If you’re still hungry for more, INSIDER rounded up a mix of classic optical illusions, baffling viral photos, and mind-boggling designs that will leave your head spinning and illustrate how our brains process and interpret colour, peripheral vision, size, and more.
One quick note: We’ve included explanations for many of the images, so scroll down slowly if you don’t want to spoil the illusion.
The image above was inspired by the famous illusion 'Rotating Snakes,' created by Japanese psychologist and professor Akiyoshi Kitaoka in 2003.
Both are examples of a peripheral drift illusion, in which we perceive still images as moving ones. Interestingly enough, when you stare at one part of the photo without moving or blinking your eyes, that part stops 'swirling' (while the circles in your peripheral vision continue to 'move').
You can read about the science behind this phenomenon on Business Insider.
This innocent photo of a cat went viral back in 2015 as people wondered whether the animal was going up or down the flight of stairs.
Internet users used everything from architecture to biology to defend their answers to the hotly debated question. INSIDER's Megan Willett, for example, broke down why the cat is 'definitely' going down the stairs -- and after reading her explanation on Business Insider, I'm convinced.
Called the 'checker shadow illusion,' the effect has to do with the way our brains interpret colour and shadow.
As Slate explained, 'your brain is always comparing things.' Square A is surrounded by lighter squares, making it appear darker, while Square B is surrounded by darker squares, making it look lighter. The shadow also 'messes with your perception' and 'amplifies the effect,' Slate added.
If you're still not convinced, open the image in Photoshop, use the Dropper or Colour Picker tool to select the colour in Square A, and draw a straight line to Square B (or vice versa).
MIT also has a great resource that explains the science behind this phenomenon.
Earlier this month, this humble shoe went viral after people started debating whether it was pink and white or grey and teal. It felt like the second coming of The Dress debate from 2015, in which the internet could not agree on the true colour of a bodycon dress.
Just like the photo of The Dress, the original photo of the sneaker was taken in poor lighting with a bluish tint, INSIDER's Susanna Heller explained. Your perception of the shoe's colour depends on your individual sensitivity to the lighting in the image.
Keep reading to learn more about this phenomenon.
In 2015, the debate over the true colour of this dress spawned hundreds of online comments, articles, and even peer-reviewed scientific analyses. People either saw it as black and blue or white and gold -- and both sides were convinced that they were right.
In simplest terms, it all has to do with how your brain processes colour. Basically, light bounces off objects in the world and reaches your eyes in 'a mix of wavelengths,' which your brain then interprets as colour.
As Slate's Pascal Wallisch explained, 'this mix depends on two things: the colour of the object and the colour of the light source. (...) To achieve what colour vision scientists call 'colour constancy,' the brain calculates colour-corrections for an image on the fly. It takes note of the illuminating light and tries to figure out how it might be affecting the colour of an object.'
Since the photo of the dress was taken in poor lighting with a bluish tint, your brain either sees the dress in shadows (and colour-corrects the dress to be white and gold) or in 'a fair amount of illumination' (and perceives the dress as blue and black).
Like 'Rotating Snakes,' this illusion was also created by Japanese psychologist and professor Akiyoshi Kitaoka, who studies visual perception at Ritsumeikan University. Professor Kitaoka shared the photo on Twitter earlier this year.
The colour red has been completely removed from the image, yet people still see red strawberries. Why?
Well, as INSIDER's Jacob Shamsian explained, the brain 'knows that the colour of an object is more useful than the colour of a light source' in determining the colour of an object. Thus, 'it's trained to ignore information' it receives about the colour of a light source. Since your mind recognises that the objects in this photo are strawberries, and it knows that strawberries tend to be red, it colour-corrects the grey and green pixels in the image to be red.
Still confused? Read Shamsian's full explanation here.
First published in 2000 in the academic journal 'Perception' by Jacques Ninio and Kent A. Stevens, this illusion went viral after Professor Kitaoka shared it on Facebook and game designer Will Kerslake reposted it on Twitter.
While you should be able to see any dot you look at directly, the dots in your peripheral vision seem to appear and disappear. Why? Well, in simplest terms, our peripheral vision sucks.
You can read about the science behind this phenomenon here.
Reddit users had a hard time finding the tan-coloured cat, which blended in with the piles of chopped wood.
This floor design by UK-based tile company Casa Ceramica recently went viral on Reddit.
