by Alex Tabarrok
on October 13, 2007 at 7:10 am
in Science |
This optical illusion is so compelling it is hard to believe that it is an illusion and not a computer trick. I have my doubts about the left-brain right-brain story but check it out. Which way does she spin and does this fit your profession?
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Repeatedly opening and closing my eyes, or looking away and back again, I sometimes see clockwise rotation and sometimes counter-clockwise rotation. My background is in the hard sciences.
I have my doubts about the left-brain/right-brain story, as the first time I saw it, she was spinning clockwise, and it was very hard to see it the other direction, but I’m definitely a left-brain sort. Maybe the rotation pattern is reversed for Australians?
I see it clockwise and can’t get it to change. And I’m about as left-brained as you can get! A computer programmer by trade, with no artistic talents and frequently confused by spatial relationships.
I see it clockwise and I can’t get it to change. I’m a computer programmer with artistic talent.
I can’t get any effect except clockwise. I wonder if it’s because my two eyes aren’t exactly the same — one is better for close, one is better for distance. The right-brain/left-brain theories are often over-interpreted (to say the least). Maybe there are better explanations.
When I first looked, it was counter-clockwise. Then, after staring at it for a couple of minutes trying to get it to change direction, it was still counter-clockwise and I was dizzy. Economics graduate student.
Also, based on proportions, is this a rotating pornstar?
It´s a trick. You only have to wait 30 sec. and you´ll see her change the spinning way.
This is an example of what we who study perception call a bistable percept. That is, it’s a stimulus that has two stable interpretations that someone exposed to it will flip between, given a long enough period of time. This is really just an advanced version of the Necker Cube (findable through a brief search). It’s interesting in that sense, but it has very few implications for neural processing.
The right/left brain story is utterly ridiculous. While there is some differentiation between the right and left hemispheres of the brain, it has absolutely nothing to do with how “logical” one is, or “creative.” If you needed any proof beyond the say so of someone who works on brain stuff, consider people who’ve undergone hemispherectomies, i.e. people who have had an entire hemisphere of their brain removed. This is sometimes done in childhood for intractable epilepsy. If done early enough, these people end up being developmentally normal. One of them a few years ago completed a degree at the University of Cambridge. No major functions can be entirely localized to a hemisphere in light of evidence like this.
Also, which hemisphere is more active in a given task seems to be correlated mostly with handedness. Are all lefties holistic artists?
It was initially counterclockwise but I can now make it shift back and forth about every 10 seconds. I focus on the foot that is on the ground and the spinning leg to get it to shift.
Very interesting – initially I saw it as CCW, I am a PhD student in the hard sciences.
I second Sol’s opinion – the illusion is real. When going CCW, the perspective on the dancer is at a slight upward angle, so the ellipse the hand traces is higher when the hand is closer to you, and lower when away. When going CW, the opposite is true – the perspective on the dancer is at a slight downward angle, so the hand is higher when away from you, and lower when closer to you. This allows the same animation to go both CW and CCW. All other body parts trace similar ellipses.
To switch direction, focus on one body part (foot, for example), and mentally switch perspectives from higher to lower or vice versa.
Clockwise, although by hiding the legs I could see it turning the other way. Diplomat
My wife and I saw opposite directions at the same moment, so not a trick, I suppose. I saw it mostly clockwise, but some the other way.
Programmer, clockwise. Can occasionally switch it.
Oh dear. She’s, impossibly, turning both ways at the same time. What does THAT mean?
Clockwise – that doesn’t fit. But, um, she was kind of stacked, that might have activated the emotional part of my brain more. … uh, it’s been awhile.
I did get counter clockwise for just a second, immediately after I went to the page the second time. That was after reading more of MR, so maybe my left brain was still heavily engaged.
Wow, I thought there was no way to see her spinning counter-clockwise, but the commenters who suggested looking at the shadow of the feet are correct… You can change the direction spin immediately by doing that. very cool
Another programmer who sees it clockwise and cannot get it to switch. I was upset at this, so I took a screen capture video of the animated gif, loaded it into a video editor, played the video backwards and… she still went clockwise!
I think it’s a conspiracy. All you people who say she switches (including my wife) must be having a pretty good laugh at my expense. Obviously the makers of the video editing software are in on it too…
Here’s the umpteenth computer programmer who can only see the dancer going clockwise. Sounds like the left-brain/right-brain interpretation is a bunch of malarkey.
Focus on the feet (and what may be the shadow or the mirror image in a shiny floor, whatever). The dancer is turning anti-clockwise. Mask out the bottom part of the image, or just focus on the torso, and there seems to be less clues regarting the rotation. The dancer may be turning either way. (No, I haven’t measures the hands for a hint of perspective.)
Rather than the left brain vs right brain theory I’m inclined to subscribe to a simpler “name your favourite body part” theory.
Clockwise. Can’t get it to turn counter-clockwise. I’m a retired programmer, with no spatial sense at all. Do I sense a pattern here?
