[HN Gopher] "Pigeon Neck" Illusion (2014)
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"Pigeon Neck" Illusion (2014)
Author : mnem
Score : 312 points
Date : 2023-01-28 00:28 UTC (22 hours ago)
(HTM) web link (michaelbach.de)
(TXT) w3m dump (michaelbach.de)
| aliqot wrote:
| I get what I'm supoosed to see but i dont see it, its pixels
| gliding continuously.
| tolmasky wrote:
| Hey, this is built with Cappuccino!
| newaccount74 wrote:
| Here's my attempt at explaining this phenomenon:
|
| Our Retinas don't send raw data to our brain like a camera sensor
| would. Instead, the neurons in the retina already do some pre-
| processing, like boundary detection, or movement detection. The
| brain then receives signals where movement was detected.
|
| This movement detection is basically just detecting changes in
| light level, so it works better when the contrast is high (dark
| gray vs. white) and works less good when contrast is low (dark
| grey vs black).
|
| So our brain gets stronger "movement" signals when there is high
| contrast, and it looks like the part that has high contrast is
| moving faster. Since the image is designed in a way that the
| boundary of head/body always have low/high contrast or vice
| versa, it seems they are moving with different speeds.
| albert_e wrote:
| The illusion was very strong on my mobile screen and non-existent
| on my desktop screen. The screen calibration was different in the
| latter I believe so the pigeons were appearing as a slightly
| different colored grey blocks visually distinct from the vertical
| bars.
| jrumbut wrote:
| Funny, I still get the illusion after turning the pigeons every
| color from dark grey to bright yellow.
|
| Brighter colors make it a bit less strong but still very much
| there.
| Enginerrrd wrote:
| On my laptop, I am only able to see the illusion if I looked
| at the striped background and blur my vision a little. Then
| it is quite impressive and strong. Otherwise, it always
| appears perfectly smooth for all colors.
| userbinator wrote:
| This seems to be, for lack of a better analogy, an effect of
| rounding colour intensities in the "motion compensation"
| processing of the brain. The grey and black become perceived as
| identical and thus no motion is detected in those areas where the
| two colours are overlapping.
| illegalmemory wrote:
| It would have been interesting to control the width of the
| vertical stripes too , to see at what point it "starts" being a
| illusion. I assume for very thin stripes it might not work so
| well .
| sorokod wrote:
| I wonder what is the maximal extent of the craining and the
| shrinking illusion that can be achieved. Is it to do with the
| velocity? The grid thiknes?
|
| If the illusion is an error, what maximizes it?
| [deleted]
| xwdv wrote:
| Jesus, this illusion is so powerful, you'd have to have a very
| poorly optimized brain to really see anything else.
| cornstalks wrote:
| It took me several minutes before I could see the illusion. I
| just saw grey rectangles and pigeons smoothly moving to the
| right and had no idea what the "illusion" was supposed to be.
| WarOnPrivacy wrote:
| > It took me several minutes before I could see the illusion.
| I just saw grey rectangles and pigeons smoothly moving to the
| right and had no idea what the "illusion" was supposed to be.
|
| Same here. After a bit I could see some worm stretching if I
| focused on particular points in the image.
|
| I noticed that as soon as I registered all of the movement,
| my eyes fixed a certain way that they do when I'm driving and
| navigating an overly complex traffic situation. I was super
| reluctant to try to focus them any other way.
| glasss wrote:
| When I started messing with the color I ran into that. If I
| shifted to a different grey, it just looked smooth to me. But
| either extreme, black or white, and the illusion was there.
| viraptor wrote:
| Now I wonder how much it depends on the gamma. I understand
| there's some differences depending on the hardware, browser
| and image format/metadata. By default we may all see a
| different shade of grey, affecting how much of an illusion we
| get.
|
| Edit: checked Firefox and Chrome on Android and they look
| exactly the same (work on me). Low brightness works better
| than full brightness.
| cornstalks wrote:
| That's certainly a possible factor. I'm on an iPhone 14 Pro
| with brightness at medium levels in an averagely lit room
| using Safari. I just tried on my Mac's XDR display and it's
| similar: I can either see or not see the illusion (now that
| I know what the illusion looks like I can turn it on/off in
| my head).
