Do We Really See What Our Eyes See?

An introduction to optical illusions and other visual stunts that fool our brains

Introduction

Our eyes are amazing, but do they really present what we actually see? Actually, no. Our brains, the powerful machines they are, receive the images that the eyes are projecting and alter them to make them more comprehensible for us.

Without these subtle alterations, we’d actually be seeing everything upside down. Our brains subconsciously work around the clock to fix the images so that we don’t have such a hard time in general (imagine seeing everybody hanging off the face of the earth while feeling absolutely planted to the floor!).

However, there are some cases where it is unclear to the brain what we’re seeing and thus filters it wrong. This is what is known as an optical illusion. It is our brains failing to comprehend the image in question and thus leave it for us to figure out.

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Optical illusions go back as far as 450 B.C.E. in Ancient Greece when philosopher Epicharmus first tried to explain them. He said that the mind wasn’t the problem and that it was our senses instead that were behind the trickery.

“The mind sees and the mind hears. The rest is blind deaf.” he was believed to have said.

Another Greek philosopher Protagoras disagreed with Epicharmus’ explanation. He stated that our eyes had nothing to do with the problem and that it was instead the environment influencing the way certain objects and images were perceived by the brain.

After years of debate about this perplexing topic, around 350 B.C.E. Greek philosopher Aristotle decided to tackle the issue himself. He claimed that both Epicharmus and Protagoras were correct by sitting on the fence between the two viewpoints - He said that Protagoras was correct in saying that we rely on our senses too much to place them at fault, but also said that our senses are very easy to trick.

To make things more confusing, another philosopher, Plato, took matters into his own hands and said that our brains and eyes together make up our vision of the world, which included optical illusions. He ultimately said that these illusions are purposely there as part of the picture that the brain and eyes create for us.

Regardless of what they are and where they come from, these illusions have evaded logical sense for centuries. Since Aristotle’s time, we have been able to categorize these tricks into three kinds: Physical illusions, physiological illusions and cognitive illusions.

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Physical Visual Illusions

The first type of illusion is the physical illusion. A common example of this illusion is when you’re staring at a line of cars waiting at a traffic light. Why does the first car always look bigger than the second car?

This is because of our ability to see in 3D. We are able to perceive the world in three dimensions and the distance of an object. Using the environment around us, we subconsciously judge where objects are in relation to other objects and ourselves.

This is why mountains look further away when there’s haze. The haze adds another layer of perspective to the picture thus pushing the mountains “further away”, whereas without the haze, the mountains, without that extra layer separating you and the mountains, appear closer.

Going back to the cars in a line, the closest car always looks the biggest, with the car behind being smaller and the car behind that being smaller, etc. This is because each car adds another layer to the picture. The more layers (cars) you add between yourself and the object in question, the further away it will look, and obviously the further away something is, the smaller it looks.

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Physical illusions also explain one-point perspective. The idea that parallel lines don’t always have to look straight and that smaller objects in the distance may actually be the same size as objects in front of you.

The best visual example is standing and staring directly inside the rails of a train track. In your view, the long rails that run parallel to each other angle into each other until they reach the horizon.

This indicates that the rails as they angle in are further and further away from you. The perpendicular rail supports also look shorter as they go along the rails.

When comparing a support right in front of you and another support further away in your vision, the closer support looks dimensionally longer than the one further away, and that is because of physical illusions.

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Physiological Visual Illusions

The next type of illusions is physiological illusions. Physiological illusions are the effects on the brain when exposed to excessive amounts of lasting effects (this ranges from bright lights to colours to movements, etc).

When you look into a bright light for a long time and then suddenly look at something else, sometimes the shape and colour of the light are still in your vision when you’re looking at this other object. That is a classic example of a physiological illusion.

The subject in question doesn’t have to be luminous either, staring at a black piece of paper and then suddenly turning to look at a white one creates a grey colour on the white paper (because grey is the combination of black and white).

This can simply be thought of as the brain not having enough time to switch colours and it simply blends the two together. The better the colour combination, the stronger the effect. This is why turning from yellow to purple for example, wouldn’t create such a strong illusion, because yellow and purple are complementary colours (colours opposite each other on the colour wheel).

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Colour and brightness consistencies also fall under physiological illusions.

The easiest example is to imagine a gradient going from black to white horizontally. Then overlap the gradient a smaller line with a single grey colour.

Even though the colour of the line doesn’t change, it looks lighter against the black side and darker against the white side.

This again has to do with the brain not having time to separate the colours from one another and automatically associates them together.

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Cognitive Visual Illusions

The final type of optical illusions is called cognitive illusions. These illusions are formed purely by the brain by associating certain images to other concepts, even if there is no correlation whatsoever between the concepts.

The most common example is when you’re looking up at the sky and commenting on how a particular cloud looks like a horse. The cloud and the horse have no relation to each other, your brain just randomly picks it up.

It is almost as if the brain is playing fill-in-the-blanks with itself. By associating completely random images with other existing information, the picture looks more complete and aesthetically pleasing.

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This is also the explanation for constellations. Technically they’re just a group of stars that can be grouped together in many different ways, but the constellation shape is the cognitive illusion that was formed in the astronomer’s head when he first saw them.

As explained in Mark Haddon’s The Curious Incident of the Dog in the Night-Time:

“People say that Orion is called Orion because Orion was a hunter and the constellation looks like a hunter with a club and a bow and arrow… But this is really silly because it is just stars, you could join up the dots in any way you wanted.”

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Conclusion

Our brains are amazing, but do they really present what we actually see? Actually, no, but it isn’t really the brain’s fault. These phenomena happen and maybe we aren’t supposed to understand them at all. Nevertheless, they sure are fun to observe and study!