Cognitive Daily reports nearly every day on fascinating peer-reviewed developments in cognition from the most respected scientists in the field.
Last week we asked our readers about an illusion (created by Nobuyuki Kayahara) that's been circulated very widely recently:
While the illusion can't actually determine whether you're "right-brained" or "left-brained," we were curious about what actually affects people's perception of the illusion. Over 1,600 readers took our online survey about the illusion. What's interesting about the illusion is that it's ambiguous -- it can appear to be spinning both clockwise and counter-clockwise. Here's how our readers saw it:
So roughly two-thirds of viewers initially saw it spinning clockwise, while a third saw it spinning counter-clockwise. About two thirds of viewers were able to reverse the direction of rotation from clockwise to counter-clockwise or vice-versa. Interestingly, this ability was affected by the initial direction of motion:
If you saw the figure spinning counter-clockwise first, then you were significantly more likely to be able to reverse the direction of rotation than if you saw it spinning clockwise first. This makes some sense, since more people see it rotating clockwise -- it may be that there's a natural tendency to see it spinning that way, which means it's more difficult to reverse from clockwise to counter-clockwise than the other way around.
But are there any other explanations of who can reverse the spinning? We also asked viewers if they could perceive another common illusion, the "Magic Eye":
(Click for a larger image) One method of perceiving the illusion is to move very close to the screen until the image is blurry, then move slowly away until you see a clear 3-D shape. Another is to look at the image cross-eyed and then shift back to normal vision.
Following these instructions, only about half of viewers were able to see the hidden image in this picture. Were people who could see the Magic Eye more able to reverse the dancer? Here are those results:
The effect is quite dramatic: people who can perceive the hidden Magic Eye image were significantly more likely to be able to reverse the dancer.
We asked a variety of other questions, testing for "color blindness," asked about handedness, gender, age, video-game playing, computer preferences, and a cryptic question: "Do you know who or what TK-421 is?"
This last question is based on a fairly obscure bit of Star Wars trivia. TK-421 is the only Storm Trooper that is individually identified in the entire sequence of movies. Luke Skywalker had ambushed him and stolen his armor as a disguise, and he was later found out when a commander asked "TK-421, why aren't you at your post?" We figured it might be possible that those who knew this bit of trivia were big Star Wars fans, and that might bear some relation to the ability to perceive the illusion. It didn't, and none of the other factors we studied did either. However, there was a significant correlation between knowledge of this bit of trivia and time spent playing video games. This graph shows the relationship:
Brain & Behavior
Comments
I am absolutely flabbergasted that most people see it spinning clockwise! I remember trying this a few months ago and just assumed that all the people who said they couldn't get it to change were seeing it go counter-clockwise like me.
Still can't figure out why I'm stuck counter-clockwise, but have no trouble with the magic eye. Granted, there were quite a few of us. But how many of us were clockwise spinners and how many were counter-clockwise?
Posted by: hanna jörgel | October 10, 2008 3:26 PM
@hanna focus on the shadow of the "central" foot.
Posted by: Matthew Platte | October 10, 2008 3:42 PM
I've found that I'm not particularly consistent about which way I see it initially. (I have no trouble changing it, but I can almost never see those "magic-eye" images - I've looked at hundreds, and only once have I ever seen the image.)
A test I did myself a while back was an attempt to discover whether the image itself is biased in some way to one direction or another. To investigate this, I created three additional versions of the image, by space-reversing and time-reversing (and both) the original, and seeing whether this made a difference. Unfortunately I only tested this on myself, and the fact that I don't see it consistently carried over to all four images, so I could not draw any conclusions. Perhaps a survey in which people are presented with one of the four versions would be more revealing?
Posted by: Andrew | October 10, 2008 3:47 PM
I'm able to see the dancer spinning both ways but not the magic eye. Of course I have rather poor vision and that might be why I've never been able to do magic eyes but something that moves I don't have as much difficulty with. I know optical illusions are primarily related to the brain but do you know if there has there been any research on how someone's visual acuity affects optical illusions? That's always been something I've wondered about.
