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What's in the stripes?
Shake your head to see what's in the stripes (Image credit: Dr Michelle Dickinson via Twitter)


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Spinning Discs
No, it's not a GIF but a still image – though the wheels appear to turn in front of your eyes. It happens because of how your eyes process an image, scanning it repeatedly while autofocusing and adjusting. If it feels too much, try concentrating on a single wheel to make it all stop.


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Impossible Trident
The Impossible Trident, clearly has three prongs. Except, well, it doesn't. In fact, the central prong is formed from the empty space between the prisms. When you follow the prongs up to the top, you can see it only has two openings, with the top surface of the furthest prism transforming into the third prong and the surface becoming the empty space.


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Super Illusion Brothers
The "Super Illusion Brothers" depicts a bunch of figures walking up the steps and jumping off the top. Doesn't it? No, it doesn't. Those little green people are actually completely static. This is a 'bright phi' illusion, which plays with our brain's perception of bright objects.

According to Stanford University, this is a "basic effect" whereby "If a bright point appears at one position, and then reappears at a position shifted to the right, we tend to see a single object moving left to right."


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Double Whammy Dots
This one is two illusions in one. Depending on which part of the illusion you look at, the dots around the outside will either change colour or completely vanish. To make the dots change colour, simply follow the light grey spot around for 30 seconds. Eventually, you should be able to see the rest of the dots turn a teal/green shade. And to make them all completely disappear, stare at the cross in the centre of the circle for 30 seconds.

This phenomonon is known as the Troxler Effect, discovered by Swiss physician and philosopher Ignaz Paul Vital Troxler (1780-1866). In 1804, Troxler made the discovery that rigidly fixating one's gaze on some element in the visual field can cause surrounding stationary images to seem to slowly disappear or fade. They are replaced with an experience, the nature of which is determined by the background that the object is on.


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Expanding Black Hole
Scientists have created a flabbergasting optical illusion that makes the viewer feel as if a black hole is getting bigger and is about to engulf them. Whereas in reality, the illusion is just a still image of a black hole surrounded by tiny black dots.

The deceptive image is called the 'expanding hole'. It was created by Akiyoshi Kitaoka, a psychologist from Ritsumeikan University in Osaka, Japan. Kitaoka further studied the image with a team of researchers at the University of Oslo in Norway and discovered that his illusion could affect the dilation of pupils in human eyes. The researchers tested the expanding hole on 50 subjects falling in the age group of 18-40 years and having normal eyesight.

Interestingly, the illusion worked perfectly even when the size or color scheme of the image was changed during the experiments. "The circular smear or shadow gradient of the central black hole evokes a marked impression of optic flow as if the observer were heading forward into a hole or tunnel," Professor Kitaoka told The Sun while explaining how a human eye perceives the image.


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Twelve Black Dots?
There really are 12 black dots in the image. But (most) people can't see all 12 dots at the same time...

In this optical illusion, the black dot in the center of your vision should always appear. But the black dots around it seem to appear and disappear. That's because humans have pretty bad peripheral vision. If you focus on a word in the center of this line you'll probably see it clearly. But if you try to read the words at either end without moving your eyes, they most likely look blurry. As a result, the brain has to make its best guess about what's most likely to be going on in the fuzzy periphery — and fill in the mental image accordingly.

That means that when you're staring at that black dot in the center of your field of view, your visual system is filling in what's going on around it. And with this regular pattern of gray lines on a white background, the brain guesses that there'll just be more of the same, missing the intermittent black dots. Those dots disappear and reappear as your eye jitters around "like a camera that's not being held stably," Arnold says.

There's also another thing that could be going on. If you look at the grid pattern closely, you might be able to see faint white squares where the gray lines meet. That's similar to the dark patches you can see at the intersection of white lines in the Hermann grid illusion. This happens because retinal ganglion cells in the sheet of tissue called the retina at the back of the eye detect contrasts.

"At a non-intersection, you've got a strip of gray line and it's surrounded by a lot of white," Arnold explains. "When you get to an intersection, you've got multiple gray lines intersecting, and not as much white." Because there's less contrast at these intersections with more gray than white, the brain thinks the dot where all the gray lines intersect is lighter than the rest of the gray line, and creates the illusion of a faint white square.


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Vector Illusions by Yurii Perepadia
Miscellaneous illusions by graphic artist Yurii Perepadia, posted on Bored Panda. Stare long enough and things start moving...


From Yurii Perepadia facebook. Stare long enough and things start moving...