If a baby sleeps better, it cries less. If it cries less, it attracts fewer predators and helps both parents sleep better at night and have more energy. It also allows the mother to do things with her dominant hand if she is right-handed.
Given the left-handed cradling bias exists even with left-handers, it means there is something specific with left-handedness and infant rearing. A baby in the left hand and a tool (or weapon) in the right is biologically efficient.
Most studies take this from the perspective of evolutionary advantage of the individual. They should take it from the perspective of evolutionary advantage of the family, without which the baby does not survive.
If the bias confers evolutionary advantages, that is also important for the longer childhood humans have compared to primates, which supports our larger brains. Any differential here would have a feedback effect.
Wouldn't it be interesting if a key reason humans are the way we are is a mother's love ♥?
[1] https://sites.psu.edu/clarep/2024/04/12/the-left-cradling-bi...
In a nutshell, the paper basically says that the lateralization that led to the predominance of right-handedness occurred around the time humans became bipedal and around the time of neuroanatomical expansion, possibly related to bipedalism.
In other words, before these two changes, we used all four limbs for locomotion and had no preference for either forelimb for grasping. Then one or two things happened and right-handedness predominated. It seems that that neuroanatomical expansion took over the areas of the brain that previously allowed our left hands to be as capable as our right hands.
I write "one or two things happened" because it wasn't clear to me from the paper whether the neuroanatomical expansion that led to lateralization was necessary to and part of bipedalism, i.e., caused by our locomotion bits taking over other parts of the brain to manage our balance, or whether it was merely coincident with it.
Interesting questions asked and answered, more research needed.
My take is that when they added extra factors to the Bayesian model, the plot was such that humans were no longer outliers.
Whether or not that's scientifically rigorous, or even interesting, I leave to others to determine.
Paraphrase: Amongst primates there is a correlation between brain size and bipedalism with handedness… (unless you exclude humans, in which case there isn’t.)
That’s like saying: “Alongst animals there is a correlation between height and neck length… unless you exclude giraffes, in which case there isn’t.”
If a correlation disappears when you remove one datapoint, then the correlation was not really a broad pattern across the dataset. It was mostly a story about that one datapoint.
I mean, I get it… you gotta publish something. But, geesh… this is beyond stupid.
Also fun fact, kangaroos have this same 90-10 split: https://www.nationalgeographic.com/animals/article/150618-ka...
It's a bit more varied, even in the Indo-European family. What does tend to happen is that the words for handedness get positive (right) or negative (left) associations in idioms, but additional meanings are not universal. In French, "droit" additionally means right (as human right), but not "correct" (yes it does have a bunch of adjacent meanings). In German, "recht" gets to mean "law" or "justice", shared by some Slavic languages ("pravo") -- but not all of them, which have the word "desno", without any association with rights/justice/correctness. The Latin "dexter" gave us "dexterity" and "dexterous", but also nothing alluding to justice. Et cetera.
As an aside, "left" originating from "left over" sounds like folk ethymology to me. Dictionaries point to "weak" as the original meaning.
Edit: or maybe indo-european and semitic to be more broad.
In ping-pong where it is pure competition it stabilises at 50:50. In everyday life where we largely collaborate it settles around 90:10.
Would be interesting to see if there are variations over populations in time or space with differing levels of competition/conflict. Ofc these would need to persist long enough for the populations to adjust.
P.S. This is probably just another plausible sounding evo-psych bs theory. Idk why people give AI such a hard time for hallucinations. We are just the same. I guess we generally just apply more filters before expressing ourselves publicly. The problem with AI content is that humans take it at face value and publish without scrutiny.
Over the years, I (and I imagine many others) switched over to WASD to play newer games with mouse + keyboard, but this meant using the left hand for "arrow keys"
Now I can directly compare how proficient I am with WASD vs Arrow Keys and the result surprised me. I was way worse with arrow keys (right hand) even though back when WASD was becoming a thing I'd rebind WASD to arrow keys because it felt too weird! I would've never imagined back then that WASD could ever feel as natural as arrow keys.
Makes me wonder how much of handedness is truly innate vs learned.
1. Some schools actively punished children for writing left-handed.
2. Pretty much every utensil was made for right-handed people. I don't recall ever seeing left-handed scissors, for example.
3. You learn by copying those around you. If your parents, teachers, and peers are predominantly right-handed (and are even actively encouraging you to be right-handed), then you're likely to toe the line.
