Sleights Of Mind Part 3

The Gorilla in your Midst.

More Cognitive Illusions.

Apollo Robbins is having a blast fleecing George at the Magic of Consciousness symposium. He turns to face him for another demonstration of his wiles. "When I approach somebody," he says, "I find that if I go straight in, I enter their personal s.p.a.ce. It's like a bubble surrounding their body. The distance is different in different cultures and in different people, but everyone senses the s.p.a.ce and tries to protect it." Apollo then turns his body to stand shoulder to shoulder with George. "But if I move to the side, like this, the gap is much smaller. You don't feel invaded." One more thing. "As I move into your personal s.p.a.ce, I need to break eye contact with you, so that you don't keep your gaze on me." Apollo looks down. George looks down. Apollo pops up next to George's shoulder. He is now safely inside George's bubble. He can get away with magical murder.

Apollo's observation is fascinating. What he calls personal s.p.a.ce, neuroscientists know as peripersonal s.p.a.ce. (Scientists can never resist a good game of Pin the Greco-Latin Root on the Simple Word.) People have always had a strong intuitive sense of this s.p.a.ce, and neuroscience has recently begun to decode its neural foundation in the brain. It turns out to be more than a mere metaphor but less than a real, tangible aura. It is a construct your brain actively creates as part of your mind's body. As far as your brain is concerned, the s.p.a.ce immediately around you is literally a part of your body. This is why you can tickle a child by wriggling your fingers in the air over her ribs, and why you are physically as well as emotionally sensitive when someone "punctures" your bubble uninvited.

Finally, Apollo reveals a principle of the pickpocket's art that particularly thrills us as neuroscientists. "In years of doing shows," he says, "I noticed that the eye is more attracted to arches than to straight lines." He starts patting George's pockets again. George looks on with interest. "If I want to take something out of his pocket, I can keep his eyes occupied on my free hand if I move it in an arc. But if I move it in a straight line, his attention will snap back to my other hand" like a rubber band, he explains.

We had first heard Apollo describe this principle when we came out to Las Vegas a few months prior to the Magic of Consciousness symposium, in one of the meetings where we got together with magicians to share knowledge and ideas and to brainstorm about the upcoming conference. (We don't mind telling you that after every meeting with Apollo we check the credit cards in our wallets to see if they've been swapped for fakes. He's really that good.) Teller had called for this particular meeting in his office so that we could present to the magicians our scientific research on illusions and visual perception. The initial purpose of our collaboration with magicians was to enable us to use magic in the lab, but it would obviously help for the magicians to know what cognitive research looks like. After showing them some of our work on visual illusions, Susana presented what we know about the neuroscience of eye movements. There are two main kinds, and they serve different purposes and are probably controlled by different subsystems of the oculomotor system.

In the first kind of eye movement, called saccade, your eyes jerk almost instantaneously from one point to another. The fleeting moments between saccades, when your eyes are for the most part motionless, are called fixations. Saccades are critical to vision because your eyes can make out fine detail only in a keyhole-sized circle at the very center of your gaze covering one-tenth of one percent of your retina; the vast majority of the surrounding visual field is of shockingly poor quality.

You can prove this to yourself with an ordinary deck of cards. Separate out the face cards and shuffle them. Fix your gaze on something directly across the room and don't let your eyes move at all. Draw a random face card and hold it out at arm's length at the very edge of your peripheral vision, then slowly pivot your arm forward, bringing the card toward the center of your unflinching forward gaze. a.s.suming you can resist the urge to let your eyes dart off to steal a glimpse, you will find that the card has to come quite close to your center of vision before you can identify it.

The reason it doesn't feel like your vision is ninety-nine point nine percent garbage is because of saccades. Your eyes are constantly darting around the world like a hummingbird on meth. Your brain edits out the motion blurs and integrates the small bits of information received from each fixation in order to present your visual awareness with a detail-rich, stable-seeming portrait of the visual scene before you.

Saccades are also related to adaptation. Recall that the neurons in your visual system are designed to detect change. But when conditions remain static, your neurons adapt by slowing their firing rate. They cease giving you reliable information, and your perceptions are limited. It is as if your neurons actively ignore a constant stimulus to save energy so as to better signal that a stimulus is changing. The visual scene threatens to fade away.