| sneak wrote:
| I can consciously toggle the illusion on or off.
| eyelidlessness wrote:
| I see it, but it doesn't feel optimal. What my brain is telling
| me I see is different from what I know is true about what's on
| the screen. It seems to be interpolating between nearly and
| actually overlapping with each alternating stripe.
|
| There are a lot of ways it's optimal to be able to approximate
| and fill in details like this with normal visual processing,
| but literally not being able to unsee falsehoods (and I can't
| switch it off in my brain like another commenter said they
| could) doesn't feel like one of those optimal scenarios to me.
| xwdv wrote:
| A highly optimized brain doesn't bother wasting time on
| getting fine details like this correct, it's too slow and
| will lead you to getting killed in situations where a rough
| approximation of what you are seeing is good enough. People
| have to focus very hard to turn off the optimizations and see
| what is really going on, some can't do it at all. Some people
| seem to be able to see the smooth linear motion by default,
| perhaps descendants of those who lived in simpler
| environments.
| cornstalks wrote:
| Why do you think it takes more time and brain power to see
| the rectangles and pigeons correctly (smooth movement)? It
| was instantaneous and natural for me. I'm not convinced by
| your logic. It doesn't seem like a disadvantage for a brain
| to naturally register the image correctly rather than being
| fooled by an illusion, especially when it takes zero
| effort.
| eyelidlessness wrote:
| I agree with you.
|
| (I think people like to call this "steel man" or whatever
| but just generally applying a charitable
| interpretation...) I think their take on optimization is
| about falsehoods about reality that our brains assimilate
| to make functioning or survival possible under certain
| circumstances, like perceiving magenta as not-green or
| being able to observe a field of grass without being
| hyper aware of each blade of grass within it.
|
| All of which is good insofar as it actually serves us,
| but it's _really weird_ to me to frame it so absolutely.
| It's not an optimization if it doesn't serve us and we're
| just misperceiving reality for no purpose, and there's
| nothing wrong with you or anyone else who doesn't. If
| anything it's just... "wow, electrified meat evolved to
| be conscious is really wacky and super subjective!"
| mafuyu wrote:
| Yeah, this effect is pretty strong. After staring at it a bit,
| the only way I found to 'break' it was by noticing that if I
| flicked my eyes towards a bird, there was a brief period before
| the illusion kicked in. By constantly flicking my eyes between
| each bird, I was able to perceive them as moving linearly.
| ancientworldnow wrote:
| They're just sliding smoothly for me unless I look at it
| without any focus as a disinterested viewer. I work on fixing
| moving pixels all day though so maybe I'm not an average
| subject.
| aoeusnth1 wrote:
| Both me and my wife had to consciously blur our vision to see
| the illusion.
| kerpotgh wrote:
| [dead]
| stefncb wrote:
| If I look directly at a point, the illusion goes away there.
| And I don't really see anything strong anyway, so I wonder how
| you see it.
| [deleted]
| bella_sm wrote:
| DaVinci would have loved this!
| clhodapp wrote:
| Something I noticed and got a kick from: If you set the color to
| black or white then the real motion and the illusion are
| indistinguishable.
| d4mi3n wrote:
| I was in bed reading this with an eye closed and was very
| confused until I discovered the illusion works for me only when I
| watch it with both eyes open.
|
| I found this surprising--I know three dimensional optical
| illusions depend on focus and perspective, but I was unaware two
| dimensional optical illusions were as well.
| soxocx wrote:
| Thats interesting. I see it with either or both eyes.
| jareklupinski wrote:
| I... only see it happening with either both eyes or my right
| eye...
|
| My left eye is immune? This is uncanny...
| meitham wrote:
| I'm the opposite! My right eye alone can't see it, but can
| do with both or left only!
| yazzku wrote:
| Sounds like your perception can't exactly be _pigeonholed_.
|
| Boom, baby.
| 867-5309 wrote:
| your taxi to the nearest _wormhole_ awaits..
