PINBALL WIZARD
By Michael Pickard • University of Sunderland, U.K. • 2008 Finalist
A semitransparent screen is positioned over a series of drifting spheres, and semitransparent blobs on the screen take on properties of both the foreground and the background. When the screen is over a drifting sphere, that sphere takes on the blobs as a surface property, making the sphere rotate and roll rather than drift (although there is no rolling motion in the display). Simultaneously, when the blobs are not overlaid on a sphere, they appear as splotches on the background, behind the spheres.
DRIFTING BACKGROUND ILLUSION
By Masaharu Kato • Uppsala University, Sweden • 2007 Finalist
A small pink dot moves back and forth in front of a background of static noise. But when this background noise is dynamic (albeit not moving), the pink dot’s motion makes the background appear to drift in the opposite direction.
SWIMMERS AND EELS
By Emily Knight and Arthur G. Shapiro • Bucknell University, U.S.A. • 2007 Finalist
Oval dots (“swimmers”) stand in the foreground of a multicolored grating. The swimmers bob up and down with the grating. Remove the grating and replace it with a uniform background, and the bobbing disappears.
STEEL MAGNOLIAS AND BREEZE IN THE TREES
By Michael Pickard • University of Sunderland, U.K. • 2007 Finalist
Leaves and flower petals blow in the breeze, though the whole image is actually stationary. The coloring of individual petals and leaves merely cycles from light to dark, whereas the two opposite edges of each petal or leaf remain dark or light.
PERPETUAL COLLISIONS
By Arthur G. Shapiro and Emily Knight • Bucknell University, U.S.A. • 2008 Finalist
Pink and yellow columns seem to keep colliding or moving apart. But they never actually meet and never grow farther apart. In reality, the columns are not moving; the illusion of motion is created by spinning black-and-white diamonds within them.
ILLUSIONS FROM ROTATING RINGS
By Stuart Anstis and Patrick Cavanagh • University of California, San Diego, U.S.A., and Université Paris Descartes, France • 2011 Finalist
When the overlapping portions of these rings are opaque, the rings rotate as a single connected whole, as if welded to each other. But when the overlapping portions appear transparent, the rings rotate as if they are separate and sliding over each other.
THE BREAK OF THE CURVEBALL
By Arthur G. Shapiro, Zhong-Lin Lu, Emily Knight, and Robert Ennis • American University; University of Southern California; Dartmouth College; and State University of New York College of Optometry, U.S.A. • 2009 First Prize
Arthur Shapiro and his colleagues showed that a baseball pitcher’s curveball is an illusion created by the peripheral visual system of the batter. The ball rotates, certainly, but what that actually does—rather than physically changing the trajectory of the ball—is to bias the peripheral-motion sensors in the visual system of the batter in the direction of the spin. Viewing the image of a spinning ball as it exits your fovea—just as the image exits the batter’s fovea as it approaches home plate—makes it look as if the ball is both spinning and curving.
CRAZY DIFFERENCES IN FOVEAL AND PERIPHERAL VISION
By Emily Knight, Arthur G. Shapiro, and Zhong-Lin Lu • Bucknell University and University of Southern California, U.S.A. • 2008 Finalist
This illusion is another striking example of the dichotomy between our foveal and our peripheral vision. Three visual targets appear to move horizontally when viewed directly, and diagonally when viewed from the corner of your eye.
THE INFINITE REGRESS ILLUSION
By Peter Tse • Dartmouth College, U.S.A. • 2006 Second Prize
Several of the illusions in the contest launched the analysis of peripheral perception in the new millennium. These perceptual effects highlight how our peripheral vision (but not our foveal vision) uses local motion cues within an object—such as the appearance of spinning—to indicate direction of motion. Tse employed this principle to make objects appear to move in specific (and wrong) directions infinitely.
