An interesting anecdote that comes to mind is playing old computer games with arrow keys, which used my right hand. I got pretty proficient with this.
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.
I remember in elementary school being amused by the idea of handedness so I decided to practice writing with my left hand as well. I'm not great at it but even to this day I can write legibly with my left hand from that little bit of practice as a child.
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.
I realized at some point as a leftie I could trivially learn to write a mirror image of what everyone else was writing so learned to write backwards. Since the motions are exactly what others do it’s actually easier in a lot of ways for me. Left handed writing is all scrunched up and annoying, and I got constant smudges on my hand. Frixion ink pens are the only pen I’ll buy because they don’t smudge at all. My guess is it’s actually because it’s heat reactive so it just vanishes on skin, but that works for me! (It doesn’t disappear on the page except the time I put a hot bowl of oatmeal on my hand written deployment reminder notes, which was a bit of a surprise. Took me about an hour to recover gathering data, haha).
Children have better neuroplasticity but worse persistence than adults.
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 :)
I’m left handed and never understood left handed mice at all. I write with my left and swing and kick left handed, but all gaming stuff has always been the same way anyone else does. I’m pretty sure up down left right switching to wasd is a function of that setup being more comfortable with the mouse to the right of the keyboard, correct?
For this sort of motor skill, it’s definitely learned. For stringed instruments, for example, it’s the left hand which has the more finely managed manipulation than the right (it’s interesting to note that only guitar-family instruments are commonly made in left-handed versions, although some of that may come down to logistics of string ensembles where having one left-handed violin in the violin section would cause a bit of chaos with colliding bows that is less of an issue with guitar ensembles where there are fewer musicians and they’re less tightly packed in the performance space). Likewise, the fingering on woodwind instruments doesn’t really favor one hand over the other. In contrast, brass instruments are decidedly right-handed (I suppose one might be able to manage a trumpet left-handed, but I’ve never tried. I don’t think other brass instruments could be fingered with the left hand at all.
The article didn't really help me understand what it was about bipedalism that resulted in a right handed preference. Also in my family left hand dominates, we are a cluster of left handed people. My theory is if any child wants help with fine motor control the help is provided by a left hand to a left hand.
The original paper is titled "Bipedalism and brain expansion explain human handedness". It doesn't seek to explain why we have a right-handed preference specifically (vs left-handed), but rather why humans have such a strong handedness preference compared to ancestors who had only a mild right-handed preference.
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?
There is also a category of people who are “mixed-handed”, who have a strong handedness preference for a given task, but which hand one prefers varies based on the task. I didn’t know about this category until recently, but it describes my personal experience.
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.
Funny enough, this made me realize that although I'm right-handed, I'm left-footed when it comes to football. As an amateur player, using my right foot with proper shooting form still feels surprisingly awkward to me.
All our maths teachers were at school were left handed, along with 25% of the top maths set in our year. The teacher and student population of left handed people were close to the normal 10% levels too.
As someone who is fairly ambidextrous, but predominately a lefty - the things that are harder to switch between are some of the gross motor skills.
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.
This is true for me as well. I can't really play volleyball, because you are supposed to hit the ball with both hands, but my left hand is constantly ahead of my right hand. All my shots are crooked.
I always faced left when riding a skateboard back in the day, otherwise known in skater parlance as being "goofy-footed". Facing right felt as difficult as writing with my left hand. I always wondered whether that was just the way I first rode a skateboard and it stuck, but if that was the case, I would expect the distribution of which skateboarders face which way to be about even. But goofy-footed riders are in the minority. I'm right-handed as well. I wonder what's up with that.
I think this is probably related to which eye is more dominant for you. I've never skateboarded, but if I imagine myself doing it, it would also be facing left. And it's because my right eye is dominant and I would like that to be facing forward.
> I think this is probably related to which eye is more dominant for you.
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.
Quick test to find out which is pick a point in the distance, make a triangle with thumbs and fingers to look through, and slowly bring it toward your face. Wherever it ends up is your dominant eye.
I'm goofy footed as well - skate boarding with my left foot forward is like trying to throw a ball with my left hand. I also found that if I was rollerblading or ice-skating, turning to my left (counter clockwise) with a foot-over-foot action I can do super easy, but turning turning clockwise I always struggled with.
Me too, but on a snowboard. (I suppose I'd be the same on a skateboard) My second time snowboarding was quite a few years after my first, and I just could not get the hang of it, wondering how I was faring so much worse than before. It took me all day to remember I was "goofy", and once I switched it was much better.
Yeah, I went snowboarding once in my life (loved it but it was exhausting) and naturally rode goofy-footed. They only thing I really needed to learn was slowing myself down.
I'm right-handed, but I snowboard goofy. Coincidence (or not?) my left leg is dominant. I can kick a ball just fine with my left foot, but when I try to kick with my right foot I feel like I'm going to capsize. When I'm riding a bike and I have to stop, my right foot goes down. When I start again I use my left leg to muscle the crank through the first revolution or two.
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!
I’m the opposite… write lefty bit bat/swing (rackets and gol) righty. Not sure about surfing - I only paddle board and the stance is more straight-on (because you paddle both sides to avoid turning in a circle).
Of course, I’m terrible at baseball and my handwringing is atrocious, so maybe I’m just broken.
