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 arms 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 while weighed down. But it didn't.
The only noticeable gap appeared when participants had a lightweight stick attached to their forearm, which they moved like a pen or racket. Only then, with those finer motor skills, did the dominant hand excel, since it had a lifetime of practice honing these details.
The researchers then asked volunteers to write using a pen strapped to their elbow instead of their hand, testing an even stranger kind of motor control. Both elbows performed equally poorly. But after some training, participants improved with both elbows at roughly the same rate, regardless of whether the elbow was on the dominant or nondominant side.
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.