Dream Unicorns & Imaginary Shadows: Why Your Eyes Tell You Lies

Hallucination is a word that most people associate with drug-use or psychotic disorder. However, the ability to distort and add to the information that we perceive as reality is a standard function of a healthy mind. If we’re to go by the definition above — taken from the Oxford English Dictionary — then we all hallucinate on a moment-to-moment basis.

In this article, we’re going to explore the different ways in which your eyes can tell you lies. Then, we’re going to take a look at how you can start to see past the more limiting illusions.

Sleepy fantasies

Let’s ease in with something not-so-shocking. Perhaps the most obvious type of convincing fantasy that we experience is dream imagery.

Take a moment to recall one of your dreams. Looking back, you know that dream environment was not your actual reality. It was a construct of sights, sounds, feelings and other sensations, compiled from a stockpile of memories in your mind. But did that space not seem entirely real while you were “in” it?

Our dreams feel real because there’s very little difference between the type of information we process while asleep and while awake. To the observing part of your consciousness, the unicorn you dreamt of last night was just as tangible as the boss you had a meeting with this morning. It’s what you decided about those experiences afterwards that set them apart.

What the brain adds

In his fascinating book on perception, The User Illusion, Tor Nørretranders asserts that 90% of what we perceive is internally generated. This means that the vast majority of what we see, hear, feel, taste and smell is fabricated in much the same way that our dream imagery is. The mind adds extra information to the raw data received by our sensory organs. And because this happens just before conscious recognition, it all seems entirely real.

You may have heard of the “blind spot” in human vision. This is a great example of the brain’s ability to create convincing imagery in lieu of actual information.

There’s a sheet of photoreceptors covering the retina at the back of the eye. This functions like the photosensitive film at the back of an old-school camera. It records the information transmitted via rays of light from the outside world.

However, at the point where the optic nerve attaches to the retina, there’s a hole in this sheet. What this means is that the brain can receive no information about that particular part of the picture. As a result, we have two blind spots: one for each eye.

But we don’t experience gaps in our vision and there are two reasons for this. Firstly, the blind spots in each eye are in different places so one eye sees what the other does not. Handy. However, even if you close one eye, you still don’t have a big black hole in your sight. This is because your brain is anticipating what it thinks should be seen in the blind spot based on what surrounds it. It then uses its estimation to plug the gap. That part of your vision is nothing more than a guess, and it’s not an insignificant size. Imagine a full moon in the night’s sky. Your blind spot could delete a moon ten times as big as that.

To actually see the blind spot being filled in, you can use the diagram below.

Instructions: Cover your left eye with your hand and focus on the cross with your right eye. Now, slowly move your head closer and farther away from the screen. There will be a point — probably around four inches on a desktop, much closer on a phone— at which the invisible man disappears. Don’t look directly at him, just keep looking at the cross and he’ll pop in and out of your peripheral vision as you move.

More than just pictures

The brain adds more than just simple imagery to our everyday experience. Let’s take a look at a familiar optical illusion.

This is called the Necker Cube. With this image, we’re presented with two different options. We either see a cube with its front panel in the bottom left corner of the picture. Or, we see one with its front panel in the top right. You can alternate between the two different cubes but you can’t see both at the same time.

The important point here is that neither is true. Of course, we’re not looking at a cube at all. It’s just an arrangement of lines. But although you know this to be the case, it’s very hard to look at the illusion without being aware of one of those imaginary shapes.

This means is that the brain has added extra information and presented us with something that is greater than the sum of its parts. We look at straight, flat lines but we perceive a 3D object.

With the Necker diagram, the illusion is obvious. But with the information our brains add to what we perceive around us, the fabrications can be much more convincing. So convincing, in fact, that we may not ever really be able to tell the difference between fantasy and reality.

Knowing the real

In 1781, Kant argued that there are two worlds:

1. The “nouminal world,” which is the real, objective world.
2. The “phenomenal world,” which is our version of the nouminal world as perceived by our individual minds.

Here’s what Steven Lehar has to say about this in The World in Your Head: A Gestalt View of the Mechanism of Conscious Experience.

“The only way we can perceive the nouminal world is by its effects on the phenomenal world. Therefore, the world we experience as external to our bodies is not actually the world itself, but only an internal virtual reality replica of that world generated by perceptual processes within our head.”

So, what we are seeing at any one time is not objective reality. Rather, it’s our own idiosyncratic version of reality. It’s embellished, much like the cube that we see when we observe the Necker diagram.

And, just as that cube is perceived as a result of our prior experience with cubes, the phenomenal world is also affected by what we have experienced in the past. It’s based almost entirely on what we already know (or think we know) to be true.

Take this next illusion. As Nørretranders points out, this diagram “shows that we are living on a planet that orbits a star!”.

The shapes in this image clearly appear as dimples or pimples depending on whether the “shadow” is at the top or the bottom.

But there are no shadows in this image. These are just 2D circles filled with a gradient. Yet, having lived its life on a planet that receives light from the sun (i.e. from above), the brain interprets the gradient as a shadow and converts the circles into 3D protrusions and indentations respectively. It does this because that’s what it’s used to seeing.

The question is, then, what else are we so used to seeing that we’ll project it into our environment and call it real?

The role of identity and self-image

The lens through which we view the world is based on more than just our beliefs about external things like sunlight and three-dimensions. We take our preconceptions everywhere we go. And the ones that can create the biggest illusions, almost certainly, are those that concern our sense of self.

I once had a friend who believed so strongly that she was unattractive that whenever someone gave her a compliment she would snap back angrily. Because of her negative self-image, she was convinced that they must be playing with her. And so, just like the straight, flat lines of the Necker Cube, she found it very hard to perceive the raw information (the compliment) for what it was. Instead, she added a third dimension of falsity and sarcasm.

But we don’t only add negative information to what we see. A guy once gave me a knowing wink when he caught me looking at him. He was clearly pleased to register the admiration on my face. But things got awkward just moments later when I made my real intentions known. The extra dimension this confident bartender had added to my straight lines was lusty desire. All I actually wanted from him was a beer. Cringe.

Hallucination as an acquired skill

Everyday hallucination isn’t something that just happens to us. It’s a skill, learned by the brain as we grow up to help us make (rapid) sense of reality and ease our existence in the world.