I saw it counterclockwise–couldn’t get it to switch very effectively. I’m a graduate student in math. My girlfriend saw it as only clockwise and couldn’t get it to switch at all. She’s a computer science major.
I mean, look at the ponytail and the nose. The figure is turning to the left when she is looking at you. That’s counter-clockwise. When she is looking away from you, she is turning to the left. You can see the shadow of the left leg turning from 3 o’clock to 2 o’clock to 1 o’clock to 11 o’clock to 10 o’clock. I don’t understand how people see the figure turning clockwise, and can’t make it switch with any of the tricks suggested here.
But at the same time I was looking at it, my girlfriend claimed to see it going clockwise, and she also saw it switch. We’re both economics-trained attorneys who claim to be left-brained, but I’m probably more mathematically inclined than she is.
When she’s spinning CCW, her left leg is the one that’s up in the air. When she’s spinning CW, it’s her right that is up in the air.
So, it has to be a trick. I can actually see her change directions if I watch long enough.
Programmer here. Excellent spatial ability. She goes CW until I see the shadow, which SHOWS she is going CCW. But if I look away and back, she’s going CW again.
There’s a slew of optical illusions, at http://www.michaelbach.de/ot/, Bach calls them visual illusions. The illusion at http://www.michaelbach.de/ot/fcs_hollow-face/index.html seems related, sorta.
My first perception was CW. After a bit, I could switch it at will. Electrical engineer.
I think her nipples are more erect when she spins counterclockwise.
Initially saw it as CCW, but was able to get it to switch after about 10 sec. I didn’t notice the shadow on that viewing.
Read the comments and returned; since my attention had been called to the shadow, it was CW. But if I scrolled up so that the shadow was off the screen, I could get it to go CCW again.
CCW seems to be my natural inclination: if I hide the shadow and look at the screen after ~5 sec, that seems to be the direction I get.
Math/physics background; for what it’s worth, strongly left-eyed.
Hey guys, just cross your eyes… It will switch
Wow that just gave me a huge headache trying to see the other direction (I can only see clockwise)…. And yes, that left side/right side is BS.
I can only see clockwise but my partner (a farmer) can see both at the same time I can only see clockwise.
I write on public policy and have economics training.
If I do the focus on the foot thing I can’t get it to change direction but if I look long enough the speed of her rotation seems to slow down.
This is cool, thanks for posting it.
Actually, I just figured it out — there definitely is a change.
When she’s going clockwise, her left ankle crosses her right calf on the backswing almost exactly at the apex of her calf muscle.
When’s she going counterclockwise, the ankle dips down lower, and you can see the bottom of her foot just before it does.
Keep your eye solely on her airborne ankle and tell me if you see the difference.
Cool graphic, regardless.
I’m a vagrant, and she only goes CW. Couldn’t get her to swtich directions or anything. She did slow down, but that could’ve been the connection.
A trick to help you switch back and forth which way you see it: cover her up with another window, except for her foot, now it’s easy to imagine the foot going either way. Then reveal the rest again.
No there isn’t. There is no change – which ought to be clear from all the people who can only see it going one way or the other. I can pretty much switch it at will, though it dose tend to get “stuck” going one way sometimes.
Let’s take the case of the ankle crossing mentioned above. First, when she rotates around once the elevated ankle is going to cross the pivot leg twice – once in front, once in back. Clearly one of these crossings is higher than the other – but which one is which depends solely on your perception of the direction of spin.
When you perceive the rotation to be CW the pivot leg is the left leg and the right ankle crosses high on the pivot leg’s calf when you perceive her to be facing away from you and lower on the calf when you perceive her to be facing towards you. The low crossing as she faces you means you perceive seeing the top of her right foot as it swings across her left leg, passing closer to you.
However, when you perceive the rotation to be CCW the pivot leg is the right leg and the left ankle crosses high on the pivot leg’s calf when you perceive her to be facing towards you and lower on the calf when you perceive her to be facing away from you. The low crossing as she faces away means you perceive seeing the bottom of her left foot as it swings across her right leg, passing farther away from you.
Another thing you can watch for is the hand position. When she faces to the left, there is a greater separation in vertical distance between her hands. When she faces to the right there is very little (if any) vertical separation between her hands. But, when you perceive her as spinning CW the higher hand (as she faces left) appears to be the right hand, yet when you perceive her as spinning CCW it now becomes the left hand.
There is no difference in the graphics either way – only in how your brain is assigning meaning to it. First of all a silhouette is simply a two-dimensional projection of a three-dimensional object. Assuming the object is small enough that we can neglect any difference in apparent size of the parts that change their distance to us during the rotation (which is anything off the rotational axis – for example her hand) then the silhouette cannot contain any rotational information because rotational information requires information about depth which a 2-dimensional figure lacks.
