I can change directions at will.  Well, maybe not quite at will, but if I look away for a second when I look back it will have reversed directions, regardless of which way it was going before.

All of the “left brain right brain you’re crazy no you’re crazy” talk is pretty funny though, for an optical illusion that can be either.

“This ain’t no thinking thing, right brain, left brain, it goes a little deeper than that...”

What Theocrat said.  It doesn’t actually do a 360 at all, the 34 frames are too few.  It just oscillates in a 180.  I think Hussar is right that our brains make a snap decision on which foot is extended upon first seeing it, and it has nothing to do with which side of your brain is dominant (I’m sick of hearing about right and left brain dominance, it may be valid in some things, but it gets used way too much to explain parts of human behavior, kinda like Quantum Physics seems to be the answer to all the strange, unexplained stuff in the world.).  If you stare at it long enough, or you change focus then come back, there is a chance your brain will orient on the other foot and see the figure moving in the other direction. 

It definitely is not rigged though, it’s a .gif file.  If it was a flash file, I’d be more inclined to think it was rigged to randomly change direction, but a 34 frame gif just can’t be made to do that, at least not with the frames that are in this one.  Of course, it really doesn’t have to.

I’ve always considered myself more right-brained than left, but no matter how hard I try, I cannot see the dancer moving in a clockwise direction.

Try this.  Look at the thing head on for a second.  Then, move your focus to off screen, so that you see it with your peripheral vision.  I don’t know if it will happen for anyone else, but I see it moving clockwise while viewing it directly, counterclockwise when viewing it peripherally, and clockwise when I look at it directly again.

It’s pretty strange that my wife and I can tell when it changes at the exact same second...How can that be ? Do it with another person setting beside you…

I’ve now managed to see her turning counterclockwise, briefly, by looking at her feet from well above the screen and slowly moving down.

And it’s true that it’s not as symmetrical as I thought: because she jumps once per turn, she is seen facing away when on the ground if seen clockwise, and facing front when on the ground if seen counterclockwise.  Her outstretched hand also moves up and down, as flaky pointed out.  These clues may account for some subtle differences in our tendency to see her one way or the other.

But it’s not rigged- what’s there to rig?  Theocrat’s interpretation of her changing legs and direction is one possible one, but it’s no more “real” than seeing her rotate continuously- I for one can’t see her Theo’s way.  And Theo’s labels of “left” and “right” are dependent upon which direction we see her as facing- the opposite ones are just as “true”.

All in all, a great illusion.

I think this whole “right-brain/left-brain” dichotomy is junk science.  But that must be my left brain talking…

Paul I think it’s a coincidence that you and your wife are seeing the perceived shift at the same time.  Perhaps it’s a good indicator that you both think a lot alike?

Anyway, after further analysis of this phenomenon, I’ve come up with the following:

The dancer image is not 3D at all.  It has no shading, texture or anything at all to really convey depth.  Neither does the shadow.  However, the background is lighted and appears to convey some depth to the figure. This is just an illusion though.  The figure is in front of the background, not in the background as the lighting appears to make it look.  I think the combination of 2D and faux 3D background is where our brains are having trouble.

I’d like to remove the background and shadow and see if that makes it easier to see the oscillation (I cannot see it oscillating without viewing it frame by frame myself, even though I know it is.)

This whole thing reminds me of a quote from Jerry Andrus I heard on the Skeptic’s Guide to the Universe:

“I can fool you because you’re a human,” said Andrus.  “You have a wonderful human mind that works no different from my human mind. Usually when we’re fooled, the mind hasn’t made a mistake. It’s come to the wrong conclusion for the right reason.”

LOL! I bet some asshole is laughing his ass off saying, “Dude look at how many people I got to stare at this picture...”

The first thing I noticed was a naked lady twirling, then I actually looked to see what the post was about. Then I saw clockwise, nothing else.

I’m with DOF on this one.

I’m still scratching my head at the rest of you… no matter how I look at it… every time it’s the same… It looks like a 3-D model blacked out into shadow and EVERY feature seems to suggest turning in a clockwise direction.

Those stills Theocrat posted seem to leave out some parts of the animation… really, looking at her motion in the face, the ponytail, the shadow, the breasts, the arms, the legs, etc… I can’t see any suggestion of clockwise movement at all… she’s always moving counterclockwise for me!

I think what’s missing from this picture is an iPod and headphones…

Duckhugger:

I’m still scratching my head at the rest of you… no matter how I look at it… every time it’s the same… It looks like a 3-D model blacked out into shadow and EVERY feature seems to suggest turning in a clockwise direction.

