging a golf club).

In closing...

As I was preparing this article, I started thinking about how much we rely on computers for communicating (emails, chat lines, etc). Could handwriting eventually become extinct in future generations? Just a thought.

Learn More!

Several informative articles on handedness. Click here.

Understanding the Human Brain. Click here.

Test your handedness. Click here.

References:

Kirkwood, J. 2004. Are you a strong-hander or a mixed-hander? Eagle-Tibune. Sunday, May 2, 2004.

Linke, D.B., and S. Kersebaum. 2005. Left out. Scientific American Mind. 16(4).

Perelle, I.B. and L.E. Ehrman. 2005. On the other hand. Behavior Genetics. 35(3): 343-350.

Rogers, L.J. 2003. Seeking the right answers about right brain-left world. Cerebrum. 5(4).

Stan Megraw

Stan is a writer/researcher, a PhD graduate of McGill University and was a member of the CurioCity team for several years. As a kid he dreamed of playing hockey in the NHL then becoming an astronaut with NASA. Instead, he ended up as an environmental research scientist. In his spare time Stan enjoys working on DIY projects, cooking and exploring his Irish roots.


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