When the new book Champions of Illusion: The Science Behind Mind-Boggling Images and Mystifying Brain Puzzles arrived at the Mental Floss offices, we couldn’t flip through it—and flip our brains out—fast enough.
Created by Susana Martinez-Conde and Stephen Macknik, professors of ophthalmology, neurology, physiology, and pharmacology at SUNY Downstate Medical Center in Brooklyn, New York, the book is a fascinating compilation of award-winning images from the Best Illusion of the Year contest, which Martinez-Conde and Macknik first created for a neuroscience conference in 2005. Since then, the contest has produced some truly mind-bending mind tricks that challenge our sense of perception of the world around us. As the authors write:
Your brain creates a simulation of the world that may or may not match the real thing. The “reality” you experience is the result of your exclusive interaction with that simulation. We define “illusions” as the phenomena in which your perception differs from physical reality in a way that is readily evident. You may see something that is not there, or fail to see something that is there, or see something in a way that does not reflect its physical properties.
Just as a painter creates the illusion of depth on a flat canvas, our brain creates the illusion of depth based on information arriving from our essentially two-dimensional retinas. Illusions show us that depth, color, brightness, and shape are not absolute terms but are subjective, relative experiences created actively by our brain’s circuits. This is true not only of visual experiences but of any and all sensory perceptions, and even of how we ponder our emotions, thoughts, and memories. Whether we are experiencing the feeling of “redness,” the appearance of “squareness,” or emotions such as love and hate, these are the result of the activity of neurons in our brain.
Yes, there is a real world out there, and you perceive events that occur around you, however incorrectly or incompletely. But you have never actually lived in the real world, in the sense that your experience never matches physical reality perfectly. Your brain instead gathers pieces of data from your sensory systems—some of which are quite imprecise or, frankly, wrong.
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It’s never been so fun to be wrong. Here are 10 of our favorite images from Champions of Illusion, accompanied by explanations from the book of how and why they work.
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1. “THE COFFER ILLUSION,” ANTHONY NORCIA, SMITH-KETTLEWELL EYE RESEARCH INSTITUTE, U.S.A., 2007 FINALIST
Information transmitted from the retina to the brain is constrained by physical limitations, such as the number of nerve fibers in the optic nerve (about a million wires). If each of these fibers was responsible for producing a pixel (a single point in a digital image), you should have lower resolution in your everyday vision than in the images from your iPhone camera, but of course this is not what we perceive.
One way our visual system overcomes these limitations—to present us with the perception of a fully realized world, despite the fundamental truth that our retinas are low-resolution imaging devices—is by disregarding redundant features in objects and scenes. Our brains preferentially extract, emphasize, and process those unique components that are critical to identifying an object. Sharp discontinuities in the contours of an object, such as corners, are less redundant—and therefore more critical to vision—because they contain more information than straight edges or soft curves. The perceptual result is that corners are more salient than non-corners.
The Coffer Illusion contains sixteen circles that are invisible at first sight, obscured by the rectilinear shapes in the pattern. The illusion may be due, at least in part, to our brain’s preoccupation with corners and angles.
2. “THE ROTATING SNAKES ILLUSION,” AKIYOSHI KITAOKA, RITSUMEIKAN UNIVERSITY, JAPAN, 2005 FINALIST
This illusion is a magnificent example of how we perceive illusory motion from a stationary image. The “snakes” in the pattern appear to rotate as you move your eyes around the figure. In reality, nothing is moving other than your eyes!
If you hold your gaze steadily on one of the “snake” centers, the motion will slow down or even stop. Our research, conducted in collaboration with Jorge Otero-Millan, revealed that the jerky eye motions—such as microsaccades, larger saccades, and even blinks—that people make when looking at an image are among the key elements that produce illusions such as Kitaoka’s Rotating Snakes.
Alex Fraser and Kimerly J. Wilcox discovered this type of illusory motion effect in 1979, when they developed an image showing repetitive spiral arrangements of luminance gradients that appeared to move. Fraser and Wilcox’s illusion was not nearly as effective as Kitaoka’s illusion, but it did spawn a number of related effects that eventually led to the Rotating Snakes. This family of perceptual phenomena is characterized by the periodic placement of colored or grayscale patches of particular brightnesses.