To overcome adaptation, you make microscopic eye movements during each fixation between large eye movements. Such fixational eye movements are essential for vision. Indeed, without these minuscule ocular meanderings, you would be blind when you fix your gaze. Our studies indicate that when your gaze stops on an object and does not move, activity in your visual neurons is suppressed. The object disappears!

In the second kind of eye movement, called smooth pursuit, your eyes move in a continuous, uninterrupted path without any pauses or jerks along the way. Smooth pursuit takes place only when you track a moving object. It cannot be faked. This is one of the reasons that some scenes in movies fail: when an actor pretends to track an object that doesn't actually exist, but is added in postproduction, the eye movements inevitably look wrong on-screen. Pursuit eye movements allow you to track moving objects, while saccades systematically search and gather information from a visual scene.

Saccadic eye movement vs. smooth pursuit: the left figure shows the zigzagging path an observer's eyes might trace while looking at a magician. The right figure shows the eyes' smooth, unbroken pursuit path as they follow the tip of his wand raising in a gentle arc. (Photograph by Matt Blakeslee) You can observe the difference between these two types of eye movement by holding up your thumbs in front of you about a foot apart. Now, holding your hands still, ask a friend to slowly move her eyes as smoothly as possible from one thumb to the other. Notice that her eyes make little jumps along their journey. Those little jumps are saccades. No matter how hard she tries, she cannot make her eyeb.a.l.l.s swivel smoothly between the thumbs. Now try it again, but this time ask her to watch your left thumb as you move it slowly over to touch the right one and then back out again. Notice this time how her eyes track perfectly smoothly.

All the magicians were fascinated by these facts, but for Apollo they triggered a eureka moment. He said that as a pickpocket he differentiates between straight-line and curved hand movements when managing his marks' attention. He now realized the reason might be the difference between saccades and pursuit eye movements.

When you see a hand quickly moving in a straight line, your eyes-and your attention-automatically jump to the end point. So a pickpocket will make a fast, linear gesture if he wants to minimize your ability to pay attention to the path itself. But a hand that moves in an arc triggers a different tracking mechanism. You cannot predict where the hand is headed, so you fixate on and follow the hand itself, and you fail to notice when Apollo's other hand slips into your pocket.

Pickpockets have a whole toolkit of misdirection techniques. We were already familiar with some of them. Such thieves often ply their trade in dense public s.p.a.ces and rely heavily on socially based misdirection-eye contact, body contact, and slipping, ninja-like, inside the personal s.p.a.ce of the mark. But Apollo's observation was new to us, and it immediately sp.a.w.ned new ideas for experiments.

It is well established that visual perception is suppressed during saccades, which could explain the way pickpockets make use of fast linear movements. But what about attention? Is it also suppressed during eye movements? Scientists do not yet have an answer, but Apollo's suggestion was so intriguing that we wanted to take it to the lab. This conversation marked a sea change in our relations.h.i.+p with the magicians. Our original intention had been simply to poach their best techniques so that we could design better experiments, but now we realized that magicians might actually know things about mind and behavior that neuroscientists do not.

You already know about your capacity for "overt" and "covert" attention. Overt attention is when you purposefully direct your eyes to an object while paying attention to it. Covert attention is the act of looking at one thing while paying attention to another. Magicians, diabolical as ever, have exploited these properties of your brain in designing some of their favorite tricks. To describe these methods, we coined the terms overt misdirection and covert misdirection.

In overt misdirection, the magician moves your gaze away from the method behind the trick. He draws your eyes to something of false interest while he carries out a secret action at another location. This is what most people think about when they hear the word "misdirection." An explosion lights up the stage, and a miniature mushroom cloud billows its way up to the rafters. Whoops! Where did that rabbit come from on the other side of the stage? When you were looking at the explosion, the magician used any one of a dozen methods to make the rabbit appear while you were distracted. That's overt misdirection, and it's the same thing Steve did when he swiped Halloween candy as a kid. "Hey, Jimbo! Is that the Goodrich blimp?" Candy gone. And by the time the theft is discovered, it's half eaten. Yes, Jimbo is Steve's younger brother, and this is a fond memory of nutty, chocolatey, stolen goodness.

