2007 Second prize
(© 2007 Pietro Guardini and Luciano Gamberini)
Read more about the illusion and possible explanations
Where Has All the Motion Gone?
2007 Third prize
This movie requires Flash Player 9
(© 2007 Arthur Shapiro and Emily Knight)
Click on the big button to toggle between a blurred version of the display and an unblurred version. When the display is blurred, the motion is dramatic; when the display is not blurred, there is only minimal motion. The effect can also be seen with a defocused lens. Blur eliminates high-spatial frequencies. It does not add information to the image. Why, therefore, does the removal of high-spatial frequencies add motion to the display? The buttons and levers allow control over the many of the parameters in the display.
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Bouncing Brains
This movie requires Flash Player 9
© 2007 Thorsten Hansen, Kai Hamburger, & Karl R. Gegenfurtner
Please relax and look at the colorful brains: aren’t they rotating and bouncing?! They are, but only in your head.
What’s going on? Some regions in the brains are darker, some lighter than the background. The perceived location of the separation between light and dark regions changes as the background is modulated, causing each brain to jiggle and bounce. In some regions these illusory motions of neighboring brains are coherent and are grouped together to give rise to an even stronger illusion.
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’Weaves’ and the Hermann Grid
This movie requires Flash Player 9
© 2007 Kai Hamburger and Arthur Shapiro
Read more about the illusion and possible explanations
Drifting Background Illusion
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(© 2007 Masaharu Kato)
In the illusion , a small pink object can be seen moving back and forth in front of three types of background. When observers track the pink target moving back and forth in front of a background consisting of dynamic noise, they report the percept of a drifting background. The direction of this drift is opposite to that of the small pink object, even though the background in fact does not move into a particular direction. This illusory motion arises for a static gray Gaussian background, but is actually much stronger when the background is dynamic random noise. However, the illusion does not occur when the background consists of static random noise.
Swimmers, Eels and Other Gradient-Gradient Illusions
This movie requires Flash Player 9
(© 2007 Emily Knight and Arthur Shapiro)
The red button adds/removes half of the background grating. The swimmers bob up and down when they are in front of the grating but not when they are in front of a uniform background
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Kaleidoscopic Motion and Velocity Illusions
(© 2007 Peter van der Helm) Note: you need java installed in your computer to see this illusion.
You will see a rotating wheel that pulsates each time it aligns with two stationary shapes. You may also see that, at the same time, the inner stationary shape wiggles. The pulsations seem to be caused by color assimilation, and the other effects by ambiguous figure-ground segregation.
Read more about the illusion and possible explanations at Peter van der Helm’s website
For another interactive version of this Illusion, see Michael Bach’s “Optical Illusions & Visual Phenomena” website.
Kaleidoscopic motion and velocity illusions Peter A. van der Helm Vision Research, 2007. 47:460–465
It’s a Circle, Honest!
(© 2007 David Whitaker)
The illusion in the figure on the left consists of two sinusoidal gratings at 45° and 135° which combine to form a plaid. The contrast of this plaid is windowed by a perfect circle. Despite this, the percept is far from circular – rather, it appears octagonal with distinct sides. The percept is generated by attraction and repulsion of the circular envelope in the orientation domain by the sinusoidal carrier gratings. It relies upon the sharp transition between Fraser illusion (attraction) and Zöllner illusion (repulsion) at the knee-points of the octagon.
Whilst the illusion is scale-invariant in that it does not change with viewing distance, if the scale of the carrier grating is lowered (Figure on the right) relative to the circle, the percept changes from an octagon to a diamond. This is well-predicted by the variation in the strength of the Fraser and Zöllner illusions as the relative spatial scale of carrier and envelope is varied (Skillen et al. (2002) Vision Research 42, 2447-2455).
The Freezing Rotation Illusion
2006 First prize
(© 2006 Max Dürsteler)
An object (e.g. airplane) is turning on a surround (greenhouse), which is swaying back and forth. Observe the rotation of the object. Is it turning smoothly all the time? Or does it “freeze” from time to time? Convince yourself by covering the swaying surround that the object is really turning continuously. If the object is swaying back and forth and the surround is turning continuously we do not perceive a slow-down of the surround. Assuming a stable surround, our visual system probably uses the surround as a reference to measure motion of the included objects.
Read more about the illusion and possible explanations
See an interactive version of the The Freezing Rotation Illusion at Michael Bach’s “Optical Illusions & Visual Phenomena” website
The Freezing Rotation IllusionMax R. DürstelerNature Precedings 2007. 371.1