"Of the 4,000 skaters in the Skatepark of Tampa Database, about half are goofy (44%) and half are regular (56%). But this near equality between skate stances doesn’t align with statistics on handedness. According to Scientific American, 90% of people are right-handed." ¹
"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
Why is there handedness on stringed instruments? If you're right handed, you strum a guitar with your right hand, fret with the left. But both are fine motor skills requiring coordination. Left handed players go out of their way to acommodate doing it the other way around; either finding left-handed instruments (challenge: most things they might like/want are not available in lefty version) or suffer with a flipped right handed instrument (control positions on electrics are wrong, asymmetric cutaways for reach are wrong, nuts are slotted wrong for a mirrored string order).
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!!!"
To drain pasta or noodles quickly, I put it in a colander, hold it above my kitchen sink, and swirl it around in quick circles. I realized about a month ago my circles are always counterclockwise, and very efficient, but that I can't keep a clockwise spin going for more than a few cycles before messing up. Since then I keep trying to spin my pasta clockwise (such are the small excitements and adventures of my wfh life), starting with very slow movements, but I just can't do it. There's something weird about this motor skill specifically that eludes me. I'm left-handed but my right-handed writing is reasonable and I play piano with matched abilities in both hands. Maybe one day, with enough practice, my pasta will go clockwise.
My first thought was, "language". The Broca's area is on the left side of the brain, which is the center of control for logic, language and the right hand. It makes sense to me that an evolutionary feedback loop would develop between the hands and complex language development. So it's not odd that the average human brain would develop -somewhat better control over the right hand than the left.
So why are us southpaws a rarity? The article and the linked research paper both point to bipedalism and bigger brains as the cause, and the paper vaguely seems to hint at selective pressures leading to the right hand getting favoured by the majority of the population, but why?
The question from the headline is excellent, if only it was actually answered.
I would think right-handedness is largely reinforced through learning gross motor skills as an infant. If you always use your right, your brain optimises for that.
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.
Here's my five minute lunchtime hypothesis: it's because the heart is on the left. As human behavior demanded increasing precision from the hands, being a little farther from the heartbeat was a slight advantage.
That's a long time hypothesis of mine as well, but I think it stems from being stung or bitten by venom. If venom is injected into the bloodstream, it is desirable to be injected as far away from the heart as possible.
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.
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.
That's a good idea, a very good idea actually, but I wonder about it's effectiveness due to a very small total number of snake bites nowadays, compared to the past.
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.
Wikipedia on Situs Inversus (visceral organs are mirrored, heart on the right, liver on left) [0], mentions mixed results regarding handedness. There would be a load of other confounding factors here and I know nothing about medicine.
Situs inversus ("dextrocardia") is a rare disorder. What I postulated is a (very) small selective advantage leading to a neurological mechanism evolving over generations, not a direct line from the heart to handedness during development. Anyway, the effect would be very slight, and even if it did exist, it could have gone away later, but dexterity would have been baked in at that point (see also the ocular blind spot).
Here’s my multiple years of anatomy classes response: the heart isn’t on the left. The aorta is, sure, but the vena cava is on the right. Also people with situs inversus (essentially all organs flipped laterally from
“normal”) aren’t obviously more prone to left-handedness.
I’ve wondered ever since fourth grade (where an anatomical model in a corner of the classroom always made it clear that the heart is centrally located) how the vernacular conception of the heart as located on the left originated and persisted.
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!
> Also people with situs inversus (essentially all organs flipped laterally from “normal”) aren’t obviously more prone to left-handedness.
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.
Why are you assuming situs inversus, which occurs in species with no handedness (or, indeed, hands) came after 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.
It might be hard to eliminate confounding factors depending on when the research was done. A lot of people in my generation were still dissuaded pretty heavily from writing with their left hands. I'm not entirely convinced anymore as a lay person that "handedness" is a real, distinct phenomenon that's primarily genetically determined or a result of the organization of the brain. It's equally possible that it's a learned preference and that the way the brain organizes around it is as a result of the preference's impact on how you have to solve problems with your preferred hand in a society that preferences right-handedness.
Not disagreeing that handedness is probably unrelated to heart position.
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.
Genes don’t favor (or not favor), but if a natural selection bias for precise dexterity exists AND heart lateral orientation affects dexterity precision THEN those with flipped lateral orientation should exhibit more dexterity in the left hand, thus they should be naturally selected for because of the same bias.
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.
not only smaller but having 2 lobes rather than 3, the left lung is possessed of a featureknown as the cardiac "notch" an involution of the lobe that corresponds to the larger left ventricle of the heart.
The heart is asymmetrical, but it’s in roughly the center of the chest. The left auricle and ventricle are larger muscles because they’re pumping through the descending aorta to the extremities, that’s the systemic circulatory branch, the plumbing for which is also largely to the right, while the right are pumping into the lungs alone as part of the pulmonary circulatory branch. The left lung (right on those with situs inversus) has two lobes and basically accommodates the extra muscle mass on its side of the heart, but if you really want to kill someone you stab them through the sternum, kind of dead center, not where they hold their hand when performing patriotism.
even this is wrong, a penetrating weapon aimed for the heart is applied below the sternum at roughly the positionof the 3rd shirt button, and thrust upward at shallow angle topass behind the manubrium, and is then levered into a pommel upward position so as to lacerate the heart
First, that’s because you want to keep your weapon, which implies you don’t really want to kill the killee. I’m assuming a half inch drill, and I’m leaving it powered up and spinning.
Second, note that what you don’t do when trying to hit the heart is aim left.
I wonder why you're getting downvoted? Even if it turns out you're completely wrong it's still an interesting point and something I never even considered before.
Sometimes I think people downvote me because they're frustrated that I didn't engage further. After twenty years of Internet discussions, I'm a little burned out and I tend to fire and forget.