IN A BIND
By Arthur G. Shapiro and Gideon Caplovitz • American University and University of Nevada, Reno, U.S.A. • 2011 Finalist
Two vertical bars, one red and one green, swept left and right across a screen. When the bars met in the middle of the screen, they changed colors and rebounded off each other, streaked back to the edge of the screen, and bounced back to the middle. Shapiro asked the audience to look at a spot above the screen while paying attention to the bouncing bars. People “oooooohed” as they saw the bars once again collide, but instead of ricocheting, now they seemed to pass through each other and retain their original color. Shapiro went on to show that the pass-through effect also works with textured, rather than colored, bars. This illusion shows that features bound to one object can rebind to a different moving object.
THE COLORED DOT ILLUSION
By Stuart Anstis • University of California, San Diego, U.S.A. • 2012 Finalist
A colored dot moves horizontally over a patterned black-and-white background. When you look straight at the dot, you see it accurately. But if you glance at the dot from the corner of your eye, it suddenly appears to glide diagonally. Anstis explained that this illusion demonstrates that our central vision sees positions very precisely, but our peripheral vision, better at seeing movement, is not well suited to determining position.
PERIPHERAL ACTION PHANTOM
By Steven Thurman and Hongjing Lu • University of California, Los Angeles, U.S.A. • 2012 Finalist
A figure appears to walk to the left when you view it directly. But wait! If you look away, the figure suddenly seems to change direction and walk to the right. Thurman and Lu positioned disks with blurry edges, called Gabor patches, to represent a person walking to the right, despite the overall leftward shift created by the motion of the texture within the disks. Our central vision does not pick up the subtle rightward-moving walking cues, but our super motion-sensitive peripheral vision grasps them at once and integrates them into our perception of the object’s trajectory.
HEIGHT CONTRADICTION
By Sachiko Tsuruno • Kinki University, Japan • 2012 Finalist
The artist Sachiko Tsuruno built an architectural model that resembles the interior of a fortress and filmed balls rolling along inclines inside it. But because of the perspective of the camera, the balls seem to roll uphill between two level surfaces, as ridiculous and impossible as that may seem to your rational mind. Among the telltale signs: If you black out the staircase (a local clue), the top of the tower looks flat, whereas if you black out the sides (another local clue), it looks as if the top is on two levels connected by a staircase.
ROTATING MCTHATCHER ILLUSION
By James Dias and Lawrence Rosenblum • University of California, Riverside, U.S.A. • 2014 Finalist
In the classic McGurk Effect, hearing the sound “ba” while viewing a face articulating “va” results in the observer’s perception of the sound “va.” Another classic illusion, the Margaret Thatcher Effect, shows that our visual systems are wired to see faces right side up, and thus fail to notice grotesque oddities when faces are upside-down. James Dias and Lawrence Rosenblum’s illusion combines the McGurk and Thatcher effects and shows that our ability to read lips depends on face orientation. As a face rotates and becomes “Thatcherized,” “ba” remains “ba”: auditory perception becomes less susceptible to influence by the visual (i.e., facial) context.
ATTENTION TO MOTION
By Peter Tse, Patrick Cavanagh, David Whitney, and Stuart Anstis • Dartmouth College; University of California, San Diego, U.S.A.; Université Paris Descartes, France • 2011 Finalist
Red circles, perfectly aligned vertically, appear fixed to an axis that slants to the left or to the right, depending on where you allocate your attention. While the transparent layer of black dots rotates in one directio
n, the transparent layer of white dots rotates in the opposite direction, and the directions reverse every 1.2 seconds. When you focus on the white layer, the red circles appear slanted to the right; when you focus on the black layer, the circles appear slanted to the left.
