A face or a peacock?

Optical illusions are a wondrous thing, showing how differently people’s brains process imagery. Some people see one image, and others see both, their brains switching between the two simultaneously. The way these illusions work is more to do with how your brain processes information, rather than how your eyes work.
How many legs does the elephant have?

We all know elephants only have four legs but this optical illusion can make it seem as though there’s more. Some people even see eight! In truth, the artist purposely used empty space to play tricks on our eye – there truly are only four legs. Still confused? Cover up the elephant’s feet.
Scintillating grids

This effect is amazing because of how fast it makes your eyes move. For a second you’re truly convinced the white dots have black spots on them, but the visual cat-and-mouse game is endless. The pattern is quite common in older kitchen and bathroom designs that use filler between tiles. In case you want the most annoying shower ever.
Young or old?

What do you see? A young woman looking over her shoulder, or an old woman looking to the side? If you can’t see the elderly lady, look at it this way – the necklace is the woman’s mouth, and the ear is the old woman’s eye, with a big nose doubling up as the younger woman’s side profile.
Shake till done

The best optical illusions are the ones that work easily, and it doesn’t take your brain a second to adjust and confuse you. Very carefully shake your head from side to side! Your brain doesn’t process all the visual information it receives from the eyes, blurring things together in a ‘good enough’ sort of way. Your treat for breaking your brain is a cuddly pal.
Spinning vortex illusion

This image never seems to sit still no matter how much your brain tries to make it. It works by over-stimulating the brain with its mixture of curves and combination of banana-grape tones. The elevation changes are also quite a lot for the eye to handle, but staring at the center should stop it from shimmying.
3d sphere illusion

Scrolling down past this illusion you might have thought your phone was loading a message from the overlords, but it’s a pretty standard two-dimensional image! The crossing line directions and black-and-white block patterns make it difficult to focus on the entire picture all at once. When stationary, the circle appears to bulge out, when in motion it looks quite ominous.
Spin me right round

This early 90s desktop nightmare is pure sensory overload, with a towering spire that wraps around to from itself. The neon color pallet assaults the retinas in the most radical way, as the texture and layers create the impression that whatever impossible world you’re trapped in is spinning on its axis.
Parallel lines

This piece is visually reminiscent of barbed wire across the snow, which with enough patience and the right weather you could easily make at home. All lines on the page are actually parallel, but the jagged, slashing lines confuse the eye as it tries to parse the space between each one.
The magic eye

What makes this spooky eye so fascinating is how stationary it looks when casually observing it. If enough of the image is covered, you might not even notice anything amiss. Stare the yellow devil in the eye though and you’ll see wonderful shimmers of purple, spiraling through the zebra print exterior.
Spinning and pulsing

This example shows how easy it is to warp your own perception. Many of the first optical illusions were in black and white because it doesn’t take much information for the brain to panic. Keep your eyes locked right in the center and slowly move your head around, as parts come in and out of focus, the striped pulse.
So many oreos

Another piece using the principle of just having too much stuff to focus on, these hypnotizing cylinders might throb, roll clockwise or counterclockwise, or even do both at once. Bursts of color from black and white images are a bizarre phenomenon, showing us that, regardless of the awesome power of the human brain, we’re not perfect.
Flipping men, ey?

Simple illusions like this are the bread and butter of caricaturists and newspaper comic artists. They’re usually accompanied by a prompt to be part of the 2% of people smart enough to see the secret, which is just mean and elitist so spoilers; Flip him upside down. There you’re a genius now, go out and save the world after you share this on Facebook.
Dr Angry and Mr Calm

This real-life Jekyll and Hyde situation was created by two scientists to test how facial perception can be influenced. By moving away from the image, the faces change to each other’s expressions! It’s done by overlapping them with both faces, only with different amounts of information on various frequencies, that our eyes adjust to with distance.
Clops or hops?

First and foremost, creating illusions on a computer is quite easy, you can control everything down to the pixel, wipe mistakes instantly and save and return whenever you wish. This pencil sketch went viral for the strength of its illusion and artistic creativity, but no artist has ever been identified. If you’re struggling, look at it like a confused dog.
All aboard

This demonstrates one of the fundamental ideas behind how optical illusions work. The Ponzo illusion as seen above features two red lines that almost certainly look different lengths, with the top being longer. Both lines are the same size, but the linear nature of the perspective makes it difficult to tell, as the top looks further away.
Kanizsa triangle

On top of being a great design for a cult about space, this is also an example of how our brain tries to fill in negative space. Although there is no triangle in the center, it’s only implied by the lack of a triangle, your eyes pick up the contextual information surrounding it and can’t help but tell you there is a triangle there.
Please stay still

Truly one of the most infuriating images on the internet. Regardless of where the eye settles, the rest of the image starts acting like someone put Earth, Wind and Fire on the playlist. The colors used beneath each individual dot act like highlights and shadows, which create the illusion of a 3-d image, the eye struggles to keep track of the orientation of each one.
Self-repairing wall

Created by a Japanese neuroscientist, this crooked grid will start fixing itself as you fixate on the center. This is thought to happen because the brain tends to order so, as you focus, your peripherals are filled in and you see something close to what your brain expects to see.
Simple and effective

It might look like the background from a PlayStation One game menu, but fortunately, it has the interactivity of one too. Look in the center and slowly move your face closer to the screen (careful not to bump your face!) and notice how the gradient in the middle suddenly blooms out to the entire image!
Big dot, small dot

Another classic from the early internet, this had people scratching their heads before their dial-up modems had even finished loading the image. Scale is difficult to judge without proper visual context. This piece uses intentionally mismatching sizes with the blue spots, which makes it look as though one of the central circles is bigger than the other.
Life in watercolor

These charming little splodges take advantage of something called the watercolor effects. It looks as though they have been shaded in around the edges, but in fact, the shapes only have colored outlines. By using two complimenting colors, the brain fills in the rest of the shape with a gentle gradient.
Hold on – I’m spiralling!

