Optical Illusions raise the question – can we really trust what we see? Neurologists say that the brain evolved to see the world not the way it is, but the way it is useful to see. The best optical illusions challenge our perception of reality and they’re actually interesting because they’re exposing gaps in our brain’s sense of reality. Here are some famous optical illusions you’ve probably seen for years, and their explanations. Does seeing mean believing?
Another Brick in the Wall
What looks different to you in this brick wall?
Ask yourself what the Illusion is. If you missed it we’re going to tell you:
This photo shows a red brick wall with large gaps between the bricks, and a small gray rock stuck in between right above the center of the image. But, it's not a gray rock. There’s a cigar stuck in the wall, sticking out at a 90° angle. Can you see it now?
The picture was taken in a way that makes the cigar aligned with a gap in the bricks, but once you’ve seen it, it cannot be unseen. Apparently, we miss obvious things right in front of our noses all the time don't we?
Try to stare at the cross in the center of this image for 20 seconds, what do you see?
After 20 seconds, you will start to see a green dot circling around, looking like it's erasing the pink dots. If you move your eyes, the pink dots will appear again.
The lilac chaser (AKA The Pac-Man Illusion) is happening because of the effect of negative afterimage. The effect occurs when our perceptual system is trying to fill the gap, and the disappearance of the pink dots creates the appearance of the green one.
The Ebbinghaus Illusion
Which of the orange circles looks bigger to you?
They're actually the same size!
Vision uses context to decide if something is small or just far away. Things that are far will usually be surrounded by other things that look small. Most people who see this image will say that the orange circle on the left is smaller than the one on the right. The illusion uses the fact that our vision relies on context to determine the size of objects. And thus, we examine the orange circle in comparison to those surrounding it. Interestingly, children younger than 7 do not seem to experience the illusion.
The Cornsweet Illusion
Which Lozenge is Darker: The One on Top or the One on the Bottom?
They’re actually the same shade! Put your finger on the white stripe and see for yourself
This illusion here works by contrast. When looking at something we perceive its color relative to other objects in its area and also by how we perceive the way it’s lit. This picture look 3D to us, and the light seems to be coming from the upper left. The upper lozenge is shaded so that it looks tilted away from us, and the bottom one look shaded and tilted to the opposite side. Our brain sees the upper lozenge lit, while the bottom one is shadowed. Combined with the contrasting shading between them, it messes with our brains and we interpret the image wrong.
T-Rex Is Watching
This video is showing a cutout T-rex that seems to turn its head and follow you as you move.
The key to this optical illusion is the way our brain sees perspective, and its ability to see faces in patterns. Our brain wants to interpret the dinosaur as a face, and though its face is actually concave, it seems convex. It sets a contradiction in our brain and thus we think the t-rex is turning to follow us.
Read the text inside the triangle below:
It’s more than likely you said, “A bird in the hand”. If so, you failed to see the second “the” in the sentence.
When we read, our brain usually skims through the whole sentence and does not scan every single word separately. It doesn’t notice the two consecutive “the’s” because we don’t need it to understand the sentence. This automatic process in our brains actually blinds us to unnecessary and superfluous information.
The Negative Photo
Stare at the dots at the center of the woman's face for 30 seconds, then look at a clear wall.
The explanation for this illusion is the effect of “negative afterimage”. It happens because the photoreceptors in our eyes lose sensitivity after staring too long. When we shift our eyes to the wall the overstimulated cells continue to send a weak signal so that the affected colors remain muted but the surrounding photoreceptors are fresh and send out strong signals, as we look at the opposite colors. The brain interprets these signals as the opposite colors and thus creates the colored image from the negative photo.
The Spinning Dancer
Which direction is she turning to?
This video shows a spinning dancer that appears to suddenly change the direction of the spin. It is possible to see the dancer spinning both right and left. You can get her to switch direction by looking at the figure and blinking or focusing on a specific part of her body.
The illusion is related to the bistable perception – an ambiguous 2-dimensional figure can be seen from two different perspectives. There is no third dimension and therefore our brain tries to construct space around the dancer.
The Ponzo Illusion
Which line is longer?
In this illusion, two lines seem to be different sizes, when placed over parallel lines that look like they converge as they are drawn to the distance. The two lines are exactly the same length though the top line appears to be longer than the bottom one.
The top line looks longer because our brain uses linear perspective to interpret the image. The two parallel lines appear to be coming closer as they draw away, and we think that the top line is further in the distance.
