BS: Left-Handism

Subject: RE: BS: Left-Handism
From: GUEST,leeneia
Date: 10 Jul 11 - 11:19 PM

Lefthanded and owns a dachshund? Sounds like w wonderful person to know. I envy you, Rap.

Rumncoke, I agree that people should use both hands as much as possible. I often tell people, "Make friends with your left hand."

It's sad to hear people say, "I wanted to play piano (for example), but I can't get anywhere with my left hand." Every task that uses both hands takes time to master. Messages have to go from one hand to the brain, across the brain and to the other hand. We need to learn that there will be a period of awkwardness and defensiveness at first, but then the skill will come.

Subject: RE: BS: Left-Handism
From: Clontarf83
Date: 11 Jul 11 - 12:29 AM

Has anyone ever heard if there is a piano for lefties?

Before I started school my mother went to the school teachers and told them I was left handed and to leave me alone. (A kid down the street developed mental function problems when the Brothers beat him into writing with his right hand.)

I play guitar , mandolin right handed. Also golf. I am told that some golfers at the PGA level play left handed even though they are naturally right handed.

I read many moons ago in a back page of the globe and mail (Canada) that cultures with a high proportion of left handedness have higher murder rates. Maybe this explains why the Latin for leftie is "sinister"...

Subject: RE: BS: Left-Handism
From: Penny S.
Date: 11 Jul 11 - 02:49 AM

I saw a paper on the violence issue - I think the idea of the researchers was that where there is a lot of fighting, lefties have an advantage because the righthanders do not expect and have not devised defences against a leftie. The Border family Kerr was one which had a lot of lefties. I remember that one family built their spiral stairs the "wrong" way, so that they had the advantage in defence. The usual curve allowed defenders to use the right hand. It occurs to me that if the curve favours leftie defenders, it also favours rightie attackers.

It also seems likely that as the number of lefties rises with increased violence, the righties would learn to defend against leftie opponents, so there would be a limit to this situation. I am rather worried about the almost totally pacifist tribe with almost no lefties at all. I suppose it isn't impossible that random processes would lead to this situation, but I would like to know what happened to lefties that did occur.

If the hypothesis that righthandedness is inherited, but lefthandedness is not, it is going to be much easier for members of lefthanded families, with weak handedness, to learn to use either hand than for genetic righties, with a strong laterality.

Penny

Subject: RE: BS: Left-Handism
From: JohnInKansas
Date: 11 Jul 11 - 11:19 AM

A perhaps curious (to some?) case of handedness is obvious among trades/crafts people in my area in the case of "metal snips" used quite commonly.

Called "aviation tin snips" (although almost nothing in the aviation industry has tin in it) the "compound lever metal snips" come in left-hand, right-hand, and "combination" versions, and it's common for them to be sold in sets of all three.

a picture

the theory?

The "right-handed" ones have the blades arranged, and a relief on the upper blade, so that they easily follow a curve that turns to the right. The blades "point" at an agle to the handles so that the hands will be well above what's being cut. They're not particularly efficient for a curve to the left. The right-handed ones always (traditionally) have a green handle.

The left-handed ones have the blades reversed so that they follow a curve to the left easily, but don't work well if the curve goes to the right. The blades are at an angle to the blades so that the hand clears. The left-handed ones always have a red handle.

The "combination" ones have symmetrical blades so that they are a little easier to use to make a straight cut, but not too suitable for other than very gentle curves in either direction. The blades are on a straight line with the handles. The combination ones always have a yellow handle.

Virtually everyone who does "mechanical" work in the aircraft industy has a green handled one in the tool box. Perhaps 10% might have a yellow handled one. Red handled ones are extremely rare.

Although an explanation for the relative popularity of the three kinds should be left for a question on the quiz at the end of the class - - -

The reason that few people have both red and green (right and left) is that either one is sufficient. If you use them with the handles above the piece being cut, the curve goes one way; but if you put the handles on the other side the curve is reversed. (Pause to think and it will be obvious.)

If it's inconvenient to "cut from the other side" you can almost always turn the sheet over and lay out the curve on the other side of the sheet.

