Naked Science Forum
General Science => General Science => Topic started by: Rodolfo Hermans on 26/07/2008 15:27:44
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Rodolfo Hermans asked the Naked Scientists:
We know about optical illusions based on the way the brain works, and not on our senses.
Is there any notorious auditory illusion other than pareidolia?
Are the any logical illusions that work in a way similar to optical or auditory
illusions?
What do you think?
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There is an auditory illusion of constantly rising pitch...
Sierpinski round (audio) (http://www.uwec.edu/walkerjs/PicturesOfMusic/Audio/Pitch_Perception_examples/sierpinski_round_(ambient).wav) An example of ambient music using the Shepard tone illusion [rising version].
http://www.uwec.edu/walkerjs/PicturesOfMusic/Audio/Pitch_Perception_examples/Shepard_tones.htm
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I think a lie or an error might qualify as a logical illusion - this would be a statement that is presented as true but is in fact untrue.
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Diana Deutsch conducts research on perception and memory for sounds, particularly music. She has discovered a number of musical illusions and paradoxes, which include the octave illusion, the scale illusion, the glissando illusion, the tritone paradox, and the cambiata illusion , among others.
http://deutsch.ucsd.edu/
I must admit that I can't perceive most of these illusions, (I'm a bit Mutt and Jeff).
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I think a lie or an error might qualify as a logical illusion - this would be a statement that is presented as true but is in fact untrue.
Yes, but in a good optical illusion you have the clear perception, even after being convinced that the reality is different, your brain may still gives the wrong idea. Also, an illusion doesn’t need to define the validity of a premise. In contrast, a lie by itself does not necessarily give the idea of being true; a false statement needs to be flawed either in the logic or in the validity of the premises.
http://en.wikipedia.org/wiki/Leaning_tower_illusion
I don't understand enough about how an illusion works, but for example in the leaning towers illusion, the same information repeated two times gives generates the perception of a whole that is different from the parts. I may understand that I am been deceived, and may understand how, but I still see the illusion.
Also an illusion is "clean" in the sense that it doesn't overwhelm with information, is not like looking to a maze, but may be more like placing the information in tricky way, like Bilbo Bolson saying; "I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve".
My guess is that an informal logical fallacy (http://en.wikipedia.org/wiki/Informal_fallacy) is what we could call a logical illusion, but I am not sure. Probably my question is then:
Are logical fallacies equivalent to optical or acoustical illusions in the way the brain is deceived?
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We know about optical illusions based on the way the brain works, and not on our senses.
Is there any notorious auditory illusion other than pareidolia?
Auditory illusions certainly exist - I have a nice collection of web links which I must dig out!
One difference compared to optical illusions is that the human visual system fairly well separates the detection (the eye as a camera) from interpretation (in the brain). You can typically look "closer" or differently at an optical illusion to figure out what's going on.
In contrast, the ear itself does quite a bit of analysis - it's much more difficult to "inspect" objectively what the sound is really doing.
There's the Barber Pole (Shepard tone) illusion http://en.wikipedia.org/wiki/Shepard_tone
which gives the illusion of an ever-rising (or ever-falling) pitch - which is clearly illogical
There are other audio illusions where you mess around with harmonic sequences and add/remove one of the harmonics and perceive things which you didn't until "conditioned"... I must find my links!
If you can find some of these illusions then it can be useful to run a spectrum analysis program (eg from my web site http://www.techmind.org/audio/#specanaly ) so you can objectively watch what's really going on.
It's not from my archive, but I just found this link which might be a start:
http://listverse.com/miscellaneous/top-10-incredible-sound-illusions/
Just found these (which I emailed myself in Nov 2007):
I'm not sure which are illusions and which are about the workings of the ear. Something to get sidetracked on anyway...
http://www.lifesci.sussex.ac.uk/home/Chris_Darwin/Perception/Lecture_Notes/Hearing3/hearing3.html
http://www.parmly.luc.edu/parmly/clifton.html
http://www.audiospeech.ubc.ca/haplab/Dimitrijevic_Stapells_precedence2006.pdf
Also
http://www.people.carleton.edu/~jlondon/Keynote%20Webdocument.htm
http://hearing.psychol.cam.ac.uk/
http://www.phys.unsw.edu.au/jw/hearing.html
http://tonometric.com/adaptivepitch/
http://www.kyushu-id.ac.jp/~ynhome/ENG/Demo/illusions.html
Grrr - I know I've visited more audio illusions sites - will append post/topic when I re-discover them...
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Found a good quality* free example of the (rising) Shepard tone auditory illusion …
http://www.freesound.org/samplesViewSingle.php?id=65591
Click on the play triangle on the top left corner of the waveform to hear the sound.
It is 100 seconds in duration, but you'll probably want to switch it off before then.
[* The wikipedia descending Shepard tone example (http://en.wikipedia.org/wiki/File:DescenteInfinie.ogg) linked to above has glitches every 20 sec]