Whether you’re left- or right-handed might not have as much to do with biology as it does with how much time and effort you’ve spent using one hand over the other. According to a new study published in the Proceedings of the National Academy of Sciences, the real advantage of your dominant hand may come from decades of practice with it rather than anything your genes are telling you to do.
The nature of handedness has been debated for decades, specifically whether it’s controlled by one hemisphere of the brain over another. Researchers at UCLA and Johns Hopkins University decided to test that idea by separating raw motor ability from learned skill.
Researchers had volunteers perform basic reaching tasks with both arms, first as they normally would and then with a four-pound weight strapped to their wrist. Both performed about the same. The dominant hand didn’t show any meaningful advantage. If one side of the brain were inherently better at controlling movement, the dominant hand would have outperformed the other since it was being weighed down. But it didn’t.
The only noticeable gap appeared when participants had a lightweight stick attached to their forearm, the tip of which they had to move around the same way they would using objects like tennis rackets, pens, and paintbrushes. Only then, with those finer motor skills, did the dominant hand excel, since it had a lifetime of practice honing these finer details.
Regardless of Handedness, No One Can Write With Their Elbows
The researchers then asked volunteers to write using a pen strapped to their elbow instead of their hand, because clearly, by this point, they were having a ball coming up with ridiculous things for the volunteers to do. The results were about as spectacularly terrible as you’d imagine, but the real scientific value here is that they were about equally bad on both the left and right elbows. Makes sense, considering that no elbow has experience writing. But, after some training, participants showed some visible improvement in their elbow writing. The improvement was in both elbows, and it happened at roughly the same rate, regardless of whether it was a dominant or nondominant arm.
All told, the findings suggest that the brain isn’t favoring one hand or the other. Instead, it seems that years of practice and the development of an extensive set of specialized movements are a better indicator of handedness than anything dictated by internal wiring.
The study doesn’t change the fact that hand preference begins before you’re even born, but it does argue that what you do with those hands afterward, the skills you develop with them, and ultimately the preference is shaped more by repetition than by genetic destiny.
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