I almost never see people using a left hand mouse these days.
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.
As a lefty I never had any problems adapting to a right hand mouse and actually find the keyboard to be better suited as a "left hand" activity and would have a hard time switching it up.
Living with laptops with touchpads for a couple of decades as a righty, I can use a touchpad perfectly fine with either hand, but a mouse is still right handed for me.
I have switched between left and right mouse every few years when I was younger, just to see what works best for me. I could adapt to both, even though I can only write and draw with my left hand. I have settled with left-hand mouse because I feel like I can be a bit more precise for graphical works and shooters.
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.
I mouse right-handed because it’s convenient, but I still naturally default to doing any novel task left-handed. It’s not a matter of fine motor skills, you can learn to do anything with either hand if you decide to, it’s just an unconscious preference.
I used right all the time. Got RSI.
Now I use left at work all day, and right at home when gaming.
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.
I am curious at what age hand preference develops. And can you exert any influence on that development?
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.
I’m a leftie from a 50% leftie family. Apparently I showed my left handedness as a baby when grasping for things and hardly used my right hand.
My mother was also a leftie, but in her generation she was forced to write with her right hand. The net result being she could write equally well with both hands. When I learnt this I tried to copy it.
Right, I know that dexterity in a hand is largely a teachable thing.
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.
The introduction of this article makes reference to a couple of papers (e.g. https://doi.org/10.1038/s41598-017-16827-y ) that handedness is observable in utero but cautions small sample sizes for these studies.
Right, my question was more meant for how well established that is. And if it is open to influence. My searches made it look like it was not positive that handedness was fixed until a bit later. Still before formal schooling, but not necessarily in babies.
>Humans sat conspicuously outside the pattern that explained every other primate, but ... once you account for upright walking and a large brain, humans stop looking like an evolutionary anomaly.
>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.
"Handedness" is two traits, not one. The paper finds bipedalism explains strength (how strongly someone prefers a hand); brain size explains direction (which one). Most coverage conflates them.
Australopithecus was already strongly lateralized — committed handers — long before the rightward consensus emerged. Two traits, evolved separately by millions of years.
I taught English in China 20 years ago. Of the thousands of students I taught, none wrote with their left hand.
"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.
Left-to-right writing systems are optimized for right-hand use. Two examples:
* 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).
Right-to-left languages don't make writing much easier. It certainly helps, but at least anecdotally, it's overstated how much more easy (how much easier? English is confusing) it is.
Due to a broken right-hand, I had to write with my left for 3 months and noticed that our alphabet is made for right-handedness. That's why I agree with your take that writing with the left hand is basically unnatural. But since typing is more important than writing nowadays (or am I in a bubble?), I don't think students should be guided to write with their right hand.
My father was left handed like me and he got in trouble from teachers.
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 would suspect the causation (if such a correlation does exist) goes in the other direction (or more likely, has a common cause), given how early handedness tends to appear (and how it can be quite resistant to pressure to conform).
I wish they'd look into footedness as well and if there is some kind of correlation. Like orthodox vs southpaw in combat sports, goofy vs regular in skateboard, or just simply left vs right in football (soccer)
I would be interested in studies into impact of left hemisphere importantce on the right hand usage, possibly the more sophisticated and "logical" usage of our hands pressured it as well.
It's true that the creative vs. logical side of the brain is mostly a myth.
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.
For the longest time Iain McGilchrist has been going on about left brain this, right brain that and it all felt very pop-psych stuff.
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.
Thanks! Although I understand there is still some specialization in each of the hempispheres, which could influence it, but I probably went too strong with my imagination here.
Left-handed people are often excluded from participating in MRI studies. To my personal dismay, as these studies often paid 25 euros per hour ~20 years ago, a significant sum for my student self that I could not partake in. It has however given me significant doubts about any strong lateralization claims...
Same but i feel many sports are weird in that i’ve never been convinced that there’s a particularly natural right or left handedness to them.
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.
Golf and baseball batting have obvious handedness - the muscles that pull your towards your centerline and then across your body and significantly stronger than the ones that push your arm back out away from your body, and the right-handed stance in these two sports uses the stronger muscles in the right arm.
phil mickelson, easily the most famous left handed golfer, is right-handed but plays lefty because he would stand across from his dad and mirror his swing as a kid
fun fact: vs the US, golf stores in Canada carry more left-handed clubs because a right handed hockey player has their right hand higher on the stick which is the same orientation as the grip for left-handed golfers.
Same which makes me very poor at sports. I write right-handed. For anything sports related (riding a board, throwing a ball, golf, batting, bowling, etc) I'm leftie. My dad is left-handed, mother is right-handed. I have wondered if I should've been a left-handed writer and was corrected either explicitly or just by the environment to write right-handed.
It happens. I can play hockey with either hand as dominant. Too bad that wasn't really a useful talent like being a switch hitter in baseball. I'm generally left handed, but play musical instruments almost exclusively right handed. I had a friend teach me drums. He was right handed and didn't even think to ask me about my handedness, or didn't want to move stuff around (lefties have to adapt to a right handed world...). It didn't feel awkward though. I don't know why I play guitar right handed. The prevailing theory in my family is that I "learned" by mirroring Kurt Cobain on the TV screen...
It is a very bad choice of words to say that "bipedalism" is a cause for hand specialization.
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.
What does it say for mixed-handed folks like myself (different skillsets per hand - in other words, throw and write with different hands)? What about cross-dominance (different body parts differ on dominant side - in other words, a right-handed person being left-foot dominant)?
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.
