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by Pat Murphy & Paul Doherty


THERE'S a hole in reality that you can look through if you like.1   Here's how:

Roll up a sheet of paper to make a tube. Hold the tube up to one eye. Keeping both eyes open, look at a white wall. One eye is looking through the tube; the other eye, directly at the wall. Compare the wall that you see through the tube with the rest of the wall.

The wall looks different through the tube, doesn't it? The eye that's looking through the tube sees a spot that's brighter (or perhaps dimmer) than the rest of the wall. No question about it.

A portal to another dimension? Probably not. But a kind of hole in reality nonetheless. We'll get back to that in a bit.

In this column, we're going to talk about the nature of reality—a topic that science fiction has been exploring since before it was called science fiction. Examples abound—ranging from Ray Bradbury's "The Veldt," that classic tale of a fictional world that comes dangerously alive, to The Matrix, to the many episodes of Star Trek involving that pesky and versatile Holodeck.

Science fiction stories have speculated that the world is all in your head. And you know what? They are absolutely right.

We're going to tell you how and why your brain makes up the world—and why this messes with your view of reality in significant and deeply troubling ways. And finally we'll tell you how science fiction is going to change the world. We have a lot of ground to cover and only a couple of thousand words to do it in, so try to keep up.


Most people think they see the world that's out there. We have two words for those people. No way.

Your eyes and brain work together to make a picture of the world. You don't see the world at all. You see a picture of the world that your brain constructs. In fact, your entire reality is a construct created by your brain, working with imperfect information received from your senses.

Take the bright spot on the wall that you saw when looking through the tube. Your view of the wall is created when light bounces off the wall and gets into your eyes. The lens of each eye focuses an image on the retina, a layer of light-receptors at the back of the eye.

Your eyes gather an amazing amount of information from that light. Each of your retinas has about 127 million light receptors—120 million rod cells that provide vision in dim light and 7 million cone cells, which are responsible for color vision.

That information travels from your eye to the visual cortex of your brain through the optic nerve. Though this nerve is the fattest bundle of nerve cells in your body, it has only 1.2 million neurons. You might think that this means your eyes must discard ninety-nine percent of the information your eyes gather and send only one percent of the signal to the brain where your perception of the visual world is reconstructed. Fortunately, it's not that simple.

To create signals that carry the most possible information, the cells in your retina process information from the light before sending it on. It's that information processing in your eye that caused the bright spot you saw through the tube. When a light receptor in your eye receives light, it signals neighboring receptors, telling them to turn down their sensitivity to light. This is called lateral inhibition.

Viewed without a tube, the white wall looks uniformly bright. That's because all the light receptors in your eye are equally simulated and equally inhibited by the light reflecting from the wall.

When you look through the tube, the situation changes. In the eye looking through the tube, one area of the retina receives light from the wall. That area is surrounded by light receptors receiving light from the ring of the tube. If the ring of the tube is darker than the wall (the more likely scenario), the spot appears brighter than the surrounding wall. That's because the light receptors seeing the spot are not inhibited by the light receptors seeing the tube. If the tube is brighter than the wall (which could happen if the tube is made of thin paper and the light is shining through it), the spot will look darker than the wall. But one way or the other, that spot definitely looks different from the wall.

Lateral inhibition, the neural mechanism that causes the bright spot you see through the tube, enhances edges and boundaries by increasing the contrast between adjoining areas. Processing at a cellular level makes a small difference into a larger one.


Okay. We can hear you saying, "So it looks a little brighter. What's the big deal?"

Ah, but that's just the beginning. The bright spot that you see through a cardboard tube is just one example of how your eyes and brain create the world you see. As any researcher in perception can tell you, optical illusions demonstrate more significant misunderstandings of reality that arise from your brain's interpretations of the signals it receives.

