Why the World Is Not What It Seems

How the Brain Fills in the Blanks

Nature is colorless, soundless, and scentless. Our senses give it content.

By Peter Gärdenfors, Ph.D.

You probably don’t remember the first time you heard music through a pair of stereo headphones. It’s an amazing experience: The music sounds as if it’s right inside your head. You’ve become so used to it that you don’t realize that this experience is an illusion. There’s no orchestra inside your head, of course.

Similar mechanisms create all forms of experience. Everything you see, hear, and feel is a magical performance created by your brain. This statement may seem surprising and scary, but it is the best way to describe how conscious experiences are generated.

Try the following experiment: Close one eye and gently press the side of the other eyeball with your index finger. Even though you are sitting still, the world seems to be rocking. It is easy to get a feeling of dizziness. This simple experiment shows that your experience of the world outside you is actually created by the vision process in your brain (and by other sensory processes). What you experience is not the world itself, to use Immanuel Kant’s term, but your brain’s construction of it: the world for you. This construction is extremely efficient—for example, the world seems to stand still when we turn our heads, even though the image on the retina changes rapidly.

The visual image we experience is adapted to our needs. When we look at an object, we perceive it as having contours, but the contours are not present in the light that hits the retina; they are an addition created at an early stage of the visual process. Another form of adaptation is that we see what we need to see. Our field of vision covers only 180 degrees in width and 135 degrees in height, while many birds and animals that need to be aware of predators have a field of vision of almost 360 degrees.

It’s commonly thought that our visual process works like a camera. It is easy to prove, however, that this is wrong. For example, we feel that everything is sharp when we look at it. But in fact, only two angular degrees of the field of vision are sharp—about two fingers’ width at arm’s length. In the periphery, we see things as blurred and we have more difficulty perceiving colors there. And yet, every time we look at something, it becomes sharp—and we therefore get the illusion that our entire field of vision is sharp. It’s a bit like the light being on every time we look into the fridge.

Another illusion is that we do not experience any gaps in our field of vision. But there is an area of the retina that has no receptors. The presence of this blind spot means that there is a part of the visual field in which we see nothing.

If my perception of the world is an illusion, then what does it really look like? It doesn’t look like anything at all. There is nothing that can see, hear, smell, or feel unless there is a brain creating the experience. If an avalanche rages far from where people and animals are, there is no sound. There are, of course, a lot of sound waves, but no one hears them.

The philosopher Alfred North Whitehead said that poets are wrong to wax lyrical about nature. Instead, they should congratulate themselves on the fact that their minds create all that they perceive as wonderful in the world around them. Nature itself is colorless, soundless, and scentless; it’s just matter moving around meaninglessly. Our senses give it content.

The brain is not a passive recipient of images and sounds from the world around us; it actively looks for patterns and interprets its surroundings. Our experience of the body is also a construct built up through sensory feedback. Here, the brain not only improves reality, but it also invents it. You have probably tried crossing your middle finger over your index finger and then feeling the tip of your nose. It feels as if you have two noses. The explanation is that the outer side of the middle finger does not usually touch the same object as the inner side of the index finger, which leads the brain to create a perception of two objects.

The following experiment provides an even more surprising illusion: Stand close behind another person, put your right index finger on their nose, and close your eyes. Then, ask a third person to slowly move her index finger up and down over your nose while holding your right index finger and moving it in sync over the other person’s nose. After a while you will experience that, like Pinocchio, you have a very long nose. Because the movements are simultaneous, your brain assumes that what your index finger feels is in the same place as what your nose feels, creating the illusion of a long nose. This shows that you do not perceive the body directly, but a virtual body created by your brain, just as you see a constructed world and not the “real” one.

A similar sensation can be induced in people who experience the phenomenon of phantom limbs—the perception of an arm or leg that is no longer there after an amputation. The phantom limb itself is a result of the body model continuing to simulate the arm or leg as part of the body despite the lack of real feedback from the limb.

The brain, therefore, goes beyond just filling in the blanks— it can also simulate that which does not exist.

Peter Gärdenfors, Ph.D., is a professor of cognitive science at Lund University, Sweden.

Why Pink Doesn’t Exist

What happens when our internal reality comes up against properties of the physical world, like distinct wavelengths of light?

By Damian K. F. Pang, M.Sc.