I imagine the final point would remain a factor long after the first two are addressed.
The question from the headline is excellent, if only it was actually answered.
In particular, I would expect the influences to be somewhat counter intuitive. With things like having to use the left hand to hold a caregiver's hand in early walking preferencing the right for accessory use. At infant ages, it would be neat to see if preference of holding a baby on a side influences things.
And, similarly, I don't think this is unique to hands. It is just that most people don't know what their "dominant" foot or eye are. (I'm now curious to know about dominant ears. That is almost certainly a thing?)
My question is largely one of curiosity to know when the dominance fully sets in.
Flat-picked guitar solos (bluegrass, metal, country, ...) keep the left hand as busy as the right, and at times more busy. The left hand can easily outpace the right, which is why there are techniques like triplet 16th notes: playing 24 notes in a 4/4 time measure, while picking as if there were only 16.
Guitar playing is ambidextrous, like piano, at the higher levels of mastery.
But at the beginner stage, like learning to strum chords, that's where right-handedness favors using the right hand for activating the string. That's probably what it is.
It can be learned both ways; e.g. Michael Angelo Batio.
I can walk a bicycle perfectly just by holding nothing but the saddle with my right hand. I can pick some spot on the ground ahead, call it, and hit it with the front wheel accurately.
Switch to my left hand and the bike's front wheel starts having a mind of its own.
"No, don't veer that way, Bike; you're not reading my mind, like you do through my right hand!!!"
But since the middle of the continuum, i.e. no-preference, would presumably be the worst situation, it would be developmentally unstable and any tilt to either side would quickly become dominant.
One possible "motive" for a particular left-right lopsided bimodal skill pattern.
I kick with my left foot too. I feel more comfortable throwing with my right. If I'm holding a bat, I do so the "normal" way (idk terminology there).
When my son was learning to write I was super excited that it looked like he would be a lefty but a week later he favored his right hand for scribbling.
Weird thing is; lefties are rare. I have a very old group of friend that I know since I was 15. We are all lefties and one friend even married a left handed woman so the lefties are in the majority.
I don't know any IRL lefties. Alas.
As younger people start using computers they generally will learn with right-handed mice and will thus develop those fine motor skills in that hand. I wonder if this will make right-handedness even more dominant.
Australopithecus was already strongly lateralized — committed handers — long before the rightward consensus emerged. Two traits, evolved separately by millions of years.
"There are no left-handed in China" might sound as ridiculous as "There are no gays in Uganda".
However of those thousands of students, none had messy hand writing. In any class in Europe or the US, around 10% of students have messy writing. Suspiciously equivalent to the supposed number of left-handed students.
But the hemispheres absolutely DO specialize in very predictable ways. Core language faculties are almost always handled by the left hemisphere, for instance.
Face processing is almost universally handled by the right hemisphere.
We know these things from people who have suffered an injury to one of their hemispheres. A person with damage to the right hemisphere has a chance of not being able to recognize faces, but that's almost never seen in an injury that exclusively effects the left-hemisphere.
Not sure if because of that being sort of torn down but recent years he has been clarifying he wasn't talking about a literal left/right device but more an analogy to different modes of thinking.
There is some hemisphere function allocation but it feels far to over played in folks trying to offer easy answers to difficult things.
Eg. For pool does the more dextrous hand need to push the cue or does it line up and guide the front of the cue? I can see tradeoffs each way and the front hand is certainly not just limp when playing.
Hockey is similar. The top or the bottom hand being the more dextrous probably has tradeoffs but I don’t see either grip as being more or less natural for handedness. I don’t play hockey but play golf and cricket which have similar grips and am similar there to you too.
>Using the same models, the team was also able to estimate likely handedness in extinct human ancestors. The picture that emerges is a gradient [from less handedness to more as time goes on]
"we explored the data until we found a statistical anomaly and it implies X" may be interesting[1], but there are TONS of those that are NOT true. is there supporting evidence for this, or is it just "hey this math says maybe"? it sounds more like the latter (as it quite literally seems like they're claiming roughly "big arm + big brain = big handedness", both in this site and in the paper itself), in which case they might also be interested in this study that pirates keep the global temperature down: https://www.forbes.com/sites/erikaandersen/2012/03/23/true-f...