Since the "right-cut" (green handled ones) give better visibility of the curve you're trying to follow if you're right handed, the "green" ones are more popular. Since there's no need for both, and either will do, there are lots of green ones the "lefties" can "borrow."

It shoud be noticed in this case that it's the tool that has "handedness" and it makes no difference which hand the user favors.

Quite obviously there's no such thing as a "curve right" or a "curve left" if you look at it from the other side.

So by extrapolation, we may conclude that those odd people are not left-handed. They're just upside down.

As a side note, these snips are commonly called "Dutchmans" because the original maker (pre WWII) was named "Deutsch Mfg." Someone might holler "gimme a green dutchman" and everyone would know what was meant.

The original maker is now called Wiss," but I don't recall anyone yelling "gimme a green wiss" on the shop floor. (Sometimes it's best to respect traditional names?)

John

Subject: RE: BS: Left-Handism
From: MikeL2
Date: 11 Jul 11 - 03:25 PM

hi

I don't know if their is such a thing as a left handed tennis raquet??

But I heard somewhere that Raphael Nadal the World No 2 player is right handed but plays tennis left handed....go figure....

Incidently there is such a thing as a left-handed cricket bat.....really !!!

Does left-handedness follow in the genes?? In my family from my maternal grandmother down, all the females are lefthanded and the males right.

cheers

Mikel2

Subject: RE: BS: Left-Handism
From: Penny S.
Date: 11 Jul 11 - 04:33 PM

Cricket gloves and pads, yes. Bats, no.

Penny

Subject: RE: BS: Left-Handism
From: GUEST,Jon
Date: 11 Jul 11 - 04:52 PM

Cricket bats are handed. The bottom of the bat is shaped a little different where it passes your feet.

Subject: RE: BS: Left-Handism
From: Penny S.
Date: 11 Jul 11 - 04:57 PM

I've just read up the manufacture, construction and purchase of cricket bats, on several sites and not a word about handedness.

Penny

Subject: RE: BS: Left-Handism
From: GUEST,Jon
Date: 11 Jul 11 - 05:06 PM

Try shopping for this bat for example. You will see there are right and left handed options.

Subject: RE: BS: Left-Handism
From: GUEST,Jon
Date: 11 Jul 11 - 06:19 PM

I must admit that looking around now, that Grey Nicolls bat seems to be the only example I can find and that seems to be handed because the handle is offset.

Maybe they don't do it now but I'm pretty sure that at least at one time, if you looked at the edges of a bat, one was longer than the other at the bottom.

Subject: RE: BS: Left-Handism
From: Rapparee
Date: 11 Jul 11 - 07:42 PM

There is DEFINITELY handed-ness in fencing! Lefties have an advantage over righties because righties are used to fencing righties. Now if you want to REALLY throw off an opponent, use an Italian foil (ambi) and switch from right to left. Of course, it would help a lot if you practiced both hands first....

Subject: RE: BS: Left-Handism
From: gnu
Date: 11 Jul 11 - 07:47 PM

JiK... I have a full set of tin snips and they have nothing to do with hands as far as cutting goes but they are ALL right-handed snips because the grips are made for a righty. Don't they make a full set for a lefty?

Subject: RE: BS: Left-Handism
From: JohnInKansas
Date: 12 Jul 11 - 01:10 AM

gnu -

Most snips have a single pivot, and the cutting of a metal sheet is pretty much a matter of brute force on the handles. The force applied by the cutting blades against the metal is a simple mechanical ratio between the length of the handles and the distance from the pivot point to where the blades make contact with the metal.

The aviation snips have a second pivot point that allows the handles to apply a "multiplied force" to the smaller "headpiece" snip asssembly, so that the force applied to the handle is multiplied, usually by about 4x at the point where it's applied to the "handle end" of the actual cutting blades, which have an additional - usually about 1.5x to 2x - multiplication of the first force to the actual cutting force at the blade. The end result is that with the aviation snips the same handle effort applies close to 8 times the effect at the cutting point on the blades as would be obtained with a pair of single-pivot snips.

