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© 2007 Kai Hamburger and Arthur Shapiro
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Swimmers, Eels and Other Gradient-Gradient Illusions
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(© 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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The Infinite Regress Illusion
2006 Second prize
Dartmouth College, USA
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(© 2006 Peter Tse)
Fixate the black fixation point on the far left side of the image. Note that the figure appears to move steadily away from the fixation point, even though it is in fact only moving up and down.
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The infinite regress illusion reveals faulty integration of local and global motion signals Peter U. Tse & Po-Jang Hsieh Vision Research. 2006. 46:3881-5
The Bar-Cross-Ellipse Illusion
2006 Third prize
(© 2006 Gideon Caplovitz & Peter Tse)
Here we present a new multistable stimulus generated by continuously rotating an ellipse behind four fixed occluders. Observers can perceive one of four percepts: (1) a continuously morphing cross, (2) two independent perpendicular bars oscillating in depth, (3) a rigidly rotating ellipse observed behind the occluders, or (4) a fixed cross observed through a continuously rotating, elliptical aperture.
The bar – cross – ellipse illusion: Alternating percepts of rigid and nonrigid motion based on contour ownership and trackable feature assignment Gideon P. Caplovitz & Peter U. Tse Perception. 2006. 35:993-7
Gradient-Offset Induced Motion
(© 2006 Po-Jang Hsieh)
When a gradient stimulus, whose luminance contrast ranges gradually from white on one side to black on the other, is made to disappear all at once so that only the uniform white background remains visible, illusory motion is perceived. This motion lasts ~700ms, as if the stimulus moves from the low to the high luminance contrast side. This gradient-offset induced motion does not occur for equiluminant color-defined gradient offsets, suggesting that it relies mainly on the magnocellular pathway. We hypothesize that this illusion is caused by the difference of decay rates within the gradient afterimage.
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Illusory motion induced by the offset of stationary luminance-defined gradients Po-Jang Hsieh, Gideon P. Caplovitz & Peter U. Tse Vision Research. 2006. 46:970-8
Coffer Illusion
(© 2006 Anthony Norcia)
First time viewers of this display invariably do not see the 16 circles segmented from the background. Rather, they see a series of rectangles that they frequently describe as “door panels”. The illusion pits segmentation cues against what appears to be a very strong prior to interpret the image as a series of 3-D structures “coffers” with closed boundaries. (A coffer is a decorative sunken panel.) It appears that the prior involves both closure and shape-from shading assumptions. The Coffer Illusion is a variation on Gianni Sarcone’s “Op Art illusion”.
The Occlusion Velocity Illusion
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(© 2006 Evan Palmer & Phillip Kellman)
The Occlusion Velocity Illusion shown in the video demonstrates that when one part of a moving object goes out of view before another part, the two pieces appear misaligned, even though they are not (top row). This illusion can be counteracted by misaligning one portion of the rod in the direction opposite to the perceived misalignment (middle row). If observers are instructed to attend to the rod’s shape only within the blue box, they are still subject to the illusion (bottom row). This final observation indicates that the illusion is obligatory and not under volitional control.
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Sinha: Hidden Strength of the Classical Simultaneous Contrast Illusion
(© 2006 Pawan Sinha)
Dynamic Luminance-Gradient Effect
(© 2006 Alan Stubbs)
For the primary effect, one should sit at a comfortable distance and then move forward toward the center of the figure. An interesting change in apparent brightness and to some degree form will result—what may be called a “here comes the sun” effect. By moving back and forth, this apparent change will repeat.
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A new set of illusionsthe Dynamic Luminance-Gradient Illusion and the Breathing Light Illusion Simone Gori & D. Alan Stubbs Perception. 2006. 35:1573-7
Motion-Illusion Building Blocks
2005 First prize
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(© 2005 Arthur Shapiro & Justin Charles)
A number of well-known motion illusions arise when luminance modulates next to a stationary edge (e.g., Anstis and Rogers, 1975; Gregory and Heard, 1983). Here, we reduce these phenomena to four novel elemental conditions and show how these conditions can be combined (like building blocks) to generate an infinite number of new illusory configurations.
Click on the “Elemental Conditions” button in the accompanying movie . In the top two panels, the luminance of the edge modulates next to stationary black or white center fields; in the bottom two panels , the luminance of the center modulates next to black or white stationary edges (Figure 1A shows one frame of the movie). In all four conditions, the fields appear to move even though they maintain a fixed spatial position. The apparent direction of motion may seem counter-intuitive: when the luminance of a modulating edge is similar to the luminance of the center, the motion is outward, whereas when the luminance of a modulating center is similar to the luminance of the edge, the motion is inward.
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Visual illusions based on single-field contrast asynchronies Arthur G. Shapiro, Justin P. Charles & Mallory Shear-Heyman Journal of Vision. 2005. 5:764-82