In order to present it as a mental illness there would have to be some kind of negative effect, wouldn't there? These differences you mention don't stand out as harmful or even disadvantageous.
southpaws are more common where at least one parent has schizophrenia. i believe it to be caused by an epigenetic change, where damage to the brain in a parent leads to the parent rewiring their brain to use the opposite hemisphere.
In short, it's hardly an illness, more of an antibody to one.
I'm otherwise a lefty but I use computer mice right handed, because when I first started using a computer in elementary school all of the computer labs were set up right handed.
FWIW, I'm a righty, but relearned to use a mouse left handed for ergo benefits at my first real job; now I left mouse for work and right mouse for home. I prefer ambidextrous mice anyway, but it's really hard to find a left hand mouse if you want that. Even the ambidextrous mice often have thumb buttons for the right thumb. It's not to hard to learn to use a pointer with either hand; IMHO as someone who can't do a lot of complex motion with my non-dominant hand. I think there's a lot of convenience gained by accepting right mousing, although it is a longer reach if you have a keyboard with stuff to the right of your letters.
Weirdly enough, I don't know why I use the mouse right-handed. I was forced into doing it in any particular way, and beside the fact that I was already an adult when I learned of the existence of left-handed mice, I can't think of any reason why I'd naturally gravitate towards right-handed mouse use.
Probably because it didn't happen to you, or kindergarteners don't know better and just play along. I only remember it because I was a little shit and got into a big fight about it. It would have been late 80s.
An elementary school teacher of mine had this happen to her (this was in the early '90s, so her experience I'm guessing would have been in the late '60s).
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 didn't know what difference it made and there was one left handed scissors so it went to the kid who knew. I'm left eyed and often wonder if I should have learned to write left handed.
wait, you just gave me an extreme epiphany about my significantly worse right eye myopia. the divergence definitely snowballed from the "use it or lose it" thing and me not wearing my glasses as much as possible
Every study in scientific examination that concept says that for myopia and such things use it or lose it does not apply. Use it or lose it does apply to some things but not that case.
My parents generation is maybe a bit older than you, one of my mom's siblings was forced to right handedness. My mom is left handed and says they tried a little with her, but it only took for some things.
it happened to me, and when my parents found out they flipped out.
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
I don't know - my grandmother (father's mom) was fully left handed. My dad writes left handed but everything else right handed.
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.
I'm sorta here too. I'm right handed, no external pressure to use one hand or the other in early age. Mother is a lefty, father is a righty. As a result I often used the computer mouse on either side as a kid, really wherever it was left by the last user.
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.
> 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.
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”.
Didn't I understood the text or is the 'why' not really part of it? I expected more than a vague 'because it slightly existed and then hands are free to do things and brains got bigger'.
I miss the point.
They don't discuss a "why", so much as present data on the "how" and "when". If this work is valid and reliable, then it will be up to later research to propose and test hypotheses as the why.
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.
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.
An interesting anecdote that comes to mind is playing old computer games with arrow keys, which used my right hand. I got pretty proficient with this.
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.
I remember in elementary school being amused by the idea of handedness so I decided to practice writing with my left hand as well. I'm not great at it but even to this day I can write legibly with my left hand from that little bit of practice as a child.
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.
I realized at some point as a leftie I could trivially learn to write a mirror image of what everyone else was writing so learned to write backwards. Since the motions are exactly what others do it’s actually easier in a lot of ways for me. Left handed writing is all scrunched up and annoying, and I got constant smudges on my hand. Frixion ink pens are the only pen I’ll buy because they don’t smudge at all. My guess is it’s actually because it’s heat reactive so it just vanishes on skin, but that works for me! (It doesn’t disappear on the page except the time I put a hot bowl of oatmeal on my hand written deployment reminder notes, which was a bit of a surprise. Took me about an hour to recover gathering data, haha).
Children have better neuroplasticity but worse persistence than adults.
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 :)
I’m left handed and never understood left handed mice at all. I write with my left and swing and kick left handed, but all gaming stuff has always been the same way anyone else does. I’m pretty sure up down left right switching to wasd is a function of that setup being more comfortable with the mouse to the right of the keyboard, correct?
For this sort of motor skill, it’s definitely learned. For stringed instruments, for example, it’s the left hand which has the more finely managed manipulation than the right (it’s interesting to note that only guitar-family instruments are commonly made in left-handed versions, although some of that may come down to logistics of string ensembles where having one left-handed violin in the violin section would cause a bit of chaos with colliding bows that is less of an issue with guitar ensembles where there are fewer musicians and they’re less tightly packed in the performance space). Likewise, the fingering on woodwind instruments doesn’t really favor one hand over the other. In contrast, brass instruments are decidedly right-handed (I suppose one might be able to manage a trumpet left-handed, but I’ve never tried. I don’t think other brass instruments could be fingered with the left hand at all.
Something super simple and revealing is try pressing on the brakes with your left foot.
A few of my relatives who grew up on a farm drives that way (right for gas, left for brakes)
The article didn't really help me understand what it was about bipedalism that resulted in a right handed preference. Also in my family left hand dominates, we are a cluster of left handed people. My theory is if any child wants help with fine motor control the help is provided by a left hand to a left hand.
The original paper is titled "Bipedalism and brain expansion explain human handedness". It doesn't seek to explain why we have a right-handed preference specifically (vs left-handed), but rather why humans have such a strong handedness preference compared to ancestors who had only a mild right-handed preference.
IOW, why handed vs ambidextrous, not so much why left-handed vs right-handed.
> why handed vs ambidextrous
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?
