Twenty-first-century illusion creators continue to produce printable illusions using still photographs or even just a few lines on paper, but computer and video technologies have made it possible to create increasingly complex moving-picture illusions. This appendix is dedicated to illusions that are best seen on the screen. To view them, visit the Best Illusion of the Year Contest website, http://illusionoftheyear.com.
GROUPING BY CONTRAST
By Erica Dixon, Arthur G. Shapiro, and Kai Hamburger • American University, U.S.A., and University of Giessen, Germany • 2011 Second Prize
This illusion expands on what researchers call the “Gestalt laws,” formulated by German psychologists in the 1920s to describe human perception. It shows that your brain tends to group objects together based on their absolute contrast—here your brain groups blinking dots in different ways, depending on their background.
ILLUSORY GLOSS
By Maarten Wijntjes and Sylvia Pont • Delft University of Technology, The Netherlands • 2010 Finalist
This illusion shows that an object’s surface can look either matte or glossy, depending on the direction of illumination.
SILENCING COLOR
By Jordan Suchow and George Alvarez • Harvard University, U.S.A. • 2011 First Prize
Suchow discovered this illusion when he dropped his laptop and noticed that a scintillating doughnut on the screen appeared to stop moving while the laptop was in midair—a phenomenon called “silencing,” by which our brain suppresses one kind of perception when confronted with another. Here the dots rapidly switch color but appear to stop when the doughnut begins rotating, even though they continue to change the entire time!
CONTRAST COLOR INDUCED BY UNCONSCIOUS SURROUND
By Haruaki Fukuda and Kazuhiro Ueda • University of Tokyo, Japan • 2009 Finalist
A simple children’s top can be a powerful visual neuroscience tool. Here the colored wedges blur into gray when the disk spins—but the black lines take on the opposite color of the wedges in which they are embedded. This color induction happens before your perception fuses the surrounding colors.
By Jason Tangen, Sean Murphy, and Matthew Thompson • University of Queensland, Australia • 2012 Finalist
Tangen and his colleagues caused perfectly normal-looking faces to appear grotesque by aligning them with other faces and displaying each image briefly. The illusion works because your visual system processes each face not as an isolated entity but in comparison with the faces that precede it.
ROTATING BY SCALING
By Attila Farkas and Alen Hajnal • University of Southern Mississippi, U.S.A. • 2013 Finalist
Rigid objects—or those that we expect to be rigid—appear to rotate when they are stretched (scaled) asymmetrically. In a dramatic example, created by the psychologists Attila Farkas and Alen Hajnal, a stationary computer-generated head appears to turn around a vertical axis when one half of the head is stretched and the other compressed.
COUNTERINTUITIVE ILLUSORY CONTOURS
By Barton Anderson • University of Sydney, Australia • 2010 Second Prize
A diamond shape alternately expands and shrinks as disks and dots move back and forth—but the diamond is entirely constructed by your visual system. Anderson’s illusion illustrates the brain’s ability to fill in much of the missing information in a scene, often creating complicated percepts from very simple constituents.
MUTUALLY INTERFERING SHAPES
By Maarten Wijntjes, Robert Volcic, and Tomas Knapen • Utrecht University, The Netherlands • 2008 Finalist
This illusion shows that the perceived trajectory of a dot depends on its position relative to other objects in the world. While an outer dot travels around a circle, an inner dot moves along the straight sides of a square—and yet it appears to follow a trajectory made up of concave curves.
TILT ILLUSION
By Siddharth Jain • U.S.A. • 2009 Finalist
A horizontally moving dot appears to follow a tilted trajectory, when it only shifts down a row. The effect may result from the phenomenon called “persistence of vision,” presented by Peter Mark Roget (who also wrote the famous thesaurus) to the Royal Society of London in 1824 as the ability of the retina to retain an image of an object for a twentieth to a fifth of a second after its disappearance—an illusion that is crucial to animation.
THREE-FOLD CUBES: AN OBJECT WITH THREE DIFFERENT FORM INTERPRETATIONS
By Guy Wallis and David Lloyd • University of Queensland, Australia • 2013 Finalist
The same object can look like two cubes, a single cube with a cube-shaped bite taken out of it, or a concave surface illuminated from below. The brain cannot decide, because each interpretation is equally correct. As a result, our perception cycles endlessly through the possibilities.
THE BAR-CROSS-ELLIPSE ILLUSION
By Gideon Caplovitz and Peter Tse • Dartmouth College, U.S.A. • 2006 Third Prize
Gideon Caplovitz and Peter Tse’s four-way illusion pushes the ambiguity envelope even further. Here the same unique moving object can be seen as a cross-shaped figure morphing nonrigidly in size and shape, an ellipse rigidly rotating behind four square occluders, two independent perpendicular bars rigidly oscillating in depth, or a stationary cross viewed through an elliptical aperture that is rotating rigidly.