1: from skimming the methodology in the paper, I honestly think this may be a fair characterization. it sounds like they combined data columns until one combo came up as P>0.95 and didn't have counter-evidence and said "that means it's probably true". but also some (all?) of that data may have been generated by models they created based on real ape data (I think?), which just sounds even more sus.
For hands, it is completely irrelevant how many legs a human has, regardless if a human had used 2, 4, 8, 14 or any other number of legs for walking, the hands would have become specialized.
The reason why the hands acquired specialized roles was that they were no longer used for locomotion, i.e. for brachiation in the trees, like in orangutans or gibbons, but their purpose became holding, controlling and moving various objects from the environment.
It is wrong to say that bipedalism has freed the hands to be used for other activities than locomotion, because the causality was reverse, locomotion became restricted to the hind legs, because the hands were used for other activities, like throwing sticks and stones, so they were no longer available for locomotion.
The strong specialization of the 2 hands has appeared because in most cases when something is transformed with the hands, e.g. bones are broken to get the marrow or stones are knapped to get a cutting edge, one hand must be used to fix in place the object that is processed, while the other hand must move against it, normally with some tool.
For the former role, the left hand became specialized, while for the latter role, the right hand became specialized.
Similar specialization is also seen at other animals where a pair of legs is no longer used for locomotion, but it is used for manipulation, for instance at crabs and lobsters.
So there is no doubt that the specialization of the hands was a necessity when they stopped being used for locomotion. However, it is not known why the right hand became the moving hand and the left hand became the holding hand, and not vice-versa. It could have been a random event or it could have been related to the asymmetry in the locations of the unpaired internal organs, like heart, liver, stomach and so on.
Twins are slightly more likely to be left handed, might be something to do with crowding in the womb where a specific hand is free more than the other.
I've been told that it's effectively a mental illness if discovered during childhood (as is ambidexterity). Yet I can't help but think that it is not a mental illness, but rather something else.
As a left-handed individual who employs a trackpad or mouse with their right hand, stick shifts are also possible, at least in the United States. Furthermore, left-handed individuals can switch-handed, bat from either side, and use both hands equally in a fight. This adaptability may be the reason why left-handedness remains prevalent in combat sports, including swordplay, tennis, boxing, and even wrestling. In certain combat situations, the initial blows are crucial for survival, especially in the past.
(although of course unlike your example it doesn't involve reaching across one's body to use it)
As a person with severe hemophilia in the third world, where the condition is very under-treated (no prophylaxis, very little clotting factor and sometimes none), I've grown up facing this issue with the dominant arm being out of commission due to a bleed for days at a time. I gradually learned to do almost everything with the left hand: brush my teeth, shave, eat, shower, type with one hand (autocompleting IDEs help), even drive a stick shift (using the right hand to hold the wheel briefly while shifting, technically illegal I'll admit).
It's not that difficult to adapt. The barriers are mostly mental because it feels awkward at first. There are some dexterity issues but if you don't mind going slowly, you can get by.
Just sharing my experience, not meant to undermine the challenges faced by left-handed individuals in a right-handed world.
There are left-handed guitar players that play right-handed, such as Nick Johnston, who claim the gaps in their technique or preference for certain left-hand-only techniques are informed by being left-handed; so it seems that a life-long of an insane amount of practice does not necessary change how comfortable one is using either hand for a given task.
┌───────────────────────────┬───────────┐
│ Activity │ Hand │
├───────────────────────────┼───────────┤
│ Baseball (Bat/Catch) │ Left │
│ Hold Spoon │ Left │
│ Soccer │ Left │
│ Tennis │ Left │
│ Throw Ball │ Left │
│ Darts │ Left │
│ Write │ Left │
├───────────────────────────┼───────────┤
│ Bow and Arrow │ Right │
│ Hold Fork/Knife │ Right │
│ Play Drums │ Right │
│ Scissor │ Right │
│ Shoot Rifle (Nerf Gun) │ Right │
│ Skateboard/Snowboard │ Right │
│ Use Mouse │ Right │
└───────────────────────────┴───────────┘
Anyone can get much better at using their non-dominant hand (if they have one) with just a bit of practice. The effect is much much stronger when you do so as a child.
