An eighth grader in Virginia recently wrote me with some questions for a school project. Here are my (hurriedly composed) responses:

What do you think affects hand dominance most?
What are the physical and mental differences of left and right handed people?
Why do you think most people are right handed?
Do you think it is better to be left or right handed?(Why?)

Hello [insert name of impressive student]. Thank you for writing and for your sharp questions. Here are some quick answers for you.

1. I think biology influences hand dominance the most--at first. In other words, we are born with certain programming. But from day 1 and every day thereafter culture and environment also influence our behavior, including hand dominance.

2. Physical differences are easier to grasp than mental ones, and they are mainly the stuff you see every day; the preference for holding a pen or throwing a ball or chopping vegetables with one hand versus the other. But we also know that lefties tend to lean a little more toward the mixed-handed range, whereas righties are more often strong righties, which is to say that they do pretty much everything with the right hand.

As for mental differences, this is a mystery. For the most part, when it comes to how people think and who they are, we can't reasonably generalize and say lefties are this and righties are that. One exception is that for tackling certain tasks, the brains of lefties use both sides of the brain a little more than righties do. This isn't at all a good or a bad thing--it's just something that scientists have observed and that they, like me, find curious. And they, like you and me, hope to find answers someday as to what that might mean when it comes to who we are as people or as individuals. Maybe you will be the person to crack that puzzle.

3. The very short answer is that this is a genetic phenomenon. Having left-handed people in the population clearly isn't disadvantageous for our species. It might be a stretch to say that it's an advantage, though. The more subtle truth is probably that the genetic diversity that sometimes leads to left-handedness is good for the species as a whole.

4. It's better to be left-handed, or course! Because you're a step closer to first base, because you're like a number of recent US presidents, because you get special scissors, and because you approach the world just a little bit differently from the majority of the population.

Best wishes,

AuthorDavid Wolman