| PyWoody wrote:
| Try closing one eye and tilting your head 90deg
| kerpotgh wrote:
| I can see it irrespective of how many eyes are open or any
| tilt angle.
| yazzku wrote:
| Can you see it with three eyes opened?
| labster wrote:
| I can't but I'll ask my yoga guru tomorrow.
| javawizard wrote:
| So you can see it with zero eyes open? ;)
|
| I also see it with any number (>= 1) of eyes open and at
| any angle. Wonder if GP's phone was on night shift or
| something similar - the article mentions that color
| changes impact the illusion's visibility.
| d4mi3n wrote:
| No night shift, for what it's worth. Another commenter
| mentioned astigmatism, which I do have. I was not wearing
| my glasses at the time.
|
| Curious to see if anybody with expertise on the topic of
| optics or visual perception chimes in with some insight.
| kerpotgh wrote:
| Interesting, I have astigmatism so I tried it without my
| glasses and with both one and two eyes open at different
| angles and I still see the illusion (with no change in
| intensity of the "bobbing")
| bmitc wrote:
| The illusion is much less if I zoom in and even less if I
| close one eye, so maybe they had their device up close to
| their face?
| soxocx wrote:
| You are right. If I tilt the screen while changing distance
| to the screen and keep blinking with my eyes while I do
| this, I, besides looking like a maniac, can weaken the
| effect and even make it disappear entirely.
| IshKebab wrote:
| Worked a bit better for me with one eye closed. Weird.
| stouset wrote:
| I let out a verbal "what the fuck" when I tried this. Same
| exact thing as you, it's absolutely striking.
| d4mi3n wrote:
| I was confused as well. First impression: nothing. Get up and
| look with both eyes and there it was. Interesting stuff.
| kolinko wrote:
| For me, if I focus intensely on the head, the neck stops
| moving. When I relax, and the reference naturally changes
| to the lines in the background, the neck begins moving
| again.
| aendruk wrote:
| Astigmatism? My eyes blur at different angles so various
| anisotropies show up only when one is closed.
| d4mi3n wrote:
| I do have an astigmatism in my right eye--which was also
| closed. First time I've had this happen with an optical
| illusion, though.
| stefncb wrote:
| For me it weakens with one eye closed, but I still see it.
| Daub wrote:
| As a one-eyes person, the illusion works fine for me. However,
| it ceases to work in the periphery of my vision.
| dawatchusay wrote:
| I don't feel this is much of an illusion. I think you just can't
| see the movement of gray on black. Or maybe this is what
| illusions are in a very simple form?
| TylerE wrote:
| Pretty much. Change the color to yellow and it's very obvious.
| yazzku wrote:
| Yellow doesn't do it for me. But orange, oh boy.
| kuhewa wrote:
| With the pigeons it seemed illusory, but with just worms you
| can tell that's exactly whats happening. Dunno if it is the
| single-row shape or just less action on the screen allowing you
| to focus on one cell
| anamexis wrote:
| How would you define what an optical/visual illusion is?
| c3534l wrote:
| When your brain fudges the results of what you're seeing
| because of some hidden processing heuristic. If the bird were
| actually just colored black, then what we would see would be
| accurate. But its presented as if we should percieve
| continuous movement when we really shouldn't.
| dawatchusay wrote:
| I'm just saying upon initial thought that it seemed too
| simple to be considered an "illusion" because it doesn't rely
| on some mental trickery, just blindness. But I'm willing to
| accept that optical illusions may all rely on some form of
| blindness. Glad to spawn the conversation!
| thomassmith65 wrote:
| Let's say you recreate this effect by painting the pigeons onto
| a transparency sheet, and moving the sheet above a paper with a
| striped background. The pigeon shapes would appear to bend,
| when in fact they do not... so in physical form, it clearly
| _is_ an illusion.
|
| As a pixelated image, I dunno: our insistence on viewing groups
| of pixels as shapes is an illusion to start with.
| TheSpiceIsLife wrote:
| How is viewing an image on a screen an illusion?
|
| There really is an image there when viewed at the intended
| scale.
