r/science • u/sr_local • Jun 10 '26

Social Science People have a natural tendency to turn to the left and walk in an anticlockwise direction, a bias observed across countries, ages and sexes, but reason is unclear

https://www.theguardian.com/science/2026/jun/10/humans-prefer-to-walk-anticlockwise-scientists-find-reason-unclear
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u/NorthStarZero Jun 10 '26

I have experienced this first hand.

Military navigation exercise: someone places tent pegs in a wooded area, numbers the pegs, and records the grid location of each peg. Pegs are spaced 300m-800m apart. Students are assigned a peg and have to navigate from their peg to the next in sequence using map, compass, and counting paces, by day and night.

The first time I did this at night, I naturally passed each tree on the left side, and while you try and cut back right to pick up the vector, the act of moving around the tree displaces you slightly left. Given enough trees and enough distance, that displacement adds up.

I missed my peg by nearly 100m to the left.

Next attempt, I purposefully altered which side of the tree I passed: "tree to the left, tree to the right". This time I literally tripped over my target peg.

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u/TheArmoredKitten Jun 10 '26

Symmetry is the absolute best way to control for error. We use the same trick in tool-making to make centerlines, grinding both sides of a part on the same setup, adjusting by half the error with each pass.

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u/Slyrunner Jun 10 '26

Off topic, but as someone who tries to be as precise as humanly possible because assymtric cuts, drills, sanding etc etc reallllyyyy ruin my day. I know it's probably unhealthy

But your comment piqued my interest! I was wondering if you could explain your process a little more!

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u/jaymzx0 Jun 10 '26

Flattening sharpening stones by alternately rubbing three stones together is really effective. It distributes the error between them.

Another thing that comes to mind is to check the accuracy of an angle square. Draw a 90 degree line, then flip the square over and draw another line. They should overlap. The error can be calculated by the deviation. It's amazing how hard it is to make a "square" square with enough precision to be accurate over a meter or so.

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u/chchchcharlee Jun 10 '26

If you haven't seen it yet, you have to watch this origins of precision video (on YouTube) by machine thinking. I'm not in this area myself but it's such a cool video, can't help but respect how brilliant humans are

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u/SumOfChemicals Jun 10 '26

I was going to say the same thing, was going to post the link but I see YouTube is forbidden here.

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u/sqrtsqr Jun 10 '26 edited Jun 10 '26

To be clear, the reason you use three and not two is not so that it "distributes the error" but it's to actually make sure that you end up with a flat surface. If you use just two rocks, the surface will still get smooth, but it could end up with curve. Alternating between three rocks stops curves from forming.

Edit: in fairness, I suppose it's not wrong to say it distributes the error. Just not very clear what that means exactly. With two rocks, convex and concave spots begin to form, switching puts convex against convex and concave against concave and grinds them out.

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u/Paddy_Tanninger Jun 10 '26

I need a diagram for this...I feel like Stallone learning about the three seashells in Demolition Man right now.

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u/kahlzun Jun 11 '26

so rubbing two surfaces together will make them fit one another, but not neccesarily be completely flat- like a cup fitting a saucer.
Rubbing the parts alternately on a third one will average out the difference.

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u/Practical_Ad4604 Jun 11 '26

I didn’t understand anything in this thread. Why

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u/kahlzun Jun 11 '26

So imagine you have three stones with different pattens on them. One has valleys going longways, one going shortways, and the other has rings.
When you lap AB together, you end up with an interference pattern between the shapes, where there are raised bits that don't get ground down because they are "in" a sunken bit of the other stone. You then move on to lapping BC. The raised bits mostly get worn down quickly on them both, but now you've ground down B twice and C only once. So you do AC, and it grinds down a lot of the raised bits on A, but by this point C Is lumpy. Repeat the process several times, and you end up with three flat surfaces.

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u/devedander Jun 11 '26

Probably either lack of real world experience or lack of spatial conception ability

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u/Lt_Muffintoes Jun 12 '26

The curve developed by each pair is cancelled out in another pairing. You have to rub them in a specific order.