PAC-MAN’S INFINITE MAZE
By Sebastiaan Mathôt and Theo Danes • Centre National de la Recherche Scientifique, Aix-Marseille Université, France • 2014 Finalist
This Pac-Man-inspired video game for Android is a demonstration of change blindness, which occurs when people fail to notice striking changes happening right in front of them, for lack of attention. You can enjoy the game just as if you were playing Pac-Man, with one key difference. What looks at first sight like a regular Pac-Man maze is in fact randomly re-generated with every move! The image is always centered on Pac-Man, and the maze scrolls across the display as Pac-Man moves. Even though the maze is constantly changing, most people take a long time to realize it. If the maze becomes static, as with a regular game of Pac-Man, the changes are easily noticeable.
THE DISAPPEARING FACES ILLUSION
By Stuart Anstis • University of California, San Diego, U.S.A. • 2014 Finalist
Visual neurons “adapt”—or gradually respond less vigorously—to unchanging stimuli. Adaptation to contrast is known to act specifically on the edges or contours in an image. Drawing on this principle, Anstis reasoned that adapting to a particular photograph should render the visual system less sensitive to that precise image, but not to similar, nonadapted photos with different contours. Anstis’s illusion prompts your visual neurons to adapt to a flickering high-contrast photo of Albert Einstein on the left and one of Marilyn Monroe on the right. Once the flickering stops, two identical low-contrast overlays of Einstein and Monroe no longer look the same, but reveal Monroe on the left and Einstein on the right.
NOTES
INTRODUCTION
you may underestimate or overestimate: Russell E. Jackson and Lawrence K. Comack, “Evolved Navigation Theory and the Descent Illusion,” Perception & Psychophysics 69, no. 3 (2007): 353–62.
1. BRIGHTNESS AND CONTRAST ILLUSIONS
This illusion by Anderson and Winawer: Barton L. Anderson and Jonathan Winawer, “Image Segmentation and Lightness Perception,” Nature 434, no. 7029 (2005): 79–83, doi:10.1038/nature03271; B. L. Anderson and J. Winawer, “Layered Image Representations and the Computation of Surface Lightness,” Journal of Vision 8, no. 7 (2008): 1–22, doi:10.1167/8.7.18.
The neural bases of this effect: “Dynamic Luminance,” aka “Here Comes the Sun,” aka “Luminance Star,” published in Bangor Daily News, Sept. 11, 2006; in “The Art of Perception,” UMaine Today, Sept.–Oct. 2007; and in Michael Baziljevich, Sansenes Vidunderlige Verden.
If you look at a textured surface: Lothar Spillmann, Joe Hardy, Peter Delahunt, Baingio Pinna, and John S. Werner, “Brightness Enhancement Seen Through a Tube,” Perception 39, no. 11 (2010): 1504–13, doi:10.1068/p6765.
The classical explanation: G. Baumgartner, “Indirekte Grössenbestimmung der rezeptiven Felder der Retina beim Menschen mittels der Hermannschen Gitteräuschung,” Pflügers Archiv für die gesamte Physiologie des Menschen und der Tiere 272: 21–22, doi:10.1007/BF00680926.
This perceptual effect: Mark Vergeer and Rob van Lier, “Capturing Lightness Between Contours,” Perception 39, no. 12 (2010): 1565–78, doi:10.1068/p6539.
contrast is an important cue: Richard Russell, “A Sex Difference in Facial Contrast and Its Exaggeration by Cosmetics,” Perception 38, no. 8 (2009): 1211–19, doi:10.1068/p6331; Richard Russell, “88: The Illusion of Sex,” in The Oxford Compendium of Visual Illusions, ed. Arthur G. Shapiro and Dejan Todorovi´c (Oxford, U.K.: Oxford University Press, 2017).
Once neurons have adapted: Stuart Anstis, “108: The Disappearing Faces Illusion,” in Oxford Compendium of Visual Illusions.
2. COLOR ILLUSIONS
an even more striking version: Yuval Barkan and Hedva Spitzer, “109: The Color Dove Illusion—Chromatic Filling In Effect Following a Spatial-Temporal Edge,” in The Oxford Compendium of Visual Illusions, ed. Arthur G. Shapiro and Dejan Todorovi´c (Oxford, U.K.: Oxford University Press, 2017).
a single multicolored image: Rob van Lier, Mark Vergeer, and Stuart Anstis, “Filling-In Afterimage Colors Between the Lines,” Current Biology 19, no. 8 (2009): R323–24, doi:10.1016/j.cub.2009.03.010.
