Sleights Of Mind Part 12

Oddly, the app's creator, Grigor Rostami, noticed that not long after the program was launched his ratings on iTunes went from an average of five stars (the best) down to an average of three stars (middling). When Pogue checked the bad ratings, he found that people were saying the nicest possible things about the app.

"This app is amazing!" (one star) "Awesome app! One of the best and funniest apps ever. Great job!" (one star) "Wow-the best $3 I have ever spent! Keep up the low ratings!" (one star) So why would such a great app get super evaluations but low star ratings?

Rostami started reading magic forums and discovered that magicians were intentionally giving his app a one-star rating (the worst) to keep it secret from everyone else in the app store. The magicians conspired to reduce his sales by sabotaging the star ratings. This would reduce exposure and keep the trick viable (for them) as long as possible. Verbal evaluations don't affect the rating that the app has in the listings, so they were honest in their written praise.

Rostami, who is a magician, told Pogue that once the one-star ratings began coming in his sales dropped substantially.

This kind of screw-the-compet.i.tion mentality is unfortunately pervasive among some magicians who regard exposure as magic's highest sin. Yet the professional magician organizations issue no ethical guidelines against this kind of behavior. It's an indicator that the overwhelming concern about exposure may fundamentally be an ultimately self-destructive drive to maximize one's own take while reducing the success of others-as if magic were a zero-sum game.

Of course, some tricks are more resilient to exposure than others. For example, the dovepan we used in our act at the Magic Castle is a cla.s.sic gimmick. Once you know how it works (see chapter 11), you lose your sense of wonder. It's cheapened, no longer intriguing.

But Teller describes a trick that became more intriguing the more he knew. This is the famous Cups and b.a.l.l.s, a sleight of hand that was performed by Roman conjurers as far back as two thousand years ago. The trick has many variations, but the most common one uses three b.a.l.l.s and three cups. The magician makes the b.a.l.l.s pa.s.s through the bottom of cups, jump from cup to cup, disappear from a cup and turn up elsewhere, turn into other objects, and so on. The cups are usually opaque and the b.a.l.l.s brightly colored.

Teller recalls that one day he was sitting in a diner in the Midwest with Penn, fiddling with an empty water gla.s.s and wadded-up paper napkins for b.a.l.l.s. He turned the gla.s.s upside down and put a ball on top, then tilted the gla.s.s so that the ball fell into his other hand. The falling ball was so compelling that it even drew his own attention away from his other hand, which was deftly and automatically loading a second ball under the gla.s.s. He was so well practiced that he no longer needed to consciously control his hands. In fact, Teller found that the sleight happened so quickly he himself did not realize he had loaded the transparent cup. The great magician had misdirected himself!

The Illusion of Exposure.

Apollo Robbins is onstage with Susana, discussing magic and the brain at the Chicago Cultural Center. He's stuffing a large silk handkerchief into his fist. With one eyebrow raised a la Dr. Spock, he's showing the audience how their angles, meaning their sight lines, are critical to successful magic. The audience feels as though it is learning secret magic techniques. It's exposure as entertainment.

When the silk is fully crammed, Apollo opens his fist and, voila!, the handkerchief has been transformed into an egg. He then pulls the silk from his hip pocket, as if the silk had magically transported itself there from his hand.

"It's an easy trick," he explains. "All you need is a fake egg and two identical silk handkerchiefs." He turns the egg around and reveals that it has a hole into which he stuffed the silk. The crowd laughs as he slowly pulls the stuffing back out through the hole.

"Here's why the angles are important. First, the setup," Apollo says. He refolds one of the silks and puts it in his hip pocket, along with the fake egg. He puts the other silk in his jacket breast pocket. He is now set to repeat the trick.

"Step one, I palm the egg," he says as he secretly extracts the egg from his pocket. "But you can't see that from where you're sitting." His hand is in an ice-cream cone eating position, egg tucked neatly within. "Then I take the silk from my breast pocket and stuff it into the egg like this." Again he stuffs the silk into his fist. "Make sure n.o.body is behind you or has an angle that allows them to see the egg in your hand."