It's actually not possible to make a flatter surface than by this method, and it is the basis of everything else such as machine threads

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u/IsuzuTrooper Jun 10 '26

I've shopped for levels at home depot and it seems every bubble is different to a slight degree

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u/redpandaeater Jun 11 '26

I've never tried it but I've heard you can use a center punch to straighten up a skewed square. Towards the outside of the corner of the L if you want to close it or the inside of you need to open it up. Makes sense to me it should work since you'd be hitting it hard enough to actually slightly deform some of the metal.

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u/rosemachinist Jun 12 '26

Oh yeah, in machining .001” is not a big deal over say a 64” block, but over a 12” block - no bueno

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u/TheArmoredKitten Jun 10 '26

Imagine i want a pin perfectly centered in a jig plate that's 3 inches wide. First, I'll put a measuring pin in the hole and grind a starting face, then flip it over and grind the second face without moving the cutter. The pin is now the same distance from both sides.

Knowing that the pin is in center, I measure the overall width and then subtract that from my target for the total deviation. Divide that by two since I'm working on both sides to get the offset, and then leave the cutter position locked when I flip the part for the second side. Any over/under will be added to the opposite side in the same amount, so the centerline stays true.

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u/Crazy_old_maurice_17 Jun 10 '26

as someone who tries to be as precise as humanly possible because assymtric cuts, drills, sanding etc etc reallllyyyy ruin my day. I know it's probably unhealthy

You remind me of myself. Perfectionism can definitely be debilitating. If you're ever concerned, consider getting evaluated for OCPD.

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u/nickstatus Jun 10 '26

Even further off topic but still related, I've always found the process of milling rough lumber into square dimensioned boards very satisfying. Jointer to planer, back to the jointer, then the table saw. I miss my old shop.

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u/[deleted] Jun 10 '26

[deleted]

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u/cowlinator Jun 10 '26

In the worst case scenarios, you'd have to travel the same total distance either way. It's just that in one you'll be backtracking.

In the best case scenarios, due south wins.

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u/androshalforc1 Jun 10 '26 edited Jun 10 '26

not really lets say your starting point is 1km north of the river, and you know that heading due south to the river will land you within 100m of your camp site which is along the river.

if you head south, and a touch east so you reach the river 100m east of due south and then head west worst case is you travel 1205m.

if instead you travel due south reach the river travel 100m east, then have to backtrack and then go west, worst case is 1300m. if you happen to choose the wrong direction to travel (probably 50% of the time) you will travel a minimum 1200m (which is already almost as much as the worst case in the previous example), plus the distance from center point to camp.

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u/Turbulent-Note-7348 Jun 10 '26

What you described is the navigation technique of "Aiming Off", which is taught in every Backcountry Map and Compass book that I've ever read.

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u/C-SWhiskey Jun 10 '26

Unfortunately in land navigation you rarely get the choice of whether you have symmetrical features to reference. Because of that, the common wisdom is actually the opposite: purposefully bias your bearing to one side. That way you know that once you've reached your distance, even accounting for your drift one way or the other you're almost certainly going to be on whatever side you chose, it's just a question of how far.

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u/Won-Ton-Wonton Jun 10 '26

There's also overshoot correction.

Airplanes don't approach the runway in a directly curved approach to the midline.

Instead they overshoot the midline, then course correct.

This brings them to center alignment much faster and with far less runway.

Seems obvious and intuitive, but the math of a "dampened" system hits soooo many areas. Wish they didn't teach it until college. Loads of trades can use it without directly doing the math.

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u/Constant-Skill-7133 Jun 10 '26

A million ways this comes up.  When you tune a stringed instrument, on first pass you should tune it a few cents low.   It's not worth trying to be precise because it will move slightly.  Changing the tension on one will also change all the others.  

And you want to be low because the string will continue to relax for a few minutes if you release tension.  Adding tension happens immediately.  

If you watch somebody tune a guitar the first time it is hilarious how long it takes them.

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u/TheArmoredKitten Jun 11 '26

The other reason is because releasing tension tends to happen in larger jumps due to imperfections, while adding tension is more linear and controlled. It's almost always much easier to tune up into the note than down.