TWO SINUSOIDS: SIX PERCEPTIONS IN ONE
By Jan Kremlá∘cek • Charles University in Prague, Czech Republic • 2010 Third Prize
Caplovitz and Tse’s 2006 record of a tetra-ambiguous illusion stood until Kremlá∘cek created his six-in-one sinusoids in 2010. Kremlá∘cek’s illusion combines stationary and moving sinusoids in an animation that can be perceived in any of six different ways, including a rotating double helix, a waving ribbon, or a set of dots bouncing up and down.
ROLLING EYES ON A HOLLOW MASK
By Thomas Papathomas • Rutgers University, U.S.A. • 2008 Third Prize
This hollow mask is concave, but because your brain assumes that all faces are convex, that’s how it appears. Whereas a convex face would look in only one direction, a hollow face seems to look forward when the viewer is directly ahead, but at an angle when the viewer moves sideways. The vision researcher Thomas Papathomas attached three-dimensional eyeballs and a nose ring to a hollow mask; when the mask rotates, the eyeballs and nose ring appear to rotate in the opposite direction.
EXORCIST ILLUSION
By Thomas Papathomas, Tom Grace Sr., Marcel de Heer, and Robert Bunkin • Rutgers University, U.S.A. • 2012 Finalist
Papathomas and his colleagues also created a “hollow body” illusion, with a critical twist: they paired a hollow mask with a nonhollow torso, and vice versa. The sculptures have no moving parts, but when the head-torso composites are rotated, “the effect is a flexible, twisting neck out of a 3-D rigid [body], like in The Exorcist,” Papathomas says. This illusion reveals some of the biases the brain uses to interpret the orientation of faces and bodies. For example, your brain assumes that people’s faces and bodies are lit from above, by the sun. So when you view a hollow mask or body and the lighting orientation appears reversed, so does the rotational direction.
STEREO ROTATION STANDSTILL
By Max Dürsteler • University Hospital Zurich, Switzerland • 2008 Finalist
The wagon wheel shape in this illusion exists solely within stereoscopic space. When it rotates at an angular velocity greater than thirty degrees per second, the turning stutters and skips, and sometimes completely stops, even though it actually rotates smoothly.
TRANSLATION WITH A TWIST
By Jun Ono, Akiyasu Tomoeda, and Kokichi Sugihara • Meiji University, JST, CREST, Japan • 2013 First Prize
Ono, Tomoeda, and Sugihara showed that two identical stationary pinwheels appear to spin in opposite directions when a grid moves across them.
TUSI OR NOT TUSI
By Arthur G. Shapiro and Alex Rose-Henig • American University, U.S.A. • 2013 Second Prize
This illusion takes advantage of the fact that we group individual moving objects into global structures depending on the statistical relation among those objects. Depending on where you focus your attention, you’ll see different kinds of motion.
DANCING DIAMONDS
By Michael Pickard and Alessandro Soranzo • University of Sunderland and Sheffield Hallam University, U.K. • 2013 Finalist
Nothing actually moves in this illusion, though your brain begs to differ. The edges of the diamonds do not move, or even change—it’s the diamonds’ insides that cycle between dark and light—but there is a distinct sense of movement nevertheless. Further, the entire collection of diamonds appears to move as a whole—like objects drawn on an elastic surface that is blowing in the wind—rather than as individual parts.
PIGEON-NECK ILLUSION
By Jun Ono, Akiyasu Tomoeda, and Kokichi Sugihara • Meiji University, JST, CREST, Japan • 2014 Finalist
An object progressing at constant speed in front of a vertical grid of stripes appears to shift backward and forward. The motion is similar to the action of a walking pigeon’s neck.
HYBRID MOTION
By Arthur G. Shapiro and Oliver Flynn • American University, U.S.A. • 2014 Finalist
Shapiro and Flynn’s illusion consists of an array of rectangles that change from yellow to blue to yellow over time. The physical positions of the rectangles never change, but they appear to move in opposite directions, depending on whether the observer is close to the monitor or far from it.
THE WILE E. COYOTE ILLUSION
By Alan Ho and Stuart Anstis • Ambrose University College, Canada; and University of California, San Diego, U.S.A. • 2013 Finalist
Alan Ho noticed that a computer representation of a turning fan blade appeared to spin twice as fast after he doubled its number of blades. Likewise, cartoon animators often draw multiple legs and feet on fast-moving characters, such as Wile E. Coyote, to convey the illusory feeling of speed. Ho and Stuart Anstis showed that increasing the number of orbiting circles around a larger one makes the smaller circles seem to be moving faster, even though their speed remains constant. This illusion has commercial and practical applications for computer games, advertising, and even road safety.