There is also a category of people who are “mixed-handed”, who have a strong handedness preference for a given task, but which hand one prefers varies based on the task. I didn’t know about this category until recently, but it describes my personal experience.
Mildly informative Wikipedia article: https://en.wikipedia.org/wiki/Cross-dominance
>why handed vs ambidextrous
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.
> My theory is if any child wants help with fine motor control the help is provided by a left hand to a left hand.
Neither of my parents were left handed, and yet, here I am; despite attempts otherwise I might add.
Oddly enough, a lot of my "nerd friends" are left handed, and I'm also left handed. /shrug
Funny enough, this made me realize that although I'm right-handed, I'm left-footed when it comes to football. As an amateur player, using my right foot with proper shooting form still feels surprisingly awkward to me.
All our maths teachers were at school were left handed, along with 25% of the top maths set in our year. The teacher and student population of left handed people were close to the normal 10% levels too.
Autistic people are 2 to 3 times more likely to be left handed than the general population.
without reading .. my immediate guess is that one hand is needed for maintaining upright balance, while the other hand grasps something important ?
As someone who is fairly ambidextrous, but predominately a lefty - the things that are harder to switch between are some of the gross motor skills.
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.
This is true for me as well. I can't really play volleyball, because you are supposed to hit the ball with both hands, but my left hand is constantly ahead of my right hand. All my shots are crooked.
Fun little nugget, Australian Sulphur Crested Cockatoos almost universally favour their left feet as a holdfast. They're also left eye dominant.
I always faced left when riding a skateboard back in the day, otherwise known in skater parlance as being "goofy-footed". Facing right felt as difficult as writing with my left hand. I always wondered whether that was just the way I first rode a skateboard and it stuck, but if that was the case, I would expect the distribution of which skateboarders face which way to be about even. But goofy-footed riders are in the minority. I'm right-handed as well. I wonder what's up with that.
I overused my right hand with computers - mouse + many keyboard keys like arrows, enter, backspace, etc
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 think this is probably related to which eye is more dominant for you. I've never skateboarded, but if I imagine myself doing it, it would also be facing left. And it's because my right eye is dominant and I would like that to be facing forward.
> I think this is probably related to which eye is more dominant for you.
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.
Interesting. Never really thought about one of my eyes being dominant. I do have a bad habit of covering my left eye when reading in bed.
Quick test to find out which is pick a point in the distance, make a triangle with thumbs and fingers to look through, and slowly bring it toward your face. Wherever it ends up is your dominant eye.
I'm goofy footed as well - skate boarding with my left foot forward is like trying to throw a ball with my left hand. I also found that if I was rollerblading or ice-skating, turning to my left (counter clockwise) with a foot-over-foot action I can do super easy, but turning turning clockwise I always struggled with.
Me too, but on a snowboard. (I suppose I'd be the same on a skateboard) My second time snowboarding was quite a few years after my first, and I just could not get the hang of it, wondering how I was faring so much worse than before. It took me all day to remember I was "goofy", and once I switched it was much better.
Yeah, I went snowboarding once in my life (loved it but it was exhausting) and naturally rode goofy-footed. They only thing I really needed to learn was slowing myself down.
I'm right-handed, but I snowboard goofy. Coincidence (or not?) my left leg is dominant. I can kick a ball just fine with my left foot, but when I try to kick with my right foot I feel like I'm going to capsize. When I'm riding a bike and I have to stop, my right foot goes down. When I start again I use my left leg to muscle the crank through the first revolution or two.
You can be right handed and left footed (and vice versa), and you'd typically snowboard and skateboard etc with your dominant foot.
Do you hold a baseball bat lefty too?
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!
I’m the opposite… write lefty bit bat/swing (rackets and gol) righty. Not sure about surfing - I only paddle board and the stance is more straight-on (because you paddle both sides to avoid turning in a circle).
Of course, I’m terrible at baseball and my handwringing is atrocious, so maybe I’m just broken.
I think skate stance is much more evenly distributed (closer to 50/50) than handedness (about 10% left).
Citation needed
"Of the 4,000 skaters in the Skatepark of Tampa Database, about half are goofy (44%) and half are regular (56%). But this near equality between skate stances doesn’t align with statistics on handedness. According to Scientific American, 90% of people are right-handed." ¹
"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...
What does "face left" mean? Left foot front? That's regular.
When I stand on a skateboard, both feet on, I face to the left. My right foot is in front, which I steer with while pushing myself with my left foot.
Missing is the assumption that "direction of travel" is forwards.
Why is there handedness on stringed instruments? If you're right handed, you strum a guitar with your right hand, fret with the left. But both are fine motor skills requiring coordination. Left handed players go out of their way to acommodate doing it the other way around; either finding left-handed instruments (challenge: most things they might like/want are not available in lefty version) or suffer with a flipped right handed instrument (control positions on electrics are wrong, asymmetric cutaways for reach are wrong, nuts are slotted wrong for a mirrored string order).
Here is a funny thing.
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!!!"
To drain pasta or noodles quickly, I put it in a colander, hold it above my kitchen sink, and swirl it around in quick circles. I realized about a month ago my circles are always counterclockwise, and very efficient, but that I can't keep a clockwise spin going for more than a few cycles before messing up. Since then I keep trying to spin my pasta clockwise (such are the small excitements and adventures of my wfh life), starting with very slow movements, but I just can't do it. There's something weird about this motor skill specifically that eludes me. I'm left-handed but my right-handed writing is reasonable and I play piano with matched abilities in both hands. Maybe one day, with enough practice, my pasta will go clockwise.