The "compound lever" effect is similar (conceptually) to using an enormous pair of pliers to squeeze the handles of your simple snips together - and the same effect as using simple snips 8 times as long as what you've got.

When you shear something the material on one side of the blade has to go in one direction and the stuff on the other side has to go the other way. When cutting sheetmetal (or the &#$@! #@$@! that HP puts their ink cartridges in) the cut sheet "springs back" and may bind on the blades and also may make it difficult to shove the shears further along the cut to make the next squeeze.

A secondary feature of the aviation snips is that the blades are "exotically shaped" to create a small amoung of "crimp" to the sheet as it's cut, so that it takes less effort to retract the blades (re-spread the handles) and advance them for the next cut.

Especially with soft metals like aluminum or copper, the "springback" as the blades are reopened is enough to require some effort to get the shear off the metal after you've made a cut. In most cases the simple snips have "loops" on each handle so that you can pull them back apart after making the "snip," and with some materials it can require almost as much force on the loops to open the blades as it does to make a cut. The shaping of the av snip blades reduces the "withdrawal" force suffiently that a small spring is sufficient for the return stroke, and the loops are not needed.

Especially since it's not necessary to have the loops to reopen them for the next cut, the handles of av snips are perfectly symmetrical, so that it doesn't matter which-handed the user is to use either-handed snips. The compound lever construction also permits a very massive pivot at the actual cutting blades, so that they're stiff enough that there's no need to apply "hand torque" to keep them from spreading.

Aviation snips are commonly "rated" for about 18 ga (0.050") steel, but occasionally the packaging will say 16 ga (0.0624"). Because I'm old and feeble, for steel that thick I'd probably use a hacksaw (or a cutting torch if I had one), but I've recently cut a few short snips in some 1/8" thick fairly soft aluminum with little difficulty.

With simple snips of sizes I have^*, cutting .06 thick steel probably would mean propping the snips up and hitting the handle loop with a 3 pound hammer. (And then I'd use a short crowbar to pry the blades back open.) It would be a little easier if the sheet was "dead annealed" but it's seldom found that way.

^* I think I've got a 14" pair somewhere in a toolbox?

But when we get to the bottom line here, about the only thing we can conclude with reasonable certainty is that gnu didn't look at the "theory" link in my previous post.

He probably thought the link was to something too technical, but the picture's actually from an article about how to use tin snips (av style) to crack pecans..

Incidentally, I actually do keep an old pair of Dutchmans next to the spare ink cartridges, because I recently broke a pair of kitchen (bone cutter) shears trying to get a fresh HP Inkjet cartridge out of their ridiculous package.

John

Subject: RE: BS: Left-Handism
From: JohnInKansas
Date: 12 Jul 11 - 01:31 AM

To answer gnu's question more specifically, I have seen left-handed simple tin snips, but it's possible the guy using them made his own. The couple of lefties I've seen had symmetrical handles, so in their case it was only the way the blades crossed that made them left-handed. Left handed (and left-handled) snips probably do exist as commercial items; but it's unlikely they would sell in sufficient volume to be in stock at any common retail tool outlets.

You might get help on it with a request for a special order through a hdw store that shows a decent tool selection. (That way the mfr guys will laugh at the dealer who wrote the order, instead of at you? Or you could use your real name on the order and just take the heat.)

My suggestion for the mid-sizes is that you pop in at Home Depot - or any other reasonably well-stocked hardware shop - and get one pair of Dutchmans (Compound Lever Aviation Metal Shears) in either right-cut or left-cut version, and after you try them out you'll want to decide which of your current set you want to move down to the bottom drawer where they're out of the way. The extra leverage, and some of the blade/jaw features, really do make them a lot more fun to use.

The Av Snips, incidentally, come in a whole bunch of "specials" like the one with double jaws that cuts a strip about 1/8" wide out of the middle of a piece of air conditioner duct - without significantly bending the adjacent metal on either side (so that you don't have to disassemble things to replace a bent area in a long run).

John

Subject: RE: BS: Left-Handism
From: GUEST, topsie
Date: 12 Jul 11 - 02:57 AM

Maybe the very old cricket bats had started off symetrical but the lower edges had worn away with much use.

