Why "Handedness"?

Why is it that the majority of humanity favor a hand, either left or right? Is there such a thing as being truly ambidextrous?

Is it brain-hemisphere related? Or a heavy combination of factors?

I believe it is brain hemisphere related, and I also believe it is hereditary. Someone more knowledgeable will be by soon to explain it all.

BTW, the majority of humanity is right handed.

It’s not just humans. Horses have a “side” as well, and I believe dogs as well.

(Being right-handed myself) I think we all know the indescribable feeling that our thoughts and words seem to flow right from your mind to that hand without having to think about it. I’m not sure I can ever divert that “flow”, in the same degree, to my left hand, if I ever lost use of my right.

So it could even be a deeper “mammalian trait”?

When you use a hand more often, you get better at using it. And being really good with one hand is usually more useful than being mediocre with both.

Also, if there’s anyone here that had to struggle with a situation like this, I’d love to hear your story.

An interesting idea, and seems the most intuitive. There are some areas I think most humans are naturally ambidextrous in; like typing or drumming.

Would we really be mediocre with equal dexterity in both, or would they both be just as adept? Or perhaps can reach maximum dexterity, but would take longer to achieve, over favoring a hand?

The really odd part is the frequency of right-handedness in humans. I don’t know if any other mammal shows anything but a 50:50 split in handedness.

There is also footedness, which doesn’t necessarily correspond to handedness.

I think I read somewhere, most people favored an eye. I don’t notice this, but maybe for aiming?

Also, I know for myself, that I feel my comprehension for conversation is much easier in my left-ear when using the phone; to a noticeable degree over using the right ear.

I think practice does have something to do with it. I recall seeing people who have lost the use of their hands be able to type, drive, and do a lot of grasping with their feet. I have virtually no control over my toes, except maybe my big toe.

So if a person can train his feet, they should be able to do it with their hands.

I think it seems a bit more ingrained than it is, since we put so much importance, on writing.

For instance, I write right handed, but my left hand is much more dominant in other areas. I bat left, bowl left, I hammer with my left hand, and can use a mouse with my left or right hand equally as well. But because I write right handed it “handedeness” may be a bit too much emphasized on writing.

This guy says that of 500 horses examined, 75% were right sided, and less than 1% were “extremely” ambidextrous.

There is definitely a genetic/environmental component to it as well, though. If it were only practice, the world would be evenly split between right- and left-handers. But something like 90% of the world is right-handed.

Of course, you can learn skills on the other hand through enough practice. Ask anyone who got ruler-thwacked by a nun for writing lefty.

I had a teacher that was truly ambidextrous; I have heard that this is very rare.

A couple of generations ago it was common to try and convert left-handers to right-handedness for writing and other activities. This was, by virtually every account, a disaster for left handers. Many of them developed a stutter (see The King’s Speech), dyslexia or other learning disabilities.

My father was “turned” to right-handedness in elementary school. As a result, he never developed fine motor skills with his left hand, although he retained more physical strength with his left. And with both me and one of my sons being left-handed, I can testify first-hand that, while we can do far more with our right hands than most right-handed people can do with their left hands, we’re a long way from being “just as adept” even with a lifetime of practice.

Back when I was studying sport psychology, we were told that the word ambidexterity doesn’t mean what most people think it does. True ambidexterity, they said, is a disorder called “incomplete dominance”.

You need to have a dominant side, probably because of how the brain works. The example I remember was this:

Three kids are waiting for a bus on a snowy day. One is right handed, one is left handed and one is ambidextrous / incomplete dominant. Three other kids throw snowballs at them. The right handed kid uses his right hand to block the snowball, while the left handed kid uses his left hand to block the snowball. However, the “ambidextrous” kid is hit in the face because he does not have a fast enough autonomic response, lacking a dominant side. He has to choose which hand to use.

A person who does have a dominant side may also become skillful using his other side, but these people do retain a dominant side. This is seen frequently in left handed people for a couple of reasons - our society is mostly set up for right handed people, which forces lefties to adapt, and in the past left handedness was actively discouraged and this forced some lefties to change. I believe this was known to harm people.

I also seem to recall that it’s a warning sign for developmental problems if a child hasn’t shown a dominant side by around age 6 or so. Earlier than that, they experiment with various tasks using both sides.

Edit: Just read Kunilou’s post - that’s what I meant by causing people harm in trying to change their dominant side.

Pick out a fairly small feature across the room (say in an office a sprinkler head on the ceiling.) Make a triangle out of your hands and position your hands so you can see the sprinkler through the triangle. Close your eyes for a few seconds. Open them. Close your left eye. Close your right eye. Through which eye can you see the sprinkler? That’s your dominant eye. It does matter in shooting.

ETA - and in pool.

“Dexterity”, of course, comes from a root meaning “right-handed”.

I was born a lefty and my mom ‘turned’ me. I qualified ‘Expert’ on the M-16 with both my left and right hands, but my penmanship sucks.

I throw with my right hand, but I hold my camera to my left eye.

I’m right-handed but left-eyed. Instead of trying to learn to shoot with my right eye, I found it was easier to learn to shoot lefty. Though it makes working most bolt-actions difficult (unless it’s a left-handed gun) when trying to shoot for scoring.