As an adult I just practiced writing with my left hand loads for basically no reason, it's not that useful, but I still did it for some reason. Now I can write illegibly with either hand :)
Then there's guitar.. some, or actually most left-handed people can learn to play a right-handed guitar if they simply start with a right-handed guitar. But there are also some people (some of them very well known) who tried learning the guitar for a very long time, and couldn't. Until they switched to a left-handed guitar. (Why it's natural to actually use the left hand for something which looks complicated - fingering, and the right hand for something simple - strumming - has been discussed forever. Apparently that's because a right-handed person typically has better timing in their right hand, and that's why it matters).
After that re-trained myself a few times out of interest to do it the other way around, and one goes through the four odd phases of having to focus on it vs it just happening correctly without thinking about it.
From what I remember it could take 2-4 weeks before you would just do it both without thinking and correctly.
I write with my left too but using right handed peripherals feels natural. I also use my phone right handed.
Still I prefer to use scissors with the left hand and most are right-handed. It's a damn nuisance as the loop handles are the wrong way around/wrong size for a leftie.
As a left-hander, it's very obvious to me. That said—because of the above point—my right hand is much stronger and more adept at playing. In short, I'm right handed when playing the piano.
No sarcastic comments please, I well know more practice and playing those damn Czerny scales ad nauseam would have restored proper balance. :-)
The specialization goes both ways, though, I'm much better playing Alberti bass with my left hand compared to the right.
I'm right-handed, but I trained myself to use a mouse/trackball left-handed due to better ergonomics. I was getting back/shoulder pain and thought that it was related to computer use and realised that with the typical keyboard with numeric pad and a mouse setup, that my body was twisting more due to the mouse being more to the right than it needed to be. Using my left hand instead means less twisting as there's no numeric keypad on the left.
It took probably a couple of weeks to get comfortable with left-handed mouse use and these days, I am fairly ambidextrous on a computer.
The other thing that makes me think that handedness can be learned is learning to juggle. I found that it's easier to start doing a new movement (i.e. a trick) with my right hand, but once I learn it with my left hand, the left hand becomes more accurate than my right.
IOW, why handed vs ambidextrous, not so much why left-handed vs right-handed.
Did it even explain that? I'm ambidextrous, I have no handedness bias, so whichever I pick up to first learn something is the hand I use. So I'm a mix of left-handed and right-handed depending on the task. And yet I didn't really understand why that's odd because of my bipedalism?
may be high dexterity is expensive, brain-wise, i.e. may be the choice given average brain is either 2 hands with mild dexterity or a one of high dexterity at the expense of the other. With tools, etc. the latter choice seem to be preferable and was selected for (and the lucky ones get to have 2 of high dexterity) Bipedalism and brain expansion in this situation are indirectly connected to the handedness as they are enablers and drivers of tools use.
Neither of my parents were left handed, and yet, here I am; despite attempts otherwise I might add.
As for which hand is chosen as a baby, it might be most typical to mirror one's parents, but it doesn't always have to be like that. Some babies may just randomly start doing things with a hand different to the preference of their parents due to not having them or other adults in their sight at critical moments. As for parents trying and failing to stop their kids from using their left hand, they might've just caught it too late.
So, I guess what I'm saying is that both you and GP can be correct.
For example, throwing (or kicking) with your non-preferred side is not as simple as picking up and throwing a ball or simply kicking it. You have to adjust your position and stride to lead with the correct foot. I found learning right-handed pace bowling in cricket (for fun) especially challenging as you have to land your back foot in the right place as you bowl through the popping crease. A few steps and rolling the arm over to spin was easy, and I actually can get more spin on the ball with my right hand.
My theory is that the handedness came about through learning basic survival activities such as running and jumping, throwing spears or rocks, etc that require using a preferred or learned hand.
so I switched to a left-handed mouse. I cursed for about a week, then sometimes fumbled, and then it just worked.
Now years later, if I use a right-handed mouse to do say a first-person-shooter, I overcorrect like I'm drunk on wildly pitching ship.
left-hand is dialed in and precise.
I think some of this stuff is learned and not innate.
but yeah, goofy-foot on skateboard feels... just wrong.
I overused my right hand with computers...
I think it's more about a person's personal stability/biomechanics. The back foot is the stable one, forward is the "quick" lead. The preferred "plant" foot when kicking a ball is the stable one (though many people use both, so this is best used only when there is a strong preference), the one used to push off with when at the bottom of stairs or jumping is the stable one (the lead foot is the `quick` one). The best way I found to help determine footedness: have a person stand straight (feet together) walk around them (pretending to look at posture or something), once behind them push them forward (evenly with some force). Watch for which foot they catch themselves with. Thats the lead foot.