In this image, the horizontal lines seem to be slanting, but they’re actually parallel!
It’s rather easy to see the line between two black tiles or two white ones, but much harder to see it between a black tile and a white tile. Our brain fills the gap by seeing it as part of either one of the two colored tiles. It makes the tiles look wider in one end and narrow at the other and creates the illusion of slant lines.
The Barcode Illusion
What do you see when you shake your head?
There’s a man portrait hiding behind the black vertical lines.
If you zoom in you’ll see that there are not just black lines but also pixels with different gray tones in the white areas. When we move our head sideways we perceive the gray tones also. There’s a high contrast between the black lines and the white background and thus we don’t see the mid-tones.
Do you see the vase or the two faces?
This effect shows two shapes' interpretations, but only one of them can be maintained at the same time. It happens because the bounding contour is seen as belonging to the figure shape, which appears against a formless background, or in the other interpretation the same bounding contour is part of it.
Simultaneous Contrast Illusion
Does the bar change its color?
The bar looks eventually graduated, moving from light to dark gray in the opposite direction as the background. But, the bar is actually monochrome (try to cover everything but the bar and you’ll see).
Our brain interprets the two ends of the bar as being under different illuminations and therefore presumes what the bar’s shading should be.
Can you say the color of each word instead of reading it?
Hard isn’t it?
J. Ridley Stroop discovered this phenomenon in the 1930s. The words have a strong influence over our ability to say the color. The interference between the different information your brain receives, what the words say, and the color of the words causes a problem.
It happens because of the speed of processing, in which words are read faster than colors are named, and also because of selective attention, in which the interference occurs because we need to give more attention to naming colors than to reading words.
The Penrose Triangle
If you follow the shape of the triangle (or the ball in this video) you will be able to note how the left side seems to extend away from you, and the right side seems to extend towards you. Yet, they appear to be lying on the same plane and are actually connected by the bottom vertices.
It looks like something that is physically possible, but we know it is not. The shape of the triangle might at first appear feasible, but upon reflection, one can see that it would be physically impossible to construct such a shape
Does the image move in waves?
This image appears to wave and wobble, and it may seem like a camera trick to you at first sight, but it in fact it is just a picture.
The illusion has a simple pattern of light and dark green squares.On every corner of the squares, there is a pink or white shape that looks like a plus sign. Those little symbols on the corners are the thing that makes the picture appear to move.
Look at the black dot, get close to the screen, and then back again. Can you see the rings moving?
The motion-detecting neurons in the brain receive their input from neurons in our visions. They have a small receptive field, so they see as if through a pinhole. These neurons don’t respond directly to motion, but to changes in contrast that are usually caused by motion. So, when the small parallelograms with their white and black edges move across the neurons’ pinhole, each cell sees a shift in contrast and detects a motion.
Look at one yellow dot and see how the rest disappear.
The dots don’t actually disappear but our mind perceives them as they have.
This blindness is a way of separating unchanging background stimuli from 'artifacts of damage.'Motion-induced blindness is not a failure that occurs in order to cope with visual input, but is actually a functional response, acting as 'logic of perception.' Our mind is knowingly eliminating certain objects from view.
The Smaller Cigarette
Are the two cigarettes different sizes?
Like the Ponzo Illusion seen before, this illusion too is using the perspective of the surroundings with two parallel lines. Our brain thinks the cigarette that's further away is bigger, because of the lines getting closer to each other. Unlike the one seen earlier, this is a video so you can actually see that the two cigarettes are the same size if you didn't believe us.
Colors Like You've Never Seen Before
Look at the dot in the center of the picture. Follow the instructions.
Look at this video for 30 seconds and then look up. You're welcome.
It looks like they're trudging along block by block but when you take away the stripes you realize they're going at the same speed and smoothly too. Your brain is just confused by the black and white stripes!
Did you think the car would hit the bars? Good thing it's flat on the ground and not actual poles.
Our head hurts from the image...
Here's another fun color test on your brain to help you see color, check it out!
Have A Seat
Were you also surprised by this eye trick? Well, get ready to see a whole lot more!
Ferris Wheel Magic
Which way does the "London Eye" go?
How many rings can you count?
Pour Some Water
Look closely, and the water will appear to move.
What Does It Say?
Look closely to read the hidden message
Look at this image for 30 seconds, then look at the wall. The lightbulb will appear glowing.
What is going on with this box?
Track The Lines
Can you say which horizontal line is longer?
How many animals can you spot in the image?
What is wrong with this picture?