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The Spinning Dancer and the Shepard Tone
Posted: 30 August 2011 06:36 AM   [ Ignore ]   [ # 16 ]
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Some day she switches for me no problem (I look away for a second), but some days, like today, she will not switch no matter what I do. (Pretty much the same pattern I seem to follow when interacting with women in real life.  cheese )

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Posted: 30 August 2011 06:55 AM   [ Ignore ]   [ # 17 ]
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GdB - 30 August 2011 01:21 AM

About switching the direction: I nearly cannot switch the direction too. But what helps me is to scroll down so much that I only see her feet. Then I can switch. If I then slowly scroll up again, it keeps this direction. Until at some moment, without changing anything the direction has changed. (My preference is to see her turning clockwise (seen from above): how with all of you? Also any preference?)

What do you think changes, kkwan? A qualium? Your attention?

Invariably, my initial perception is a clockwise spinning dancer. On first seeing the animation I could not perceive how she could change her spinning direction at all. However, by adverting my gaze from the animation, i.e. by looking to the right of the animation for a few seconds while keeping it in my left peripheral vision, I suddenly noticed she had changed direction. The remarkable thing is, after some time, even by looking at the animation directly, she can abruptly change from spinning clockwise to anticlockwise and vice versa just like that.

The animation has not changed. Apparently, the human visual/auditory/olfactory system and mind/brain has bistable or multistable perception.

From the wiki on multistable perception

Perceptual multistability can be evoked by visual patterns that are too ambiguous for the human visual system to recognise with one unique interpretation. Famous examples include the Necker cube, structure from motion, monocular rivalry and binocular rivalry, but many more visually ambiguous patterns are known. Since most of these images lead to an alternation between two mutually exclusive perceptual states, they are sometimes also referred to as bistable perception.

Auditory and olfactory examples can occur when there are conflicting and so rivaling inputs into the two ears or two nostrils.

Characterization:

Transitions from one percept to its alternative are called perceptual reversals. They are spontaneous and stochastic events which cannot be eliminated by intentional efforts (although some control over the alternation process is learnable).

What is a qualium? Do you mean quale (as the singular of qualia)?

There are obvious epistemological issues wrt to instances of ambiguous perception/interpretation. However, there are much more instances of unique perception/interpretation, otherwise we would all be dead.  smile

[ Edited: 30 August 2011 07:01 AM by kkwan ]
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Posted: 30 August 2011 06:58 AM   [ Ignore ]   [ # 18 ]
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This thing is driving me CRAZY! I can only see her spin clockwise. If I look partially away and relax my gaze a bit, I can sometimes get her to switch for a second or two, but as soon as I look directly at her again, she resumes going clockwise.

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Posted: 30 August 2011 07:13 AM   [ Ignore ]   [ # 19 ]
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George - 30 August 2011 06:36 AM

Some day she switches for me no problem (I look away for a second), but some days, like today, she will not switch no matter what I do. (Pretty much the same pattern I seem to follow when interacting with women in real life.  cheese )

Try the technique I mentioned in my post to GdB. I hope it works for you, i.e. for spinning dancers. 

wink

[ Edited: 30 August 2011 07:40 AM by kkwan ]
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Posted: 30 August 2011 07:22 AM   [ Ignore ]   [ # 20 ]
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kkwan - 30 August 2011 06:55 AM

What is a qualium? Do you mean quale (as the singular of qualia)?

Ah! Sorry, me not English. The discussion is most of the time about qualia, I do not often see the singular form ‘quale’. Maybe it’s Freudian, because of one of the best vice presidents the US ever had… wink

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Posted: 30 August 2011 07:33 AM   [ Ignore ]   [ # 21 ]
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FreeInKy - 30 August 2011 06:58 AM

This thing is driving me CRAZY! I can only see her spin clockwise. If I look partially away and relax my gaze a bit, I can sometimes get her to switch for a second or two, but as soon as I look directly at her again, she resumes going clockwise.

Paradoxically, the more anxious you are to see the effect, the less likely your perception will change and hold.  grin

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Posted: 30 August 2011 08:35 AM   [ Ignore ]   [ # 22 ]
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GdB - 30 August 2011 07:22 AM

Ah! Sorry, me not English. The discussion is most of the time about qualia, I do not often see the singular form ‘quale’. Maybe it’s Freudian, because of one of the best vice presidents the US ever had… wink

Neither am I English. And I suppose you mean Dan Quayle?

Okay, qualia or what is it like to be…........is important for phenomenologist, but not for physicalist/materialist philosophy of consciousness.

A short quote from this article HERE

The status of qualia is hotly debated in philosophy largely because it is central to a proper understanding of the nature of consciousness. Qualia are at the very heart of the mind-body problem

Consider your visual experience when you saw the clockwise spinning dancer and subsequently it changed direction. This is a phenomenal experience of an illusion.

From the same article:

The phenomenal character of an experience is what it is like subjectively to undergo the experience. If you are told to focus your attention upon the phenomenal character of your experience, you will find that in doing so you are aware of certain qualities. These qualities — ones that are accessible to you introspectively and that together make up the phenomenal character of the experience are standardly called ‘qualia’

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Posted: 30 August 2011 12:06 PM   [ Ignore ]   [ # 23 ]
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kkwan - 29 August 2011 06:16 PM

My computer speakers cannot reproduce 18KHz, so I am not surprised that I could not hear anything at all. Perhaps, through my hi-fi speakers, I would hear something. When I was 35, I could hear 20KHz, but now….......I would rather not know.  grin

To tell you the truth, I was kind of surprised that my speakers could produce that frequency. A lot of speakers nowadays are built as cheaply as possible, and one way to cut down costs is to reduce the frequency response of the vibrators. Mine is a decent Bose computer speaker system.