Their illusion shows that a single image: Mark Vergeer, Stuart Anstis, and Rob van Lier, “Flexible Color Perception Depending on the Shape and Positioning of Achromatic Contours,” Frontiers in Psychology 6 (May 18, 2015), doi:10.3389/fpsyg.2015.00620.
the vision scientist Michael White: M. White, “A New Effect of Pattern on Perceived Lightness,” Perception 8 (1979): 413–16.
Purves’s idea: D. Purves, R. B. Lotto, S. M. Williams, S. Nundy, and Z. Yang, “Why We See Things the Way We Do: Evidence for a Wholly Empirical Strategy of Vision,” Philosophical Transactions of the Royal Society of London, 356, no. 1407 (2001): 285–97.
3. SIZE ILLUSIONS
Recent research shows that spiders: M. W. Vasey, M. R. Vilensky, J. H. Heath, C. N. Harbaugh, A. G. Buffington, and R. H. Fazio, “It Was as Big as My Head, I Swear!: Biased Spider Size Estimation in Spider Phobia,” Journal of Anxiety Disorders 26, no. 1 (2012): 20–24; D.M.T. Fessler, C. Holbrook, and J. K. Snyder, “Weapons Make the Man (Larger): Formidability Is Represented as Size and Strength in Humans,” PloS ONE 7, no. 4 (2012): article e32751.
the size of a moving object: Ryan E. B. Mruczek, Christopher D. Blair, and Gideon P. Caplovitz, “Dynamic Illusory Size Contrast: A Relative-Size Illusion Modulated by Stimulus Motion and Eye Movements,” Journal of Vision 14, no. 3 (2014): 2, doi:10.1167/14.3.2.
Our own research showed: J. Otero-Millan, S. L. Macknik, A. Robbins, M. McCamy, and S. Martinez-Conde, “Stronger Misdirection in Curved than in Straight Motion,” Frontiers in Human Neuroscience 5 (2011): 133.
Blair, Caplovitz, and Mruczek created: Ryan E. B. Mruczek, Christopher D. Blair, Lars Strother, and Gideon P. Caplovitz, “The Dynamic Ebbinghaus: Motion Dynamics Greatly Enhance the Classic Contextual Size Illusion,” Frontiers in Human Neuroscience 9 (Feb. 18, 2015), doi:10.3389/fnhum.2015.00077.
The Fat Face Thin Illusion: Peter Thompson, “Margaret Thatcher: A New Illusion,” Perception 9, no. 4 (1980): 483–84, doi:10.1068/p090483; Peter Thompson and Jennie Wilson, “Why Do Most Faces Look Thinner Upside Down?” i-Perception 3, no. 10 (2012): 765–74, doi:10.1068/i0554.
The Head Size Illusion demonstrates: K. Morikawa, K. Okumura, and S. Matsushita, “Head Size Illusion: Head Outlines Are Processed Holistically Too,” Perception 41 (2012), ECVP suppl., 115; Kazunori Morikawa, Soyogu Matsushita, Akitoshi Tomita, and Haruna Yamanami, “A Real-Life Illusion of Assimilation in the Human Face: Eye Size Illusion Caused by Eyebrows and Eye Shadow,” Frontiers in Human Neuroscience 9 (March 20, 2015), doi:10.3389/fnhum.2015.00139; S. Matsushita, K. Morikawa, and H. Yamanami, “Measurement of Eye Size Illusion Caused by Eyeliner, Mascara, and Eye Shadow,” Journal of Cosmetic Science 66, no. 3 (2015): 161–74.