"Here's the egg just like before," he says, opening his fist. The silk is gone, as expected. "But if you look closely, you can see there's another way to keep people from seeing the hole." He now turns the egg, revealing the small opening. Then, to everyone's amazement, he peels the hole off the egg, showing that it was not an actual hole but a sticker. Yet the handkerchief is gone! Apollo now removes the silk from his hip jacket pocket and flicks the sticker away. To prove that the egg is real, he grabs a gla.s.s from the table, and cracks the egg into it.

Magicians call the silk-to-egg trick a sucker trick-the magician does a trick and then apparently exposes its secret method, only to immediately show that the explanation was bogus. It's similar to apparent repet.i.tion except now the audience thinks it knows how the trick is done. Sucker tricks are based on apparent exposure, rather than the actual exposure done by the Masked Magician.

Magician Whit Haydn says that if the exposure is better than the routine, expose away. One reason sucker tricks are popular could be that exposure deepens the audience's appreciation for the art of magic and for the skill and cleverness of the performer-even if the exposure itself is an illusion.

Teller further realized that all of this took place despite the fact that he should have been able to see the secret ball as it was loaded under the cup. Its image was on his retina, but he nevertheless missed it because his attention was so enthralled with the falling ball. He surmised that if it worked for him with a transparent cup, it would work with an audience. The transparency of the cups would make the trick all the more magical to the audience. And that is how Penn & Teller came up with the idea for a cups and b.a.l.l.s routine using transparency. They claim that their version of the trick violates four rules of magic: don't tell the audience how the trick is done, don't perform the same trick twice, don't show the audience the secret preparation, and never perform cups and b.a.l.l.s with clear plastic cups. The exposure is what makes this trick a superstar.

At the magic symposium in Las Vegas, Teller told the scientists that "the core of a successful trick is an interesting and beautiful idea that taps into something that you would like to have happen. One of the things I do in our live show is to squeeze handfuls of water and they turn into cascades of money. That's an interesting and beautiful idea. The deception is really secondary. The idea is first, because the idea needs to capture your imagination."

There's another reason, aside from fairness to their colleagues, that magicians should be generous in revealing their methods: magic can help increase the rate of discovery in brain science. The discovery of inattentional blindness and change blindness in recent decades (detailed earlier in chapter 5) has greatly advanced the cognitive sciences. Magicians evidently knew implicitly about these phenomena for centuries, judging from the design of their tricks, and so scientists have been inadvertently reinventing the wheel. By studying magic, scientists could have made these advances earlier. We propose that the study of magic is now poised to help to derive new principles to optimize attentional resources in people with cognitive decline, as well as to create heuristics to improve education in our schools.

In another example of magic helping science, David Copperfield, through his foundation, generously designed and funded a program called Project Magic. Teams of magicians and occupational therapists work together to teach sleight of hand to physically challenged people to help with their rehabilitation and improve their self-esteem.

If magic can promote scientific discovery and clinical practice, then magicians might be morally obligated to make their secrets available for use. We're not saying they should give up their knowledge for free. Like all experts, they deserve acknowledgment and remuneration for their creativity and invention. Perhaps they could think of it as enlightened self-interest.

A few years ago, neither of us had ever been to a magic show, nor had we given this ancient art a nanosecond of attention. But now that we understand how it works, we are unabashed groupies. The more we learn about magic, the more interested we become as consumers. We go to magic shows whenever we get the chance, because we love being fooled, even though we have read explanations of many of the tricks. Experiencing a master magician fling our attention around like a fly fisherman's lure, forcing us to strike at the morsel and then reeling us in, is unlike any other cognitive experience we've had outside of the science we do in our labs. It's as though somebody took all of the cool things we study every day and suddenly made them beautiful and dramatic. We like some shows so much that we go to them over and over and never come away disappointed. We have traveled the world meeting magicians, learning from them, collaborating with them, and racking our brains for ways to explain what they do and how they do it. We've taken magic lessons and bought thousands of dollars' worth of magic paraphernalia.

Returning from the front lines, we can say that having expertise in magic makes it more appealing, not less. To understand why, you need to know a little more about mirror neurons. Recall that these are the brain cells that become active when you carry out an action and when you observe another person carry out that same action. When you wave good-bye, mirror neurons in your premotor cortex fire away. When you watch someone else wave good-bye, those same neurons fire, but you don't move your body. In other words, mirror neurons link action and perception.

