Visual and Auditory Illusions

Visual and Auditory Illusions

 

Ambiguous Figures



Duck/Rabbit

Photograph of a suck on water that also looks like a rabbit
A photographic version of the Duck/Rabbit

Dog/cat/mouse ambiguous figure
Continuing on the animal theme: Dog/cat/mouse ambiguous figure


Young Woman/Old Woman 


One for academics: book or cleavage?

How many circles can you see in this picture? Focus on the cross and they'll start to appear!


  
 


 

Notice that when one triangle seems to point in a certain direction so do all those around it. 
  
  

Saw-Tooth Illusion 


  

An illusion similar to the Necker Cube. 

You may wish to read Fiona Macpherson (2006) "Ambiguous Figures and the Content of Experience", Nous, 40(1): 82-117, about experiences of ambiguous figures and their philosophical significance.

Shape Illusions  


   Muller-Lyer 
  
 
 
  Zollner Illusion 


 
  
Ebbinghaus Illusion

 

Impossible Figures 


  
Penrose Triangle 



  
Impossible Figure by Oscar Reutersvard 


 
  
  
Impossible Figure by Oscar Reutersvard 


  
 
Impossible Figure by Oscar Reutersvard

 
  Impossible Figure by Oscar Reutersvard 


  
  
 Impossible Figure by Oscar Reutersvard 

Escher's Belvedere

Many of Escher's pictures depict impossible figures, such as Belvedere.

Photograph of a figure that when taken from the right angle looks like an impossible triangle Photograph of a figure that when taken from the right angle looks like an impossible triangle

These photos show a piece of wood that when looked at (or photographed) from the right angle appear to be of an impossible triangle.

Photos of a sculpture that looks like an impossible figure when seen from the right angle in Perth, Australia

These pictures show a sculpture in East Perth, Australia that, from the right angle, looks to be an impossible triangle.

 

To learn more about impossible figures you may wish to read Fiona Macpherson (forthcoming, 2009) "Impossible Figures", Sage Encyclopedia of Perception, edited by E. Bruce Goldstein, Thousand Oaks, CA: Sage Publications, Inc.

The Leaning Tower Illusion

© Kingdom, Yoonessi and Gheorghiu
(Winner of the 2007 Best Visual Illusion of the Year Contest)
The two images of the tower are identical although the one placed on the right looks to be leaning more.


 

 

Colour Contrast Effects 


The two central grey squares are the same colour. 


  
 

The two central green squares are the same colour. 


  

  
The two central pinkish squares are the same colour. 

 

The red colour is the same across this band. 

blue/green colour contrast picture     

In this picture on the left the shades of colour that look to be different shades of blue and green are in fact the same shade. They look to be so different on account of the shades that surround them. You can see this clearly when all colours except the blue and the green have been blacked out, as is the case in the picture on the right.


The square marked A and the square marked B are the same shade of grey.
(Really! You can print out the image and put the squares physically together to check.)
  
  

Neon Colour Spreading and Similar Black and White Effects 

 

  
 Hermann Grid 

 

 
Scintillating Grid

Apparant Motion Effects

Please stop looking at the images if they cause you to feel dizzy or unwell.
These images were created by Akiyoshi Kitaoka.
The images are stationary and only appear to move.

"Boats" - The boats appear to move in a clockwise direction.


"Rollers" - the rollers appear to rotate in different directions.


"Rotating Snakes" - the circles appear to rotate in different directions.

Figures for Producing After-Images


 
By fixating on the bottom right corner of the yellow rectangle for 30 seconds or so and then looking at a white surface and blinking a few times, one can have an after-image of  the American flag in the correct colours.

An effect similar to after-images in certain respects, but perhaps even more vivid, can be got by first staring at the picture below and fixating on the centre spot for 30 seconds. Afterwards, roll the mouse over the picture and keep fixating on the centre spot (this is important). You seem to see the picture in colour even though it is really in black and white, as you can easily verify. These images are taken from John Sadowski and on one of his webapages he provides a tutorial on how to make such pictures.

http://www.gla.ac.uk/t4/cspe/i/manzana2.jpg



Motion After-Effects

Fixate on the centre of the rotating spiral for 60 seconds and then look at a non-moving surface - preferably one with a pattern on it, such as the pattern below it. Note the illusion of movement when looking at the stationary pattern.

Rotating spiral

 

brightly coloured and highly patterned non-moving test pattern

The motion ater-effect is also called the waterfall illusion. See a waterfall-stlye version of and read about its connection with Scotland here.


The Barber Pole Auditory Illusion
(also called Shepard Scales)

The tones below sound as if they are ever increasing or decreasing in pitch. However, this is only an illusion. The same sequence of notes, an octave, is simply being played over and over again. The illusion is an auditory equivalent of the apparently ever rising lines on a rotating barber's pole or the steps on Escher's lithograph 'Ascending and Descending'. The illusion is created because each note is composed of many pitch frequencies that are carefully crafted to create ambiguity and hence this illusion. See Shepard, R. N. (1964) "Circularity in Judgments of Relative Pitch", The Journal of the Acoustical Society of America, Vol. 36, No. 12, pp. 2346-2353.


Shepard tone falling

shepherdfalling.mp3

Shepherd tone rising

shepherdrising.mp3

 A similar effect can be made to occur with rhymn, again exploiting ambigiuities in sound. One can create a beat that sounds as if it is always speeding up, as Jean-Claude Risset did:

Rissett rhymn

Risset.mp3

Further information: J. C. Risset (1986) “Pitch and Rhythm Paradoxes: Comments on “Auditory Paradox Based On Fractal Waveform”,” Journal of the Acoustical Society of America, 80(3): 961–962.

 

 

Escher's Ascending and Descending

 

Some modern music exploits these effects for example: ‪Astronivo & DJ Zombi‬ Anything You Want (Miki Litvak & Ido Ophir Remix) and ‪Christian Smith & John Selway‬‪ Total Departure‬.


Change-Blindness

To find out about change-blindness and to test your own vision click here.

Links to Further Interesing Perceptual Effects: