# Spinning silhouette illusion **URL:** \ **Category:** Factual Questions\ **Created:** [July 18, 2013, 10:09pm UTC](https://boards.straightdope.com/t/spinning-silhouette-illusion/663884 "2013-07-18T22:09:27Z")\ **Posts on this page:** 19\ **Page:** 2
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [July 19, 2013, 3:37am UTC](https://boards.straightdope.com/t/spinning-silhouette-illusion/663884/21 "2013-07-19T03:37:54Z")
I don’t know if it’s bistable or multistable or something else, but the[Paper Dragon](http://jclahr.com/science/illusions/3d/paper_dragon.html)designed to celebrate the [Gathering for Gardner](http://gathering4gardner.org/)is a great one to put together yourself and look at close up. The site has links for .jpg and .pdf patterns which you can print, cut out, and tape together. You might get some idea of the illusion from the video clip, but if you make your own and find the sweet spot it is a remarkable illusion. ---
**Author:** ![copperwindow](https://avatars.discourse-cdn.com/v4/letter/c/4af34b/32.png) [@copperwindow](https://boards.straightdope.com/u/copperwindow)\ **Post date:** [July 19, 2013, 3:41am UTC](https://boards.straightdope.com/t/spinning-silhouette-illusion/663884/22 "2013-07-19T03:41:59Z")
> [@Indistinguishable](#): > > It depends on how you look at it. You can imagine that as the swinging leg is moving, it passes in front of the stable leg as it moves to the right and behind the stable leg as it moves to the left (thus, she would be spinning counterclockwise, as viewed from overhead), or, alternatively, you can imagine that the swinging leg passes behind the stable leg as it moves to the right and in front of the stable leg as it moves to the left (thus, she would be spinning clockwise, as viewed from overhead). This bothers me for a couple of reasons. If she is only turning in the direction you think she is than she does change direction and it is not an illusion. Even if the windmill illusion, the blades **were** spinning in one direction. Whoever made this video must have told the computer to spin the image, I’m guessing in one direction or another. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [July 19, 2013, 3:45am UTC](https://boards.straightdope.com/t/spinning-silhouette-illusion/663884/23 "2013-07-19T03:45:44Z")
> [@copperwindow](#): > > This bothers me for a couple of reasons. If she is only turning in the direction you think she is than she does change direction and it is not an illusion. Even if the windmill illusion, the blades **were** spinning in one direction. Whoever made this video must have told the computer to spin the image, I’m guessing in one direction or another. The image is not spinning. It’s 2 dimensional, it can’t spin unless you spin your monitor around. There is no direction, it’s all in your mind. ---
**Author:** ![Tangent](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tangent/32/3098_2.png) [@Tangent](https://boards.straightdope.com/u/Tangent)\ **Post date:** [July 19, 2013, 5:10am UTC](https://boards.straightdope.com/t/spinning-silhouette-illusion/663884/24 "2013-07-19T05:10:38Z")
> [@TriPolar](#): > > The image is not spinning. It’s 2 dimensional, it can’t spin unless you spin your monitor around. There is no direction, it’s all in your mind. Correct. For example, [this version](http://www.moillusions.com/wp-content/uploads/i207.photobucket.com/albums/bb234/vurdlak8/2007b.gif) is an animated gif. If you save it and open it in Photoshop, you’ll see that it is actually 34 still images or “frames” that make up one apparent revolution when viewed in succession. It continuously loops so that it looks like she is continually spinning. The direction of the spin is up to the viewer. Even though the same 34 frames are playing in the same order each time, I can see her spin one way, and then make myself see her spinning the other way. There is no “correct” answer. ---
**Author:** ![Keeve](https://avatars.discourse-cdn.com/v4/letter/k/f07891/32.png) [@Keeve](https://boards.straightdope.com/u/Keeve)\ **Post date:** [July 19, 2013, 11:56am UTC](https://boards.straightdope.com/t/spinning-silhouette-illusion/663884/25 "2013-07-19T11:56:40Z")
From what I can see, she is standing on her left foot, turning in a direction that she might call “falling backwards”, and which could be described by someone looking down from above as “clockwise”. That’s all I can see. I have tried to look away, or to pause/restart, but there is nothing I can do to convince my brain that she is on her right foot, going forwards or counterclockwise. I tried to simulate slow-motion by repeatedly tapping on the space bar, but that was inconclusive, as that motion was too choppy. If anyone can suggest a way to generate a genuine slow-motion playback, I’d like to try that. … after writing the above, I found [this](http://www.youtube.com/watch?v=GlFePHhd-0M) video, which might help. I have no time now, but I’ll try it later. ---
**Author:** ![Floater](https://avatars.discourse-cdn.com/v4/letter/f/dc4da7/32.png) [@Floater](https://boards.straightdope.com/u/Floater)\ **Post date:** [July 19, 2013, 12:05pm UTC](https://boards.straightdope.com/t/spinning-silhouette-illusion/663884/26 "2013-07-19T12:05:37Z")
> [@Keeve](#): > > … after writing the above, I found [this](http://www.youtube.com/watch?v=GlFePHhd-0M) video, which might help. I have no time now, but I’ll try it later. It really did help. ---