Subject: RE: BS: Left-Handism
From: Penny S.
Date: 12 Jul 11 - 04:52 AM

Thinking about early bats, they had a pronounced curvature of some sort, and so maybe needed a leftie version. If people were allowed to play lefthanded back then, when writing was switched. It's odd, but my first thought was that modern ones would have an asymmetry 9n the thickness - but with Jon's exception, apparently not. There isa pub debate on the net on the subject, with not conclusion.

Penny

Subject: RE: BS: Left-Handism
From: JohnInKansas
Date: 12 Jul 11 - 06:34 AM

A few reference sites of Wiki ilk seem to agree that there's no such thing as a left-handed cricket bat, and multiple dealers offering "left handed cricket equipment" don't offer one.

There seems to be an implication that batting left or right is done for purposes of game strategy rather than to suit the handedness of the person using the bat. It is implied that all players should learn how to bat from either side. Most "Lessons on how to bat left handed" seem to start with unintelligible (to me) explanations of why and when you should switch from right to left for certain game situations.

This would imply that there is some sort of assymetry in how the playing field is laid out, or in some difference in preference for how players move left or right.

In circumstance other than cricket, many in the US observe that Brits in general are a bit "off-center" in certain respects, so those of us native to the US would be likely to easily accept that cricket fields (and players?) probably are mostly a bit cock-eyed.

John

Subject: RE: BS: Left-Handism
From: MikeL2
Date: 12 Jul 11 - 06:36 AM

hi

I played cricket for almost fifty years and when I first started there were definitely both left and right hand bats. As Jon said earlier the difference was the small cutout at the corner of the bat.

My son and grandsons still play and I note that my son still plays with a righthanded bat but my grandsons has "universal" ones.

Is this another sign of "progress" ????

Cheers

MikeL2

Subject: RE: BS: Left-Handism
From: GUEST,Jon
Date: 12 Jul 11 - 07:00 AM

Thanks Mike (and Penny, we are not talking about very early cricket bats).

Looking at bats now, it seems there is a lot more variation in the profiles of the bat there used to be (In say the late 70s there was a Gray Nicolls with a scoop out the back but that's the only one I remember that looked different to a "standard bat"). So usually a "universal bat" but with more options in terms of shape around?

I wonder how they make them these days. I've always thought of them as hand made but I wonder if CNC machining is used somehow.

Subject: RE: BS: Left-Handism
From: MikeL2
Date: 12 Jul 11 - 09:26 AM

hi Jon

Yes there is much more choice in the type and style 0f cricket bats these days.

I remember well the Gray Nichols scooped out bat. Didn't use it myself. I always used Gunn & Moore. Just a personal choice.

To answer you point about whether bats are massed produced or hand made, I guess the answer is both. Players who can afford it can have specifications eg weight & weight distribution, type & length of handle, types of shoulder and even left or right handed !!!

Certainly most professionals will have hand made bats and some club players will try them in attempts to improve their performances.

There is the old chestnut about the rich woman who returned a cricket bat to the shop saying that the bat was useless as her son had used it several times and had not managed to score any runs with it.

Cheers

MikeL2

Subject: RE: BS: Left-Handism
From: Green Man
Date: 12 Jul 11 - 10:32 AM

I play the Melodeon right handed and the guitar left handed along with the mandolin and any other stringed instrument. I play the harmonica both handed, so, am I right or left handed?

Subject: RE: BS: Left-Handism
From: GUEST,leeneia
Date: 12 Jul 11 - 10:57 AM

From what I read, people who are 100% left-handed are rare. You and I, Green Man, who use one hand or another for various tasks, are more common. However, we don't have a word for that.

We label a person lefthanded merely if she writes with her left hand. That's simplistic.

As for that tribe that's lefthanded and more violent, I don't believe it exists. Or if it does, we need to look at all the facts about it.

(Did you know that Eskimos do not have a large number of words for snow? Somebody made that up, and journalists have been quoting it for decades. It's probably the same for this convenient tribe.)