| thomassmith65 wrote:
| The image is a grid of pixels. When a group of the pixels
| that the human viewer perceives as a worm appears to grow,
| we cannot claim that the pixels in the overlap _actually_
| belong to the background. It is equally valid to claim they
| belong to the worm, in which case... the worm actually
| _has_ lengthened.
| thfuran wrote:
| Yes, but the illusion occurs when the worm/pigeon and the
| grid aren't actually the same color.
| tomelders wrote:
| I feel like this is doing what an animator would do, just
| badly.
| jameshart wrote:
| Play with the color of the pigeons. Slide it all the way to
| black, and it's no longer an illusion - the edges really do
| move in steps. Slide it all the way to white and the same
| effect appears in the inverse.
|
| Somewhere in between, there are shades of gray where the smooth
| movement of the pigeons is visible. And there are shades of
| gray where your brain can't separate it from the underlying
| black motion. That's interesting, no?
|
| That's what makes all optical illusions interesting - exploring
| the thresholds where our brain's perceptual machinery takes
| shortcuts.
|
| I've noticed there's a tendency, especially among _smart_
| people, to be dismissive of optical illusions. 'I didn't fall
| for it' - because to a certain personality, it's important to
| feel like your mind can understand things and you can't be
| 'fooled'.
|
| But good optical illusions aren't _fooling_ you. You don 't
| need to feel defensive about whether you were 'tricked'.
| They're hacks that exploit edge cases in your visual cortex,
| and cause your brain to be fed erroneous data. They're
| interesting and useful because they help you calibrate the
| instruments your brain uses to collect data!
| the_af wrote:
| > _Slide it all the way to black_
|
| For the record: the illusion still works for me if I slide
| the color all the way to black. One eye, both eyes, it always
| works for me.
| IshKebab wrote:
| Not really - he's saying when it's fully black there _is_
| no illusion. The chicken is really moving like that.
| mannykannot wrote:
| On the other hand, with black-on-black, the idea that
| there is something representing a moving pigeon is a sort
| of illusion in itself, as you infer a boundary that you
| never see in full.
|
| On the third hand, movement is an illusion in all cases:
| what's really happening is that static pixels are
| changing color and brightness (the pixels may jitter
| slightly in changing color, but that's not the motion we
| perceive.)
|
| All these views seem to me to be reasonable, they are
| just different perspectives.
| maegul wrote:
| For me, just with the color slider, there was nearly always
| some sort of illusory motion. Transparent perception of the
| actual motion of the pigeons was either impossible or
| required precise conditions, which really affirms the power
| of this effect.
| justinpombrio wrote:
| I'm confused what you think an illusion is?
| tshaddox wrote:
| There is room for disagreement in some cases. "Look how the
| black text becomes invisible when it goes in front of a black
| background" is not what I would call an optical illusion, for
| instance.
| aidenn0 wrote:
| The color stepping feet version[1] I think definitely
| qualifies. The color contrast is high enough that if you
| focus on the leading or trailing edge of the "feet" it's
| trivial to see its moving the whole time, but if you look
| at the entire thing as a whole, the "stepping" effect
| appears.
|
| 1: https://michaelbach.de/ot/mot-feetLin/index.html
| justinpombrio wrote:
| I would describe an illusion as something where my (say)
| visual cortex is lying to me. This results in an image
| looking very odd: I _know_ that one thing is happening, but
| it looks like something else is happening.
|
| Black text going in front of a black background doesn't
| have that effect. My knowledge of what I'm seeing agrees
| with what I see. My knowledge is "there is black text in
| front of that black text", and my visual cortex says "sure,
| I can't see it but that's perfectly plausible". This pigeon
| video _does_ have that effect. My knowledge says that the
| pigeon image is moving smoothly, but I can clearly see its
| head bobbing; there 's a disagreement.
|
| Do other people define "illusion" differently? Or perceive
| something differently?
| lupire wrote:
| It's th e same illusion as someone walking out a door and
| somehow teleporting to another door after they walked
| around outside.
| IshKebab wrote:
| Something that relies on unexpected or weird characteristics
| of the human visual system.
|
| This just relies on poor contrast.
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