Anomalous Motion Optical Illusion

AKA Peripheral Drift Optical Illusion is characterized by anomalous motion that can be observed in peripheral vision.

Warning: This page contains some works of "anomalous motion illusion", which might make sensitive observers dizzy or sick. Should you feel dizzy, leave this page immediately.

The above is a serious warning that I borrowed from the master of anomalous optical illusions, Professor Akiyoshi Kitaoka, of Ritsumeikan University, Kyoto, Japan.

Professor Kitaoka wasn't the first to notice that certain images appear to move if viewed in your peripheral vision. But he has studied the effect and perfected the creation of these optical illusions.

The first anomalous motion optical illusion is one that I created.



Sea Sickness  (AKA The Purple Nurple)
by Walter Anthony
is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

(c)2007
Keep in mind that this is a static image. It is not animated in any way. but as your vision moves back and forth the center area seems to be moving toward the center (contracting) and the outer edges seem to be moving away (expanding) from the center. Also worth noting is that if you fixate on a point in the center and don't move your eyes this anomalous motion will stop.

The next optical illusion is by the professor himself. Take a look at these snakes, do they rotate? For an even more amazing experience click on the image. It should open in a new window and take up the entire screen. Remember this image is not animated.


"Rotating snakes #9"
Each snake appears to rotate.
Copyright A.Kitaoka 2004 (October 7)
Used w/permission
Printer Alert----> If you have access to a color printer this illusion works on paper too! Print out a large version to amaze your family or friends.

Explanation----> Professor Kitaoka has provided a more detailed explanation of the peripheral drift illusion in PDF.

Finally the last example is from a friend, Herman Verwaal from Exloo, Netherlands. Since he has retired he has taken to creating optical illusions of all types. Here is one of his anomalous motion optical illusions. Notice the attempted motion this time is side to side (lateral).

Herman Verwaal
(c)2008
Used w/permission

Well there you have examples of three forms of anomalous motion optical illusions.

1. Expanding/Contracting
2. Rotational
3. Lateral

A quick thank you to Professor Kitaoka and Herman Verwaal for allowing me to share these illusions with you.

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Color Contrast Optical Illusion

The below two cubes share some things in common. The creator of this optical illusion states the following.

"Despite the fundamental difference in the apparent colour of the 'blue' tiles on top of the left cube, and the 'yellow' tiles on the top of the right cube, all the tiles are in fact physically identical (grey in both cases)."

I'll take this one step further and let you know that the RGB value for all 11 squares mentioned is exactly the same R:136 G:136 B:136. The blue and yellow squares mentioned are the exact same color as the gray block to the right.

Dale Purves M.D.
R. Beau Lotto
(c)2007

But they are not the only tiles on these cubes that look different but are exactly the same. Can you spot the other tiles that look different but are actually the same exact color?



The truth is that the optical illusion for tiles numbered 1 are the result of color contrast and the optical illusion for tiles numbered 2 and 3 are the result of brightness contrast.

With that said you must have no doubts that what I'm stating as fact is true. What's that you say? You don't believe it? Ok, OK already, quiet down. I guess we will just have to take the steps needed to prove that I am correct.

Project: Proving all the 1, 2, or 3 tiles are respectively all the same color.

There are a few ways you can prove that the tiles are the same color.

Before we continue, right click on the top image and open it in a new window. Now you have an image to work with.

1) You can use a graphics program like Photoshop, Paint.Net, Gimp or the Colorzilla extension for Firefox browser.

My choice is Colorzilla w/Firefox. Using the eyedropper tool you can determine that the RGB values of the respective tiles are the same, for number 1 tiles the RGB value is R:136 G:136 B:136, number 2 tiles have a RGB value of R:182 G:159 B:14, and number 3 tiles have a RGB value of R:75 G:45 B:138.

Not good enough for you, heh? Still not ready to trust that the computer is correct or you don't have an eyedropper tool? Either way you can move on to step 2 or 3 below.

2) Cut out a cardboard mask.

By viewing patches of the squares without the surrounding context, you can remove the effect of the illusion. A piece of cardboard with holes created in the right spots will work as a mask for a computer screen or as a mask for a the printed illusion. Holding up this mask to the image on the screen or printed paper should be enough to convince you. But if you were like my daughter nothing but this next step would do.

3) Print the image and cut out the respective tiles.

WARNING: Do Not use any specialty scissors your mother or wife uses for any kind of crafts, IE. quilting or fabric scissors. Doing this can be hazardous to your short term happiness. When in doubt get permission to use the scissors first.