My first thought was, "language". The Broca's area is on the left side of the brain, which is the center of control for logic, language and the right hand. It makes sense to me that an evolutionary feedback loop would develop between the hands and complex language development. So it's not odd that the average human brain would develop -somewhat better control over the right hand than the left.
So why are us southpaws a rarity? The article and the linked research paper both point to bipedalism and bigger brains as the cause, and the paper vaguely seems to hint at selective pressures leading to the right hand getting favoured by the majority of the population, but why?
The question from the headline is excellent, if only it was actually answered.
I would think right-handedness is largely reinforced through learning gross motor skills as an infant. If you always use your right, your brain optimises for that.
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.
Here's my five minute lunchtime hypothesis: it's because the heart is on the left. As human behavior demanded increasing precision from the hands, being a little farther from the heartbeat was a slight advantage.
That's a long time hypothesis of mine as well, but I think it stems from being stung or bitten by venom. If venom is injected into the bloodstream, it is desirable to be injected as far away from the heart as possible.
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.
Interesting!
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.
That's a good idea, a very good idea actually, but I wonder about it's effectiveness due to a very small total number of snake bites nowadays, compared to the past.
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.
Wikipedia on Situs Inversus (visceral organs are mirrored, heart on the right, liver on left) [0], mentions mixed results regarding handedness. There would be a load of other confounding factors here and I know nothing about medicine.
0 - https://en.wikipedia.org/wiki/Situs_inversus
Childhood handedness development within the brain became independent of organ positioning, after positioning had become established.
Situs inversus ("dextrocardia") is a rare disorder. What I postulated is a (very) small selective advantage leading to a neurological mechanism evolving over generations, not a direct line from the heart to handedness during development. Anyway, the effect would be very slight, and even if it did exist, it could have gone away later, but dexterity would have been baked in at that point (see also the ocular blind spot).
If this was the case wouldn't it be easier to measure the pulse in peoples left wrists? Which doesn't seem to be a thing?
Here’s my multiple years of anatomy classes response: the heart isn’t on the left. The aorta is, sure, but the vena cava is on the right. Also people with situs inversus (essentially all organs flipped laterally from “normal”) aren’t obviously more prone to left-handedness.
I’ve wondered ever since fourth grade (where an anatomical model in a corner of the classroom always made it clear that the heart is centrally located) how the vernacular conception of the heart as located on the left originated and persisted.
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!
> Also people with situs inversus (essentially all organs flipped laterally from “normal”) aren’t obviously more prone to left-handedness.
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.
Why are you assuming situs inversus, which occurs in species with no handedness (or, indeed, hands) came after 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.
It might be hard to eliminate confounding factors depending on when the research was done. A lot of people in my generation were still dissuaded pretty heavily from writing with their left hands. I'm not entirely convinced anymore as a lay person that "handedness" is a real, distinct phenomenon that's primarily genetically determined or a result of the organization of the brain. It's equally possible that it's a learned preference and that the way the brain organizes around it is as a result of the preference's impact on how you have to solve problems with your preferred hand in a society that preferences right-handedness.
Not disagreeing that handedness is probably unrelated to heart position.
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.
Genes don’t favor (or not favor), but if a natural selection bias for precise dexterity exists AND heart lateral orientation affects dexterity precision THEN those with flipped lateral orientation should exhibit more dexterity in the left hand, thus they should be naturally selected for because of the same bias.
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.
>Here’s my multiple years of anatomy classes response: the heart isn’t on the left.
Why is the left lung smaller, then?
not only smaller but having 2 lobes rather than 3, the left lung is possessed of a featureknown as the cardiac "notch" an involution of the lobe that corresponds to the larger left ventricle of the heart.
More piping to and from the heart exists on the left instead of the right?
the Aorta and Vena Cava are muchmore central than sinistral.
the aortic arch begins decent left of the coronary corpus, but becomes centralized, tandem with the Vena Cava.
The heart is asymmetrical, but it’s in roughly the center of the chest. The left auricle and ventricle are larger muscles because they’re pumping through the descending aorta to the extremities, that’s the systemic circulatory branch, the plumbing for which is also largely to the right, while the right are pumping into the lungs alone as part of the pulmonary circulatory branch. The left lung (right on those with situs inversus) has two lobes and basically accommodates the extra muscle mass on its side of the heart, but if you really want to kill someone you stab them through the sternum, kind of dead center, not where they hold their hand when performing patriotism.
>if you really want to kill someone you stab them through the sternum, kind of dead center, not where they hold their hand when performing patriotism.
Noted, thanks.
even this is wrong, a penetrating weapon aimed for the heart is applied below the sternum at roughly the positionof the 3rd shirt button, and thrust upward at shallow angle topass behind the manubrium, and is then levered into a pommel upward position so as to lacerate the heart
First, that’s because you want to keep your weapon, which implies you don’t really want to kill the killee. I’m assuming a half inch drill, and I’m leaving it powered up and spinning.
Second, note that what you don’t do when trying to hit the heart is aim left.
Well, yes, the point of the solid bone plate right in front of your heart is to block stabbings. And it works!
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.
the risk is one of being unable to extract the weapon expediently.
there is an unacceptable risk of having to abandon it.
Unless you're also trying to send a message where leaving the weapon is the message
such as, a sculpture or other improvisation perhaps even advertising material.
https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2F... [JPG]
> Here's my five minute lunchtime hypothesis: it's because the heart is on the left.
Your hypothesis can't possibly be correct, because the only premise is false.