Posted by: Noadi | October 10, 2008 4:01 PM
You can put me in the counter-clockwise, can reverse, can see the magic eye, does know TK-421 category. But, strangely, I don't play video-games. Perhaps I should buy one!
Posted by: RoaldFalcon | October 10, 2008 4:31 PM
I can't see it counter-clockwise. It seems completely unambiguously clockwise for me. But then I tried viewing just the image in a new tab, and the favicon in mozilla changes to a really small version of the image. On the really small image, i can reverse it counter-clockwise, but in the normal sized image I can't reverse it. It's weird to see both tiny image and full-sized image at once and see them going in different directions.
Posted by: Will | October 10, 2008 4:31 PM
I found that I could only see her spin clockwise at first. I've always been able to see Magic Eyes and this was no different, then I looked at where I fell in the categories and realized, hey wait. I SHOULD be able to see her spin counterclockwise. So, I forced myself. Other people who could only see her spinning one way, try this trick:
Cover up the top half of her body, so you can only see her legs from the knees down.
Pull your hand away after several seconds and chances if you repeat this you will be able to spin her the other way. I believe it has something to do with what you perceive to be her initial stance when you start watching her.
Is it just me or does this trick work for anyone else?
Posted by: margaret | October 10, 2008 4:31 PM
for those unable to reverse the spinning dancer: if you need to convince yourself that she really does spin both ways, check out the two cool edited versions here: http://www.randominc.net/spinninglady/
in each, a few lines have been added to resolve the ambiguity in the original animation.
Posted by: curious | October 10, 2008 4:46 PM
The thing I find amazing is that we perceive her as "spinning" at all. I find the brain's image processing fascinating. It's a 2D image with all depth queues purposefully removed.
When initially seeing the image (probably within a few frames), your brain has identified it as a woman, excluded the possibility that she's just changing shape without moving (which is what is "really" happening, given the available information in the image), and figured out that for the silhouette to do what it is doing, it must represent someone spinning.
Furthermore, it adds missing information (rotational direction) to help you perceive what it decides is happening. And, of course, conservation of momentum doesn't allow someone who is spinning to change directions instantaneously and without "kicking off", so your brain bucks at the thought of "magically" swapping directions.
Posted by: Frac | October 10, 2008 4:51 PM
I've always, frustratingly, been stuck in the counter-clockwise perception. Now, thanks to Matthew Platte's advice to focus on the shadow of the central foot, I can go back and forth at will! My life is complete.
Posted by: podunk | October 10, 2008 5:14 PM
"Clockqise" looking down from the top of her head, or "clockwise" looking up from her feet?
How are you sure that all your answerers were consistent?
Posted by: Ahcuah | October 10, 2008 5:22 PM
I can switch it, but mostly I'm distracted by her nipples.
Posted by: Dave | October 10, 2008 5:30 PM
Matthew Platte's advice didn't help because I had already tried that, but thanks for trying.
Curious' website shows me that it is indeed possible, yet without the white line showing the leg she is still stubbornly twirling around counter-clockwise and no manner of covering up, standing up or sheer force of will seems to do change.
Grrrrr I've spent enough time on this. Sigh, my life will never be complete.
Posted by: hanna jörgel | October 10, 2008 5:39 PM
Very good point Ahcuah.
I would like to see some discussion on this point. To not specify is to assume every individual would innately have the same perspective as every other which contaminates the data.
Posted by: Charles Janecka | October 10, 2008 5:54 PM
Initially (when doing the survey), I couldn't get her to change directions. Here, where I can scroll the image, I can choose which way I want her to spin by scrolling the image until all I can see is the shadow of the foot. Then i just pick a direction, see it, and scroll her back into view.
Posted by: Morejello | October 10, 2008 5:58 PM
I always initially see it rotating counter-clockwise. If I look at the shadow, it immediately snaps to the other direction, and I cannot get back the original rotational direction at all.
Posted by: Marc | October 10, 2008 6:13 PM
This is fascinating. Methinks I've seen this before but I can't recall where or when. Today I saw her spinning clockwise first but was able to see her spinning counter-clockwise after reading your post. I can always see these 'magic eye' images almost immediately and w/o any special effort and this was no exception.
