This illusion is so bizarre that you'll probably call bullshit on it even after you see it explained. Take a look at squares A and B in the above picture. The squares are the exact same shade of gray. Not the letters -- the squares themselves.

We know you don't believe us. Take it into Photoshop -- cut out the "B" square and move it up:

Adrian Pingstone / Edward Adelson via Wikipedia

Now scroll back up and look at the original again. Bullshit, right?

What the Hell?

Every human should have this tattooed onto their arm, just so they don't forget it:

You see with your brain, not your eyes.

Dynamic Graphics Group/Dynamic Graphics

When you observe the world, your eyes aren't just lenses that coldly record whatever is in front of you. Instead, your brain adjusts the image for context from moment to moment. And in this case, it's filtering what you see based on a built-in knowledge of what shadows are.

Your brain understands that the floor is a checkerboard pattern of dark and light squares. It sees that there is an object casting a shadow over it. It knows that square B is still one of the "light" squares, even though it's the same color in the shadow as the dark squares are in the light, so in order to avoid confusion, it automatically adjusts the lightness of square B for you before that s**t reaches your consciousness. It's like you've got an entire Hollywood VFX crew living in your skull, fixing the world in post-production before you actually get to see it. Keep that in mind the next time you hear some eyewitness testimony.

We could give you endless examples of this trickery. Take these two yellow lines, which are exactly the same length:

Most people see the top line as being bigger, obviously because it thinks that one is farther away due to the "tracks." And even beyond the visual, you're unconsciously adjusting the world for context all the time. For example, if you hold a large and small box of equal weight, you will perceive the large box as lighter. Or, if you drink soda after eating cake, it will taste less sweet.

What's amazing is that you cannot unsee or unfeel these illusions despite all of the information to the contrary.

What the Hell?

The blue lines are tricking your brain into believing that you're moving toward the image, in much the same way you use lines in a doodle to show which way something is moving. Your brain interprets lines as motion, like in Star Wars, where we knew they were going fast because the stars turned into a vortex of white lines in their windshield:

Lucasfilm/20th Century Fox

So why are the red lines bulging? Here's where it gets really weird -- that's the way your brain expects them to look in the future.

As we've already mentioned, there's a fair bit of calculation going on in your head from the time the light hits your eyes to the time you actually perceive something. This calculation is super quick, but it still takes time -- about one-tenth of a second. That means that you're actually living one-tenth of a second in the past at any one time. It's like a really s****y superpower.

Agri Press/Lifesize/Getty Images

So why are we still able to dodge fast-moving objects and not getting brained by flying baseballs? Because your brain has that s**t covered. It actually predicts the future and adjusts the world accordingly. The world you're seeing is actually your brain's prediction about what the world will look like one-tenth of a second after you actually perceive it. That is to say, it brings you back to the present.

Because of perspective, two parallel poles will appear to bulge out a tiny bit as you pass between them. Your brain knows this, so it automatically puts that bulge in when it thinks you're hurtling toward the red lines. That's right: Precognition is real, but it only allows you to see into the present.

Here's a picture of President Obama upside-down. You recognize him right away and nothing looks off about him, other than the fact that the image is flipped. Turn him over, though, and you realize you've been lied to. It's actually a terrifying alien parody of a human being.

What the Hell?

Your brain processes visual stimuli in pieces before it makes a whole image. When you look at a face, you see a face. But what your brain sees are pieces of a face -- eyes, nose, and mouth. Each piece of the puzzle is recognized separately, so even if we flip Obama's head over, we don't see anything weird about him as long as his eyes and mouth are the right way up. It doesn't work the other way -- your brain sees an upside-down face on a right-side-up head and just throws its arms up in confusion. Its brain-arms.

Creatas/Creatas/Getty Images

This is due to a flaw in what's called vestibular correction -- it's your eyesight trying to adjust for anything that's weird about how your head is oriented (in this case, seeing it as if you were upside-down). Think of it this way: Why are movies like Cloverfield, with their shaky camera, so headache-inducing? Aren't our eyes whipping around just as much as that camera when we're running, or even just looking quickly around the room? Yes, but under normal circumstances, your brain steadies all of that shaky, unsteady input and gives you one smooth, coherent picture.

And your innate sense of balance tells your subconscious which way is up, so even if you tilt your head to the side, you still see a diamond as a diamond and a square as a square. Try it:

That team of graphic designers living in your head picks out every individual object in your visual field and adjusts them separately so that what you're looking at makes sense, and it does all of this in a fraction of a fraction of a second. But it does it without a ton of attention to detail, which is why a horrible monstrosity can pose as the president just by standing on his head.

