Pinball Wizard

Michael Pickard

Sunderland University, UK


© 2008 Pickard

The interesting thing about the Pinball Wizard illusion is that it breaks the ‘rules’. Whilst the classic Rubin Vase illusion demonstrates how we automatically segregate foreground and background in an image, in this illusion a single image is seen acting simultaneously as both, giving rise to an illusory sense of rotation.
Using visual cues to create an impression of depth and carefully chosen colour values, a static screen is combined with an animation of horizontally traversing spheres. The screen appears simultaneously as background and as foreground surface on the spheres – inducing a sense of rotation as the spheres move.

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The Leaning Tower Illusion

2007 First prize
Frederick Kingdom, Ali Yoonessi and Elena Gheorghiu

McGill University, Canada

© 2007 Kingdom, Yoonessi & Gheorghiu

Here is a novel illusion that is as striking as it is simple. The two images of the Leaning Tower of Pisa are identical, yet one has the impression that the tower on the right leans more, as if photographed from a different angle. The reason for this is because the visual system treats the two images as if part of a singlescene. Normally, if two adjacent towers rise at the same angle, their image outlines converge as they recede from view due to perspective, and this is taken into account by the visual system. So when confronted with two towers whose corresponding outlines are parallel, the visual system assumes they must be diverging as they rise from view, and this is what we see. The illusion is not restricted to towers photographed from below, but works well with other scenes, such as railway tracks receding into the distance. What this illusion reveals is less to do with perspective, but how the visual system tends to treat two side-by-side images as if part of the same scene. However hard we try to think of the two photographs of the Leaning Tower as separate, albeit identical images of the same object, our visual system regards them as the ‘Twin Towers of Pisa’, whose perspective can only be interpreted in terms of one tower leaning more than the other.

Leaning tower illusion Frederick A. A. Kingdom, Ali Yoonessi, Elena Gheorghiu Scholarpedia 2007. 2(12):5392.

The Leaning Tower illusion: a new illusion of perspective Frederick A. A. Kingdom, Ali Yoonessi, Elena Gheorghiu Perception. 2007. 36(3):475-477

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Motion-Illusion Building Blocks

2005 First prize
Arthur Shapiro & Justin Charles

Bucknell University, USA
This movie requires Flash Player 9

(© 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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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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The Rotating-Tilted-Lines Illusion

Simone Gori & Kai Hamburger

Brain Research Unit University of Freiburg, Germany

(© 2005 Simone Gori & Kai Hamburger)

When one approaches the stimulus pattern, the radial lines appear to rotate in a counterclockwise direction, whereas when one recedes from it, they appear to rotate clockwise. In the complex version of the pattern, the illusory rotation is stronger and there may be some residual counter rotation in the surround.

Read more about the illusion and possible explanations

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