Hugs and blessings,
Posted by: storyteller | October 10, 2008 6:23 PM
At first I thought it was impossible to see her spinning counter-clockwise and that the people who saw that were just gullible. But I was immensely wrong.
I managed to switch and got stuck to counter-clockwise, but then I figured out how to switch easily. It is about seeing her stretched leg passing in front or behind the support leg. If, when coming from left to right, you see it going behind the other leg, than it is clockwise, and the opposite for counter clock-wise.
Posted by: Fernando | October 10, 2008 8:51 PM
What I find really neat is that I can't seem to change the direction purposefully. The direction of spin doesn't change, no matter how much I try to make it change, until suddenly something backfires in my brain and she's suddenly going in a different direction. Even when I blink or when I cover it with my hand, it's always going in the same direction. No matter what I try, those gosh-darned top-down effects just can't be defeated!
Posted by: Eve | October 10, 2008 10:06 PM
I saw counterclockwise at first, then "noticed" it was going the other way, and, basically, it got "stuck" going clockwise. I could not conjure it going in the other direction.
I really thought that Stormtrooper was "teekee-421!" Now I can't see it any other way other than TK421!
Eep!
HJ
Posted by: Bing | October 10, 2008 11:28 PM
It happened again. I reloaded the page, and, damn, the image was spinning counterclockwise again. I had not scrolled down the page, so I was only looking at her upper torso. When I scrolled down to see the leg, she "flipped."
Now I'm going to move objects with my mind.
HJ
Posted by: Bing | October 10, 2008 11:32 PM
Nope. Always counter-clockwise. There is no doubt in my mind that this is the only way the image rotates. I even did the scroll down thing. No. The shadow. No.
Counter-clockwise. That is it.
Posted by: Bill | October 11, 2008 12:51 AM
Clockwise.
Won't reverse no matter how many times I reload or how hard I stare.
Not sure I've ever been able to see a "magic eye" image.
Posted by: Azkyroth | October 11, 2008 2:16 AM
@Ahcuah: The original survey didn't use clockwise/counterclockwise; it showed arrows representing her direction of motion (which would appear the same from the top or the bottom). I'm assuming Dave converted the arrows to CW/CCW for ease of graphing (since most graphing programs won't let you use an arrow as a category label...)
Posted by: Dr. Kate | October 11, 2008 8:13 AM
For some really fun games with your perception system, go to the link provided by curious (above) where some dude added a couple of perspective grey lines to the legs, and watch the two together while covering up the area of the legs of one, both ladies spin the same direction, when you uncover the legs they continue to spin the same direction, until your visual system notes (I didn't even have to look "at" where the grey line was, when spontaneously one changes direction and the other doesn't...
very cool.
Posted by: dph | October 11, 2008 11:00 AM
I saw her spinning clockwise, but was able to reverse it in two ways. One - I crossed my eyes, and magically, as the image split into two, the one on the left was spinning counter clockwise! Two - I stared at her raised foot, it grows and shrinks, and the odd thing is, it doesn't get bigger at a single point, as it should when it gets closer to you, instead it gets bigger at the sides and shrinks both times that it passes through the middle. Watching that enabled me to flip her spin. Even then, It was difficult for me to hold it, my brain 'corrected me' each time and the reverse would flip back to my initial impression instantly
Posted by: shank | October 11, 2008 12:46 PM
I just had a DOH! moment.
I've never understood why people saw this as spinning one way or the other.
I just realised that it's an animated GIF, and I have animation turned off in my browser! :-)
Posted by: jim | October 11, 2008 2:54 PM
So you lied to us to get us to give you information? I'm sure we'll participate in future tests.
Posted by: Scott | October 11, 2008 3:22 PM
Just continue to stare up and down from waist to knees and the switch from CW to CCW happens alot. Tricky, indeed.
Posted by: kurt l hanson | October 11, 2008 3:29 PM
When I look somewhere else on the page and use peripheral vision on the figure, it's easier to change the direction.
It seems I use peripheral vision to make some preliminary judgments about the image, then my brain fills in corresponding details. By the time I am looking directly at it, my mind is made up and it is very difficult to reverse the direction.
