Dominant Hand Preference May Stem From Practice, Not Innate Wiring, Study Finds

For years, the prevailing belief was that a dominant hand, whether right or left, was an inborn trait dictated by how the brain controls movement. However, a recent study by scientists at the University of California, Los Angeles (UCLA) and Johns Hopkins University challenges this notion, proposing that hand dominance is largely a product of extensive practice with complex tasks.

The researchers devised an unusual experiment to separate innate abilities from learned behaviors. Since most people use their dominant hand throughout their lives, it's difficult to isolate the effects of practice. They asked healthy right-handed individuals to write not only with their hands but also with their elbows – a part of the body rarely, if ever, used for such a task.

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Dominance of one limb is often considered evidence that the dominant hemisphere of the brain has better motor control. We tested an alternative hypothesis - that dominance reflects years of practice using tools and objects that require precise and complex movements.

Participants first wrote the letter 'A' and the number '8' eight times each with their dominant and non-dominant hands. They then repeated the task using a pen attached to their elbow, requiring them to write with their entire arm. If hand dominance were purely innate, the expectation was that participants would write better with their dominant elbow than their non-dominant one.

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There were no significant differences between the dominant and non-dominant elbow. The dominance disappeared.

However, analysis revealed no significant difference between the dominant and non-dominant elbows. The expected advantage vanished. This finding led to a second part of the study where half the participants practiced writing with their dominant elbow and the other half with their non-dominant elbow. Initially, both groups performed poorly, but after practice, the quality of writing improved significantly for both.

"The dominant hand is not more capable because one hemisphere of the brain controls movement better. It is more successful because we have practiced complex movements required for writing and using tools throughout our lives. When we remove that practice and transfer the task to the elbow, the advantage disappears," explained neurologist Ahmet Aradž. The study suggests that many fine motor skills, often attributed to inherent brain differences, may actually be honed through years of dedicated practice.

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The dominant hand is not more capable because one hemisphere of the brain controls movement better. It is more successful because we have practiced complex movements required for writing and using tools throughout our lives. When we remove that practice and transfer the task to the elbow, the advantage disappears.