Two identical gears, each with eight teeth, rotate at the same speed with their teeth touching as they rotate. When viewers focus on one gear, the other, as seen through peripheral vision, appears to spin faster — though both are moving at the same speed.
This visual trick was revealed Tuesday at the Best Illusion of the Year Contest, sponsored by the Museum of Illusions, headquartered in Zagreb, Croatia, with more than 70 museums globally. A panel of scientists, artists, communicators and previous winners selected the top contenders from several dozen submissions, and thousands of people voted online to determine the winners.
The illusion, called “Cogs in a Machine,” created by Jacky Z.J. Yueh and Joan Danielle K. Ongchoco of Canada, demonstrates that our peripheral vision is more sensitive to motion and speed than our central vision.
“Making sense of the causal connections between objects is not just a task of reasoning. We can also sometimes perceive these connections, as when two discs collide with each other,” the creators note of their illusion.
“If you just look away, the rotating gear will appear to rotate faster than if you look at it directly,” said Susana Martinez-Conde, a neuroscientist at SUNY Downstate Health Sciences University in Brooklyn and one of the contest founders.
The illusion intensifies when the teeth of the two gears are offset. The teeth don’t touch directly when they rotate; instead, they interweave, alternating, between one another. The one seen through the peripheral vision appears to rotate even faster than before.
It is one of 10 illusions chosen as finalists for the contest, now its 20th edition. Martinez-Conde and her partner in life and laboratory, Stephen Macknik, also a neuroscientist at SUNY Downstate, founded the contest to shine a spotlight on the brain mechanisms that shape how we see the world.
Martinez-Conde said the contest features “novel” illusions — illusions for which we don’t yet have a complete understanding.
In “Cogs in a Machine,” Martinez-Conde suggested two factors may be at play. One is that our peripheral vision tends to see objects moving faster than our direct vision.
“Our peripheral vision is more sensitive to motion, due to the kinds of neurons that are activated by movement,” Martinez-Conde said. “ She added, “the neurons that process information from your central visual field are generally more sensitive to form and shape, as opposed to motion.”
She speculated as to why offsetting the teeth intensifies the illusion: Instead of processing eight pairs of teeth during each rotation, our visual system processes 16 separate events. Because our visual system responds strongly to transient changes, particularly sudden ones, this increased frequency of visual events may trick the brain into perceiving faster motion.
How might this play out in everyday life?
“Just navigating the world, whether we’re walking or especially driving at higher speeds, your perception of motion is going to depend on whether you’re looking directly at a moving object versus looking at it out of the corner of your eye with your peripheral vision.”
Why neuroscientists study illusions
Martinez-Conde’s interest in illusions was initially fueled by an interest in the neural mechanisms behind our subjective experience. Understanding the neural mechanisms of perception is not only important to understanding the healthy brain, she said, but also the brain that is suffering from neural injury or neural disease.
“An illusion is a phenomenon in which our subjective perception is different from the objective reality,” Martinez-Conde said. “So understanding how our brains, our neural mechanisms, arrive at that experience tells us a lot about what our brain does in general to construct our experience, our consciousness, and our awareness of ourselves and the world.”
As the contest has evolved over the past 20 years, Martinez-Conde has seen nonscientists, such as artists, become more informed about the psychology and neuroscience of perception. Conversely, scientists have become more interested in introducing an artistic dimension to their perceptual phenomenon.
“There are many different entries to illusions, and one of them is having an aesthetic appreciation,” Martinez-Conde said. “I do believe that there’s a very nice intersection where art and science can meet and blend very wonderfully in an illusion.”
Color perception
Taking second prize is the illusion “9 Purple Dots,” by Hinnerk Schulz-Hildebrandt, an instructor in dermatology at Harvard Medical School. He found his inspiration through a random experience.
“I was looking at a flight map, FlightRadar24, and I was seeing a purple line that seemed to change color depending on my gaze,” he noted with his submission.
Schulz-Hildebrandt describes his illusion as revealing a surprising property of color perception: When purple elements are shown on a bluish background, only the element you directly look at appears purple — while all others shift toward blue. As you move your gaze, the purple spotlight follows your eyes.
Color perception is key.
Martinez-Conde said there are three types of cone cells in the retina that enable color vision in the brain; they are sensitive to red, green and blue wavelengths. But the very center of the retina lacks blue-sensitive cones, which makes it less sensitive to blue light.
“The very dot that you’re looking at appears less blue than the surrounding dots,” she said, “because the center of our vision — which we use to look at the dot — lacks the blue-sensitive cones found elsewhere in the retina.”
The only way we are able to see any color is through the activation of color processing mechanisms in the brain, she added.
“We often think of colors as objective properties of the world, and this is not true,” the neuroscientist explained. “The world does not have color. Color is always a brain construct.”
Questioning beliefs
The third-place winner, “The Hole Truth,” by Matt Pritchard from Britain, demonstrates how a change in perspective can shift truth to falsehood. The same physical object looks completely different depending on your vantage point.
“A sign with cut out letter holes makes a different word when reflected in the mirror. One side reads true, the other false,” Pritchard explained in his submission.
The illusion is called a 3D ambigram — a word that can be read differently depending on the angle. There are shapes that have been printed in black ink, with holes that show a black background on the other side. The shapes are viewed as a whole, due to the very low contrast of the black ink, and the black background. This is enhanced under lower light conditions.
Martinez-Conde said this illusion relies on different perspectives and vantage points and also on how the visual system groups elements together to make sense of what we see.
In this illusion, the brain mistakenly groups parts of the cutouts with parts of the background, creating a misleading perception of the letter shapes.
In everyday life, Martinez-Conde said, we may become very convinced about certain ideas, and we may be completely wrong about them.
“It can be very hard or even impossible to overcome our neural wiring,” she said.
“Exploring illusions and making interesting illusions helps you — maybe gives you some pause — when you encounter certain claims or opinions, even your own opinions, to stop and wonder: Am I absolutely sure this is the complete truth?”
The post How this year’s best optical illusions trick your brain appeared first on Washington Post.