**Author:** ![Keeve](https://avatars.discourse-cdn.com/v4/letter/k/f07891/32.png) [@Keeve](https://boards.straightdope.com/u/Keeve)\ **Post date:** [July 19, 2013, 12:09pm UTC](https://boards.straightdope.com/t/spinning-silhouette-illusion/663884/27 "2013-07-19T12:09:46Z")
Yes indeed! That video does show it! Part of my problem was how I formulated it. I was seeing her falling backward, and I expected that in the reversal she’d be going forward. Nope. She always falls backward. The difference is whether she’s on her left foot going clockwise, or her right foot going counterclockwise. The alternate video (here’s the [link](http://www.youtube.com/watch?v=GlFePHhd-0M) again) demonstrates it with a split screen: The center is like the OP’s version. But on the sides, here left and right halves are clearly marked by running a red line through her left side, and a blue line through her right. ---
**Author:** ![Chief\_Pedant](https://avatars.discourse-cdn.com/v4/letter/c/a6a055/32.png) [@Chief\_Pedant](https://boards.straightdope.com/u/Chief_Pedant)\ **Post date:** [July 21, 2013, 3:54am UTC](https://boards.straightdope.com/t/spinning-silhouette-illusion/663884/28 "2013-07-21T03:54:00Z")
For what it’s worth, in the version show in the the link from the OP, the dancer is bouncing up and down on her right leg and rotating counterclockwise as seen from above. You can prove this by pointing out that the shadow of the extended foot is visible only when the extended foot is at a point where the shadow would be closest to the center point. That happens when the extended foot is away from our perspective as a viewer, which means she is rotating counterclockwise. If she were rotating clockwise, then her left leg is the one she’s pivoting around, and the right leg is extended away from us when that left foot hits the ground. If that were the case, the shadow of the extended foot would be in the image. But it’s not. So even though the brain sees her as going either way, if she’s a backlighted silhouette, she’s rotating counterclockwise. The images in [this link, above,](http://math-fail.com/2011/04/the-spinning-dancer-illusion.html) make this easier to understand. ---
**Author:** ![copperwindow](https://avatars.discourse-cdn.com/v4/letter/c/4af34b/32.png) [@copperwindow](https://boards.straightdope.com/u/copperwindow)\ **Post date:** [July 24, 2013, 5:26pm UTC](https://boards.straightdope.com/t/spinning-silhouette-illusion/663884/29 "2013-07-24T17:26:29Z")
> [@Chief\_Pedant](#): > > For what it’s worth, in the version show in the the link from the OP, the dancer is bouncing up and down on her right leg and rotating counterclockwise as seen from above. > > You can prove this by pointing out that the shadow of the extended foot is visible only when the extended foot is at a point where the shadow would be closest to the center point. That happens when the extended foot is away from our perspective as a viewer, which means she is rotating counterclockwise. > > If she were rotating clockwise, then her left leg is the one she’s pivoting around, and the right leg is extended away from us when that left foot hits the ground. If that were the case, the shadow of the extended foot would be in the image. But it’s not. > > So even though the brain sees her as going either way, if she’s a backlighted silhouette, she’s rotating counterclockwise. > > The images in [this link, above,](http://math-fail.com/2011/04/the-spinning-dancer-illusion.html) make this easier to understand. Quite right. After blocking the shadow with my thumb, I got to see her spining CC, thanks. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [July 24, 2013, 6:25pm UTC](https://boards.straightdope.com/t/spinning-silhouette-illusion/663884/30 "2013-07-24T18:25:04Z")
> [@copperwindow](#): > > Quite right. After blocking the shadow with my thumb, I got to see her spining CC, thanks. But it’s the shadow that is the biggest cue that she is going counter clockwise! ---
**Author:** ![copperwindow](https://avatars.discourse-cdn.com/v4/letter/c/4af34b/32.png) [@copperwindow](https://boards.straightdope.com/u/copperwindow)\ **Post date:** [July 27, 2013, 8:23pm UTC](https://boards.straightdope.com/t/spinning-silhouette-illusion/663884/31 "2013-07-27T20:23:17Z")
> [@Colophon](#): > > But it’s the shadow that is the biggest cue that she is going counter clockwise! I meant clockwise ---
**Author:** ![mandala](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mandala/32/95_2.png) [@mandala](https://boards.straightdope.com/u/mandala)\ **Post date:** [July 28, 2013, 1:47am UTC](https://boards.straightdope.com/t/spinning-silhouette-illusion/663884/32 "2013-07-28T01:47:45Z")
I naturally saw the figure rotating L-R, and with some difficulty could see her moving R-L too. The real question is, what does it mean to see her move one way or the other? Does it indicate which brain hemisphere is calling the shots at that instant? And, does it really say something about how your brain is working? ---
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [July 28, 2013, 2:06pm UTC](https://boards.straightdope.com/t/spinning-silhouette-illusion/663884/33 "2013-07-28T14:06:57Z")
