10 Award-Winning Optical Illusions and Brain Puzzles

"The Spinning Disks Illusion"
"The Spinning Disks Illusion"
Used by permission of Johannes Zanker

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.

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.

1. "THE COFFER ILLUSION," ANTHONY NORCIA, SMITH-KETTLEWELL EYE RESEARCH INSTITUTE, U.S.A., 2007 FINALIST

coffer illusion by Anthony Norcia, Stanford University
"Coffer Illusion"
Used by permission of Anthony Norcia, Stanford University

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

"The Rotating Snakes Illusion"
Used by permission of Akiyoshi Kitaoka

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

healing grid illusion by Ryota Kanai
"The Healing Grid"
Used by permission of Ryota Kanai

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

mask of love by Gianni Sarcone, Courtney Smith, and Marie-Jo Waeber
"Mask of Love"
Courtesy of Gianni Sarcone, Courtney Smith, and Marie-Jo Waeber. Copyright © Gianni A. Sarcone, giannisarcone.com. All rights reserved.

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

age is all in your head illusion by Victoria Skye
"Age Is All in Your Head"
Used by permission of Victoria Skye

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.

6. "THE ROTATING-TILTED-LINES ILLUSION," SIMONE GORI AND KAI HAMBURGER

rotating tilted lines illusion by Simone Gori and Kai Hamburger
"The Rotating-Tilted-Lines Illusion"
Used by permission of Simone Gori and Kai Hamburger

To experience the illusion, move your head forward and backward as you fixate in the central area (or, alternatively, hold your head still and move the page). As you approach the image, notice that the radial lines appear to rotate counterclockwise. As you move away from the image, the lines appear to rotate clockwise. Vision scientists have shown that illusory motion activates brain areas that are also activated by real motion. This could help explain why our perception of illusory motion is qualitatively similar to our perception of real motion.

7. "PULSATING HEART," GIANNI SARCONE, COURTNEY SMITH, AND MARIE-JO WAEBER, ARCHIMEDES LABORATORY PROJECT, ITALY, 2014 FINALIST

Pulsating Heart illusion by Gianni Sarcone, Courtney Smith, and Marie-Jo Waeber
"Pulsating Heart"
Courtesy of Gianni Sarcone, Courtney Smith, and Marie-Jo Waeber. Copyright © Gianni A. Sarcone, giannisarcone.com. All rights reserved.

This Op Art–inspired illusion produces the sensation of expanding motion from a completely stationary image. Static repetitive patterns with just the right mix of contrasts trick our visual system's motion-sensitive neurons into signaling movement. Here the parallel arrangement of opposing needle-shaped red and white lines makes us perceive an ever-expanding heart. Any other outline delimited in a similar fashion would also appear to pulsate and swell.

8. "GHOSTLY GAZE," ROB JENKINS, UNIVERSITY OF GLASGOW, UK, 2008 SECOND PRIZE

ghostly gaze illusion by Rob Jenkins
"Ghostly Gaze"
Used by permission of Rob Jenkins

Not knowing where a person is looking makes us uneasy. That's why speaking with somebody who is wearing dark sunglasses can be awkward. And it is why someone might wear dark sunglasses to look "mysterious." The Ghostly Gaze Illusion, created by Rob Jenkins, takes advantage of this unsettling effect. In this illusion, twin sisters appear to look at each other when seen from afar. But as you approach them, you realize that the sisters are looking directly at you!

The illusion is a hybrid image that combines two pictures of the same woman. The overlapping photos differ in two important ways: their spatial detail (fine or coarse) and the direction of their gaze (sideways or straight ahead). The images that look toward each other contain only coarse features, whereas the ones that look straight ahead are made up of sharp details. When you approach the pictures, you are able to see all the fine detail, and so the sisters seem to look straight ahead. But when you move away, the gross detail dominates, and the sisters appear to look into each other's eyes.

9. "ELUSIVE ARCH," DEJAN TODOROVIC, UNIVERSITY OF BELGRADE, SERBIA, 2005 FINALIST

Elusive Arch illusion by Dejan Todorovic
"Elusive Arch"
Used by permission of Dejan Todorovic

Is this an image of three shiny oval tubes? Or is it three pairs of alternating ridges and grooves?

