Hand dominance—the preference for using one hand over the other—is not a hardwired biological trait but an emergent effect of life-long practice with complex tools, according to research published in the journal PNAS. A team led by neurologist Dr. Ahmet Arac at UCLA found that the perceived superiority of the dominant hand disappears when individuals perform tasks that require no prior experience, such as writing with an elbow.
Why Practice Trumps Brain Wiring
For decades, the prevailing theory suggested that one hemisphere of the brain held an innate, superior control over motor functions, dictating hand dominance. However, the study conducted by Dr. Arac and coauthors, including Dr. John W. Krakauer of Johns Hopkins University and the Santa Fe Institute, challenges this. By using motion-capture cameras to track the 3D arm movements of healthy adults, the researchers demonstrated that both arms perform similarly during basic, simple reaching tasks.
The distinction only becomes apparent when tools are introduced. Tools require curved, controlled trajectories that the nondominant hand has rarely practiced. When participants were asked to write with their elbows—a motion they had never performed—the traditional dominance effect vanished. Both arms struggled equally at the start, but with repetition, both improved at the same rate, effectively leveling the playing field.
“The dominant arm isn’t more capable because one hemisphere of the brain is simply better at controlling movement,” said Dr. Arac. “It is because we’ve spent a lifetime practicing the specific, complicated movements that tools and handwriting demand.”
Did you know?
The study suggests that limb dominance is essentially a record of our experience. When you switch to a body part that has never performed a specific task before, the “advantage” of your dominant side disappears entirely.
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The research, supported by the NIH, the US-Israel Binational Science Foundation, NVIDIA, and UCLA’s Department of Neurology, suggests that the brain’s representation of movement is highly flexible.
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Frequently Asked Questions
Is being left-handed or right-handed determined by genetics?
While genetics play a role in initial preference, this study indicates that the performance advantage we associate with that preference is largely a result of practice and experience with complex tools.
Can I train my nondominant hand to be as good as my dominant one?
Yes. The study shows that when the dominant hand’s “practice advantage” is removed—such as by using an untrained body part like the elbow—both sides learn new, complex tasks at similar rates. Consistent, task-specific practice can significantly improve the performance of the nondominant limb.
Why did the study use elbows for the experiment?
The researchers used the elbow as an “effector” because it provided a neutral ground. Since humans do not use their elbows for writing in daily life, both the dominant and nondominant sides started with zero experience, allowing the team to measure pure motor learning without the bias of a lifetime of habit.
Have you ever tried to train your nondominant hand to perform a complex task? Share your experiences in the comments below, or subscribe to our newsletter for more insights into the latest developments in neuroscience and human performance.
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