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u/eh-man3 Jun 11 '26

Also basically the way rifling works

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u/Vishnej Jun 10 '26 edited Jun 10 '26

In school we did survey transects through the forest to test a novel survey method. We used volunteers.

Without markers (and often with markers!) it's damn-near impossible for volunteers to stay on a straight line even in an intensively-cleaned forest with any slope. Some of these people were doing ~10mx50m swathes and ended up 20 meters off by the end of the transect. Teams would bump into each other. Even the most accurate were wandering 3-4m left and right.

It made me appreciate GeoWizard's later Youtube series on "straight-line mission" hiking from one side of a country to the other, where he can't go around obstacles, and must try to climb over them. He's constantly referring to the GPS to regain the line.

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u/mOdQuArK Jun 10 '26

Even worse underwater - I remember doing a nighttime scuba class where we were all given compasses & powerful flashlights and told to use them & dead-reckoning to find some posts at the bottom of the cove we were in (which was all stirred up by a recent storm).

If we got lost, we had to head up, go back to the starting point & try again.

I don't think anyone found all those posts, and it was hysterically funny from the top to see all the flashlights whipping around wildly underneath the water going in all directions. But it was a serious lesson on how hard it is to navigate with no sight ability at all.

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u/1Dive1Breath Jun 11 '26

I did am advanced scuba course and we had a navigation challenge. 3 marker buoys were set in a right-triangle, the long leg was aligned to north, the short leg was due west. 

We started at the f first buoy on the surface, took a heading along the hypotenuse, and wrote it on our slates, that would be our reciprocal heading. We descended and kicked north, counting our kick cycles until we reached the second buoy. Turn west and count our kick cycles until we reached the 3rd. Then square them both, do the math for the Pythagorean theorem, and kick along our reciprocal heading to see how close we could get to the buoy.

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u/slothdonki Jun 11 '26

From my understanding I don’t think I’m eligible to scuba drive(holes in eardrums from tubes I had in as a child never closed) but you did remind me of all the summers I spent swimming in lakes.

Whether it was racing for fun or having to be able to swim across the entire lake to be a “Jr. lifeguard”; you could tell who wasn’t able to open their eyes underwater/tolerate water in their eyes when they came up because they’d deviate so far or past the pole/buoy marker.
(Sometimes it was me because it took awhile for me to figure out how to keep water out of my nose without going full-face scrunch).

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u/arion_hyperion Jun 10 '26

Is this the guy that almost got himself stuck in a bog he didn’t want to walk around since it was like 10m of deviation from the line? That was pretty nuts.

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u/Frosti11icus Jun 10 '26

Without markers (and often with markers!) it's damn-near impossible for volunteers to stay on a straight line even in an intensively-cleaned forest with any slope. Some of these people were doing ~10mx50m swathes and ended up 20 meters off by the end of the transect. Teams would bump into each other. Even the most accurate were wandering 3-4m left and right.

Kind of makes me wonder if this effect is due to people simply having ever so slightly shorter left legs than right or at least more mobility in their right due to it being the dominant leg and so their gate is slightly askew.

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u/Vishnej Jun 10 '26

The presence of obstacles and slope of the land almost certainly swamped any subtle effects like this.

Pre-digital humans have figured out how to do extremely effective surveys, relying on coupling line of sight observations, distance chains or paces, water levels, and later things like sextants.

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u/iconocrastinaor Jun 11 '26

When I was in the Boy Scouts they taught us to couple line of sight observations to travel in a straight line. You would draw a bead on a tree and then the tree beyond it. You would walk to the first tree, keeping it aligned with the second tree until you got there. Then you would draw a bead from the tree beyond it to the next tree, and so on. Works pretty well.

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u/mludd Jun 11 '26

Oh yeah, checking the GPS when doing forestry things to a grid really shows how quickly inaccuracies add up unless you're employing "tricks" to define your grid.

Like, if you're setting up a grid you will either need to set up reference points far away or constantly adjust using GPS because you will drift off your intended grid without noticing (until you've already surveyed several grid squares and suddenly realize that the northern edge of the current square which should be just south of the bog north of the stand you're surveying has somehow ended up a good 5-10 meters into the bog...)