I wonder why you're getting downvoted? Even if it turns out you're completely wrong it's still an interesting point and something I never even considered before.
Sometimes I think people downvote me because they're frustrated that I didn't engage further. After twenty years of Internet discussions, I'm a little burned out and I tend to fire and forget.
You might enjoy this: https://serjaimelannister.github.io/hn-words/
I remember reading that there is evidence that Neanderthals tended to be left handed. Someone else might be able to confirm/debunk this.
I almost never see people using a left hand mouse these days.
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.
As a lefty I never had any problems adapting to a right hand mouse and actually find the keyboard to be better suited as a "left hand" activity and would have a hard time switching it up.
Living with laptops with touchpads for a couple of decades as a righty, I can use a touchpad perfectly fine with either hand, but a mouse is still right handed for me.
I have switched between left and right mouse every few years when I was younger, just to see what works best for me. I could adapt to both, even though I can only write and draw with my left hand. I have settled with left-hand mouse because I feel like I can be a bit more precise for graphical works and shooters.
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.
I mouse right-handed because it’s convenient, but I still naturally default to doing any novel task left-handed. It’s not a matter of fine motor skills, you can learn to do anything with either hand if you decide to, it’s just an unconscious preference.
With modern controllers the main joystick/thumbstick is on the left side. People are using both hands for fine control in different circumstances.
Keyboard is also both hands equally used. With handwriting less common, I wonder if people are shifting mostly towards using both hands equally now.
I used right all the time. Got RSI. Now I use left at work all day, and right at home when gaming.
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.
I am curious at what age hand preference develops. And can you exert any influence on that development?
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.
I’m a leftie from a 50% leftie family. Apparently I showed my left handedness as a baby when grasping for things and hardly used my right hand. My mother was also a leftie, but in her generation she was forced to write with her right hand. The net result being she could write equally well with both hands. When I learnt this I tried to copy it.
Right, I know that dexterity in a hand is largely a teachable thing.
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.
The introduction of this article makes reference to a couple of papers (e.g. https://doi.org/10.1038/s41598-017-16827-y ) that handedness is observable in utero but cautions small sample sizes for these studies.
Right, my question was more meant for how well established that is. And if it is open to influence. My searches made it look like it was not positive that handedness was fixed until a bit later. Still before formal schooling, but not necessarily in babies.
>Humans sat conspicuously outside the pattern that explained every other primate, but ... once you account for upright walking and a large brain, humans stop looking like an evolutionary anomaly.
>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.
"Handedness" is two traits, not one. The paper finds bipedalism explains strength (how strongly someone prefers a hand); brain size explains direction (which one). Most coverage conflates them.
Australopithecus was already strongly lateralized — committed handers — long before the rightward consensus emerged. Two traits, evolved separately by millions of years.
I taught English in China 20 years ago. Of the thousands of students I taught, none wrote with their left hand.
"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.
Left-to-right writing systems are optimized for right-hand use. Two examples:
* 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).
Right-to-left languages don't make writing much easier. It certainly helps, but at least anecdotally, it's overstated how much more easy (how much easier? English is confusing) it is.
Chinese was traditionally written top-to-bottom, and I can see that making it more a matter of taste which hand you painted with.
Today it's always left-to-right, though.
Due to a broken right-hand, I had to write with my left for 3 months and noticed that our alphabet is made for right-handedness. That's why I agree with your take that writing with the left hand is basically unnatural. But since typing is more important than writing nowadays (or am I in a bubble?), I don't think students should be guided to write with their right hand.
Seems probable that's simply because it isn't tolerated as a choice.
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
https://en.wikipedia.org/wiki/Chen_Hao_(baseball)
In many parts of Asia they will 'correct' children who are using their left hands.
It was pretty common practice in the rest of the world too until a few decades ago.
That's only meaningful if the messiness of the handwriting correlates significantly with the handedness.
(and none out of thousands seems statistically unlikely: China has lower numbers of reported left-handers, but it's 3% vs 10%)
My father was left handed like me and he got in trouble from teachers.
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.
In my own personal and subjective experience, the correlation between left handed people I know and "edginess"-level is almost 1.
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).
I would suspect the causation (if such a correlation does exist) goes in the other direction (or more likely, has a common cause), given how early handedness tends to appear (and how it can be quite resistant to pressure to conform).
What?
I wish they'd look into footedness as well and if there is some kind of correlation. Like orthodox vs southpaw in combat sports, goofy vs regular in skateboard, or just simply left vs right in football (soccer)
I would be interested in studies into impact of left hemisphere importantce on the right hand usage, possibly the more sophisticated and "logical" usage of our hands pressured it as well.
One of many articles out there debunking the pop-psych mythology around brain lateralization: https://themindcompany.com/blog/left-brain-right-brain-myth
It's true that the creative vs. logical side of the brain is mostly a myth.
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.
For the longest time Iain McGilchrist has been going on about left brain this, right brain that and it all felt very pop-psych stuff.
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.
Thanks! Although I understand there is still some specialization in each of the hempispheres, which could influence it, but I probably went too strong with my imagination here.
Left-handed people are often excluded from participating in MRI studies. To my personal dismay, as these studies often paid 25 euros per hour ~20 years ago, a significant sum for my student self that I could not partake in. It has however given me significant doubts about any strong lateralization claims...
I am right handed but left handed for some very specific things such as playing pool or hockey
Same but i feel many sports are weird in that i’ve never been convinced that there’s a particularly natural right or left handedness to them.
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.