Your mirror neuron system gets more active the more expert you are at an observed skill. When pianists listen to someone else's piano performance, the finger areas in their primary and premotor cortex increase above their baseline activity. Their mirror neuron systems automatically run the performer's keystrokes in emulation. The same thing does not happen in the brains of nonmusicians. While they can certainly appreciate the music deeply, their experience is inevitably shallower than the pianist's in at least one way, because they are not experiencing what it is like to actually produce it.

The same goes for athletics: the better your own skills, the more deeply you understand the skilled performances you witness. For example, when cla.s.sical ballet dancers and experts at an Afro-Brazilian art form that combines martial arts and dance called capoeira watched video clips of each kind of dance, the dancers' brains showed distinct patterns. Both disciplines require exact limb positions, ch.o.r.eographed movements, extreme muscle strength, and years of practice. You would think that their mirror neuron activity would be equivalent, yet when ballet dancers observed capoeira movements, their mirror neuron activity was weaker compared to when they watched other ballet dancers-and vice versa. The actions you mirror most vividly are the ones you know best.

We are willing to bet that the same holds true for magicians. If Teller watches Mac King perform a fake coin toss, his mirror neurons are going to have robust responses. If an ordinary muggle watches Mac do the same trick, she will be entertained, but we suspect her mirror neurons will not respond as strongly.

Now imagine that everybody in the world could perform one trick and perform it well. Would magic suffer from this vast increase in exposure? Would ticket sales to shows fall? On the contrary, the more you learned, the more interesting magic would become, because you, and your brain's motor control pathway, would empathize with the activity more deeply.

We think the enduring mystery about magic is how the brain constructs-and falls for-illusions. In this regard, we hold a minority view among our fellow visual scientists. To the generation that preceded us, illusions were considered errors of perception. The late Richard Gregory, the British psychologist who is widely known as one of the most prolific perception scientists in the world, liked to say that illusions are where the visual system got it wrong.

We disagree. Illusions are not exceptions and they are not necessarily mistakes. They are integral to perception and represent fundamental aspects of your visual and cognitive processing. They are adaptive shortcuts that your brain makes to speed up such processing, or reduce the amount of processing necessary to provide you with the information you need to survive and to thrive, even if the information isn't technically accurate.

Try this for yourself: look at this page indoors, and then take it outside and look at it under direct sunlight. It's remarkable in that it's unremarkable. The page looks exactly the same-black letters on a white background. But how can that be? Depending on the nature of your indoor lighting, there is about one million to twenty million times more light56 under direct sunlight than indoor light. Outside, there are millions of times more photons reflecting off the black letters than there were off the white paper inside, so why don't the black letters, when outside, look brighter than white?

Furthermore, the colors of the photons (the distributions of wavelengths) are probably different inside and outside, too. Your visual system can see color and brightness only as a function of the numbers of photons and their wavelengths that fall upon your retinas. Thus the page cannot possibly be "white" both inside and outside.

If the photons inside and outside are so different (and we a.s.sure you that they are), why does the page look the same in both environments? The answer is that your visual system ma.s.sages the visual data with two processes called brightness constancy and color constancy, so that the page looks the same to you under very different lighting conditions. But this is an illusion, which means the physical reality doesn't match your perception. In reality, the book has a different physical appearance57 in each environment, even though you see it as the same.

Visual illusions help you survive in a visually complex world when you exit from the cave. They help you recognize ripe versus unripe fruit in the tree or by firelight. Similarly, cognitive illusions help keep you alive. You make a.s.sumptions, confabulate memories, and attend to only one thing at a time, because it's an efficient way to navigate the world and to find the resources you need. It's more efficient than the alternative, which is to try to process everything you encounter. Accuracy is usually not needed and it's difficult to achieve. You'd need a much bigger head to hold a brain large enough to be always accurate, and humans already have enough of a problem with childbirth because of the size of our noggins.

Magicians have tapped in to the power of cognitive illusions more effectively than scientists have, though less systematically. The magician's goal is to misdirect you and create a sense of wonder (though some con artists use these same tricks to steal). Our goal is to take magic into the neuroscience laboratory and to use it for evil-No, no, we want to use it to increase the rate of discovery about our cognitive processes. We believe that magical methods will prove invaluable in determining the circuits in the brain that process cognition, as well as in revealing important new perspectives on how the brain functions.