Subject: RE: BS: Left-Handism
From: Rapparee
Date: 12 Jul 11 - 06:52 PM

Go and seek a left-handed trumpet or trombone or any brass instrument (bugles and such excluded).

Subject: RE: BS: Left-Handism
From: Penny S.
Date: 13 Jul 11 - 12:31 PM

Here's the article about violence, the tribal variations.

Are lefties sinister?

There's a piece in Wikipedia as well.

As to the cricket field, the placing of the fielders varies according to how the bowler is expected to bowl and the batsman to deal with the ball, so does have a varying asymmetry.

And bat making, no reference to handedness.


Making bats.

Subject: RE: BS: Left-Handism
From: GUEST,MikeL2
Date: 13 Jul 11 - 02:52 PM

hi penny

Please don't think that I am being pedantic. The example of making a bat was of just one manufacturer.

If you Google "Talent Cricket Specialists younwill see that they do offer left-handed bats. <" Gray Nicolls Edge Pre - Prepared Cricket Bat".

I am going away for a few days so will not be around on Mudcat for a while.

Kind Regards

MikeL2

Subject: RE: BS: Left-Handism
From: GUEST,leeneia
Date: 14 Jul 11 - 10:30 AM

I read Penny's link. It is based on only two tribes, one in South America and one in Africa.

Presumably the author searched the literature until finding two tribes out of all those available that supported his/her prejudice.

I was amused by the parellel to boxing. I doubt very much if these poeple engage in conflict by standing up, man-to-man, and demanding a fair fight. No, skulking in the underbrush and throwing a spear (blow gun, rock from a sling) is lot more like it. In that case, handedness doesn't matter at all.

To me the interesting question is why does the South American tribe show 22% left-handedness. (How exactly do you determine handedness in unlettered people, anyway?)

Subject: RE: BS: Left-Handism
From: GUEST,mg
Date: 14 Jul 11 - 03:04 PM

Well, they still eat, comb their hair, throw things, stir pots. mg

Subject: RE: BS: Left-Handism
From: Rapparee
Date: 14 Jul 11 - 04:27 PM

Try this sometime:

1. Close one eye.
2. The one that remains open is your "dominant eye."
3. If your left eye is dominant, you would shoot (archery, rifles, blowguns) best left-handed.
4. This has no relation to your "strong hand" but rather to your eye-brain-hand coordination.

Subject: RE: BS: Left-Handism
From: Penny S.
Date: 14 Jul 11 - 05:48 PM

MikeL2, I wasn't trying to counter the Gray Nichols bat, just adding to what someone else posted about the making of bats with a link I had found interesting.

Penny

Subject: RE: BS: Left-Handism
From: Penny S.
Date: 14 Jul 11 - 06:28 PM

Leeneia, here's another link to reports on the paper. It mentions different tribes out of the nine studied. Apparently the study went further than that and did involve more than a literature search. I'm trying to find the original paper, but presumably it was peer reviewed. On the other hand, (oops, accidental, but I'll leave it) the link in the wikipedia article references doesn't go anywhere, so it might have been one of those things where scientists release stuff unreviewed to the press as part of their grant bid process. It seems that the study was related to the number of lefties in sports being larger than the proportion in the non-sporting population.

Another report

I don't think the idea was to say that lefties were more violent, but that a society which was more violent would favour lefties.

I would imagine that handedness would show up in pre-literate societies in craft activities as well as hunting and fighting. Any sort of making activity would need a dominant hand.

But one thing does bother me about the study, more than the high numbers of lefties in bellicose groups. The pacifist societies had far lower numbers than would be expected, and I wonder if those societies also have a strong pressure not to be lefthanded, with individuals learning to use their right hand rather than be ostracised. Most lefthanders can learn to use the right, as was shown in the case of handwriting in schools before the schools became enlightened. I don't like to think about the other possibility.

Penny

Subject: RE: BS: Left-Handism
From: GUEST
Date: 14 Jul 11 - 08:30 PM

Hotter than a whore in the electric chair...

Going thru three changes of clothes every day just to keep workin'... Set up a drying rack in the garage and just recycling...

Nasty...