Covert misdirection is more subtle. The magician draws your attentional spotlight-and focus of suspicion-away from the method without redirecting your gaze. You may look directly at the method behind the trick, but you are entirely unaware of it because your attention is focused elsewhere. You look, but you do not see.

Cognitive neuroscientists know quite a lot about covert misdirection-it's a critical element in inattentional blindness. With inattentional blindness, you fail to notice an object that is fully visible because your attention has been directed elsewhere. It pertains to how your brain sees and processes information. We also study a closely related phenomenon called change blindness. With change blindness, you do not notice a change in a scene. It pertains to how your mind fails to remember what it has just seen.

Can You Keep us from Reading Your Mind?

Can you explain the astounding results of the following mind-reading experiment by Clifford Pickover, a prolific author of popular books about science and mathematics? The editors of Scientific American prepared a simulated Pickover test that you can take here, or you can try the even more puzzling online version at http://sprott.physics.wisc.edu/pickover/esp.html.17 By using ESP, we think we can predict the outcome of your choice with 98 percent accuracy. To begin, pick one of the six cards below and remember it. Say its name aloud several times so you won't forget it. Once you're sure you'll remember it, circle one of the eyes in the row below. Then turn to page 82 to see if we are right.

While many magicians strive to exploit inattentional or change blindness in their acts, the grand master of these deceptions is the Spanish magician Juan Tamariz. In the hierarchy of illusionists, he is Yoda. Dai Vernon, the legendary magician who fooled Houdini (chapter 2), used to say that in his eighty-plus years of career as a magician, n.o.body had been able to deceive him like Tamariz. But you wouldn't know it from looking at him. Sure, we've discussed some weird-looking magicians. But when you conjure up the image of a world-famous magician in your mind's eye, you nevertheless probably think cla.s.sy: well dressed, well coiffed, well mannered. You think Copperfield, Henning, even Penn & Teller in their matching suits.

But an unkempt Spaniard with long stringy hair and crooked teeth who wears huge eyegla.s.ses, goofy vests, and a purple top hat? This guy has the propensity, at the climax of a trick, to jump into a Gollum-like, bent-over posture and point at you while he screams "Chaan ta ta chaaaaaan!" No one would imagine that this comical Cat-in-the-Hat character would be a top mage-which is one of the primary reasons he is so effective at duping you.

Tamariz is a founder of what is known as the Madrid School of Magic (Escuela Magica de Madrid). It's a magic think tank of like-minded conjurers from around the world who are interested in improving the art of magic through the application of human psychology. Members consider every aspect of the art, from the minor issue of which way to reveal a card (it's better to flip it head over heels rather than heels over head18) to the important question of exactly when and when not to introduce humor during a trick.19 Their goal is to understand magic methods and the human mind to such a high degree that magic tricks make you feel as though a miracle has just happened.

Tamariz uses inattentional blindness to create many small miracles. He figures that you probably don't know you are blind to things outside your spotlight of attention. So when he performs a trick obviously right before your eyes-and you miss it-you will be incredibly surprised; the only explanation is magic. In one such method, called Crossing the Gaze, Tamariz makes a coin disappear from one hand while keeping both hands openly visible.

We Read Your Mind...

We have removed your card! Did we guess the card you picked? If so, does Pickover's ESP system explain our correct answer, or is there a simpler explanation? Read no further until you want to know the answer.20 Give up? Look once more at the six cards, then compare them with the five cards pictured. Notice any differences? If the act of circling an eye distracted you and you fell for the trick (most people do), you are a victim of what psychologists call change blindness. A change-even a big, obvious change-can be all but invisible until you take another look.

SPOILER ALERT! THE FOLLOWING SECTION DESCRIBES MAGIC SECRETS AND THEIR BRAIN MECHANISMS!.