And it could work the other way around, too. We've been planning a collaboration with Mac King, who does such a fantastic fake coin toss. He's so quick you can't catch him doing it. Mac has shown us how he does it, and it looks almost identical to a real coin toss. He can toss the coin (or fake it) for many repet.i.tions before we're able to tell a real toss from a fake toss.

The goal of our project will be to determine if known principles of visual processing might enhance the perception of a magic trick. For example, can Mac intentionally adjust where people look and increase the feeling of magic? Should he adjust the speed at which he tosses the coin to be optimized to visual processing? And if so, does such adjustment actually help create the illusion? The precise answers to these questions can be obtained only through direct scientific experimentation. By answering them, we will determine if the perception of magic is tied directly to the way we optimally perceive stimuli with our eyes.

In order to determine whether magicians have discovered new perspectives on the brain that scientists have missed, we intend to test their intuitions in our labs. For example, as we described in chapter 5, Apollo Robbins intuits that, in some circ.u.mstances, a curved motion is more effective than a straight motion for misdirection, whereas straight motion is more effective than curved motion in other situations. One underlying neuroscientific hypothesis is that curved versus straight motion results in different types of eye movements and that those eye movements have different effects on attention. If this is correct, Apollo's insight may reveal an important new perspective on the relationship between cognition and the oculomotor system.

Will all this science make the magic go away? We believe that the wonder and awe of perceiving magic will no more disappear than did the beauty of the sunrise after Copernicus discovered that the earth is a sphere rotating around the sun. Both revelations-that we are hurtling around the sun and that magic works because our brains are inherently limited-are simultaneously deeply humbling and awe-inspiring. Increased humility deepens the mystery rather than dispels it.

A few years ago, Steve stood on the summit of Haleakala, a sacred mountain rising ten thousand feet above sea level on Maui, to watch the sunrise. His father once ran an observatory on the same spot, shooting lasers at mirrors left on the moon to measure how long it takes for light to return to earth. The round-trip time changed from one measurement to the next because Maui moved as the earth's tectonic plates shifted.58 Before Steve's father died, he asked to have his ashes spread on Haleakala, and so it was that on this particular morning Steve found himself standing there with his dad in mind, watching the sun's rays burn holes through the clouds from 93 million miles away.

Imagine you are standing next to Steve. You are at the highest elevation for that particular longitude of the earth. That means that at the moment of sunrise, you are the fastest-moving people on earth with respect to the sun. You are hurtling toward it at over one thousand miles an hour,59 which is more than twice the escape velocity needed to leave earth orbit. If our planet suddenly stopped spinning during that sunrise, and your speed became a thousand miles an hour relative to the earth as well as to the sun, you would "see" nothing but that sunrise until you burned up in the heliosphere on your way to the center of our solar system-approximately eleven years later. Now imagine all this science as you enjoy the incredible raw beauty of the moment, and try not to drop your jaw.

A mundane explanation for that same sunrise is that you are standing at an arbitrary position on a not-very-special planet that happens to rotate once every twenty-four hours so that the local star's solar terminator pa.s.ses over an island in the middle of one of the planet's oceans every twelve hours. So what. To Steve, the extraordinary scientific facts only enriched what was already a very emotional experience.

And the same is true for magic, or anything else, for that matter. The science adds to the experience, makes it deeper, fuller, more satisfying. When you see a great trick and can sense the effect it's having on the neural circuits that are at the core of your being, it's as breathtaking as a Haleakala sunrise.

The basis of all science is a fundamental love of and curiosity about nature. Magic profoundly manipulates the nature of our conscious experience. As such, it holds the promise of revealing some of the most compelling scientific discoveries imaginable.

You might wonder whether magic, with all its complexities, its emotional, attentional, and cognitive components, might be too complex to use as a tool to discover the fundamental principles of cognitive neuroscience. But we think that anyone who takes this point of view may not realize that such arguments have been made before in biology, psychology, and physics and proven wrong.

For example, the study of the neural basis of consciousness used to be considered an impossible field of inquiry. Now things have changed and dozens of labs, including both of ours, investigate the activity of neurons in relationship to conscious versus unconscious perception. Christof Koch and Francis Crick,60 who championed the neurobiological study of consciousness back when it was considered uncouth, made the a.n.a.logy to the question of life as a scientific topic. It seemed an impossibly complex problem, until James Watson and Crick's discovery of the structure of DNA showed how straightforward it really was.

