Optical illusions are created through color, contrast, shape, size, patterns and perspective and trick our brains. But how exactly does this happen? Why do straight lines appear oblique, and the same line segments are different in length?
Optical deceptions, different realities and the behavioral benefits of visual errors: Neurologist Bo Lotto explains how the brain creates visual illusions (optical illusions) and why the world is not really what it seems.
Take a close look at the floor tiles in the picture below. First, focus on the tile directly below the houseplant, in the shadow of the table. Then look at the tile on the right, which is off the table.
Which one is brighter? Left?
Alas! In fact - as you can see in the image below - the colors of the tiles are identical. This trick is known as the illusion of brightness. We perceive an object against a light background as darker, in contrast to the same object against a dark background. This optical illusion occurs because our visual systems are tuned to perceive contrasts that help us distinguish between shapes (such as an advancing predator). It turns out that we do not always see things as they are.
As a neuroscientist who studies illusions at University College London, Bo Lotto knows all about the ways in which the brain deceives us, distorts reality for our evolutionary advantage. Nautil.us journalist Claire Cameron talked to him about fraudulent perception and tried to figure out if we could ever see the world as it is.
The beautiful thing that visual illusions and optical illusions teach us is that everything we do is based on assumption.
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KK: What did the illusion of brightness tell us about how we see?
B. L.: Everything we do is connected with our perception. Our experience of ourselves, other people, the world - everything that we think about, what we believe, what we understand, begins with perception. And brightness is a simple mode of visual perception, the function of which is limited to a simple one - to see light. The illusion of brightness tells us that even at the most basic level, we cannot see everything. The brain has not developed to the ability to see something absolute. It has evolved to acquire the ability to see relationships and to look, which is more behaviorally useful. If it works with luminosity, it must be true for a variety of things, down to abstract concepts.
KK: Do you mean that we learn to navigate the world by recognizing patterns?
B. L.: Yes and no. The main problem is that our brains have evolved to deal with uncertainty - the ambiguity of information. Information doesn't tell us about itself; she doesn't tell us what to do. So the first thing the brain does when you look at images is to find a pattern, which is nothing more than a statistical relationship. A pattern, a pattern, by itself, has no meaning - just like the meaningless image you are looking at. And you have no instructions on what to do. But as you interact with the world, you create either "good behavior" that allows you to stay alive or "bad behavior" that leads to death. And your brain associates behavioral meanings with the pattern. This is the behavioral benefit that you see. Or it could be a behavioral benefit,which your ancestors saw long before you. As humans, we are coded by our cultural history as well as our evolutionary history.
KK: But can we find evidence of this encoding in the human brain?
B. L.: Unfortunately, we know almost nothing about how it all works mechanically. We use bumblebees as a model because their brains contain roughly a million cells compared to our billions. And they see the same visual illusions that we see. Although the mechanisms may be different, the principles will remain the same. If we can understand the principles, we can understand mechanisms and apply them to other systems, such as robots.
KK: You've created a wearable device called LumaKey that converts light into sound. What for?
B. L.: We wanted to create a new kind of experience that could be recorded. The physical structure of sound is very different from the physical structure of light. When we translate light into sound, the brain also receives visual information, and we can see how the speaker system creates this sensation. The question is this: can people begin to "hear" visual illusions? This is one of the reasons why we created LumaKey. Another reason is that it is potentially a great way to compose music.
K. K.: Is it possible to change our perception?
B. L.: I think so. The beautiful thing that visual illusions and optical illusions teach us is that everything we do is based on assumption. If you look at an illusion without knowing that it is an illusion, you experience a sense of reality. But as soon as I show you that this is an optical illusion, your brain starts doing something amazing: It holds onto two realities that are at the same time mutually exclusive. The two tiles look different, but I know they are the same. Conceptually, this is not much different from the meaning of the phrase "I experience one reality today, but I can imagine a different reality tomorrow." And the only way to learn to see differently is to realize it.
Why optical illusions trick our brains
People have been familiar with optical illusions for thousands of years. The Romans made 3D mosaics to decorate their homes, the Greeks used perspective to build beautiful pantheons, and at least one stone figurine from the Paleolithic era depicts two different animals that can be seen depending on the point of view.
A lot can get lost on the way from your eyes to your brain. In most cases, this system works fine. Your eyes move rapidly and almost imperceptibly from side to side, delivering scattered pictures of what is happening to your brain. The brain organizes them, determines the context, putting the pieces of the puzzle into something that makes sense.
For example, you are standing on a street corner, cars are passing through a pedestrian crossing, and the traffic light is red. Pieces of information add up to the conclusion: now is not the best time to cross the street. Most of the time this works great, but sometimes, even though your eyes are sending visual signals, the brain makes a mistake in trying to decode them.
In particular, this is often the case when templates are involved. Our brains need them to process information faster with less energy. But these same patterns can be misleading. Also, the brain is often mistaken about color. The same color may look different on different backgrounds. An optical illusion can also be created through perspective.
Scientists suggest that the illusion is created due to the combined action of neural mechanisms of different levels: retinal neurons and visual cortex neurons. Due to the fact that the brain is familiar with the laws of perspective, it seems to you that the distant blue line is longer than the green in the foreground. They are actually the same length.
The next type of optical illusion is pictures in which two images can be found. The brain can also complement pictures with color. Scientists still do not know what such illusions are connected with.
The brain creates an image from pieces of information received. Without this ability, we would not be able to drive or cross the road safely.
When you are just learning to read, you read each letter, but then the brain memorizes whole words, and while reading you recognize them as a whole image, glancing over the first and last letters.
As you can see, despite the fact that our brain does an excellent job of everyday tasks, in order to deceive it, it is enough to break the established pattern, use contrasting colors or the desired perspective.
And some more interesting visual trickery:
The blue and green spirals are actually the same color - green. There is no blue color here.
Look here at the squares in the centers of the upper and closest faces to you.
The brown square in the center of the top edge and "orange" in the center of the front edge are the same color.
Look closely at the board. What color are cells "A" and "B"? It seems that "A" is black and "B" is white? The correct answer is below.
Cells "B" and "A" are the same color. Gray.
You can load the first picture into a graphics editor and compare the color of the cells yourself.
Does the bottom of the figure appear to be lighter? Close the horizontal border between the top and bottom of the shape with your finger.
See a chessboard with black and white squares? The gray halves of black and white cells are of the same shade. Gray is perceived as black or white.
The horse figures are of the same color.
How many shades are there, apart from white? 3? 4? In fact, there are only two - pink and green.
What color are the squares here? Only green and pink.