B~

Subject: RE: BS: Left-Handism
From: Crowhugger
Date: 14 Jul 11 - 10:41 PM

«You and I, Green Man, who use one hand or another for various tasks, are more common. However, we don't have a word for that.»

The word I settled upon to describe it is "bidextrous."

Subject: RE: BS: Left-Handism
From: GUEST,leeneia
Date: 15 Jul 11 - 09:57 AM

Unless somebody spent hours and hours over a period of months and months and kept records while they were at it, they couldn't say whether a person in a nonliterate society is lefthanded or not.

When it comes to tasks, people cannot predict what hand they will use, and they may use one hand one time and the other hand another time. They may prefer the left hand for one task and the right for another, similar task.

For example, when I wore contact lenses, I washed them with my right hand and inserted them with my left. It was years before I even noticed that I was switching hands.

My husband, who I thought was the most right-handed guy in the world, demanded a left-handed mouse. One never knows, do one?

Subject: RE: BS: Left-Handism
From: Rapparee
Date: 15 Jul 11 - 10:18 AM

Well, as the song says "...that's the hand you use...well, never mind."

Subject: RE: BS: Left-Handism
From: JohnInKansas
Date: 16 Jul 11 - 02:15 AM

Has ayone seen an explanation for the several languages that are written right-to-left? Is there some tradition for the "scholars" to be (or affect being) left handed?

A couple of eastern(?) languages are commonly written top-to-bottom in columns, but all of those that I've seen "explained" are also right-to-left when going from one column to the next. Any explanations?

Da Vinci wrote most of his stuff in Latin but reversed (right-to-left) and the common explanation was that it was "a code" to make it harder for anyone to read and steal his secrets. I'd suspect the real reason was that he was a leftie, but I don't think I've ever seen an "authoritative" comment on it. (?) Maybe he was actually dyslexic, since he seemed to think out of both sides of his brain (and outside his head sometimes?).

John

Subject: RE: BS: Left-Handism
From: Penny S.
Date: 18 Jul 11 - 02:07 PM

I've been using my sewing machine this weekend, and realised I was using it lefthanded, according to the picture in the instruction book. That shows the right hand nearest the user, feeding the fabric under the foot, while the left hand moves it away behind the needle. I do it the opposite way. But then, I learned on a hand-turned machine, and my right hand was otherwise engaged. You can probably tell people who learned that way from those who learned on electric machines by the way they use their hands.

Penny

Subject: RE: BS: Left-Handism
From: GUEST,Stringsinger
Date: 19 Jul 11 - 11:06 AM

I've heard that there is a correlation with being left-handed and left-eyed and vice versa. Pick up a camera or a piece of paper with a hole in it and bring it quickly to your face. Which eye is used? Does this correlate with your strong hand? Sometimes, when one is right-eyed and left-handed or vice-versa, this is called "cross dominance".
Some psychologists say that this will create problems in behavior.
Don't know if that is true. Ambidextrous people seem to fare all right.

Subject: RE: BS: Left-Handism
From: GUEST, topsie
Date: 19 Jul 11 - 11:39 AM

I have heard that there is an association between "cross-dominance" and dyslexia.

Subject: RE: BS: Left-Handism
From: GUEST,Jon
Date: 19 Jul 11 - 11:47 AM

Just tried the camera. I (left handed) seem to use my left eye. I'm not sure it's to do with eye dominance (and trying holding a finger up and closing each eye seems to suggest I'm right eye dominant) though.

It just feels more natural/comfortable for me to hold that way and I'd guess has more to do with handedness.

Subject: RE: BS: Left-Handism
From: GUEST,Jon
Date: 19 Jul 11 - 11:53 AM

And a further thought...

Sometimes, I debate "handedness" in the sense of using a better hand. With some things, eg. playing a guitar (which I do right handed) or using a cricket bat (which I would left handed - although oddly enough to me bat and guitar both feel like holding an object the same way round if that makes sense) but one of (I suppose) position/orientation.

Subject: RE: BS: Left-Handism
From: JohnInKansas
Date: 19 Jul 11 - 12:32 PM

The "accepted" test for eye dominance requires a couple of steps.