Pink is a bright, bold, and happy color with a long history. It was described in Homer’s Odyssey and was fashionable among Europe’s 18th-century upper crust as a symbol of class, style, and luxury for both men and women. Elvis Presley drove a pink Cadillac and former First Lady Mamie Eisenhower used pink extensively in her attire and her White House decorations.

Here is the problem, though: Pink doesn’t exist.

Light can be described as electromagnetic radiation that comes in different wavelengths. We perceive a narrow spectrum of this radiation as visible light. At the low end of the frequency spectrum is red light and at the high end, violet. Artists often use a color wheel to show the relationships between colors.

But light comes to us on a spectrum that doesn’t connect at its ends. When we sort objects, like apples, on a spectrum from small to large, there are medium-size apples in the middle. But we cannot combine the property of being large and small in a new way to create a big-small apple that is different from a medium-size one. The same is true for color: The midpoint between red and violet is somewhere in the green range but there isn’t any light that corresponds to the areas between red and violet on a color wheel. In a way, these are imaginary colors. (This is why there are no pink or magenta lasers.)

The fact that there is no light frequency or wavelength that corresponds to what we see as pink led to the striking headline in Time magazine stating that scientists aren’t sure if pink exists. For the record, though, scientists know a great deal about light and about how we perceive it. We see shades of pink or magenta when we sense red and violet (or blue) light in close proximity; there isn’t any scientific debate about that.

The “debate” over pink, however, highlights a profound aspect of human experience: What we perceive is not the world around us, but only our brain’s interpretation of it.

Sensation was traditionally understood to be a single unit of experience produced by stimulating a sensory receptor. Current research rejects this notion, though, because we now understand that experiences and awareness do not come directly from sensory receptors. We can sense things without being aware of them and as our sense of the color pink shows, what we are aware of is not simply the sum of what our senses pick up.

Our experiences—or what we perceive to be our experiences—are the heavily processed and filtered interpretations our brains give us. Our sensations, then, represent a physiological response to external stimuli: They are how our bodies respond to the world around us. Perception, on the other hand, is how we experience our world. Sensations can occur unconsciously, but perception is directly linked to conscious experience and forms one of the key dimensions of consciousness.

This view of perception is profound because it suggests that we have no direct access to the external reality around us. We experience only our brain’s internal representation of the outside world, which is limiting in two main ways.

First, we pick up just a very small range of things. For example, we can see only a very narrow band of electromagnetic radiation—what we call visible light. X-rays, radio waves, and even microwaves are essentially the same as light, but they have frequencies outside of what we can perceive.

Unlike the many animals that have magnetoreception, which means that they can sense magnetic fields—a bit like having an internal compass—we are oblivious to this part of reality; no real estate ads praise the lush or harmonious magnetic field of a home, but many exalt the view from the property. While we know about the Earth’s magnetic field, there could be many aspects of reality of which we are completely ignorant. We don’t know what we don’t know.

Second, as we have discovered, the brain filters, corrects, and interprets the overwhelming amount of sensory data we encounter, which is essential if we are to make any sense of the world around us and to act within a complex environment.

Our experiences, then, are different from what is actually out there in the world. This does not mean an objective reality doesn’t exist, or that what we experience is any less “real.” But it does mean that they are different.

Pink may not exist as a distinct wavelength of light—we can say that it doesn’t exist in the external reality—but there is a specific external configuration of light that makes us perceive something as pink. So, the question of whether pink is “real” depends on whether we’re referring to our internal world of experience, where it very much is, or the external world, where it very much isn’t.

Sadly, our conundrum doesn’t end there. We can confidently say that a sound exists as vibrations traveling through the air. But why do vibrations sound like something to us? Why are some of those sounds pleasant and others dissonant? And why is experiencing a sound different from experiencing a color?

Philosophers call these experiential qualities qualia. American philosopher Thomas Nagel described experiences and consciousness as having a uniquely subjective aspect that he summed up in the question, “What is it like to be a bat?” According to Nagel, being a bat has a distinct qualitative experience: It is like something to be a bat, while being a rock doesn’t share that quality—there is no “what it is like” associated with being a rock.

Regardless of where you find yourself in this debate, you should understand that your internal experience is different from our external world, factually and qualitatively. Which is real? I would argue that both are, but in different ways. Despite advances in psychology and neuroscience, we still cannot fully explain our internal experience based on what we know of the external world. Some believe we never will. Any complete description of reality must therefore include both the experiential and the physical.

Damian K. F. Pang, M.Sc., researches consciousness, perception, memory, and the philosophy of mind.

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