Take, for example, the "hollow face" illusion. Suppose you see a concave face—the inside of a mask, for example—in the proper lighting. Chances are good that you will see this hollow face as a normal solid face. You see the hollow face as a solid face because it's far more common to see a solid head than a hollow head-shaped space. In this situation, as in many others, you see what you expect to see, not what is really there.

With the hollow face illusion, the real surprise comes when you move back-and-forth while watching the face. As you move, you will see the face turning to follow your movement.

But don't take our word for it. Check out this illusion for yourself at If you want to make a version of this illusion for yourself, use the template at and while you're there, check out a hollow face illusion of Einstein's face. We recommend you make the dragon and try the experiment. Even when you know the model is made of paper—and you are confident that no robotics are involved—you see the dinosaur turning its head to follow you when you move.

The hollow face and the hollow dragon look solid because your brain tries very hard to make sense of the information it gets from your eyes. One way your brain makes sense of the world is to relate new information to past experience. Your brain is convinced that the face and the dragon model are solid because most faces and objects are solid.

But why does the dragon turn its head? Blame your brain. Your brain is sure the dragon is a solid model. But when you move, your view of the model changes in a way that a solid model would not change. There's only one way your brain can make sense of the changes in what it sees—and that is to assume that the head of the paper dragon is turning to follow you as you move.

That's clearly ridiculous—but that's the only thing that makes sense to your brain, so that's what you see. Because your brain expects the dragon to be solid rather than hollow, your brain adjusts what you see to match its interpretation of reality.


We could give you many examples of optical illusions that work just like the hollow face illusion. In all of them, your brain sees what it expects to see. Your brain, with the best of intentions, tells you lies. But don't think the brain's deceptions are limited to optical illusions. To see how your expectations color what you see in everyday life, Paul suggests you try this experiment.

You'll need a ruler and a friend. Have the friend stand four large strides away from you and face you. Notice how tall your friend appears.

Have your friend take four more large strides away from you to stand eight strides away. Now note how tall your friend appears.

We are guessing that you are not yet amazed. So start over and repeat the experiment. This time when the person is four strides away, hold the ruler vertically at arm's length and measure your friend's height. Let's say it's about twenty-four cm from head to toe. Measure your friend again at eight strides away. Your friend will be half as tall as measured by the ruler—about twelve cm.

With the ruler, you are measuring how your friend's image is mapped on your retina. The image of the person on the retina is half as tall at eight strides away compared to four strides away.

But the map on the retina doesn't necessarily match the picture in your head. Did that person look half as tall when twice as far away? Did you see your friend shrinking—from six feet up close to three feet at twice the distance?

Almost certainly not! When judging the size of an object, your brain takes into account the distance between you and the object—or at least what your brain thinks the distance is. (Paul speculates that an accurate perception of the size of the warrior running at you is important to your survival as a member of the species.)

This same tendency to take distance into account when judging size is at work in the tricky illusion known as the Ames Room or distorted room. (Search for Ames Room on YouTube and you'll find plenty of examples.) People walking around in a room seem to shrink and grow because your brain misjudges how far away they are. Your brain would rather accept the fantastic shrinking people than adjust its understanding of how far away they are.


One more example before we move on to more truly disturbing matters. We suspect that you, being a reader of fantasy and/or science fiction, have gazed on occasion at the rising full moon. You may have noticed that the full moon looks large as it rises and yet looks quite small in the sky overhead.

How large an object do you think you'd have to hold at arm's length to block out the rising full moon? A silver dollar? A quarter? A penny? How large an object would you need to block out the moon when it is high overhead? Don't move to the next paragraph until you have made your guesses.

Many people say it would take a quarter to just cover the moon. Some say a nickel. But the real answer is a pea or an aspirin tablet. And the answer is exactly the same for the moon when it's overhead. Next time the moon is full, try it and see.

The thing that's both startling and disturbing about all these misinterpretations by your brain is this: Even after you know how they work, you can't change the reality your brain constructs. You know the people aren't shrinking and growing, but you still see it happening. You know (at least now you know) that the full moon isn't really enormous when it's rising. But it still looks enormous.