The most common instruction is that you hold up your thumb at arms length and with both eyes open, line the thumb up with a distant object. Then close one eye.

After you close one eye, if the thumb is still lined up you closed the non-dominant eye. If the thumb/object alignment "jumps" to a different alignment you have closed the dominant eye.

This test is almost universally taught to all precision handgun shooters, since aligning with "the wrong eye" will cause "flyers" that may miss the target by a very large distance.

Beginning shooters are often taught to "block the non-dominant eye," with an eye patch or some other device to avoid alignment accidents, but once using the "correct" eye consistently is learned, blocking of the other eye is usually discarded, although a very few experienced shooters may continue to "patch" if their dominance is very weak.

Most experienced handgunners shoot with both eyes open, but consistently "form the sight picture" from the dominant image.

The degree of dominance is variable, and I've known a couple of people who claimed that one eye was "usually dominant" but that the other eye sometimes "took over" under different conditions. (Usually fatigue or eye-strain related?)

A few people have claimed that one eye is dominant for distant viewing, but the other takes over for near objects. In the one or two such persons from whom I've heard this claim, the problem went away after they got new (properly prescribed?) corrective lenses in their glasses.

Good handgun shooters with cross-dominant vision are fairly rare, but probably in about the same percentages as for the general population.

I've known a couple of "experts" who fired right-handed using their left eye with no noticeable difficulty. I've seen no (competent) reports of any accepted theories that cross-dominance is associated with any maladjustment or other effects of personality.

The somewhat faddish popularity of "3-d" pictures and posters, in which you attempt to "hyperfocus" on scrambled images to "see" the two separate images as a "sterieo picture" has been implicated as a cause of deterioration in vision, "damaging" eye strain, and in a few cases some (probably temporary?) psychoses. There was an appearance of "popular art" of this kind ca. early 1950s, and I've seen a couple of advanced text books that attempted to use the "feature" to print three-dimensional graphs of "electron trajectories" and the like, but the practice didn't last long and appears to have faded due to complaints from ophthalmologist and psychiatrist associations who made credible claims that it was being observed to cause harm.

There have been a couple of cycles of reappearances of the 3-d posters/pictures. It appears that only people with "weak eye-dominance" see the 3-d images easily, hence easier visibility for people with "young eyes" (not necessarily related to the persons' ages). During the earlier appearance, "wedge lens" glasses could sometimes be found to assist others, but I've seen no such aids during subsequent cycles of the fad.

John

Subject: RE: BS: Left-Handism
From: GUEST, topsie
Date: 19 Jul 11 - 01:30 PM

I tried the test for eye dominance and found it impossible - if I focus on the distant object I see two thumbs, and if I focus on the thumb I see two of the distant object. How distant does the object have to be?

Subject: RE: BS: Left-Handism
From: JohnInKansas
Date: 20 Jul 11 - 05:18 AM

For most people an object 100 yards away is "distant enough." If you're unable to pick a thumb (one is clearer than the other) when focusing that far away, it's likely that neither eye is sufficiently dominant for your brain to have learned to ignore the other image - or that your distant vision is poor enough that you're not really focusing on the far object^* - just "blindly pointing at it".(?)

When you focus farther away, everything up close is seen in "double vision," and if your brain doesn't "filter it" to remove one or the other of the two pictures confusion is likely.

(Perhaps we should suggest that nobody should offer "that explains a lot about topsie" but I'm not gonna say anything.)

The same thing happens when you focus on something up close. Everything farther away is seen in double vision, but most people adapt so as to ignore (or just "blur out") the parts of their field of view where the parallax effect is too significant for comfort.

If your eyes are so well matched that neither eye shows easily observable dominance, it shouldn't really cause any significant problem as long as you're aware that you may need to close one eye for some tasks that require "critical focus."

For the above cited pistol shooting, it is absolutely essential that your point of focus must be on the two sights, front and rear, of the pistol. Those two sights must be aligned with each other within about 0.001 inches or less to hit the center ring on the target. There's no problem at all if the target is nothing but a blur, because even a blur has a center and that's what you're trying to hit.