But I can reverse the direction by using a fixed, unblinking stare. By not blinking, I am probably taxing my brain's ability to construct pre-assigned patterns to what I am looking at.
Like if you stare at your face in the mirror without blinking for long periods. Your face loses shape and shifts into other images while you are staring at it. Especially try this with a candle in a dark room. The candle flickering will trigger your brain to super-impose all kinds of imagery onto the image of your face in the mirror.
This is an old meditation technique. Eventually your brain gives up and there is just an empty space where your face should be. To arrive at this point you have to persist through the stage where the eyes are tearing. The fixed gaze is crucial. You cannot move your eyes at all, or else your brain "resets" and starts throwing out patterns again.
This really attacks the idea that what you see is what you can trust is real. What you see, apparently, is a combination of sensory data and organizational patterning that the brain applies.
On other words, there is no such thing as totally interpretation-free vision.
Very interesting in its implications.
Posted by: yogi-one | October 11, 2008 4:26 PM
I've tried all the tricks, she still turns clockwise.
But then those cursed Magic Eye things? I could NEVER see those either, while everyone else I knew, could. Despite standing in front of them for ages doing all the focusing, it always looks like a mess to me.
I used to cheat, because often the poster would have a tiny indicator of what it was, so I could play along without anyone noticing that I didn't see it at all.
Posted by: Nico | October 11, 2008 8:03 PM
I could never see 'magic eye' pictures except on very rare occasions, and even then just a vague outline. This is probably because I have poor depth perception--my eyes just don't work together which is what is required for both.
I see her clockwise and I can't make her change direction, so I though about why that was. #9 is elegantly right--the brain supplies missing information. In my case though I think it's kinetic. Try spinning clockwise with your right leg raised, like in seconds 08 and 11 in the video. Not a problem. Now try spinning counterclockwise with your right leg raised...do ankles even turn that way?
Or, those of you who can see her counterclockwise--is that her *right* leg raised?
Posted by: Barbara | October 11, 2008 8:53 PM
And then I scrolled up to see just her head, reversed that, and scrolled down. Reverse completed, but my brain wants to put it back. And when it's reversed that is her left leg raised.
Interesting.
Posted by: Barbara | October 11, 2008 8:56 PM
You can read at
http://www.unitaryflow.com/2008/10/spinning-dancers-mistery.html
1. why most people see her spinning clockwise, and
2. how we can figure out that she rotates counter-clockwise using geometry.
Posted by: Cristi | October 11, 2008 9:37 PM
CW,but switched to CCW as soon as I realized I could. And I never ever see "magic eye" pictures. I exercise my eyes to compensate for an out-of-date prescription. I have this drawing of a dog and a fence, and I "jump" the dog over the fence.
Posted by: clayton | October 12, 2008 1:11 AM
To those who say they see her "unambiguously" spinning in one direction and can't make her change - I can make her switch, although I'm biased towards clockwise, and I'd just like to point out that it's perfectly unambiguous to me as well. When I see her spinning cw my brain refuses to believe she could possibly be spinning ccw, and vice versa. There is a moment of confusion when the flip happens, but otherwise it's always perfectly clear to me which direction she's spinning.
Posted by: Felicia Gilljam | October 12, 2008 7:56 AM
I like making her reverse every 180 degrees, back and forth, back and forth. I usta amuse and distance myself during sixth grade by making the lawn sprinkler (twin armed rotating type) outside the window reverse directions. In season. So it's not only 2-D representations of 3-D that work. rb
Posted by: arby | October 12, 2008 1:36 PM
It flat out bothers my eyes and brain to look at magic eye pictures, so I can never stare at them long enough.
Oddly, I don't have any vision issues, but that much visual noise just makes me wince.
Posted by: Nico | October 12, 2008 3:30 PM
I was initially unable to see the girl spinning anything but clockwise. I was unable to grasp how it should be able to spin any other way but clockwise, but after returning to it today I was finally able to see it, and now have entirely no trouble changing it from clockwise to counterclockwise and back again. I was the same with the magic eye pictures. The first one I could not see and could not see and one day I just "got it" and been able to see them all ever since.