Installed in the entrance to one of the company's showrooms in Manchester, the illusion stops people from running in the hallways.
If that's not trippy enough, the illusion only works when you face the showroom's entrance. The 'dent' in the floor disappears when you look at it from the opposite perspective.
In September, Twitter account @WHS_Carpet -- which specialises in calling out 'bad carpets' -- brought this disorienting photo to the internet's attention. While the floor is completely flat, the carpet's designer added large spaces between certain lines to add depth and create a crater-like effect, INSIDER's Jacob Shamsian explained.
This famous image was named the 'café wall illusion' by psychologist Richard Gregory in the 1970s. It's a classic optical illusion that dates back to the late 1800s. You can learn about the science behind the phenomenon in Gregory's 1979 paper here.
When the image is blurred, you can see that the lines are indeed perfectly parallel and perpendicular to one another.
'Salvator Mundi' is a painting of Jesus Christ that was lost, rediscovered, and identified as a da Vinci work in 2011.
However, some historians are questioning the authenticity of the recovered painting given one particular detail, the Guardian wrote in October.
'Solid glass or crystal, whether shaped like an orb or a lens, produces magnified, inverted, and reversed images,' writer Walter Isaacson explains in his biography of da Vinci. 'Instead, Leonardo painted the orb as if it were a hollow glass bubble that does not refract or distort the light passing through it.'
It's an especially strange choice given the artist's otherwise careful -- and scientifically accurate -- depiction of light in his works. That said, Isaacson, and many others, still believe that the painting is authentic. Perhaps, some have argued, da Vinci intentionally ignored physics in order to highlight Christ's divine powers.
The Guardian article is also now the subject of a legal complaint made on behalf of Christie's International Plc, the auction house that is due to sell 'Salvator Mundi' later this year on November 15.
The neon blue lines make it appear like there is a light blue circle in the middle of this image, but the background is white throughout.
This photo of Kendall Jenner, Kylie Jenner, and Hailey Baldwin went viral earlier this year -- but not for the reason you might think.
If you look closely at Kendall's dress, you can see the outline of her left leg against the orange fabric. As INSIDER's Jacob Shamsian explained, the model is pointing her left knee to her right side and twisting her body around to look directly into the camera.
Discovered in 1979 by Australian psychologist Michael White, this famous effect is known as 'White's Illusion.' Since then, researchers have proposed several theories to explain the cause of this illusion -- you can read about them here.
While the filtered light and air bubbles make it seem like the girl is underwater, a few clues prove that she's not.
As INSIDER's Jacob Shamsian pointed out, her hair is dry, her ponytail isn't floating in the water, and the 'air bubbles' are actually just drops of water.
Discovered by German psychologist Hermann Ebbinghaus, this optical illusion was popularised by British psychology Edward B. Titchener in 1901.
Thus known as the 'Ebbinghaus illusion' or 'Titchener circles,' the effect illustrates how our brain 'uses context to determine the size of objects.' Since the blue circles surrounding the orange circle on the left are so large, the orange circle looks smaller in comparison. Juxtapose that with the tiny blue circles on the right, and the orange circle appears relatively larger.
In case you're interested, this explanation by the Guardian breaks it down further.
It turned out the legs were completely dry.'(I) had some white paint left on my brush and put random lines on my legs,' Culverhouse told INSIDER last year. While the effect was unintentional on Culverhouse's part, the white streaks made it look like a glare of light was reflecting off the student's legs.
INSIDER's Jacob Shamsian broke it down last year. The woman in the middle, outlined in blue, is leaning her torso to her left and her head to her right, so it's hard to tell which pair of legs is hers.
To make things more confusing, the two women on the left are both wearing black jeans. The woman second from the left has one leg completely hidden behind the other women's legs. If you look closely, you can see a sliver of her other leg poking out.
The middle of these shapes look like they're tinted by the light orange outlines, but it's an illusion.
Known as a 'watercolor illusion,' this effect occurs when a white area is surrounded by a thin, brightly-coloured line which is itself surrounded by a thin, darker border.
Scientific American breaks down the science behind this phenomenon here.
The blue diagonal line on the left looks longer than the one on the right, but they're actually the same length.
Created by Meiji University professor Kokichi Sugihara, this illusion was named the 'Best Illusion of the Year' in 2016 by the Neural Correlate Society.
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