Here's one we know you've seen before. This classic illusion dates back to the 1800s, and depicts an old woman and a young woman at the same time. Can't see it? The young woman's jawline is the old woman's nose, and her ear is the old woman's eye.

But here's the key: Try to see both at the same time. You can't, can you? You can only switch from one to the other, no matter how hard you try.

Goodshoot/Goodshoot/Getty Images

What the Hell?

This gets right to the heart of the matter: The act of seeing something is different from the act of recognizing it. They're two separate stages along the surprisingly complicated process of actually perceiving. So you never stop seeing the young woman -- she's always there. But you do stop recognizing her after you focus on the old hag. These two processes are so distinct that the "seeing" part and the "recognizing" part are in two different places in your brain.

One part, the visual cortex, handles the job of rendering the image, calculating color, motion, form, and depth. The other part handles the job of recognizing what you're seeing. So, with the image above, your visual cortex maps out the lines on the screen and then passes the paperwork to a different department, which has to then decide, "OK, so what the hell am I looking at?" It's goddamn brain bureaucracy.

Christopher Robbins/Photodisc/Getty

This can lead to some really strange effects. For example, there are people out there who have suffered damage to the visual cortex and are therefore effectively blind. Like, wearing sunglasses in a photographic darkroom with your eyes closed blind. And yet they can still navigate obstacles, react to motion, and recognize facial expressions. Were they all caught in some kind of chemical accident, like Daredevil? No, they just have a condition called blindsight, where their eyes work perfectly well, but they can't form an image of what they're looking at. But their brain is still taking in the visual information, and they're still subconsciously recognizing things like motion and expression.

Have you ever walked down a crowded street and known that a friend was coming from the other way before you actually saw him? Or sensed motion out of the corner of your eye? That's your blindsight working to decode what's going on around you even when you're not paying attention to it. And if that sounds complicated, just wait ...

It's almost impossible to believe, but these two tables are the same width and length. One has simply been turned around 90 degrees. Go ahead and measure them if you don't believe us. Go ahead and use a different ruler if you think we cast witchcraft on the first one.

Or, just crop out the top of the left table in Photoshop and plop it down on the right:

R Beau Lotto via BBC

R Beau Lotto via BBC

What the Hell?

If you already think it's a bit weird that your brain is free to tell your eyes what they "see," hang on, because it's actually way weirder than that. Your brain has over 30 different sections that deal with different aspects of interpreting visual information, and they each have their own specialized function. Some handle shape, while others handle depth, or color, etc.

The turned tables illusion is just an example of the different parts of your mind disagreeing about what they see -- is it a long thin table, or is it a fat square one? With different parts of your brain putting their own interpretation on it, it's difficult to make up your mind(s).

Keith Brofsky/Photodisc/Getty Images

But hold on a second. If you have multiple mental systems, why do you feel like one person? Why don't you feel like that bickering gang from Herman's Head? Because your brain alters information to make you feel like one person. Seeing two different tables is just the result of your different brain sections coming to a kind of grudging consensus.

And our brains do this all the time. Have you ever jumped because you thought you saw a spider? There was nothing there, but you flipped out anyway. The truth is, you reacted before you even had time to consciously see a spider. Part of your brain, which science refers to as the "HOLY f**k SPIDER cortex," detected the spider threat and inserted that spider right in your visual frame, even though you'd later discover that it was merely a harmless tuft of your roommate's pubic hair.

Jupiterimages/Photos.com/Getty Images

The brain may be bullshitting you, but the alternative would be worse. Without its sweet little lies, your consciousness would remain in pieces. Researchers have observed all sorts of brain-damaged individuals who cannot resolve their internal conflicts (or resolve them very poorly). These patients include stroke victims who insist their paralyzed arms are healthy, and even a patient who believes in God in one hemisphere of his brain and not the other.

So don't feel annoyed that your brain makes you see tables weird sometimes. If it didn't find some middle ground, your life would be a schizophrenic nightmare.

For more reasons your brain is totally unreliable, check out The 5 Strangest Ways Your Mind Can Get Your Body Sick and 5 Mind-Blowing Ways Your Memory Plays Tricks On You.

If you're pressed for time and just looking for a quick fix, then check out 5 Insane Things Supposedly Seen by the Mars Rover.

And stop by LinkSTORM where everything you'll see isn't real.

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Related Reading: For some optical illusions that absolutely are not photoshopped, click here and prepare to be stunned. If you'd like to know more about how your senses lie to you, read this article and learn how your brain predicts the future. To keep your head messed and confused, try this article and then try to forget about the fact that you spend forty minutes per day completely blind.