Optical illusions may seem like silly tricks, but they reveal a basic human tendency. We tend to see what we expect to see, what we have seen before. Or to put it in a science fictional context, your brain to some extent creates its own reality.

That brings us to a couple of tests Pat took the other day. These tests left Pat annoyed with her brain—and got her started thinking about writing this column. Pat wasn't annoyed for the usual test-taking reasons—it wasn't that she forgot answers she should have known or her brain couldn't work out an answer. Nope, this particular test annoyed her because it revealed secrets that her brain had been keeping from her. And the secrets had to do with her brain's hidden expectations.

The tests that Pat took are available online. You can take them and perhaps be annoyed yourself. We recommend it. Go to and you'll have your choice of a few tests designed to measure implicit associations, attitudes and assumptions that are operating below the conscious level.

The easiest way to understand the implicit assumptions test is to log on and take one. But for those who don't have online access right now (or who just hate taking tests), we'll give you a quick description. If you take the test, you can probably skip the next two paragraphs.

Each test requires the test taker to rapidly associate certain words with particular categories. The speed with which the test taker makes judgments is measured and used to assess the test taker's attitudes. The basic idea is that people can decide and classify words more quickly when they feel (on some level) that they are putting these words into groups where they belong.

In the first test Pat took, the categories were Math, Arts, Pleasant, and Unpleasant. The first task was to decide which words belonged in Math and which in Arts. Shakespeare goes in Arts; calculus in Math, and so on. Easy.

The second task was to associate words with Pleasant or Unpleasant. Joy was Pleasant; agony, Unpleasant. Again, piece of cake. (Which is Pleasant, as far as we're concerned.)

Then came the tricky bit: Math and Pleasant were together in one corner of the screen; Arts and Unpleasant were in the other corner. The words to be categorized related either to Pleasant/Unpleasant or Math/Arts. "Calculus," for example, belonged to Math/Pleasant and "agony" belonged to Arts/Unpleasant. That's the rule, even if you think "agony" and "calculus" belong in the same category.

Pat was not surprised that her results suggested that she thought Arts were more Pleasant than Math. Though Pat did take calculus in college, her strongest memory of Math was the C she received in third grade math. Those nasty multiplication tables just didn't capture her interest.

(There was, of course, another factor: She had been skipping math class to take violin lessons, which had seemed like a fine idea when she signed up for the lessons. But the strangled cat sound of her violin playing eventually convinced her that playing the violin was even worse than learning the multiplication tables. So the preference for arts was clearly a preference for writing, not music. Had "violin" been on the list, she would have had no difficulty categorizing it as Unpleasant.)

So that was fine. Pat was perfectly willing to accept that she associated Math with Unpleasant. Then she took another test, one designed to measure whether she had any tendency to associate men with science and women with liberal arts. On her first time through the test, the results indicated that she had a slight tendency to associate men with science and women with liberal arts. This is true of eighteen percent of test takers on the site, but as a woman scientist committed to encouraging more women to work in the sciences, this annoyed Pat considerably.2  

Paul took the same test and was surprised that he too came out moderately associating men with science and women with liberal arts. After all, he knows so many great women in science and men in art.

Unfortunately, we have a lot of company in the uncomfortable place we find ourselves—as was shown by a 2012 study, in which science faculty from a number of universities considered the application of a student for a laboratory manager position. On some applications, the student had a male name; on others, a female name. Otherwise, the application was exactly the same. Yet both men and women judged John to be more competent than Jennifer—more valuable to the tune of $4000 a year in salary, more worthy of mentorship, and generally more likely to be hired.

Consciously, these folks felt they could be objective in their evaluation of candidates, treating male and female equally. But in the end, they fell victim to their brain's unconscious assumption that a man would be better qualified for a science job than a woman. That unconscious assumption had been fed and shaped by societal messages that created a certain expectation.