Here's what the trick looks like. Tamariz stands with his right side facing you. His left hand is outstretched, palm up and empty. His right hand points to his open palm. Tamariz looks at you, beckoning your gaze directly to his eyes. He has your full attention. Then he looks down at his empty palm. You follow his gaze and look at the palm. And here is the essence of the trick. During the fraction of a second while you move your eyes, Tamariz lifts his right hand toward you in a natural gesture that says "Hold on, don't be impatient." And there, in the middle of his right palm, is a bright s.h.i.+ny coin. It's in full view. But you don't see it because Tamariz has powerfully driven your attention to the empty palm. You concentrate so hard that you miss an object that is reflecting photons directly onto your retina.

Tamariz's Crossing the Gaze technique (the gaze motion should cross the hand motion, so that the two trajectories are equivalent but their directions opposite) was inspired by the Italo-Argentinian magician Tony Slydini, one of Tamariz's masters. (Courtesy of Juan Tamariz) END OF SPOILER ALERT.

So what is the point of this maneuver? You never knew the coin was there, so why is he taking the trouble to misdirect your attention? A good magician can take advantage of this situation in countless ways. For instance, Tamariz can now do something else with his right hand to produce the coin. But you "know" both of his hands were empty because you "saw" them that way. It is this kind of strong, albeit misleading, evidence that will make the subsequent appearance of the coin feel like a miracle.

Neuroscientists are equally thrilled with the possibilities raised by inattentional blindness. Several years ago, two of our colleagues, Daniel Simons and Christopher Chabris, designed a brilliant experiment that never fails to shock and delight people encountering it for the first time. The instructions are simple. You are asked to look at a short video of people pa.s.sing around a basketball. One team wears white T-s.h.i.+rts, the other wears black T-s.h.i.+rts. Your job is to count the number of pa.s.ses made by one team, or to keep count of bounce pa.s.ses versus aerial pa.s.ses. After three or four minutes, the video ends and you are asked if you saw anything unusual.21 No? Look again. This time the scientist pauses the video at the halfway point. And there, suddenly, inexplicably, you see it-a person dressed up in a gorilla suit, standing smack in the middle of the basketball players, beating its hairy chest, looking right at you. Rewind, and you see the whole impossible action. The gorilla strolls up to the players, turns toward the audience, thumps away, turns, and walks off slowly. Half the people who see this video fail to notice the gorilla.

Why? How could you fail to notice a monstrous ape amid ball-tossing college kids? It's because you are so deeply engaged in counting the number of pa.s.ses that a gorilla is not enough to draw your attention away from the ball. You look right at the hairy beast and do not see it.

We've shown this video ourselves in dozens of lectures. We often ask people who do see the gorilla, "How many pa.s.ses did you count?" The answer is usually wrong, or they admit to having not counted at all. Ironically, the better you perform the counting task, the less likely you are to notice the strolling gorilla. In other words, your focused attention ensures optimum performance in a given task but makes you blind to seemingly irrelevant data that may be more critical than the task at hand. Our own research shows that the brain suppresses distracters more strongly during a difficult task (when you are trying very hard to focus) than during an effortless task (when you are having an easy time). In everyday life, this means that even when you are focusing on accomplis.h.i.+ng some critical job, you still need to remember to look up and around once in a while or you'll risk missing important facts and potential opportunities.

The Gorilla in Our Midst experiment raises an interesting question. Where are your eyes looking? Is the ball the only thing falling on your retina? Or is the gorilla's image also reaching your eyes but not registering with your brain? Eye tracking devices might help find an answer. An eye tracking device measures eye position under experimental and natural conditions. For instance, with a video camera pointed at the eyes, a computer program can find the pupils in the camera's image and detect how much they rotate from moment to moment. This allows scientists to know what the eyeball is looking at.

In 2006, Daniel Memmert showed, using eye tracking recordings, that many people do not notice the gorilla even when they are looking directly at it. Those who miss the gorilla spend as much time (around a second) looking at it as those who see it. This was an incredibly surprising result. Many neuroscientists had a.s.sumed that the gorilla was invisible because the basketball game drew the observers' eyes around the image, but away from the gorilla, at any given instant, as in overt misdirection. Memmert's results showed that they were wrong; it was really covert misdirection. The gorilla was invisible even when you looked right at it, because the basketball counting task drew your attention away from the gorilla. The study indicates that visual perception is more than photons entering your eyes and activating your brain. To truly see, you must pay attention.