Just because you can't imagine how something works doesn't mean it's impossible to find out.

Over and over, in the history of science, the same story repeats itself: a supposedly unapproachable subject matter is shortly afterward shown to be very much approachable. philosophers such as Immanuel Kant stated that the human mind was not susceptible to measurement, and therefore a science of psychology was impossible. Then Gustav Fechner, a German physicist, contracted an eye disorder that made him resign his professorship at the University of Leipzig. After he recovered, he turned his studies to the quantification of mental processes, discovering the exact mathematical relationship between a physical stimulus and its a.s.sociated subjective perception, thereby inventing the new field of psychophysics, a fundamental cornerstone of psychology.

And it's the same issue here with developing a science of magic. If humans can build a machine like the Large Hadron Collider to examine the Higgs boson, the ephemeral particle that is the very basis of ma.s.s, it should also be possible to discover the brain mechanisms related to magic.

And if we can do that-if we can understand magic fully at the level of the brain's circuits-we will know the neural pathways underlying consciousness itself.

If there is one thing we've learned from becoming magicians, it's that your attention, awareness, intuitions, and a.s.sumptions are fair game. Even we, beginner chumps in the field of magic, are skilled enough to lead you down the garden path and eat your lunch behind your back. So what does it say about your brain that you are so easily fooled?

We've given some answers as to why you (and we) are so gullible: our brains create sensory afterimages, our memories are fallible, we make predictions that can be violated, and so on. But as we reflect on the reasons, we are drawn to one that stands above all others in explaining the neurobiology of magic-the spotlight of attention.

Recall that your visual system has a spotlight of attention. It's the region of your visual perception in which you enhance everything that occurs. But the principle holds true for hearing, touch, other sensory systems, and even cognitive functions-for everything your brain does. Your spotlight is directed to a region of your cortex and enhances the activity carried out in that region.

But attention exercises another effect in your brain, too. It not only increases the neural signals at the center of your spotlight, it also suppresses the activity in the surrounding region. In the visual system this can create a so-called center-surround attention focus in your visual field. You see better at the center, while the surrounding items are suppressed.

In your touch system, attention creates a center-surround spotlight on your skin. Apollo Robbins's tap on your shoulder forces you to pay attention to that particular location, while suppressing the more subtle sensations produced by the removal of your wrist.w.a.tch a few feet away. And in the cognitive areas of your brain, attention creates a center-surround region in whatever type of s.p.a.ce is being computed by that region. You may fixate on a given idea and suppress all others that might compete.

Our research shows that the spotlight affects visual processing from the very first stages of the visual pathway, signifying that it is a very important factor in what you see and don't see. We believe it also determines what you hear, feel, and are aware of in a magic show, and indeed in the rest of your waking life.

Our studies further show that the harder you try to attend to something, the more you enhance it and the more you suppress surrounding information. This suppression versus enhancement dynamic gets really interesting when you think about decision making and the role of intuition versus rational thinking.

Malcolm Gladwell in his book Blink extols the virtues of decision making based on gut level intuitions. In one example, he tells of a museum that purchased a statue. The inst.i.tution had experts examine the statue for three months, and they declared it to be authentic. But then the curator showed the statue to an archeologist, who took one look at the piece and advised them, "Try to get your money back." Indeed, the statue turned out to be a fake. The archeologist was able to spot immediately what prolonged scrutiny by committee had failed to detect.

On the other hand, Christopher Chabris and Daniel Simons in their 2010 book, The Invisible Gorilla, argue that you should rely on deep rational thinking, not your intuitions, to guide your decisions. For example, some parents choose not to vaccinate their children because of their deeply held intuition that vaccinations lead to autism. Chabris and Simons argue that the apparent link is no more than an illusory correlation. Rational examination reveals that there is no causal relationship between vaccinations and autism.

Who's right? Based on our exploration of neuromagic, we believe that both approaches are correct if you combine their ideas in light of the neurobiology of attention.

In terms of its underlying brain mechanism, an intuition may result from weak neural activity in a given brain circuit. The activity is not strong enough to be accessible to your logical mind and drive your rational decision-making processes.