We can give you dozens of other examples of situations when your brain makes important judgment calls based on its experience and expectations. Researchers in the field of social psychology have identified a fascinating array of cognitive biases that affect how you think about the world.

Confirmation bias, for instance, is the tendency of people to prefer information that supports or confirms the beliefs they already hold. Because of this tendency, people seek out such information and remember or interpret information in a way that reinforces their feelings. Neutral or unfavorable evidence tends to be reinterpreted to support the person's beliefs.

The relevance paradox deals with the challenge in finding the information you need to solve a problem. In an effort to gather relevant information, you eliminate information that you see as distracting or unnecessary. In the process, you inadvertently exclude or fail to find information that is important. Because you are looking for information that fits into a pattern you expect, you find what you expect to see. (Hmm. Does that sound familiar?)

The relevance paradox explains why schistosomiasis, a disease caused by parasitic worms, rose dramatically following the construction of dams and irrigation systems in Africa. The disease is spread by freshwater snails infected with the worms. The United Nations had published guidelines explaining how to minimize the spread of the snails and the disease by keeping water flow above a certain speed. But the civil engineers who designed the large-scale irrigation systems were thinking about concrete and water flow, not about snails and disease. Victims of the relevance paradox, they never ran across the U.N. guidelines.


There is indeed a hole in reality that you can look through. It's the hole that shows you what you expect to see. It's the hole you look through to find the familiar. And it's the hole that most people look through most of the time.

Your brain is trying to make sense of the world. To do this, it takes short cuts, sharpens differences, and fits the world into its predetermined expectations.

All of this is a blessing and a curse. A blessing because this enables your brain to make sense of what would otherwise be an unmanageably large collection of inputs. A curse because it can limit and distort your view of the world in ways that limit your understanding and close off possibilities. If you see what you expect to see, prefer information that confirms your expectations, avoid seeing information that might confuse the issue, how can you ever try something new?

And this is where science fiction comes in.

Science fiction writers are in the business of exploring possibilities. We consider change and its consequences—unintended consequences, for the most part. Science fiction, at its best, is the literature of the unexpected. Science fiction writers look for how things can go wrong in the most unexpected ways. Anyone can dream of a future where everything works beautifully. It takes a science fictional turn of mind to come up with a future that is royally messed up.

How can you change, for example, people's assumptions about gender roles? How can you change expectations that are buried so deep that you don't even think about them? Expectations that were formed by cultural messages that snuck past your conscious filters?

You could attack such expectations in a straightforward fashion, but you might have more success with a surreptitious approach. Perhaps you could use a literature that many regard as the province of childhood, nothing to be taken seriously.

Science fiction stories are a part of popular culture and help shape people's view of the world. When science fiction writers think outside of cultural norms, when we present unexpected situations as normal, we make tiny changes in the collective understanding of the world. We help change people's expectations, and that in turn changes the world they see.

There's a hole in reality that you can look through if you want, and it's our job to make the view through that hole a little stranger.


1   We must give credit to John Steinbeck here. A chapter in his novel Sweet Thursday is titled "There's a Hole in Reality Through Which We Can Look if We Wish." It's a line that applies so well in this situation that we just can't resist paraphrasing it.
2   Fortunately, on the second time through the test, Pat's results suggested a strong association of women with science and men with liberal arts, an association Pat shares with only one percent of the test takers on the site. This makes her happier, but leaves us wondering if Pat has learned to game the test.


Paul Doherty works at The Exploratorium, San Francisco's museum of science, art, and human perception—where science and science fiction meet. For more on Paul's work and his latest adventures, visit Pat Murphy used to work at the Exploratorium, but now she works at Klutz (, a publisher of how-to books for kids. She is the co-founder of the Tiptree Award (, which is presented each year to a work or works of science fiction or fantasy that explores and expands gender roles. You can find out more about Pat's work at her newly refurbished website at

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