A counter example where um… (apparent) size matters, would be the projection of an orbiting planet – when it is millions of miles away it might appear as a tiny dot but as it passes close to our vantage point it becomes much larger which conveys information about whether the planet is passing near or far from us and hence whether its orbit is CW or CCW. But note that here, the depth information is really contained in our knowing what it is we are looking at and knowing how apparent size changes with distance – there is no actual depth information in the 2-dimensional projection itself, we supply it from the outside. In our example of the dancer, without being able to notice a tiny change in apparent hand or foot size, as it comes closer and then draws away, means we cannot say whether the hand or foot is passing on the near side of the rotation or away from us on the far side of the rotation. Here since we have no real knowledge of depth our brain simply makes up the information and we then perceive one direction of rotation or the other.
To take one final example that helps to understand what’s going on we can remove one dimension. Imagine a standard x-y plane and a point that rotates about the point (5,0) with a radius of, say, one. If we now project that rotation onto the y-axis (like projecting a silhouette) all we will see is a point that moves up and down the the y-axis between -1 and 1. From that there is no way to deduce whether the point is actually traveling CW or CCW in the x-y plane because that information has been lost in the projection.
There’s no deliberate change — I looked at it along with another person, and more than once we were perceiving the same image going in opposite directions (and we switched in this perception, too).
Anyone who thinks this is telling you something useful about left vs right brainedness is out of either side of their mind.
Who ever first mentioned the shadow, thank you! If I just concentrate on the shadow and the legs, I can switch consciously between views.
It seems like the arms are more conducive to the clockwise motion and the shadow suggests counter clockwise, so perhaps your perception depends on which part of the body you look at first.
Amazing. At first I could only see it clockwise no matter what. Then I tried covering everything except the shadow, and it was easier to see CCW if I tried. Then slowly revealed upward; the first few times I kept reverting to clockwise, but finally saw it CCW. Now I can switch back and forth at will. I’m a lawyer.
Economics. Initially I saw it going clockwise, but I can switch it by focusing on the bottom foot because if you isolate it the pivot foot just goes back and forth. If I look up at the rest of the dancer when the foot is facing to the right the dancer goes ccw, if i look up when the foot is to the left it goes cw.
On eyes and hemispheres: it’s not the left eye that’s being processed by the right half of your brain, but the left side of the visual field, from both eyes. Try covering up the left or right half of both your eyes (still looking straight ahead), this should get her to change direction.
Count me as another computer programmer (though one with a law degree) who
can only see it clockwise. I even covered up everything but the lower foot,
and it’s still only clockwise. In fact, at this point i’m convinced that
the counter clockwise crowd has absolutely no idea how a human body is
Regarding the shadow and spin:
No it doesn’t. The shadow is consistent with both perceptions.
I beg to differ. The shadow (or it may be percieved as a reflection in a shiny floor) unambiguously defines the rotation as CCW (as when the dancer is seen from above).
However, there may be another visual clue in the image: Perspective. Things apperar somewhat larger when they’re closer. Now, look at the dancer’s arms and hands. I haven’t measured, but at first glance they seem to hint that the rotation is CW.
Anyway, due to screen size many people will not see the part of the image when clicking on the link to the news site. That’s something that may be significant when asking people what they see.
Of course, the urban legend variety of explaining this would be to assume that the coreolis force is at work and claim that the dancer is rotating CCW on the northern hemisphere and CW on the southern hemisphere. (And, I assume you could replace the phrase “urban legend” with “naive physics” in the above statement.)
Counter-clockwise initially, but while reading the list of left/right brain attributes, I perceived her spin switch to clockwise through my peripheral vision. Now the spin seems to switch with each rotation.
My husband only perceives clockwise spinning.
I teach economics and my husband is a fiction writer.
Just scanning the posts, it seems that those who intially see a clockwise spin have greater difficulty changing the spin than those who see first a counter-clockwise spin.
Clockwise, and only clockwise… despite trying, I can’t seem to perceive a counter-clockwise spin.
I don’t buy the “dominant hemisphere” theory either. I’m totally left-brained.
Financial analyst / consultant.
I have always tested out “right brain” before–and did again on this “test”. I did have some shifting to ‘left” when viewing, but quickly came back to the “right” view. Confirms with past testing such as Meyers-Briggs.
Clockwise first, got her to switch though and now I go back and forth.
I tested the Leftbrain / Rightbrain thing by closing one eye and then the other. Obvious BS.
Like many commenters, I was utterly convinced that my view was correct for quite a while. Until I tried to prove it to myself without using the concept “front leg” and “back leg”, since defining those in advance made the exercise simply tautology.
Cool just in that it shows how firmly your brain will hold on to its interpretations once it has made them.
It’s not a trick. My wife and I simultaneously viewed the dancer spinning opposite directions.
Ridiculously left-brained person who tries but can only see clockwise. The article’s prediction of my characteristics are 180 degrees off of the truth.
She changed directions quite often for me. In fact, at one point she changed so frequently that I was getting a little dizzy. Ph.D. in English.
Amazing! At first I could only see it clockwise, no matter how hard I tried or which tricks I used to try her to go counter-clockwise. Finally I succeeded though, but it takes great concentration and is unpleasant. I am an econ PhD student.
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