Brain signals can be weak for a number of reasons. The information coming from your sensory or memory systems is sketchy, as in black art, where the contrast between an object and the background is so low that the object is for all intents and purposes invisible.

Or brain signals may be weak because your attentional mechanisms suppress otherwise strong signals. For example, when Apollo Robbins pulls a quarter out of your breast pocket and moves it elegantly along an arc across your face, you follow it the way a tennis spectator follows the ball. You miss that Apollo simultaneously removes your reading gla.s.ses from the same pocket, directly under your nose, even though the image of his stealing hand is falling directly on your retinas.

In this sense, rationality and intuition are two ends of a continuum, with weak (intuitive) signals at one end and strong signals, which can be used to reason with, at the other end. Attention can serve to change the strength of any signal up or down anywhere along this continuum. Thus no decision is purely rational, because even though you see clearly in the center of the spotlight, there is darkness just outside the spotlight. Not only are you influenced by your biases, expectations, and a.s.sumptions, but you also actively suppress and ignore critical information. Conversely, the vaguest intuitions and gut feelings usually become accessible to your "rational" mind when you cast your attentional spotlight on them, making them more salient and easier to examine.

The yin and yang of attention affect all your decisions. For example, when we opened our first labs, we jointly hired a technician who cried during her job interview, worried that she would be homesick. We ignored our intuitions that this was not a good sign and relied on the fact that she was, on paper, perfectly well suited and experienced for the position, and that she explicitly told us she wanted the job despite the emotional outburst. The outcome proved unhappy for her and for the rest of our two labs. If only we had a.n.a.lyzed all of the information we had, instead of suppressing the nonrational bits, we might have made a better, more productive decision.

A crucial take-home lesson from this journey through neuromagic is that when you are confronted with the uncertainty of a complex decision with lots of variables, you cannot always antic.i.p.ate what will turn out to be most important factor, because of the suppressive and enhancing effects of your own attention. To overcome this, you must cast your attentional spotlight over each detail of the decision in turn, even if some initially appear insignificant or ephemeral. Reasoning things through is critical, but so is addressing your intuitions, so that your attentional spotlight can focus on each morsel and bring it forward for a.n.a.lysis. Only then will you be able to see the whole picture.

After our years of living magically, we will never watch a magic trick the same way again. Our appreciation of magic has been deepened, and it's been given gravitas to the nth degree by the knowledge that all of magic, every little sleight, is really happening in our minds. We've learned that misdirection and other illusions are important to us humans both on and off the magic stage.

We will now reveal one final secret. In a way, we've misdirected you, the reader, at every step. You may have purchased this book to read about magicians and tricks, sleights and secret methods, but all along you've really been learning the fundamental neuroscience at the center of your being. And that's where all the magic really takes place: inside a three-pound lump of flesh, your own brain.

Epilogue.

Lessons for Life: Bringing the Magic Home.

By tricking us so thoroughly, magicians have taught us to think about neuroscience in new ways. Here are some of the lessons we have learned from them that you can use in your own life. We will post more of these on our Web site http://sleightsofmind.com as we continue to gain insights, so please check back often for updates.

Magicians know that mult.i.tasking is myth and so they use a "divide and conquer" approach with attention. They split your attention so you cannot concentrate fully on any part of the stage at a given time. When you have a long list of things to do, you may feel tempted to do two or more tasks simultaneously, such as answering e-mails while attending a staff meeting. Chances are you will do neither task well. For your best performance, do one thing at a time.

Magicians know that memory is fallible and that the more time that has elapsed between the acquisition and the recovery of that memory, the less accurate it is. Know this about yourself and keep records of important information and conversations immediately after they happen.

Even though magicians make mistakes all the time, they set them aside and keep moving forward, and the audience hardly ever notices. You should do the same.

Some salespeople and psychics will "read your mind" by telling you exactly what you want to hear. Next time you go buy an expensive item and suspect the seller is taking you down the garden path, try changing your story along the way. For example, tell the salesperson that you are most interested in the contrast and brightness of your next TV. Once a model has been shown to you, inform the salesperson that actually you are most interested in the longevity of the device. If the best selling points of the current model change according to your request, then the salesperson is not being honest about the product, and is telling you what you want to hear.