A situation you're perhaps more likely to encounter, where suppressing (closing) one eye may aid in getting the sharpest possible focus with the other eye might be something like threading the needle on your sewing machine. With one eye shut, you lose the aid of any "stereo depth perception" but may gain enough from seeing a single image more clearly so that you can hit the hole in the needle more accurately. (For hand stitching, you don't put the thread through the hole in the needle. You hold the thread up and put the needle on it - as I'm sure you've been taught. A much easier task.)

^* As people age and their "depth of field" diminishes, it's common to prescribe lenses that actually set the maximum distance to which you can focus at about 2/3 of the way to the farthest thing you might need to see with some clarity, to take advantage of what's called the "hyperfocal point." Focused at 2/3 of the way (approximately) to the farthest point that's significant gives a camera the maximum possible depth of field, so that the largest part of what's beyond the focus, and the largest portion of what's in front of it, are "least blurred." While this (sort of) works for people, in most cases the camera only has one eye while we (mostly) have two, so "brain power" is still necessary to help us "ignore what doesn't fit."

(Maybe you're experiencing a deficit in your "ability to be sufficiently ignorant"?)

John

Subject: RE: BS: Left-Handism
From: GUEST, topsie
Date: 20 Jul 11 - 06:23 AM

Thanks - I'll try to be more ignorant (and less confused?) in future.

Subject: RE: BS: Left-Handism
From: Deckman
Date: 20 Jul 11 - 07:52 AM

I thought I'd weigh in on this thread with a rather serious, and I suspect common, problem. My father was a lefty. I was born a lefty, yet when I entered grade school in 1943, it was the accepted practice that those children who reached for the pencil with their left hands, were somehow defective. Being only six, I couldn't dispute this.

By the time I was in the third grade, and under the "teaching" of Mrs. Spaulding (she taught penmanship) I knew that I was quite a defective person. I knew this because she told me so every day. She said I couldn't "hold a pencil right" (write?), 'nor could I write well.

For most of my life I lived with serious writers block. I knew, early on that I couldn't write!

Fast forward to about 18 years ago, when my life long friend Walt Robertson passed away. Mark Moss, of Sing Out magazine, contacted me and asked me to write Walt's obituary. I totally freaked out! WHAT ... ME WRITE?

After three weeks of pure hell, I finally submitted 300 words that were published unchanged. That was a pivitol moment in my life.

Today, I find myslef writing a great deal. And the positive response I receive is most gratifying.    Take THAT Mrs. Spaulding! bob(deckman)nelson

Subject: RE: BS: Left-Handism
From: JohnInKansas
Date: 20 Jul 11 - 01:05 PM

topsie

I do like Ghandi's mention (paraphrased) that "teasing must be limited to those you respect." I hoped you wouldn't mind.

John

Subject: RE: BS: Left-Handism
From: GUEST, topsie
Date: 20 Jul 11 - 01:29 PM

John, no of course I didn't mind!

Next time we have a clear night I'll try holding out my thumb in front of the moon[s].

Subject: RE: BS: Left-Handism
From: Rumncoke
Date: 21 Jul 11 - 05:32 AM

I'm right eyed and fairly left handed, and somewhat dyslexic - though not diagnosed, as it didn't exist when I was at school.

I found that some teachers did not believe it existed - I was with a Reception class teacher who was complaining about having to do a test for dyslexia on her pupils and did not believe me when I said that I could not pick out the matching card from the third set - the first two were of things I could remember, the third were too abstract.

She was really quite angry with me. I was in my twenties then. How a little dot just four years old would cope with the experience I can't imaging.

Anne Croucher

Dorset England

Subject: RE: BS: Left-Handism
From: GUEST,leeneia
Date: 21 Jul 11 - 09:35 AM

Interesting! Thanks for the account, Anne.

Subject: RE: BS: Left-Handism
From: GUEST, topsie
Date: 21 Jul 11 - 10:33 AM

I'm wondering whether there could be a conflict between the choice of eye according to right or left handedness/eyedness and the choice of image according to which lens gives the clearest picture.