Fascinating information. Is it possible to provide a link to demonstrate these illusions?

It may be easier for me to make some MIDI files. I’ll get back to you on this.

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Posted: 31 August 2011 05:46 AM   [ Ignore ]   [ # 24 ]
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TromboneAndrew - 30 August 2011 12:06 PM

To tell you the truth, I was kind of surprised that my speakers could produce that frequency. A lot of speakers nowadays are built as cheaply as possible, and one way to cut down costs is to reduce the frequency response of the vibrators. Mine is a decent Bose computer speaker system.

If your speakers have decent tweeters, it should be possible to reproduce 18KHz. My computer speakers do not have tweeters. Bose, Altec Lancing and Logitec make good computer speaker systems with sub-woofers and tweeters.

It may be easier for me to make some MIDI files. I’ll get back to you on this.

Please do that. They should be great fun to play.

surprised

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Posted: 31 August 2011 11:13 AM   [ Ignore ]   [ # 25 ]
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This is weird.  For me, she’s spinning counterclockwise, and she never changes.

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Posted: 01 September 2011 02:16 PM   [ Ignore ]   [ # 26 ]
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kkwan - 28 August 2011 07:23 PM
Occam. - 28 August 2011 03:52 PM

Geez, maybe I’m too old and need a shot of testosterrone, but I couldn’t see her as spinning at all.  She just remained a stationary image.

Occam

You must be joking, Occam. What has it got to do with testosterone? LOL

Nah, he just forgot where he put the key to wind her up…. cheese

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Posted: 01 September 2011 02:36 PM   [ Ignore ]   [ # 27 ]
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GdB - 30 August 2011 01:21 AM

Occam, if the file is too big, just open the thread, and go for some coffee. Animated gifs should work in every browser today. Just give it some time to download completely.

About switching the direction: I nearly cannot switch the direction too. But what helps me is to scroll down so much that I only see her feet. Then I can switch. If I then slowly scroll up again, it keeps this direction. Until at some moment, without changing anything the direction has changed. (My preference is to see her turning clockwise (seen from above): how with all of you? Also any preference?)

What do you think changes, kkwan? A qualium? Your attention?

Yes, by concentrating on the heel of the lower foot it is easier to make the switch (subconsciously we know that the shadow of the foot is a 2D representation and can be interpreted as going either way)
I believe that the difficulty lies in our perception that in a 3D scene when something disappears it must be behind something. Thus, as the higher leg swirls and disappears for a moment, we perceive that as the leg swinging behind the figure, not passing in front. The 2D rendering in silouette does not give us a depth perception and we rely on our memory to create an “familiar” image, until we pick a detail and visualize a reversal of direction.

[ Edited: 01 September 2011 02:44 PM by Write4U ]
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Posted: 01 September 2011 06:14 PM   [ Ignore ]   [ # 28 ]
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Write4U - 01 September 2011 02:36 PM

Yes, by concentrating on the heel of the lower foot it is easier to make the switch (subconsciously we know that the shadow of the foot is a 2D representation and can be interpreted as going either way)

That is one way to consider the illusion. However, from this article at the NYT

The Truth About the Spinning Dancer

The silhouette image of the spinning dancer doesn’t have any depth cues. As a result, your eyes will sometimes see the dancer standing on her left leg and spinning to the right. And sometimes they will perceive her as standing on her right leg and spinning to the left. Most people, if they stare at the image long enough, will eventually see her turn both ways.

If one cannot see the flip:

Dr. Toppino says in people who can’t see the reversal, it may be that one underlying neural structure is more dominant, but once someone finally manages to see the flip, it will start to happen more often.

The amazing thing is that when she is spinning clockwise, she is rotating on her left leg, whereas when she is spinning anticlockwise, she is rotating on her right leg instead.

However, the intriguing question remains…....... is she spinning clockwise or anticlockwise?

Does it matter at all? No, as the spinning dancer is a 2D representation of a 3D object and it is not natural. It is only an illusion.

Humans evolved to survive in the natural 3D world, with two eyes for binocular vision and two ears for binaural hearing. Consequently, without natural visual or auditory cues, it is not surprising that the human mind/brain can be deceived to perceive/interpret visual/auditory illusions ambiguously.

[ Edited: 04 September 2011 10:45 PM by kkwan ]
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Posted: 06 September 2011 11:23 AM   [ Ignore ]   [ # 29 ]
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Jon Catler, experimental guitarist extraordinaire, demonstrates difference tones:

http://www.youtube.com/watch?v=8AYlsLNTjrc

grin

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Posted: 07 September 2011 07:23 AM   [ Ignore ]   [ # 30 ]
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TromboneAndrew - 06 September 2011 11:23 AM

Jon Catler, experimental guitarist extraordinaire, demonstrates difference tones:

http://www.youtube.com/watch?v=8AYlsLNTjrc

grin

Fantastic. Thanks.  smile

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