I don’t see the illusion here, to me she never changes direction. My two questions here are what direction do other people see her spinning in when she begins and is she actually spinning in one direction or the other, or does it depend on how you look at it?
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).
The illusion exists because the silhouette is ambiguous in terms of depth. Different people (or the same person at different times) can see the figure rotating CC or CCW because of that ambiguity. So, if perception of rotation is what you mean by “how you look at it” then yes, it does depend. I find it pretty straightforward to see the figure rotating in either direction, FWIW.
That one is spinning kind of fast and you might not pick it up. Try looking away for a moment, themn looking back, you might see it.
First, if you see this animation with “explanatory” text about how one hemisphere is dominant, it is 100% pure unadulterated crap.
This is a bistable percept, much like the Necker cube and others. I don’t know of anything that correlates with which direction you see first, or why individuals are different. If you extend the comments, the “look at the feet” part may help. But like autostereograms (“Magic Eye”), some people have great difficulties making it work. Sometimes it just hits them some day.
Other people have told me that. No matter what, I see her going ccw.
It’s more than just bistable. I can get her to change directions every 180 degrees (though it’s a bit difficult, and the effect tends to break after several turns).
From my own experience I can switch between the points of view easily by pausing the playback and then, with the still image to look at, visualizing the extended leg as being “in front” or “behind” the other. When I hit play again the change to CC or CCW is usually straightforward. For me, changing my perceptual point of view while the animation is playing is somewhat harder.
I see her going clockwise, as viewed from above. It is very hard for me to get her to spin CCW. The one time I was able to flip her, I had paused the video and was able to flip here when she was stationary, then kept it that way when I restarted the video.
That doesn’t work well, though, since usually the video usually jumps a couple times when I restart it after it’s paused.
That’s what bistable means. The Necker cube is the textbook example of a bistable image, and most people can get it to change orientation at will with little practice.
By the way, the spinning dancer by Nobuyuki Kayahara has been an Internet meme for a few years now but this specific illusion was originally called the “windmill illusion” and was first described by a mathematician named Robert Smith in 1738.
I would consider bouncing left and right to be a third state, independent from going continuously CW or CCW. The Necker cube has no equivalent; it’s merely bistable. Put another way, it’s possible to view the change in direction of the dancer as part of the motion itself.
There’d be two additional states: one where she’s always facing generally towards you, and one where she’s always facing generally away from you.
I know I’ve done this before and was able to get her to spin in both directions, but for me, now, I’m stuck at her spinning counter-clockwise, not clockwise as the video suggests.
Oh, nevermind. Now I can’t get her back to spinning counter-clockwise.
I had some trouble with this version too, for some reason. I can get it to switch, but it’s hard.
This one worked better for me.
Once you realise she is naked, you can’t put the clothes back on.
That’s not the same image. She’s spinning the other way.
(For whatever reason, that one “wants” to spin CCW for me, although I can get that one to spin the other way. The YouTube one goes CW, and much more forcefully. I even had to check to make sure it wasn’t really a mirror image, but her pivot foot is in the air when the other one is to the right in both of them.)
This version is great because you can temporarily “force” the perspective using the buttons on the right. (It puts eyes on her face for a few seconds, thereby differentiating between her front and back)
Of course, creepy glowing eyes aside, you’re not really changing her direction either way, you’re just forcing your *perception *of her direction to change.
Oddly enough, that one is not working for me, as far as forcing the perspective goes. The one that Digital is the New Anaglog posted does work, though.
For some irrational reason, I always get really annoyed with people who don’t see illusions. Probably because they act like they can’t see them, which isn’t true.