I had the same problem, but have seen it counter-clockwise a couple of times by focusing down at her shadow, taking care to ignore her figure in my peripheral vision.  When I convince myself the traveling shadow is going behind the fixed leg, I can get it to change.  Only after much effort and only for a short while.

BTW, the left-brain, right-brain explanations offered are not convincing.  I’d need to see some citation of reference to understand why they can make this claim.  The only thing I’ve seen about optical dominance having a basis on right-/left-brainedness were not related specifically to the twirling dancer illusion. 

But WHY is she naked?  Is this a test of the dominance of big-head/little-head thinking?

Big-head thinking:  I wonder why this illusion means I’m right-brained. You know, maybe she’s not naked, maybe she’s just like that changling Mystique character from the X-men or maybe she’s wearing body paint…

Little-head thinking:  Damn! Can you imagine the three-way with her and her sister from them mudflaps?

But WHY is she naked?

Or, perhaps, why aren’t most people naked most of the time? - in hot countries at least it’d make sense. Maybe in a few centuries time it’d be normal

I was born naked and I’m gonna die naked! 

But WHY is she naked?

Put yourself in the place of the artist.  Probably took him hours to put this together.  Choose one: Naked, Not Naked.

Now that I look at it, sometimes it looks like its going clockwise and sometimes counterclockwise, I think depending on which motion she is in during the animation when I begin to move my eyes up away from her legs and towards her head.  The moving away from the legs and towards the head seems to solidify whatever direction I thought she was rotating in when i last saw her and she continues in that direction until I take another determined look at her legs again.  Now that I’ve seen it frame by frame I can sometimes also see the actual sweeping motion of it going back and forth over the 180 degrees instead of any kind of actual spin, but when I cease to concentrate on what’s happening it begins to appear to spin again.

With a little effort I can get it to change what direction she seems to be twirling. But there is something about the animation that looks a tad off though. It seems to help to look away briefly and look back when trying to get it to change direction.

When I look about an inch or two below the picture so I’m only looking at her with peripheral vision, she just bounces back and forth. She won’t turn in a full circle. The illusion of her turning is completely negated for me.

I have always wondered about the right-brain, left brain stuff. It sounds awefully suspicious to me. Dunno.

I have always wondered about the right-brain, left brain stuff. It sounds awefully suspicious to me. Dunno.

I certainly question the methods of measurement (there is more to inteligence than what things like IQ tests measure), particularly for the subjective and unquantifiable, and without reliable data it crumbles.

I certainly think emotional intelligence has a part, and appears to correlate loosely with the ability to rationalise (look at trolls as the contrast), but it’s bound to be misinterpreted and have judgements passed on people from the results of tests that continue the misinterpretation

I’m surprised at how much attention this picture has gotten. It just so happens that the Ulead PhotoImpact (the poor man’s Photoshop) program I use to make the graphics for SEB comes with a gif animation editor. So I opened the file up in that to take a look.

As it turns out the file isn’t rigged and it is, indeed, an optical illusion. There’s a couple of key frames where I noticed my eye had a hard time determining which leg was extended and it’s entirely because the image is flat, not 3D as everyone seems to think it is. Therein lies the trick. Take another look at the sample frames Theocrat posted and you’ll see that the image is completely flat with no highlighting to suggest it’s 3D. It’s our brains trying to fill in the missing details that gives it the 3D effect.

So when we reach frames where it’s ambigious as to which leg is forward, for me it’s Frames 1, 17, and 33, our brain guesses and it affects the rest of our perception of the animation loop. As it turns out, I’m not alone in that assessment. I found an entry at I Fought The Law Blog that also makes this point and provides a visual aid to show how it works. It all depends on which leg you “think” she has raised. It still works even if you slow it down. The original animation had a 0.03 delay on each frame. Saving it with a .5 delay gives you this:

The effect remains even at a slower speed. Incidentally, the 34 frames is more than enough for her to make a complete circle as the starting and ending frames are exactly what you’d expect if the animation were continuous.

At this slower speed, I can switch her at will and keep her from ever doing a complete 360, but rather just going back and forth.

Ragman you need to improve your subliminal messsages - I could still see the fnords

Not 3D (like I said), but it’s obviously cold in that little 2D frame.

I didn’t mention the fact that its 2D as I took it as read- there are no 3D images on the web, films etc, unless you include the one by the artoo unit with no memory, in which case I’m off to Alderbarren

Technically no 3D images in that they don’t have have any depth, but you can have faux 3D images, just look at a stereoscopic photo or any CGI movie.  The animation that has us all agitated though obviously doesn’t even have that though.

Still can’t see anything but anti-clockwise.