Coffer Illusion

Anthony Norcia

Smith-Kettlewell Eye Research Institute, USA

(© 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”.

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The Occlusion Velocity Illusion

Evan Palmer & Phillip Kellman

Harvard Medical School & UCLA, USA
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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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Clones and Donors Have Opposite Inclinations (in Vision)

Oronzo Parlangeli & Sergio Roncato

Università di Padova, Italy
Clones and Donors Have Opposite Inclinations (in vision)

(© 2006 Oronzo Parlangeli & Sergio Roncato)

Fig. 1 and Fig. 2 show the same inducing pattern.
However, if the blue lines in fig 1 are seen as donors, we can easily appreciate that when they give birth to two clones as in fig 2, these clones grow apart and they show a diametrically opposed inclination: convex lines become concave and concave lines becomes convex.
A clone for each donor is sufficient to produce the effect.

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Dynamic Luminance-Gradient Effect

Alan Stubbs

University of Maine, USA
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.

See different versions of the illusion

Read more about the illusion and possible explanations

A new set of illusionsthe Dynamic Luminance-Gradient Illusion and the Breathing Light Illusion Simone Gori & D. Alan Stubbs Perception. 2006. 35:1573-7

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Catching Patches

Rob Van Lier & Mark Vergeer

Radboud University Nijmegen, The Netherlands
Catching Patches

(© 2006 Rob Van Lier & Mark Vergeer)

We present an illusion based on Hermann-grid like gratings in which the contours are quite randomly distorted. These distortions guarantee a severe reduction or complete disappearance of the visibility of the patches. Starting with these gratings we show that the patches at the crossings return when luminance edges are introduced and extended at the intersections. The ‘returned’ patches have the same relative lightness properties as they would have in a regular Herman grid (dark patches when the crossing bands are relatively light, and light patches when the crossing bands are relatively dark). In addition, the polarity of the perceived lightness difference does not depend on the lightness of the edges (i.e., whether they are dark or light). A remarkable effect here is that at the crossings the whole area between the edges is perceived to have a different lightness, irrespective of the shape of that area (i.e., whether the edges bend inward or outward etc.).

See Power Point presentation with different versions of the illusion

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Motion-Illusion Building Blocks

2005 First prize
Arthur Shapiro & Justin Charles

Bucknell University, USA
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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.

Read more about the illusion and possible explanations

Visual illusions based on single-field contrast asynchronies Arthur G. Shapiro, Justin P. Charles & Mallory Shear-Heyman Journal of Vision. 2005. 5:764-82

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Two-Stroke Apparent Motion

2005 Second prize
George Mather

Sussex University, UK

(© 2005 George Mather)

The illusion contains two pattern frames depicting a moving image (hence two-stroke) which are displayed using a technique that creates an impression of continuous forward movement.

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Two-stroke: a new illusion of visual motion based on the time course of neural responses in the human visual system George Mather Vision Research. 2006. 46:2015-8

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Elusive Arch

2005 Third prize
Dejan Todorović

University of Belgrade, Serbia

(© 2005 Dejan Todorović)

Shading is a powerful way to represent the relief of 3-dimensional objects in pictures. However, the way our vision interprets shaded images depends on the shape of their contours. Here two different contours of the same shading pattern convey two different reliefs, joined into an impossible object.

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Powerpoint Presentation

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World’s Largest Lightness Illusion

Barton Anderson & Jonathan Winawer

University of South Wales, Australia & MIT, USA

(© 2005 Barton L. Anderson & Jonathan Winawer)

In this illusion, it appears that there is one set of black figures and one set of white figures. In fact, the two sets of figures are exactly identical. They appear different because the surrounding regions they are on cause the visual system to segment the images into layers. Thus one set appears to be white figures behind dark clouds, and the other set appears to be dark figures behind light clouds. If you cut out the figures you will see that they are identical!

See the illusion: movie

Read more about the illusion and possible explanations

Image segmentation and lightness perception Barton L. Anderson & Jonathan Winawer Nature. 2005. 434:79-83

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