As for the eye dominance, in archery having the right eye dominant means your stance is regular (left foot forward). An archery open stance is near identical to a snowboard neutral stance (~ +15°, 0°). The 2 most important things to get right in (olympic recurve) archery is eye dominance and a proper open stance. As a goofy footed snowboarder and a right eye dominant archer, the archery stance took awhile for me to adapt too. It still feels weird.
Obviously it won't sudenly make you a perfect regular-stance skater though. :)
I skate/surf goofy (or used to... haven't done much of either lately :P) and prefer to hold a baseball bat or a golf club lefty, despite being right-handed. And I have an immediate family member who's left-handed but bats righty!
Of course, I’m terrible at baseball and my handwringing is atrocious, so maybe I’m just broken.
Orientations are so confusing, I thought the parent was describing regular too
I wonder whether something simple like being allowed to select and use an object with either hand rather than having it offered to your right hand retains ambidextrous by the time handedness became fixed in the brain around age 4-6.
Some centimeters might not sound much, but over millions of years, the cumulative effect might be that 1% of human population every 10.000 years gets genetically optimized to hold their heart at a more protective spot.
It also allows right-handed mothers to do something with their dominant hand while cradling the baby in that position.
[1]: https://sites.psu.edu/clarep/2024/04/12/the-left-cradling-bi...
Your hypothesis can't possibly be correct, because the only premise is false.
With the trackpad on my Laptop, I switch quite frequently and haven’t yet noticed any difference in precision. The movement is very different than mouse or pen control though and comes more from individual/multiple fingers instead of the whole hand or arm, so I guess that explains it.
At work, I don't use a left handed mouse. Just those cheaper but common symmetrical ones. And I don't bother changing handedness. I just pick up the mouse and put it to the left of the keyboard.
shrug It works.
* if you're left-handed, your hand smudges over the ink before it dries. There are various contortions that some left-handed people do (hover the hand or wrap it around from above) - right handed ones don't need any of that.
* stroke patterns, as usually learnt in school, result in pushing away if left handed, vs drawing to, if you're right handed. This results in less ideal strokes, and if you're working with a sharp pencil/pen on a sensitive paper, this can tear the paper. If you're working with a felt-tip pen, the line width/pressure suffers as well.
That said, if you really make an effort, you can have a pretty decent handwriting if you're left handed. And if you are forced to use right hand when learning handwriting, you can still have a pretty decent handwriting.
I'm not familiar with details of chinese handwriting (what's easier/better if you're left vs right handed), wouldn't be surprise the constraints are similar.
So I guess your remark about messy handwriting is related to the strict standards for the students (which includes expectation they must write with right hand).
Though the best evidence to refute "There are no left-handed in China" is that it didn't take long to find a left handed Chinese baseball player
(and none out of thousands seems statistically unlikely: China has lower numbers of reported left-handers, but it's 3% vs 10%)
It's possible that Chinese will one day obtain individuality and freedom and they can write left handed. That would kill the one last advantage the West has.
I am inclined to believe this is a learned trait rather than an innate one (excluding the obvious reasons why one would be left-handed only).
It has the most degrees of freedom, and more motion. The one in front has a whole table for stability.
But that's just like my opinion, man.
I am left handed for fine motor skills (writing, fork/knife) but throw righty and play single handed sports with my right (except for table tennis which i can do either hand at a good level). I can play two handed sports (hockey, lacrosse, golf) pretty much with either hand with little issue. Right footed, but can kick with my left pretty confidently.
Learned to shoot a bow as a kid but only learned as an adult I'm left eye dominant, and to take advantage would require re-learning the bow in my left hand(many many strikes on my arm sent be back to a righty). Shooting guns is a similar situation, but I'm a fairly good shot regardless. It definitely makes using sights weird.
I'm semi-ambidextrous too, with enough focus I can somewhat cleanly write with either hand, and I'm generally good with my hands in fine tasks, with only a minor preference to pick up a tool with my right hand.
I wonder how common this is. People seem surprised when I demonstrate my left handed writing.
https://en.wikipedia.org/wiki/Handedness#Types: “Mixed-handedness or cross-dominance is the change of hand preference between different tasks. This is about as widespread as left-handedness.”
⇒ about 20% of the population is not strictly right-handed. That’s not a majority, but I think the word to use for that is “normal”.