THE LOCH NESS AFTEREFFECT
By Mark Wexler • Université Paris V, France • 2011 Third Prize
This illusion is named for a classic phenomenon known to the ancient Greeks and rediscovered in 1834 by Robert Addams at the Falls of Foyers, the waterfalls that feed Loch Ness in Scotland. Addams noticed that after he stared at the waterfalls for a while, stationary surfaces, such as the rocks and vegetation beside the falling water, appeared to drift upward. In Wexler’s illusion, the viewer stares at a red dot surrounded by a rotating ring of dashes. Suddenly the ring jumps in the opposite direction with a rapid rotation, before continuing to turn slowly in the original direction. Wait—the ring is not really jerking backward, but its elements are simply reassorted at random. The resulting illusory motion is more than a hundred times faster than the motion described by Addams.
COLOR WAGON WHEEL
By Arthur G. Shapiro, William Kistler, and Alex Rose-Henig • American University, U.S.A. • 2012 Third Prize
This illusion was inspired by a classic phenomenon known as the Wagon Wheel Illusion, in which nested circular rows of black disks rotate clockwise but appear to do so counterclockwise. Here some of the disks are colored yellow. The result is a novel and striking illusion: a wheel that spins simultaneously in both directions.
THE STEERABLE SPIRAL
By Peter Meilstrup and Michael Shadlen • University of Washington, U.S.A. • 2010 Finalist
Multiple moving spots—special visual objects called Gabor patches—travel in a spiral toward the center of a circle. Each of them contains a small grating that moves opposite to the spot’s direction of travel. When presented alone, each spot moves in a single, clear direction. But when multiple spots are in close proximity to each other, their internal motion confounds the brain’s movement-detection circuits, and produces the perception of a false direction. The effect is dramatic when you shift your gaze from the center of the spiral to the edge of the screen: the rotation direction reverses, but only in your mind!
MOTION-ILLUSION BUILDING BLOCKS
By Arthur G. Shapiro and Justin Charles • Bucknell University, U.S.A. • 2005 First Prize
A flashing square surrounded by a two-tone alternating frame results in illusory motion. Shapiro and Charles showed that you can combine illusory building blocks of motion to create countless new movement illusions. It’s like illusion Legos of the mind!
TWO-STROKE APPARENT MOTION
By George Mather • Sussex University, U.K. • 2005 Second Prize
This effect alternates two spatially shifted images—with a gray frame between the alternations—to create the illusion of a speeding motorcycle down a country lane. The “jump” between the pictures makes the images appear to move forward, as in a movie.
BACKSCROLL ILLUSION
By Kiyoshi Fujimoto • Kwansei Gakuin University, Japan • 2005 Finalist
An object in the foreground appears to move in one direction, while a flickering grating (or static noise) occupies the background—leading to the perception that the background is moving in the opposite direction to the foreground illusory motion! For example, when an animated cartoon character appears to walk toward the left in the foreground, the flickering background appears to go to the right.
THE WINDMILL ILLUSION
By Baingio Pinna and Massimiliano Dasara • University of Sassari, Italy • 2005 Finalist
The windmill appears to turn, but it is actually stationary. Only the transparency of the middle ring causes your brain to believe that the windmill is moving. As the ring fades in and out of your vision, you are fooled into seeing the windmill turn in both directions.
THE FREEZING ROTATION ILLUSION
By Max Dürsteler • University Hospital Zurich, Switzerland • 2006 First Prize
A foreground object’s motion appears to vary with the rotation of an image in the background.
GRADIENT-OFFSET INDUCED MOTION
By Po-Jang Hsieh • Dartmouth College, U.S.A. • 2006 Finalist
When square-shaped grayscale luminance gradients disappear—all at once—you see ghostly movement that flows from left to right.
THE OCCLUSION VELOCITY ILLUSION
By Evan Palmer and Philip Kellman • Harvard Medical School and University of California, Los Angeles, U.S.A. • 2006 Finalist
When a moving object suddenly splits in half, masking the motion of one of the halves makes the two parts appear misaligned.
WHERE HAS ALL THE MOTION GONE?
By Arthur G. Shapiro and Emily Knight • Bucknell University, U.S.A. • 2007 Third Prize
If you cycle the background luminance behind a stationary gradient from black to white to black (and repeat), you can see illusory motion within the gradient. This motion illusion is strikingly enhanced when the gradient is blurred.
BOUNCING BRAINS
By Thorsten Hansen, Kai Hamburger, and Karl R. Gegenfurtner • University of Giessen, Germany • 2007 Finalist
Some of the brains in this illusion are lighter than the background, and others are darker. As the background luminance is modulated, the brains rotate and bounce. In certain areas of the image, the adjacent brains move in unison, creating an even greater illusory effect.
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.
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 direction, 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.