This is another way to isolate the patches from their surrounding context. Cut out each tile along the edges. Remove them. Hold them side by side. Overlap the cut out tiles. Yup they're the same color. No denying it now, is there?

Please note that I have heard that some printers have "enhancement" processing that increases the contrast of edges. This can cause the printed squares to have slightly different RGB values. I haven't run into one of these printers yet where the overlapped squares didn't look identical, but your mileage may vary.

4) Of course you could just go to the interactive demo that the creator has up on his site. He shows both the color contrast and brightness contrast illusions, plus a few more that will make you think twice about believing what you see.

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Photograph Optical Illusions

There are many ways to create an optical illusion. Digitally manipulating a photograph using software such as Photoshop or Gimp creates convincing images, but like special effects in the movies you know they are fake.

There are ways to setup true photographic optical illusions without altering or "faking" the image. Take the following actual photo as an example.

Chess Anyone?
(c)2002
Tim Jensen
Used w/permission

This modern photograph is reminiscent of Sandro Del Prete's famous illusion drawing "Impossible Chess Set" below.


Impossible Chess Set
Sandro Del Prete
(c) 1975


So how do you think the photo "Chess Anyone?" was accomplished?

One key to photographic illusions is the fact that photos are 2 dimensional images of 3 dimensional objects. This means most photo illusions would fall apart if you saw them first hand. If you wish to see the Chess Anyone illusion from an angle that will reveal how it was accomplished place your mouse over the below reveal screen.


Chess Anyone? Revealed
(c)2002
Tim Jensen
Used w/permission

For a complete tutorial on how this photographic optical illusion was done read Tim Jensen's explanation here.

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Muller-Lyer Optical Illusion

The Muller-Lyer illusion is a size constancy illusion. In this illusion, the red and the blue lines below are the same length, but due to the effects of the arrows the red line appears longer.

The red and blues lines are both 170 pixels long


The illusion has been well studied since it was described by German psychiatrist Franz Carl Muller-Lyer in 1889. However, there is no certain explanation for the apparent difference in the perception of the lengths.


Muller-Lyer
1889

Muller-Lyer attempted to explain the illusion he had discovered as follows: "the judgment not only takes the lines themselves, but also, unintentionally, some part of the space on either side."

One of the better explanations I've read comes in the form of a PDF file from Catherine Q. Howe and Dale Purves of the Center for Cognitive Neuroscience, Duke University.

Below is an amazingly strong illusion that combines both the Ponzo and Muller-Lyer optical illusions.


Source
The two red vertical lines are the same length.
Placing your pointer over the image will aid you in exposing this illusion.

In the tickets image above the perspective of distance lends itself to the Ponzo optical illusion, the angles at the end of each line add to this the Muller-Lyer illusion, combined they create a very effective optical illusion.


Project: Create your own illusion. See how the following variations might effect the relative strength of this illusion.

Does changing the color of the background change the effect?
Does changing the color of the arrows change the effect?
Try changing the color of the equal lines,
is there any combination of colors that is stronger then the others?
Try fat lines. Try skinny lines. Does the thickness of the lines affect this illusion?
Does the distance from which you view the illusion change the illusion?

What can you conclude, if anything, about how we perceive things from this project?

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Ambiguous Rabbit or Duck Optical Illusion

There is a whole section of illusions that are ambiguous. This means that the image is open to more than one interpretation.

One of the oldest ambiguous figures is the "Duck or Rabbit" This illusion first appeared in the October 23rd issue of Fliegende Blatter (a German humor magazine) in 1892. source.


The interesting thing about this illusion is that it is frequently credited to Joseph Jastrow 1899. Joseph Jastrow is an American psychologist who was the first to note this image in his work. He used the duck-rabbit figure to make the point that perception is not just a product of the stimulus, but also of mental activity – that we see with the mind as well as the eye - source.

Jastrow's Cartoon (1899)

The truth though is that while Jastrow used his image in 1899 it had appeared in print at least twice before both times in 1892.

Jastrow's 1899 cartoon version was based on one originally published in Harper’s Weekly (November 19, 1892, p. 1114). The Harper's cartoon, in turn, was based on the original in Fliegende Blatter.

Below is a new version of this old favorite...

The photographer found this version during a visit to the Ripley's Believe It or Not! museum in Branson, Missouri.

What do you see a duck (looking left) or a rabbit (looking right). If you slide your mouse over the image the photo will rotate giving you a slightly differ perspective.

Flickr Artist: Dropped_Stitch


So what did you see in this image a duck or a rabbit? Which version above is most effective for you?

There are an endless variety of this type of illusion. What other ambiguous optical illusions have you seen?

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