For the spinning girl, it's as someone above mentioned already; You focus on the tip of the heel (the central axis of the spin) of the "central" foot. and try to see it spinning the other direction, then work your focus upward after succeeding with getting just that one bit to consistently spin the way you want it. Now that I've got it, I only need a quick glance at the heel to change the spin to the other direction. (It took me since the first post about this illusion for me to get it this first time.)
For the magic eye pictures, the way I learned it was you focus "beyond" the picture as if you are looking at something behind it THROUGH it and then you slowly bring your focus toward the "surface" of the picture until you catch a glimpse of something that looks like a 3D "edge" and then focus on that and the picture comes suddenly clear.
The key to both is to practice shifting your focus (both your perceptual focus and the focus of your eyes) and don't give up. Keep trying, because it's a matter of building the right "muscles" if you're not already practiced in this sort of thing. (Eye muscles and brain muscles both...) ;)
Posted by: Silver Knight | October 13, 2008 12:45 AM
actually everytime I look at this illusion I see it rotating in a different direction, but then I am unable to reverse it.
Posted by: Virginia | October 13, 2008 6:36 AM
I can force myself to see it in either direction, but if I just look at it normally, i see the top half go clockwise and the bottom half go counter clockwise. its very disconcerting.
Posted by: Jeff | October 13, 2008 7:58 AM
when i reversed the image i was shocked, i wonder what else my brain can do...
Posted by: sultan | October 13, 2008 8:59 AM
I'm in the can reverse, can see the magic eye, do *not* know the star wars thingy category (and I don't play video games either). My initial perception of the image varies, sometimes clockwise, sometimes counter. I can't remember what I initially saw the very first time, which might be significant, since there is a learning effect in these phenomena.
After 15 minutes or so I can now actually see the image swaying from left to right and back, instead of rotating (that is, the woman keeps facing me). This only works in peripheral vision and I notice that the swaying leg changes place too: when the extended leg is moving from left to right, it is her right leg and from right to left it is her left leg.
Another ambiguity illusion that shows a distinct learning effect is the hollow-face dragon: Google for "dragon illusion", print and fold your own paper dragon and look at it while moving your head. First it is difficult to see the hollow face as normal. It helps a lot if you use only one eye and, if it still doesn't work, dim the light. Once you manage to see the head as normal (instead of hollow), it appears to follow you around. The interesting thing is, that the more you get accustomed to the sight of your dragon, the easier it becomes to flip your brain into the illusion, until you can easily see it binocularly and in full daylight. You seem to learn to disregard the depth cues in favor of the now familiar interpretation that you have learned.
Posted by: John | October 13, 2008 12:06 PM
I never used to have any problems with Magic Eye images until I started looking at them on a computer. I think the refresh rate on my monitor affects the focus/unfocus method I use see the images. I've only every been able to see one Magic Eye image on a monitor (this one) and it gives me quite the headache.
Posted by: Maeve | October 13, 2008 2:05 PM
you can also have similar effects with point-light figures :
http://www.perceptionweb.com/perception/misc/p5004/bistdemo.avi
the assymmetry CW/CCW could also be related to this (if the movie started at a fixed position)...
interestingly, the point-light figure bistability seems gender-dependent :
http://www.current-biology.com/content/article/abstract?uid=PIIS0960982208008117
so it would be fun to see if the ratio CW/CCW changes for a male silhouette
Posted by: Jan | October 13, 2008 2:14 PM
Clockwise all the way. Can't reverse it.
Posted by: Dan Peterson | October 13, 2008 2:33 PM
Clockwise all the way. Can't reverse it.
Posted by: Dan Peterson | October 13, 2008 2:36 PM
For a while now I could only see it counter-clockwise, and was frustrated by all the data stating that most people see it clockwise, or both.
Well I just found that if I stare at it, and blink really fast as if I'm seeing the image in stills, the still images begin to appear moving clockwise. Then if I stop, the image is moving clockwise. However, if I look away for even a second, right back to counter-clockwise.
Posted by: Lisa | October 14, 2008 10:23 AM
She tends to spin clockwise for me, but I found if I stare at a spot down and to the left of the image, I can make her spin the other way.
Posted by: William | October 14, 2008 1:08 PM
I'm getting a headache. The figure is spinning clockwise, the shadow counter-clockwise. Can't reverse either.
Also, I don't think it's true that the image doesn't contain any depth information. If you take perspective into account, so things that are further away being appearing to be smaller and pay attention to the shadow you can tell that she actual spin direction is counter-clockwise.
Posted by: Wildflower | October 15, 2008 6:28 AM
are you sure this image is not reversing its rotation? ok, probably not, but i can see both clockwise and counterclockwise but I can't change it intentionally. it starts cw or ccw each time i look at the picture (mostly cw). it once changed from ccw to cw while i was looking, but i didn't intend to.
i can see the magic eye and know tk421 by the way.
Posted by: shine | October 17, 2008 5:13 AM
For me, she turns clockwise and I cannot reverse. So I tried an experiment. I looked at her with a mirror -- but she till turned clockwise. Then I put the mirror against the screen in a 90 degree corner, to see both original and reversed at once. Incredibly, she plainly turns in opposite directions -- but I see them at once BOTH clockwise! The effect is disturbing and impossible; a reversed mirror image which is simultaneously not reversed. Sometimes, just for an instant, concentrating on the impossibility forces me to see one of the images turn the other way, but only for about one turn.
Posted by: Terry | October 17, 2008 7:16 PM
I saw her clearly clockwise, but was determined to see the other way. It was very hard, but it worked when I looked at the shadow of the foot. Looking back at her, she was going counter-clockwise, but more easily turned back clockwise. So that seems a preference for my brains!
Posted by: joitske | October 18, 2008 6:50 AM
In my eyes, she starts counter clockwise and within seconds changes to clockwise, total time is 10 seconds...which is really a long time. Funny that, my first-born, my daughter Stacy (17yo), sees the exact same thing as I and perceives the change in direction nearly identical to me!
Posted by: Karen Williams | October 19, 2008 11:21 PM
OK
First I was stuck on clockwise-then I used my pointer finger to circle counter CW-and it worked!
But it seemed like the animation slowed down for me to do that-in fact, it seemed like she paused and changed directions for me ; > And I can go back and forth, and there is always a pause n the spin for me.
So now I am convinced that the animation has her change directions every minute or so...and slows down for me to reroute my brain.
Posted by: catherine | October 20, 2008 3:27 PM
Funny, no one who saw the Magic Eye image said what they saw. I saw a tailless horse, but I wonder if somehow there is a tail that I can't see. Anyone else get that?
Posted by: Bryan | October 20, 2008 4:02 PM
#56, I could find no tail either.
Posted by: John | October 20, 2008 10:04 PM
Interesting discussion but eventhough you can see her spin both ways the shadows clearly indicate there is only one rotation
Posted by: Right Said Fred | October 21, 2008 4:26 PM
For me,it always starts ccw,and turns into cw at will,but sometimes,if I stare just long enough,it will change anyway,whether I want it to or not.
Is it just me or is she really bouncing a little bit while rotating?
By the way,I'm getting an image of an tailless horse too..
And I had absolutely no idea what is TK421 till now.
Posted by: Snjezana | October 23, 2008 5:20 AM
I see her spinning in either direction and can change at will by glancing down toward text written below the screen. If I want I can see her just moving her leg back and forth in front of her without ever making a full rotation. RE: Snjezema's comment--yes she is bouncing (backwards?) and she seems to only truly have one breast.
Posted by: michele | October 26, 2008 3:52 AM
I managed to switch and got stuck to counter-clockwise, but then I figured out how to switch easily. It is about seeing her stretched leg passing in front or behind the support leg. If, when coming from left to right, you see it going behind the other leg, than it is clockwise, and the opposite for counter clock-wise.
Posted by: estetik | October 26, 2008 10:50 AM
I agree on Right Said Fred's observation on the shadow, which, if the floor is "below" the viewer, would be counter-clockwise. I wondered, too, about gender and perspective, whether one gender was more likely to perceive a specific rotation. Then I wondered about height, capturing the subject's height (and implied eye height), and looking for correlations there. That would capture one social/average-height point of view and then a purely (we hope) height-related point of view.