Golf and baseball batting have obvious handedness - the muscles that pull your towards your centerline and then across your body and significantly stronger than the ones that push your arm back out away from your body, and the right-handed stance in these two sports uses the stronger muscles in the right arm.
My dad was a lefty and played golf right-handed. It's a common enough thing.
In golf, strength is overrated until you get to the pros.
phil mickelson, easily the most famous left handed golfer, is right-handed but plays lefty because he would stand across from his dad and mirror his swing as a kid
fun fact: vs the US, golf stores in Canada carry more left-handed clubs because a right handed hockey player has their right hand higher on the stick which is the same orientation as the grip for left-handed golfers.
Re: pool, definitely the one pushing needs to be the dominant hand.
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.
Interestingly, playing left-handed in "field" hockey is actually illegal for safety reasons and left-handed sticks don't exist.
Same which makes me very poor at sports. I write right-handed. For anything sports related (riding a board, throwing a ball, golf, batting, bowling, etc) I'm leftie. My dad is left-handed, mother is right-handed. I have wondered if I should've been a left-handed writer and was corrected either explicitly or just by the environment to write right-handed.
Same! I am specifically left handed for pool and cannot figure out how to play it right handed - absolutely zero coordination.
It happens. I can play hockey with either hand as dominant. Too bad that wasn't really a useful talent like being a switch hitter in baseball. I'm generally left handed, but play musical instruments almost exclusively right handed. I had a friend teach me drums. He was right handed and didn't even think to ask me about my handedness, or didn't want to move stuff around (lefties have to adapt to a right handed world...). It didn't feel awkward though. I don't know why I play guitar right handed. The prevailing theory in my family is that I "learned" by mirroring Kurt Cobain on the TV screen...
It is a very bad choice of words to say that "bipedalism" is a cause for hand specialization.
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.
What does it say for mixed-handed folks like myself (different skillsets per hand - in other words, throw and write with different hands)? What about cross-dominance (different body parts differ on dominant side - in other words, a right-handed person being left-foot dominant)?
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.
In order to present it as a mental illness there would have to be some kind of negative effect, wouldn't there? These differences you mention don't stand out as harmful or even disadvantageous.
southpaws are more common where at least one parent has schizophrenia. i believe it to be caused by an epigenetic change, where damage to the brain in a parent leads to the parent rewiring their brain to use the opposite hemisphere. In short, it's hardly an illness, more of an antibody to one.
You were probably a left-handed person who was taught to write/use tools with their right hand in kindergarten. I got this treatment too.
I'm otherwise a lefty but I use computer mice right handed, because when I first started using a computer in elementary school all of the computer labs were set up right handed.
FWIW, I'm a righty, but relearned to use a mouse left handed for ergo benefits at my first real job; now I left mouse for work and right mouse for home. I prefer ambidextrous mice anyway, but it's really hard to find a left hand mouse if you want that. Even the ambidextrous mice often have thumb buttons for the right thumb. It's not to hard to learn to use a pointer with either hand; IMHO as someone who can't do a lot of complex motion with my non-dominant hand. I think there's a lot of convenience gained by accepting right mousing, although it is a longer reach if you have a keyboard with stuff to the right of your letters.
Weirdly enough, I don't know why I use the mouse right-handed. I was forced into doing it in any particular way, and beside the fact that I was already an adult when I learned of the existence of left-handed mice, I can't think of any reason why I'd naturally gravitate towards right-handed mouse use.
When was that? I know it used to happen, but I haven't heard of or seen that in my lifetime, I'm nearly 60.
Probably because it didn't happen to you, or kindergarteners don't know better and just play along. I only remember it because I was a little shit and got into a big fight about it. It would have been late 80s.
An elementary school teacher of mine had this happen to her (this was in the early '90s, so her experience I'm guessing would have been in the late '60s).
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 didn't know what difference it made and there was one left handed scissors so it went to the kid who knew. I'm left eyed and often wonder if I should have learned to write left handed.
wait, you just gave me an extreme epiphany about my significantly worse right eye myopia. the divergence definitely snowballed from the "use it or lose it" thing and me not wearing my glasses as much as possible
Every study in scientific examination that concept says that for myopia and such things use it or lose it does not apply. Use it or lose it does apply to some things but not that case.
My parents generation is maybe a bit older than you, one of my mom's siblings was forced to right handedness. My mom is left handed and says they tried a little with her, but it only took for some things.
it happened to me, and when my parents found out they flipped out.
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
Hey SAME! but pre-K, trained at home by cousin who used to be a lefty as well.
I don't know - my grandmother (father's mom) was fully left handed. My dad writes left handed but everything else right handed.
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.
I'm sorta here too. I'm right handed, no external pressure to use one hand or the other in early age. Mother is a lefty, father is a righty. As a result I often used the computer mouse on either side as a kid, really wherever it was left by the last user.
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.
> 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.
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”.
Left-footed and right-handed. I find my "handedness" follows where the activity is driven from (upper/lower body).
Soccer, snowboarding, batting, golfing: lefty
Writing, throwing, tennis, pool: righty
"Left-footed and right-handed"
Same as Mickey Dolenz who drummed for the Monkees. Very unusual combination.
Didn't I understood the text or is the 'why' not really part of it? I expected more than a vague 'because it slightly existed and then hands are free to do things and brains got bigger'. I miss the point.
They don't discuss a "why", so much as present data on the "how" and "when". If this work is valid and reliable, then it will be up to later research to propose and test hypotheses as the why.
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.
Actual study here: https://journals.plos.org/plosbiology/article?id=10.1371/jou...
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.
The ‘study’ is fluff.
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.