The left side of the figure appears to be three tubes, but the right side looks like a corrugated surface. This illusion occurs because our brain interprets the bright streaks on the figure's surface as either highlights at the peaks and troughs of the tubes or as inflections between the grooves. Determining the direction of the illumination is difficult: it depends on whether we consider the light as falling on a receding or an expanding surface.

Trying to determine where the image switches from tubes to grooves is maddening. In fact, there is no transition region: the whole image is both "tubes" and "grooves," but our brain can only settle on one or the other interpretation at a time. This seemingly simple task short-circuits our neural mechanisms for determining an object's shape.

10. "FLOATING STAR," JOSEPH HAUTMAN / KAIA NAO, 2012 FINALIST

floating star illusion by Joseph Hautman, aka Kaia Nao
"Floating Star"
Used by permission of Joseph Hautman, aka Kaia Nao. Copyright © Kaia Nao

This five-pointed star is static, but many observers experience the powerful illusion that it is rotating clockwise. Created by the artist Joseph Hautman, who moonlights as a graphic designer under the pseudonym "Kaia Nao," it is a variation on Kitaoka's Rotating Snakes Illusion. Hautman determined that an irregular pattern, unlike the geometric one Kitaoka used, was particularly effective for achieving illusory motion.

Here the dark blue jigsaw pieces have white and black borders against a lightly colored background. As you look around the image, your eye movements stimulate motion-sensitive neurons. These neurons signal motion by virtue of the shifting lightness and darkness boundaries that indicate an object's contour as it moves through space. Carefully arranged transitions between white, light-colored, black, and dark-colored regions fool the neurons into responding as if they were seeing continual motion in the same direction, rather than stationary edges.

5 Signs Humans Are Still Evolving

Lealisa Westerhoff, AFP/Getty Images
Lealisa Westerhoff, AFP/Getty Images

When we think of human evolution, our minds wander back to the millions of years it took natural selection to produce modern-day man. Recent research suggests that, despite modern technology and industrialization, humans continue to evolve. "It is a common misunderstanding that evolution took place a long time ago, and that to understand ourselves we must look back to the hunter-gatherer days of humans," Dr. Virpi Lummaa, a professor at the University of Turku, told Gizmodo.

But not only are we still evolving, we're doing so even faster than before. In the last 10,000 years, the pace of our evolution has sped up, creating more mutations in our genes, and more natural selections from those mutations. Here are some clues that show humans are continuing to evolve.

1. Humans drink milk.

Historically, the gene that regulated humans' ability to digest lactose shut down as we were weaned off our mothers' breast milk. But when we began domesticating cows, sheep, and goats, being able to drink milk became a nutritionally advantageous quality, and people with the genetic mutation that allowed them to digest lactose were better able to propagate their genes.

The gene was first identified in 2002 in a population of northern Europeans that lived between 6000 and 5000 years ago. The genetic mutation for digesting milk is now carried by more than 95 percent of northern European descendants. In addition, a 2006 study suggests this tolerance for lactose developed again, independently of the European population, 3000 years ago in East Africa.

2. We're losing our wisdom teeth.

Our ancestors had much bigger jaws than we do, which helped them chew a tough diet of roots, nuts, and leaves. And what meat they ate they tore apart with their teeth, all of which led to worn-down chompers that needed replacing. Enter the wisdom teeth: A third set of molars is believed to be the evolutionary answer to accommodate our ancestors' eating habits.

Today, we have utensils to cut our food. Our meals are softer and easier to chew, and our jaws are much smaller, which is why wisdom teeth are often impacted when they come in — there just isn't room for them. Unlike the appendix, wisdom teeth have become vestigial organs. One estimate says 35 percent of the population is born without wisdom teeth, and some say they may disappear altogether.