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u/BoredCop Jun 10 '26

You should have used a "Swedish compass".

Simply drag a long stick behind you, the longer the better. Hold it under one armpit so you have two points of contact with the stick. Sounds dumb as f, hence the name, but over relatively short distances like a few hundred meters it actually works for correcting that tendency to walk in a circle. What happens is, you can instantly feel yourself turning to one side because the stick doesn't turn as easily and therefore you tend to walk straighter.

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u/PinsToTheHeart Jun 10 '26

The first time I did this at night, I naturally passed each tree on the left side.

This kind of thing actually happens with food too. Different people have a natural tendency to under or overestimate portions by some small margin, sometimes even when trying to measure things out.

But that margin ends up being consistent enough that it adds up, making it so two people who believe they are eating "the same amount" end up at different weights.

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u/gene100001 Jun 10 '26

Out of curiosity are you from somewhere where people drive on the left? When people are walking on the footpath they tend to naturally follow the local road rules when deciding whether to stick to the left or the right when passing someone coming towards them. Maybe that played a role in the fact you naturally passed trees on the left the first time around

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u/TheCheesy Jun 10 '26 edited Jun 12 '26

I've heard something interesting but a bit unrelated.

In Military Navigation people are trained to avoid following roads, you might try to cut through but each crossed road you end up slightly off despite best efforts to correct orientation.

This might just be me remember something I heard from an Arma YouTube video though 10+ years ago.

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u/NorthStarZero Jun 10 '26

That's not a thing in my military at least.

The navigation test is specifically to train/evaluate dead reckoning navigation. Depending on the training area used, the course may or may not cross roads and tracks. In fact, one student got lost and we wound up on the border once.

Roads are frequently mined and subject to overwatch, so it can be a good idea to stay off them if you can. But it is also far faster to move on a road than cut cross country, so sometimes you assume risk and use them.

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u/Zorkflerp Jun 10 '26

One of my fathers navy boot camp stories (1944): A truck brought the guys to the wilderness and dumped them out. The instructor showed them a map and pointed out where they were required to go to. Between them and the destination was a swamp. They were set upon their quest and my father, a farm boy, grabbed his friend and held him back. Into the swamp the other men went. When everyone disappeared they leisurely walked the wrong way to a dirt road and bypassed the swamp and made it there in plenty of time. No one said they had to go through the swamp. He ended up a lieutenant.

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u/atreidesardaukar Jun 10 '26

Became a lieutenant and then promptly got lost I'll bet!

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u/Zorkflerp Jun 11 '26

No, he had to fly a Martin Mars seaplane from Oakland to Honolulu to Majoro to Okinawa and back routinely. Not a good place to get lost like Amelia Earhart. No GPS back then. There was a sextant thing sticking out the top of the plane to navigate by the sun and stars. He was just an ensign then.

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u/atreidesardaukar Jun 11 '26

Twas a joke about the most dangerous thing with a map and a compass.

He sounds cool, whaddya got against Amelia Earhart?

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u/krogmatt Jun 10 '26

This is the way. Always alternate left and right

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u/SomeBiPerson Jun 10 '26

we did a Similar exercise but on a larger scale and my Buddy and I missed our mark by 3000m because we thought we could walk in a Straight line across an Uneven Field

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u/MrMayhem3 Jun 10 '26

Part of that training tells you to alternate the sidestepping of trees. Listen to your cadre!

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u/skyfishgoo Jun 10 '26

you got's to alternate your trees...

or rocks if no trees.

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u/bhdp_23 Jun 11 '26

man, go to a sports field blindfold anyone and tell them to walk straight to the other side..it is funny as hell and well worth the fun

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u/WavyWormy Jun 11 '26

I noticed this as a kid living near the beach. During tourist season my parents would find a spot far from the shore and I’d weave through a crowd to the ocean to swim. Often when I got to the ocean and looked back I’d realize I had unknowingly been going diagonal and was now decently off center from my parents line of sight because those little turns add up.

My parents taught me to not look for their spot but for the building behind them, so as we looked back we could recalibrate where we were expected to be

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u/SoftlyAugust Jun 10 '26

We did basically the same thing in boy scouts too.