Magicians use humor and empathy to lower your guard. If you sympathize with a magician, you will enjoy yourself more and be less vigilant about catching the secrets behind his magic. When negotiating interpersonal, professional, or business relationships, do as a magician and disarm with charm.

Each spectator is a "telepath." If you have something to hide from your business partner or spouse or a law enforcement agent, you will do best not to think about it while in their presence, lest your voice, gaze, or posture give you away.

Magicians know that attention enhances one small part of the world, while suppressing everything else. When making a difficult decision such as hiring somebody or taking a job offer, make a list of all the tidbits of information you have, no matter how unimportant they may seem. Then sequentially focus your full attention on each item and consider them each individually and fully. Carefully consider the ramifications of each fact and each feeling or intuition you may have. In turn, your attentional processes will enhance each particular issue, while suppressing all other information. Once you reach the end of the list, you will have a full picture based on both the hardcore facts and your gut feelings. You will be ready to decide.

Notes.

1. The Woman in the Chameleon Dress.

neuromagic: See S. Martinez-Conde and S. L. Macknik (2008), "Magic and the brain," Scientific American 299: 7279.

Margaret Livingstone's work: M. S. Livingstone (2000), "Is it warm? Is it real? Or just low spatial frequency?" Science 290: 1299.

By definition: See the recent special issue of Scientific American in which we discuss how our visual perception is dominated by illusions. S. Martinez-Conde and S. L. Macknik (2010), "The Science of Perception Special Issue," Scientific American Special 20(1).

To get at the neural correlates of PTSD: Read more at http://www.smithsonianmag.com/science-nature/How-Our-Brains-Make-Memories.html.

This is where you first detect the different orientations: The discovery of neurons selective to line orientation won the 1981 n.o.bel Prize in Physiology or Medicine for David Hubel and his partner, Torsten Wiesel. Once orientation selectivity was discovered, the field of visual neuroscience set out to categorize all of the various types of features encoded by the visual system.

You also make up a lot of what you see: A receptive field is a region of s.p.a.ce that, when acted upon by a particular stimulus, will cause that neuron to respond. It is the part of your retina that each neuron can see. Haldan Keffer Hartline won a n.o.bel Prize in Physiology or Medicine in 1967 for showing that the retinal neurons that transmit information to the brain respond best to those parts of a visual scene containing the edges of objects. By adding, subtracting, or even multiplying receptive fields, your brain creates a zoological tree of neurons with individual preferences for various aspects of a visual scene or features of objects.

This response causes a ghostly image: S. L. Macknik and M. S. Livingstone (1998), "Neuronal correlates of visibility and invisibility in the primate visual system," Nature Neuroscience 1(2): 14449.

Auzinger immediately grasped the implications: Ottokar Fisher, Ill.u.s.trated Magic (New York: Macmillan, 1943).

Today a black art act: Two brothers, Joe and Bob Switzer, invented fluorescent paint and Day-Glo paint in the 1930s. Joe wanted to be a magician when he was younger and started fooling around with black light that he and his brother learned to make from popular Science magazine. They sneaked into their father's pharmacy and shone light on different chemicals; some glowed brightly. So they mixed chemicals to develop various kinds of paint that fluoresce under ordinary ultraviolet light. Fluorescent pigments seem brighter than standard pigments because they reflect more visible light than they would if they were not fluorescent.

"the sky is filled with stars": All celestial bodies, including galaxies, project dots of light smaller than any photoreceptor in your eye. But then how is it that some stars appear bigger than others? The answer is that some celestial bodies are so bright that the extra light they produce reflects off the back of your retina. This reflection in turn excites many more photoreceptors in a larger circular area. The result is that bright stars seem larger.

2. The Secret of the Bending Spoon Two normal depth perception cues: You may be surprised to learn that the depth perception your brain creates by comparing the images in your two eyes (called stereopsis) is an illusion, wholly a construct of your mind. Your left eye and right eye convey slightly different views of the world to your brain. If you close your left and right eyes in rapid succession and look at an object, you will see that the object shifts left to right. With both eyes open, your brain triangulates these two images into a single stereo image, which gives you a sense of depth. This is the principle behind stereo-depth illusions such as in the Magic Eye books.