3. We're resisting infectious diseases.

In 2007, a group of researchers looking for signs of recent evolution identified 1800 genes that have only become prevalent in humans in the last 40,000 years, many of which are devoted to fighting infectious diseases like malaria. More than a dozen new genetic variants for fighting malaria are spreading rapidly among Africans. Another study found that natural selection has favored city-dwellers. Living in cities has produced a genetic variant that allows us to be more resistant to diseases like tuberculosis and leprosy. "This seems to be an elegant example of evolution in action," says Dr. Ian Barnes, an evolutionary biologist at London's Natural History Museum, said in 2010 statement. "It flags up the importance of a very recent aspect of our evolution as a species, the development of cities as a selective force."

4. Our brains are shrinking.

While we may like to believe our big brains make us smarter than the rest of the animal world, our brains have actually been shrinking over the last 30,000 years. The average volume of the human brain has decreased from 1500 cubic centimeters to 1350 cubic centimeters, which is an amount equivalent to the size of a tennis ball.

There are several different conclusions as to why this is: One group of researchers suspects our shrinking brains mean we are in fact getting dumber. Historically, brain size decreased as societies became larger and more complex, suggesting that the safety net of modern society negated the correlation between intelligence and survival. But another, more encouraging theory says our brains are shrinking not because we're getting dumber, but because smaller brains are more efficient. This theory suggests that, as they shrink, our brains are being rewired to work faster but take up less room. There's also a theory that smaller brains are an evolutionary advantage because they make us less aggressive beings, allowing us to work together to solve problems, rather than tear each other to shreds.

5. Some of us have blue eyes.

Originally, we all had brown eyes. But about 10,000 years ago, someone who lived near the Black Sea developed a genetic mutation that turned brown eyes blue. While the reason blue eyes have persisted remains a bit of a mystery, one theory is that they act as a sort of paternity test. “There is strong evolutionary pressure for a man not to invest his paternal resources in another man’s child,” Bruno Laeng, lead author of a 2006 study on the development of blue eyes, told The New York Times. Because it is virtually impossible for two blue-eyed mates to create a brown-eyed baby, our blue-eyed male ancestors may have sought out blue-eyed mates as a way of ensuring fidelity. This would partially explain why, in a recent study, blue-eyed men rated blue-eyed women as more attractive compared to brown-eyed women, whereas females and brown-eyed men expressed no preference.

Now Ear This: A New App Can Detect a Child's Ear Infection

iStock.com/Techin24
iStock.com/Techin24

Generally speaking, using an internet connection to diagnose a medical condition is rarely recommended. But technology is getting better at outpacing skepticism over handheld devices guiding decisions and suggesting treatment relating to health care. The most recent example is an app that promises to identify one of the key symptoms of ear infections in kids.

The Associated Press reports that researchers at the University of Washington are close to finalizing an app that would allow a parent to assess whether or not their child has an ear infection using their phone, some paper, and some soft noises. A small piece of paper is folded into a funnel shape and inserted into the ear canal to focus the app's sounds (which resemble bird chirps) toward the child’s ear. The app measures sound waves bouncing off the eardrum. If pus or fluid is present, the sound waves will be altered, indicating a possible infection. The parent would then receive a text from the app notifying them of the presence of buildup in the middle ear.

The University of Washington tested the efficacy of the app by evaluating roughly 50 patients scheduled to undergo ear surgery at Seattle Children’s Hospital. The app was able to identify fluid in patients' ears about 85 percent of the time. That’s roughly as well as traditional exams, which involve visual identification as well as specialized acoustic devices.

While the system looks promising, not all cases of fluid in the ear are the result of infections or require medical attention. Parents would need to evaluate other symptoms, such as fever, if they intend to use the app to decide whether or not to seek medical attention. It may prove most beneficial in children with persistent fluid accumulation, a condition that needs to be monitored over the course of months when deciding whether a drain tube needs to be placed. Checking for fluid at home would save both time and money compared to repeated visits to a physician.

The app does not yet have Food and Drug Administration (FDA) approval and there is no timetable for when it might be commercially available. If it passes muster, it would join a number of FDA-approved “smart” medical diagnostic tools, including the AliveKor CardiaBand for the Apple Watch, which conducts EKG monitoring for heart irregularities.

[h/t WGRZ]

SECTIONS

arrow
LIVE SMARTER