I found the easiest answer was to just scroll the image so that I could only see the feet, which would allow me to reverse the direction. The link with the eyes didn’t help me–one direction just looks hollow, like the eyes are on the other side and glowing. Quite an odd experience. ---
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [July 28, 2013, 2:08pm UTC](https://boards.straightdope.com/t/spinning-silhouette-illusion/663884/34 "2013-07-28T14:08:35Z")
> [@Chief\_Pedant](#): > > For what it’s worth, in the version show in the the link from the OP, the dancer is bouncing up and down on her right leg and rotating counterclockwise as seen from above. > > You can prove this by pointing out that the shadow of the extended foot is visible only when the extended foot is at a point where the shadow would be closest to the center point. That happens when the extended foot is away from our perspective as a viewer, which means she is rotating counterclockwise. > > If she were rotating clockwise, then her left leg is the one she’s pivoting around, and the right leg is extended away from us when that left foot hits the ground. If that were the case, the shadow of the extended foot would be in the image. But it’s not. > > So even though the brain sees her as going either way, if she’s a backlighted silhouette, she’s rotating counterclockwise. > > The images in [this link, above,](http://math-fail.com/2011/04/the-spinning-dancer-illusion.html) make this easier to understand. I marvel at your ability to discern shadows in such a banded, pixelated image. It seems the OP’s video is a double conversion, from a video to a GIF back to a video. Also, because of your name, I wanted to let you know that “backlit” is a word. Or, if you want to be even more pedantic, it’s “back lit.” ---
**Author:** ![thelurkinghorror](https://avatars.discourse-cdn.com/v4/letter/t/7c8e57/32.png) [@thelurkinghorror](https://boards.straightdope.com/u/thelurkinghorror)\ **Post date:** [July 28, 2013, 11:34pm UTC](https://boards.straightdope.com/t/spinning-silhouette-illusion/663884/35 "2013-07-28T23:34:19Z")
> [@hniyer](#): > > I naturally saw the figure rotating L-R, and with some difficulty could see her moving R-L too. The real question is, what does it mean to see her move one way or the other? Does it indicate which brain hemisphere is calling the shots at that instant? And, does it really say something about how your brain is working? No. The direction means that you are currently perceiving a stimulus as that direction, even though it’s ambiguous. Pop psych interpretation of hemispheres is suspect. Neither is dominant in an overall sense, although you could make the case that the LH is more sophisticated. The only “switching” that would occur is task-dependent, e.g. for the majority of people, LH would be more active when listening to speech than its mirror, or the RH when memorizing faces. ---
**Author:** ![copperwindow](https://avatars.discourse-cdn.com/v4/letter/c/4af34b/32.png) [@copperwindow](https://boards.straightdope.com/u/copperwindow)\ **Post date:** [August 12, 2013, 1:03am UTC](https://boards.straightdope.com/t/spinning-silhouette-illusion/663884/36 "2013-08-12T01:03:29Z")
> [@Colophon](#): > > But it’s the shadow that is the biggest cue that she is going counter clockwise! This leads me to another question. If the shadow shows me that she’s going ccw, why doesn’t everyone see her going ccw? ---
**Author:** ![Tangent](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tangent/32/3098_2.png) [@Tangent](https://boards.straightdope.com/u/Tangent)\ **Post date:** [August 12, 2013, 1:42am UTC](https://boards.straightdope.com/t/spinning-silhouette-illusion/663884/37 "2013-08-12T01:42:44Z")
Because if you’re not paying attention to the shadow, she could be spinning either way. ---
**Author:** ![Digital\_is\_the\_new\_Analog](https://avatars.discourse-cdn.com/v4/letter/d/a88e4f/32.png) [@Digital\_is\_the\_new\_Analog](https://boards.straightdope.com/u/Digital_is_the_new_Analog)\ **Post date:** [August 12, 2013, 2:28am UTC](https://boards.straightdope.com/t/spinning-silhouette-illusion/663884/38 "2013-08-12T02:28:51Z")
> [@Tangent](#): > > Because if you’re not paying attention to the shadow, she could be spinning either way. Even paying attention to it, I can see it spinning the other direction. It creates an odd effect, with the shadow moving in time, but in the opposite direction, with the dancer. ---
**Author:** ![Chief\_Pedant](https://avatars.discourse-cdn.com/v4/letter/c/a6a055/32.png) [@Chief\_Pedant](https://boards.straightdope.com/u/Chief_Pedant)\ **Post date:** [August 12, 2013, 4:01am UTC](https://boards.straightdope.com/t/spinning-silhouette-illusion/663884/39 "2013-08-12T04:01:15Z")
> [@BigT](#): > > I marvel at your ability to discern shadows in such a banded, pixelated image. It seems the OP’s video is a double conversion, from a video to a GIF back to a video. > > Also, because of your name, I wanted to let you know that “backlit” is a word. Or, if you want to be even more pedantic, it’s “back lit.” In the OP link, as well as the other link I referenced, the shadows from the backlighted figurine are clear. Perhaps something is wrong with your device or connection. “Backlighted” is an acceptable past tense, and “back lit” is neither “more pedantic” nor more correct. [Previous page](https://boards.straightdope.com/t/spinning-silhouette-illusion/663884.md?page=1)