That later point seemed to work better for me...when I have her at the top of the screen, above my eyeline, I tend to more easily see her going CCW, where if she is at the bottom of my screen, below my eyeline, I tend to more easily see her going CW. This would equate a perspective change on the girl, where the outstretched leg, which passes lower as it traverses leftwards across the standing leg than it does rightwards, both in position in the frame and in relation to the standing leg, would be perceived as anterior when viewed from above (below eyeline, or looking down on the girl) and as posterior when viewed from below (above eyeline, or looking up at the girl).
I would be curious to put a grid behind her, first a regular (equilateral) grid, then perspective grids for divergent and convergent angles, and see how they impact the outcome. Then perhaps a simple and easy visual field, like a regular wallpaper/pattern, changed to provide perspectives from 90 degrees, and then some angles above and below (looking down on a wall from above or up at a wall from below).
Negative-space objects like this often cause such referential confusion, revealing how anglular details can be ambiguous without a frame of reference. Do the same thing with a dining-room chair and you'll prolly get the same result.
I have yet to resolve the autostereogram, but as that's really a matter of training the eyes to diverge (in this case at least) it could, in theory, be perfected with practice and perhaps some exercises. I can easily stand close before a wall with 2" tiles and be able to get two horizontally-adjacent tiles to "merge into one". I can do the same with two different pens (one green and one white in my case) held out at the same focal distance with some gap between them, and then merging them into one pen in the middle. The autostereogram doesn't appear to give such clean sight references, but the principle would be the same in diverging the eyes to infinity. Perhaps printing it on a transparency and holding that up before some distant (visually "infinite") reference field would ease the process.
Posted by: Scot Harkins | October 27, 2008 4:18 PM
I taught myself to see her spinning the other way by covering the upper half of her body and looking at the feet and picturing, in my mind, how the shadows would change if the foot was moving the other way. Once I trained myself I can make her go either way with a quick glance at her feet.
There's a great lesson here about perspective and seeing things "our way."
Great blog entry!
Posted by: Michael Plishka | October 28, 2008 9:36 PM
Interesting follow-up! I was also able to switch her rotation by looking at the upper right corners and upper left corners of the browser and catching the rotation in the corner of my vision as opposed to looking straight at it.
Very interesting...
Posted by: Michael Plishka | October 28, 2008 9:45 PM
wow! if i concentrate on her bottom foot, i can get her to switch directions real-time i watch her spin!
at first i ONLY saw her counter clockwise, then the next day clockwise for a second then back to counter clockwise, now i can get her to switch by concentrating. maybe these things take metal manipulation, or "practice"?
Posted by: rhiannon | October 29, 2008 7:24 PM
Okay, this is odd; initially I could only see clock-wise, and without the link with the addtional visual cues, I couldn't switch it (although I could conceptualize the switch theoretically, I couldn't get myself to see it.) However, while on the page with the added cues, looking from the counter-clockewise image to the clockwise one, I found on one occassion that I was unable to switch direction back to clockwise for several "revolutions," making it appear that she passed her raise leg right through the other leg! I also found, in covering the upper half of the original version, that I couldn't hold the counter-clockwise direction for a full revolution, but I could perceive her as swinging back and forth 180 degrees instead, with the raised leg either toward me or away from me.
The post that asked "Which leg does she have raised?" hits it right on the money, I think. It's more natural for someone to spin in the opposite direction from the one in which their leg is raised, so once I had it in my mind that it was her right leg raised in front of her, I could only see her falling (not spinning, oddly) back and to her right, clock-wise. (Try raising your right leg in front of your and rotating counter-clockwise; it's kinda akward and off-balance.)
Posted by: Lisa | November 20, 2008 12:55 AM
I see the lady spinning side to side. But I can not see the eye at all
Posted by: DJ | November 25, 2008 2:38 PM
Sorry , when enlarged I can see the horse fine
Posted by: DJ | November 25, 2008 2:41 PM
ok, I just can't see it counter-clockwise.
and I tried, I really did. I even tried changing the image size and everything.
But it's just impossible. I don't know how some people can see it counter-clockwise, and it's driving me crazy so I'll just give up.
Posted by: Mari | December 1, 2008 7:23 PM