Casual Fridays: What makes the spinning woman spin?

Nice! A coincidence: I was just updating my site, adding a symmetric silhouette, when I saw this. Amazing.
What prompted the last question in the questionnaire? Now I now more, but do I need to know it ;-) ?
Great work! Best, Michael.

I can never see anything in thos dang hidden pictures!

Michael: I guess I was thinking that people who had the sort of knowledge necessary to answer that last question might also be the sort of people who could see/not see certain types of illusions. But mostly it was completely random. I saw the reference on another web site and thought I'd toss it into the survey.

Dave: ah, so those would be "real geeks", right? It also probably discriminates against "good old Europe" ;-). Which reminds me: In Germany, it's a holiday today (reunification!), this gave me the time for writing so many comments and working on my site.

I can see you're trying to make a connection between handedness, the illusions and geekdom.

I'd say that anyone who's actually watched a real live ballet- (or other-)dancer spinning can tell you instantly which leg the silhouette is standing on, on the basis of the non-symmetrical way the rest of her body is arranged. If you know which leg she's standing on, there's only one direction she can be spinning in.... (When I first saw it, I was in no doubt about which way she was spinning, but it did take me a few minutes to work out why I was so certain.)

I was very dissapointed that I couldn't see her spinning both ways. But the realization that 'magic eye' works on computer screens made up for it! For some reason, I though they would only work on paper.

I can never see anything in thos dang hidden pictures!

Oddly enough, I never usually see anything either; indeed, I nearly answered 'no' without trying. But this time I actually got it to work.

My first impression was that she spins clockwise. I thought about it a bit and reasoned that, following her left hand as it passes the centre of the image, it is sometimes higher and sometimes lower.

If you usually see spinning women (like at balet) from higher up, then perspective tells you that the higher up bit is further away, so she spins clockwise.

Continue watching that left hand, and when it passes the centre high up, say 'back'. When it passes the centre low down, say 'front'. What you say reinforces what your sense of perspective tells you.

Now swap places and say 'back' or 'front' at the places you previously said 'front' or 'back'. Now you see she spins counter-clockwise, or at least I did. My perspective sense adjusted to match what I said.

This is the only way I was able to make her seem to change direction.

PS - ain't nipple erection way hot!

I think the right brain thing may actually have some sense to it. Not when relating it to if you like math or impressionist art or anything, but dominance of secondary visual areas.

So, when I heard the right brain/left brain explanation, and that my parents were unable to make it switch directions, I used some rudimentary neuroanatomy to try to come up with a trick to get them to be able to switch the direction and it worked! I wonder if it actually works for other people...

So, my maybe-bull-shit sotry goes something like this.

Both eyes project to both hemispheres of your brain, however, not all parts of both eyes project to both halves. The far right part of your visual field in your right eye projects only to the left hemisphere, and vica versa, so lets say you only get the clockwise rotation, which is supposed to mean you use predominately the right side of your brain. To get the figure to switch to counter-clockwise, close your left eye, and look with only your right start to look to the figure's left. Soon, the figure will actually half-disappear. the figure is now in your blind spot, which is caused by the optic nerve and you are almost there. Look a bit farther and the figure should be in your far peripheral visual field, and for me and my parents both this should get the figure to start moving counter-clockwise.

Obviously reverse this if the figure only spins counter-clockwise for you: close your right eye and look to the right of the figure...

Work for anyone else?

Thanks, Kevin H. That got her to finally (briefly) spin clockwise for me. She went back to counter-clockwise when I focused on her after getting her to switch out of the corner of my eye. At least I believe it now; at first I thought it was a psychological experiment to see if people would claim to see it the wrong way just for the study, since it didn't seem possible to me that she wasn't spinning counter-clockwise :)

I love those "hidden images"; they are fun to look at.

I usually make the woman change direction with the shadow/foot trick, but this time I discovered that it was much easier if I just moved away a bit from the screen. When When I approached the screen again she changed back. If I got to close she would not rotate at all, just flip back and forth.

At first I only saw her rotate clockwise. Then I scrolled down to answer and could only see her feet. Suddenly she was spinning the other way. It took a few scrolls up and down to see her whole body rotate counter-clockwise but I finally got it to work.