4. SHAPE ILLUSIONS
The circle on the left: David Whitaker, Paul V. McGraw, David R. T. Keeble, and Jennifer Skillen, “Pulling the Other One: 1st- and 2nd-Order Visual Information Interact to Determine Perceived Location,” Vision Research 44, no. 3 (2004): 279–86, doi:10.1016/j.visres.2003.09.014; Paul V. McGraw, David Whitaker, Jennifer Skillen, and Susana T. L. Chung, “Motion Adaptation Distorts Perceived Visual Position,” Current Biology 12, no. 23 (Dec. 2002): 2042–47, doi:10.1016/s0960-9822(02)01354-4; Jennifer Skillen, David Whitaker, Ariella V. Popple, and Paul V. McGraw, “The Importance of Spatial Scale in Determining Illusions of Orientation,” Vision Research 42, no. 21 (Sept. 2002): 2447–55, doi:10.1016/s0042-6989(02)00261-4.
a novel variant of the Shepard Tabletop Illusion: Lydia M. Maniatis, “Alignment with the Horizontal Plane: Evidence for an Orientation Constraint in the Perception of Shape,” Perception 39, no. 9 (2010): 1175–84
, doi:10.1068/p6681; Lydia Maniatis, “23: Symmetry and Uprightness in Visually-Perceived Shapes,” in The Oxford Compendium of Visual Illusions, ed. Arthur G. Shapiro and Dejan Todorovi´c (Oxford, U.K.: Oxford University Press, 2017).
discovered this illusion serendipitously: Lydia Maniatis, “24: Bath Tub Illusion,” ibid.
this illusion also works for a face: Rob van Lier and Arno Koning, “The More-or-Less Morphing Face Illusion: A Case of Fixation-Dependent Modulation,” Perception 43, no. 9 (Sept. 2014): 947–49, doi:10.1068/p7704.
Our own research has shown: Y. Chen, S. Martinez-Conde, S. L. Macknik, Y. Bereshpolova, H. A. Swadlow, and J. M. Alonso, “Task Difficulty Modulates the Activity of Specific Neuronal Populations in Primary Visual Cortex,” Nature Neuroscience 11, no. 8 (2008): 974–82.
how overall context affects: Jisien Yang and Adrian Schwaninger, “Yang’s Iris Illusion: External Contour Causes Length-Assimilation Illusions,” Japanese Psychological Research 53, no. 1 (March 2011): 15–29, doi:10.1111/j.1468-5884.2010.00455.x.
The Illusory Pyramid: P. Guardini, “The Illusory Contoured Tilting and Rotating Pyramids,” Teorie e Modelli 3 (2008): 323–34; Pietro Guardini and Luciano Gamberini, “Depth Stratification in Illusory-Contour Figures on Heterogeneous Backgrounds Is Independent of Contour Clarity and Brightness Enhancement,” Perception 37, no. 6 (2008): 877–88; P. Guardini, “The Illusory Contoured Tilting (and Rotating) Pyramid,” in Il Posto della Fenomenologia Sperimentale nelle Scienze della Percezione, Convegno-Workshop Università di Milano, Bicocca, Milano, Feb. 21–22, 2008.
The neural bases of this illusion: Stefano Guidi, Oronzo Parlangeli, Sandro Bettella, and Sergio Roncato, “Features of the Selectivity for Contrast Polarity in Contour Integration Revealed by a Novel Tilt Illusion,” Perception 40, no. 11 (2011): 1357–75, doi:10.1068/p6897; Sergio Roncato and Clara Casco, “A New ‘Tilt’ Illusion Reveals the Relation Between Border Ownership and Border Binding,” Journal of Vision 9, no. 6 (June 1, 2009): 14 (1–10), doi:10.1167/9.6.14; Sergio Roncato and Clara Casco, “Illusory Boundary Interpolation from Local Association Field,” Spatial Vision 19, no. 6 (Nov. 1, 2006): 581–603, doi:10.1163/156856806779194008.
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