Soccer, snowboarding, batting, golfing: lefty
Writing, throwing, tennis, pool: righty
I've never had any pretense at being good enough to entertain people with those works as everyone knows them so well (from professional recordings). Even Mozart's a problem here. For example the Romance in the D Minor Concerto, K.466 looks deceptively simple (at least in parts) but it's anything but after hearing someone like Brendel play it. Everyone knows it so well it's not worth the embarrassment of even trying (except perhaps in secret).
(Mozart has a habit of looking simple until one tries to play it, Bach is none of that—one knows what one's in for at pretty much first glance.)
The “hypothesis presumes that athletes in interactive sports are much more likely to play and practice against right-handed opponents. As a result, these athletes develop both greater familiarity and highly specific skills to anticipate the action outcomes of their right-handed opponents via attunement to crucial perceptual information”
"Out of the 610 professional skateboarders, 291 ride regular and 329 ride goofy. This means that 53% of skateboarders ride goofy and 47% ride regular! Way more skateboarders than expected ride goofy." ²
---
¹ Dobija-Nootens, N., & Harrison-Caldwell, M. (2017, October 12). What determines your skate stance? Jenkem Magazine. https://www.jenkemmag.com/home/2017/10/12/determines-skate-s...
² Bande-Ali, A. (2024, August 25). Skateboarding: How many people ride goofy? Azeem Bande-Ali. https://azeemba.com/posts/skateboarding-how-many-people-ride...
The tendency to associate the right with positive and the left with negative is pretty much ubiquitous in Western civilization up until fairly recently.
I have a fairly exotic viewpoint on this. The left/right asymmetry (for the lack of a better term) is a small part of a larger asymmetry that's difficult to explain (at least to my satisfaction): up is better than down, light is better than dark, positive is better than negative, higher human faculties are better than lower desires, right is better than left. In my mind, none of these should inherently have a good/bad association. Is a valley worse than a hill? Is a positive electric charge better than a negative one? But, for some reason we have this cultural, linguistic baggage where what seem like highly abstract objects are rooted in a very basic world of good and bad.
I find this fascinating.
I would go as far as to add the male/female asymmetry to this: seemingly senseless, yet historically present. I'd say the rabbit hole truly starts when you get into Western esotherics and see how they associate right, up, light, male, order, knowledge as if they're different expressions of the same thing, and analogously for left, down, dark, etc.
Makes sense; up gives you a better vantage point, so its easier to see danger. Not to mention that it gives you a fighting advantage; your attacker would have to run uphill to get to you, tiring them out.
> light is better than dark
Humans rely heavily on our sight, and we tend to operate in the daytime. If you were a nocturnal animal, I'm sure you would consider dark to be better than light.
> positive is better than negative
Getting something is better than giving it away.
> I would go as far as to add the male/female asymmetry to this: seemingly senseless, yet historically present
What do you mean by this?
In clothing you have the right side and the reverse side while here it's oikea ja nurja. Again similarities but nurja has this twisted and dark connotation. Or upside down = nurinperin.
A four-legged animal's right front paw makes clockwise circular with respect to the sagittal plane of its body, as it walks.
On a recumbent bicycle with hand pedals, the right hand crank goes clockwise. It would be weaker the other way.
For all kinds of motions, it's better when the hand is coming down in the extended-arm position, working with gravity.
Extreme example: if you are hammering something with your right hand, of course, you raise the hammer and extend your arm, let it fall and then retract your arm. That creates a clockwise motion. Counter-clockwise hammering something upward from below is awkward. You also wouldn't want the workpiece close to you so that you are raising the hammer with your extended arm, bringing it it in and dropping it with closed arm. It's bad leverage: raising with the extended arm is harder.
This hammering motion applies when doing something like winding a rope onto a bobbin. You have to raise your right hand and forearm against gravity and that is better when it is closer to your chest. Then drop it down slightly away from your chest. Clockwise winding has compellingly better ergonomics for the right hand.
OTOH: I am convinced I can't snap my fingers with my right hand and never will because my specific mix of handed-ness makes it impossible for me to do so, no matter how hard I try and practice. No problem at all with my left hand.
I would have said the opposite. The fretting hand only needs to press onto the strings in the correct places whereas the picking hand is responsible for all the subtlety of expression in terms of how you attack the string.
Saying this as a professional mandolin player fwiw.