I've never been able to see her rotate clockwise until this time, when I really tried. I watched her foot and forced myself to think of it rotating back the other way, and all of a sudden her whole body looked like it was going clockwise. Creeepy.

i can't stop laughing at the TK-421 question

*hugs shibboleth*

I was not sure how to answer the question about video games. What counts as video game? I play quite a lot of games on the computer, but rarely the sort that call for quick reactions and high visual acuity (neither of which I have). There is a big difference, surely, between some high-speed, graphically complex shooting game and, for example, Solitaire. It seems plausible that playing a lot of the former sort of game might improve or otherwise affect visual responsiveness, but too much Solitaire (or, come to that, Myst, or Second Life) will, at most, just give you eyestrain. Is it not important to distinguish for matters like this?

Mind you, despite my aging eyes (I have had cataract surgery in both) I was, to my surprise, able to see the 3-D figure after following the instructions (move in close and pull back slowly).

I answered clockwise to the first question, and "yes" I can get it to change to the second. The thing was, at least in a short time-span, I then couldn't get it to change back to clockwise again.

Am I alone in this?

What computer system are you using: Mac, PC or Linux/Unix?

My geeky mind is weeping a bit :)

*is running a PC with Linux*

Every time I come across this I feel like someone's asking me to go snipe hunting.

Here's my sob story though: I developed lazy eye at a very young age. And, because of that my vision is strongly dominated by my right eye. (I see her moving clockwise, btw.)

I have never been able to see "magic eye" images.

I'd like to echo in on a comment that her asymmetrical body position. With a disclaimer that I can only see her as rotating clockwise, I can not imagine a real person who's body is positioned such as hers rotating counter-clockwise without losing balance.

That has me wondering if there might be a connection between the direction in which a person perceives her rotating and a person's training in martial arts, boxing, etc. - activities that require a heightened ability to predict body movements based on posture and already initiated motion.

I first saw her spinning clockwise. I was able to see her spinning the other direction by turning my head upside down (bending my back forward and twisting sideways). As I slowly twisted my head back to normal, I could still see her spinning counterclockwise until within about five to ten degrees of normal; once I passed that threshold, I couldn't stop her from seeming to spin clockwise.

As you probably know (you can verify this by looking in a mirror), when you twist your head slightly to one side (raising one ear higher than the other), your eyes automatically rotate to maintain level, but they can only do this for relatively small twists. When you twist too much, your eyes stop trying to remain level.

I hypothesize that I can see her spinning counterclockwise when my head is twisted enough to stop my eyes from automatically maintaining level; otherwise, I can only see her spinning clockwise. For me, at least, it seems that the illusion is somehow connected to my vestibular system.

The 'random dot stereography' was cool! I spotted the 'x' in a matter of few seconds. I've seen images like this before. Looks like I got to wait till next Friday!

I see here rotating to her left, then back round to her right, never doing the full circle... didn't seem to be an option for this in the survey!

I looked a second time, using the suggestions by both Kevin H (search for blind spot) and Peter Turney (turn head sideways). Using Peter's suggestion, I was FINALLY able to get it to change directions! For some inexplicable reason, this made me quite pleased.

Did you measure the time it took for someone to answer the question whether they could see the woman spinning the other way? Slow switches might be an interesting half-way point between no switching and easy switching.

In any case, I'm curious as to which direction most people saw the mannequin spinning!

I was disappointed at not being informed as to how I had done, whether my brain was right, left or no brain at all!!

For the longest time I could only see her rotating counter-clockwise, but then the GIF glitched and she suddenly was going the other way. I've found that a short break in the "flow" of the image is often enough to change my perception of it. I can now easily change the perceived direction by blinking rapidly. You can also stretch out your hands in front of the image, using your fingers like a grate. Then just slide your hands past one another at varying speeds.

This method probably just affects how your perception is primed base on which frames you initially see.

I can see the dancer spinning in 2 directions. What I think is interesting is that to get the dancer to change direction, I read something for a minute, and then look at it.

I noticed this when I saw this illusion before - when I was reading the explanation, the direction changed for me.

Maybe this is completely psychological, but I can do it reliably, and it's fun for me to play with!

In my blog
http://www.unitaryflow.com/2008/10/spinning-dancers-mistery.html
I explain why:

1. Most of the subjects see first the dancer spinning clockwise.

2. The laws of perspective indicate that the "correct" spinning is counterclockwise.

The "correct" spinning is the one original in the 3d movie from which the 2d animation was exported.

I found a solution to this illusion mystery.

First focus the spinning foot, when it spins to the corner of the box/screen, then quickly switch your focus to the same hip, then it will change direction.... is that simple!?