In 2005, Bevil Conway and his colleagues showed that Kitaoka’s illusory layout drives the responses of motion-sensitive neurons in the visual cortex, providing a neural basis for why most people (but not all) perceive motion in the image: We see the snakes rotate because our visual neurons respond as if the snakes were actually in motion.
Why doesn’t this illusion work for everyone? In a 2009 study, Jutta Billino, Kai Hamburger, and Karl Gegenfurtner, of the Justus Liebig University in Giessen, Germany, tested 139 subjects—old and young—with a battery of illusions involving motion, including the Rotating Snakes pattern. They found that older people perceived less illusory rotation than younger subjects.
3. “THE HEALING GRID,” RYOTA KANAI, UTRECHT UNIVERSITY, THE NETHERLANDS, 2005 FINALIST
Let your eyes explore this image freely and you will see a regular pattern of intersecting horizontal and vertical lines in the center, flanked by an irregular grid of misaligned crosses to the left and right. Choose one of the intersections in the center of the image and stare at it for 30 seconds or so. You will see that the grid “heals” itself, becoming perfectly regular all the way through.
The illusion derives, in part, from “perceptual fading,” the phenomenon in which an unchanging visual image fades from view. When you stare at the center of the pattern, the grid’s outer parts fade more than its center due to the comparatively lower resolution of your peripheral vision. The ensuing neural guesstimates that your brain imposes to “reconstruct” the faded outer flanks are based on the available information from the center, as well as your nervous system’s intrinsic tendency to seek structure and order, even when the sensory input is fundamentally disorganized.
Because chaos is inherently unordered and unpredictable, the brain must use a lot of energy and resources to process truly chaotic information (like white noise on your TV screen). By simplifying and imposing order on images like this one, the brain can reduce the amount of information it must process. For example, because the brain can store the image as a rectilinear framework of white rows and columns against a black background—rather than keeping track of every single cross’s position—it saves energy and mental storage space. It also simplifies your interpretation of the meaning of such an object.
4. “MASK OF LOVE,” GIANNI SARCONE, COURTNEY SMITH, AND MARIE-JO WAEBER, ARCHIMEDES LABORATORY PROJECT, ITALY, 2011 FINALIST
This illusion was discovered in an old photograph of two lovers sent to Archimedes’ Laboratory, a consulting group in Italy that specializes in perceptual puzzles. Gianni Sarcone, the leader of the group, saw the image pinned to the wall and, being nearsighted, thought it was a single face. After putting on his eyeglasses, he realized what he was looking at. The team then superimposed the beautiful Venetian mask over the photograph to create the final effect.
This type of illusion is called “bistable” because, as in the classic Face/Vase illusion, you may see either a single face or a couple, but not both at once. Our visual system tends to see what it expects, and because only one mask is present, we assume at first glance that it surrounds a single face.
5. “AGE IS ALL IN YOUR HEAD,” VICTORIA SKYE, U.S.A., 2014 FINALIST
The magician, photographer, and illusion creator Victoria Skye was having a hard time taking a picture of a photo portrait of her father as a teen. The strong overhead lighting was ruining the shot, so she tilted the camera to avoid the glare, first one way and then the other. As she moved her camera back and forth, she saw her father morph from teen to boy and then to adult.
Skye’s illusion is an example of anamorphic perspective. By tilting her camera, she created two opposite vanishing points, producing the illusion of age progression and regression. In the case of age progression, the top of the head narrows and the bottom half of the face expands, creating a stronger chin and a more mature look. In the case of age regression, the opposite happens: the forehead expands and the chin narrows, producing a childlike appearance.
Skye thinks that her illusion may explain why, when we look at ourselves in the mirror, we sometimes see our parents, but not always. “I wonder if that is what happens to me when I look in the mirror and see my mom. Do I see her because I tilt my head and age myself just as I did with the camera and my dad?” she asked.
