Friday, September 24, 2010

The Spinning Dancer

 

This image of The Spinning Dancer pops up frequently in advertisements on ScienceBlogs. I find it fascinating. If I concentrate hard I can make the dancer switch from spinning right to spinning left (and vice versa) but I can't tell you how to do it and I can't always succeed.

How about you? Can you make her switch? Is it easy or hard? Do you prefer one direction over another? I my case, I have trouble switching her from clockwise spinning to counter-clockwise spinning but not the other way around.




15 comments :

  1. If you like that, you're gonna love this site.

    Incidentally, I was amazed to learn that some people are unable to perceive some of the illusions presented on that site. Apparently, some people are wired differently :-)

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  2. She switched on me, but I think it was not due to anything I was purposely doing.

    Notice the foot shadow.

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  3. I find it easy to switch with a change in the frame of reference - I visualize it from the top down or bottom up; clockwise and counter clockwise change respectively. Perspective is everything :)

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  4. I too can see it going either way, and make it switch with only a little effort. For me, the key is to focus on the raised foot and concentrate on seeing it coming 'forward' from the left if I want the dancer to spin counterclockwise, or forward from the right if I want to see her spinning clockwise.

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  5. I too can switch at will by changing perspective.

    Of all the illusions I've ever seen, I find the gray color in the shadow most unbelievable:
    http://www.michaelbach.de/ot/lum_adelsonCheckShadow/index.html

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  6. We use this one quite a lot on our undergrad neurobiology course. It's a great source of frustrated giggles for the students.

    I've spent so much time looking at it that I can pretty much change it at will. But it was hard at first, it seemed to change on its own. It's easier if I focus slightly to the left and above the figure, so that I'm not looking at it directly. It also takes a little while between me deciding I want it to change, and me actually perceiving it to change. I haven't been able to come up with a good explanation for that.

    The weirdest thing at this point is that sometimes the foot seems to be rotating in the opposite direction compared to the rest of the body.

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  7. I too find it absolutely fascinating, and like qetzal I concentrate on the raised foot. But some days it's easier to convince myself than others.

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  8. I usually see the dancer rotating anti-clockwise at first and find it difficult to change. It seems that looking to the top right corner and blinking destroys the fluidity of the movement and allows the subjective switch to clockwise movement.

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  9. Weird. I couldn't not see her spinning clockwise and I watched the video several times. I had my friend look at it too and he couldn't switch. I then told him "I see her clockwise but can't see counter-clockwise." At that instant I saw her change directions! Interestingly enough, my friend had seen her spinning counter-clockwise and switched to clockwise when I switched the other direction. Very strange.

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  10. I just have to look at the heel or shadow for about 3 turns, and she switches.

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  11. I saw her going counter clockwise and once I got her to switch to clockwise, I cant make her go back...

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  12. Whenever I see the dancer, the caption underneath says "is the dancer spinning left or right?" and it drives me crazy. Does the average person really have that much difficulty with clockwise/counter-clockwise?

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  13. At first I thought that she spins only one way. Then I realized that, since she's a two-dimensional shadow, we have to assume that one aspect is her back and one is her front. Once I realized that, I could change my decision about which way she was facing and suddenly she was spinning the other way.

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  14. I found closing one eye alternatively back and forth can help in switching the apparent rotation direction.

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  15. In this software you can see the solution!

    http://martik-scorp.blogspot.com/2010/05/do-you-see-dancer-spinning-clockwise-or.html

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