This hypnotic spiral is actually nothing of the sort. The image shows a series of concentric circles that simply get smaller as they reach the middle, but the overlapping colors of the gingham-like background stop the eye from perceiving them as such. Trace a few of the circles with your finger and find out!
O, Christmas tree

Color is one of the easiest ways to engage the mind, we think about complimenting colors all the time when creating things, since the brain finds certain combinations pleasing and easy to look at. Here, it might look as though the Christmas trees are two different shades of green, but they’re the same.
Pivot… Pivot…PIVOT

Perspective and depth are difficult to judge in two-dimensional space, as this image proves. By skewing the tables at precise angles, it seems impossible that they are the same size. You would swear the left is lengthy and the right is girthy, but the plank of wood fits perfectly over both.
Hidden text

At the distance you’re probably reading this article, this picture may just look like a series of blocks and shapes. Put some distance or distortion between you and the image, however, and you see it has been specifically designed to contain text in its negative space!
Side-eyeing

Other than being just a little bit cursed, this effect shows how blur and shadows can imply details that aren’t really there. On the left, it appears as though the woman is looking to the side, but the un-blurred image reveals she was Medusa the entire time. The secret to beating her isn’t a mirrored shield – just being short-sighted!
Checkered bulge

You know how this works by this point, there is no bulge in the middle of the left image and your brain is just turning to mush from having to process so many things designed to upset it. Regardless, it’s astonishing how effective the placement of the dots is in creating a sense of depth and curvature on the checkerboard.
Criss-crossing colors

Another example of color changing your perception, take a look at the grid lines and see what color you think they are. The top left is reddish, below that they look green. They’re all the same color, a dull grey, but the lovely pastel backgrounds make them appear a different tone. Utterly magical.
The floating square

The detail and fidelity of a picture have a lot to do with how we perceive it. When shapes have white and black sides, we can’t help but try and judge depth since it looks like shadows and highlights. That’s what makes this cube pop, seeming to float above the minefield of spiky diamonds.
All snakes, no ladders

This is a spruced-up version of one of the most classic optical illusions on the internet. The famous spinning snakes are one of the most powerful moving still images you can find, and this version enhances it by understanding what makes it work. By enhancing brightness and adding colors for a chromatic shift effect, the snakes never seemed so funky.
Count the dots

Sound easy? Well, it pretty much is, there are only 12. You’ll notice though that it’s incredibly difficult to see all of them at once. Focus on one of the corner dots and try to catch the opposite one in your peripheral vision. It’s not exactly clear how this phenomenon works, but we know our eyes process information imperfectly, especially outside of our focus.
Hay, what’s going on here?

Another classic from the pre-internet era, this illustration is famous for stumping, or hoofing rather, pretty much everyone who sees it. Officially there are seven horses in the image, though many people contend there are only five. It’s humbling that, even before social media, people would tell artists they were wrong about their work.
Mixed messages

Be honest here because scientists say the first thing you read determines absolutely everything about your love life, career ambitions, and choice of pizza topping. That’s a joke, it’s more of a simple graphic design trick if anything. The way the brain can shift between the readings for a few seconds, making the other text seems impossible to see, is impressive.
Nod along

Time for some more interaction! As per usual, stare at the black dot in the middle, then rock your head back and forth like you’re watching the Bohemian Rhapsody scene from Wayne’s World at about 40% speed. You’ll notice that, depending on the motion, the two circles spin in opposite directions in time with your movement.
Spot the splotches

This is easier to spot for women, to the point it might not even look like an optical illusion. It can take a while but once you see through the little splotches and get to the text, you’ll wonder how you ever even missed it in the first place.
Scene or portrait

This wonderful little illustration uses perspective and its black-and-white palette to create two pictures that can flicker back and forth with a little dart of the eye. The Native American man’s eye line sits on the back of the Inuit’s head, so by looking to the right means seeing the hood contrasted against the cave. A simple but lavishly detailed piece.
Eye eye, Captain

While more of a puzzle than an illusion, the effort put into creating the effect of the sails slowly morphing into clouds as the horizon expands and the pillars appear is worthy of appreciation. Try and spot which ship in the sequence is the final one before it becomes only cloud! And yes, there’s a correct answer.
Make it disappear

As simple as they come and still pretty astounding, this one probably works best on your phone. First, look at it from afar and notice the small dark area of the gradient around the dot. Now move your face closer and focus on that spot. You should see the darker area start to disappear before vanishing entirely if you manage to stay concentrated.
Back to school

This illusion is most commonly seen in mathematics class since it’s easy to draw and they have to do something to make math interesting. The diagonal line through the left parallelogram looks much longer than the one opposite, but they’re exactly the same size. You were probably taught why and forgot it, so you’ve failed the one instance in life math would have been useful.