Mildly informative Wikipedia article: https://en.wikipedia.org/wiki/Cross-dominance
Ambidextrous means: "that the person has no marked preference for the use of the right or left hand".
Unlike what is normally assumed, it doesn't mean you've mastered both hands, it doesn't imply you can write equally well with the left or the right, but that you could have just as easily learned either. You had no marked preference when you picked up the activity initially.
Cross-dominance seem to imply there was a marked preference, but that it is the left or right hand differs per activity.
That said, I wonder if they're really the same. Often people say ambidextrous as you are equally good with both hands, which would always require practice on both side. But maybe cross-dominant people can equally learn?
Under that reading, cross-dominance could be what ambidexterity actually looks like in practice. If you genuinely have no preference, there's no reason you'd consistently land on the same hand across all activities, you'd be influenced by context, who taught you, which hand was free, etc.
Have you ever tried your other hand at activities? And are you surprisingly good with it, even if not as good? I tend to be better using my other hand at most things than say a fully right handed person, but never as good as the hand I've been using for that activity consistently.
I'm right-handed. I'm definitely sure of that. It's just that what hand I use depends on which hand I start with from the beginning. And that'll be the preferred hand, except for things where it's natural to switch from the very beginning.
But there are also some things I've learned to do with both hands much later, e.g. washing dishes - there was a reason for having to do that for a while, and now I just switch when I like it, or if the kitchen happens to be arranged in a way which makes one side more preferable.
(BTW, when building carpenters still used common hammers it was completely normal to use either hand, as access space may be limited and there's basically no choice sometimes.)
Today it's always left-to-right, though.
Handedness is probably not (often) captured in healthcare records, but I'm wondering if epidemiologists could mine insurance claims (or some other data rich resource) to see if there's a correlation with serious outcomes (death, hospitalization, etc.) from venom and handedness.
Hundreds of thousands years in the past, hominids lived into much more tropical areas than today and there are a lot more spiders, scorpions, lizards and snakes in these warm places. It makes sense that insects and especially reptiles pushed the evolution of mammals in certain directions and the positioning of the heart in the human body might be one of them.
Today people live a much different lifestyle than having to deal with insects and reptiles all day long. I don't know if it is possible to decipher the past from today's data.
In golf, strength is overrated until you get to the pros.
One day she wrote her name twice on the whiteboard and asked us to identify the difference between the two; visually they were identical, but she wrote one with her left hand and one with her right. She said as a kid she was made to use her right hand when she started showing signs of left-hand dominance.
i found out about my parents reaction like everyone else,, suddenly there was a bunch of screaming profanity and acoustic violence coming from the principals office
Your post finally made it click for me – the aorta extending to the left gives the superficial impression of that being the heart’s location because it’s easier to feel the heartbeat through the skin, versus the more deeply embedded vena cava on the right.
Presumably this means, evolutionarily, greater vulnerability on the left, predisposing the left hand to shielding duties, leaving the right to more dexterous tasks like spearing. The cardiological hypothesis of right-handedness holds!
I feel like this isn’t really an argument against the theory. If right handedness did evolve because of heart position, a later genetic mutation to have the heart on the opposite side wouldn’t suddenly undo the previous evolution towards right handedness.
The argument is that the selection bias was towards precision and the hypothesis was that precision is influenced by heart position (which is, still, in the middle in humans)… individuals with situs inversus would be more precise in the left hand, thus if the causal hypothesis is correct AND the argument holds then there should be a selection bias that would result in a correlation between situs inversus presence and left-handedness.
In the end I don’t believe either the argument or the hypothesis hold even as much water as I can in either hand.
But why would situs inversus somehow be tied to this at all? If there's a gene that favors right-handedness, it's not like it would somehow "choose" left-handedness because the individual has their internal organs flipped.
Now, I’d seriously doubt there’s any evidence whatsoever for the assumed selection bias in the first place, never mind any causal relationship between fine motor control and heart asymmetry, but the selection bias should apply to both flips of the anatomical mirror.
Why is the left lung smaller, then?
the aortic arch begins decent left of the coronary corpus, but becomes centralized, tandem with the Vena Cava.
Noted, thanks.
Second, note that what you don’t do when trying to hit the heart is aim left.
If you had a weapon that wasn't bothered by the presence of the sternum, and you wanted to stab the heart, you'd go right through the sternum.
there is an unacceptable risk of having to abandon it.
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