Eye tracking has also been used to study attention and magic. In 2005, Gustav Kuhn and Benjamin Tatler, in the first study to correlate the perception of magic with a physiological measurement, employed an eye tracker to follow the eye movements of people watching a trick where a magician makes a cigarette "disappear" by dropping it in his lap. The researchers wondered: Do you miss the trick because you do not look at the right time? Or do you not attend no matter where your gaze falls? They found that the failure to notice the cigarette drop cannot be explained at the level of your retina. Detection rates were not influenced by blinks, saccadic eye movements, or the cigarette's distance from the center of the observer's vision at the time of the drop. The magician manipulates your attention rather than your gaze.

Inattentional blindness can get you into trouble in everyday life. How often have you been chatting away on a cell phone, only to find yourself b.u.mping into another pedestrian? In 2009, psychologists at Western Was.h.i.+ngton University looked at four categories of college students walking across a main campus square. One set simply walked along minding their own business. A second walked in pairs, talking. A third listened to iPods as they walked. The fourth was gabbing on cell phones. In each instance, an outrageously costumed clown on a unicycle pedaled up to the students, circled them with comic abandon, and rode off.

Students who walked in pairs were most likely to see the clown. Those using iPods or walking alone were only slightly less attentive. But half of the students talking on cell phones entirely missed the clown on the unicycle. They also walked more slowly, weaving as they crossed the square. The researchers concluded that cell phone conversation leads to inattentional blindness and disrupts attention. It even disrupts walking.

On Mult.i.tasking.

Think you can text while driving? Listen to music while you pay your bills, send tweets, and monitor a football game on television? Write an e-mail, play solitaire, and check stock quotes while you have an argument with your spouse?

Think again. A decade of research clearly shows that mult.i.tasking-the ability to do several things at once, efficiently and well-is a myth. Your brain is not designed to attend to two or three things at a time. It is configured to respond to one thing at a time.

Research shows that you can't simultaneously give full attention to both the visual task of driving and the auditory task of listening, even if you use a hands-free device. In fact, people who talk on cell phones while driving a car have the same attentional focus as people who are legally drunk.22 When you attend to the phone conversation you "turn down the volume" on the visual parts of your brain and vice versa.

Studies also show that people who are bombarded with several streams of electronic information do not pay attention, control their memory, or switch from one topic to another as well as those who complete one task at a time. Chronic mult.i.taskers "are suckers for irrelevancy," says Stanford communications professor Clifford Na.s.s. "Everything distracts them." They can't ignore things, can't remember as well, and have weaker self-control.

Another of our colleagues, Russ Poldrack at UCLA, has shown that people use the striatum, a brain region involved in learning new skills, when they are distracted and the hippocampus, a region involved in storing and recalling information, when they are not distracted. "We have to be aware that there is a cost to the way that our society is changing, that humans are not built to work this way," says Poldrack. "We're really built to focus. And when we force ourselves to mult.i.task, we're driving ourselves to perhaps be less efficient in the long run even though it sometimes feels like we're being more efficient."

Magicians know that mult.i.tasking is an urban legend 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 your task list is pages long, you may feel tempted to do two or more things simultaneously. For instance, answering e-mail on your iPhone while attending a staff meeting. Chances are, you will do neither task well. For best performance, do one thing at a time.

Eric Mead, the mentalist whose knowledge of human nature never ceases to amaze, has joined the two of us at the Monterey Fish House in California, where we are bibbed and slurping down giant bowls of cioppino and gla.s.ses of Chianti. Susana asks Eric if he ever uses his training as a magician in everyday life. Without missing a beat, Eric closes his eyes and describes in detail the diners sitting all around us-how many are at each table, their genders and approximate ages, what they are having for dinner, even their conversations and apparent dispositions.

The couple on the left are celebrating a birthday. The family in the back attended a funeral earlier in the day. The ceremony was presumably for someone outside their immediate family (since they're here for dinner) but close enough to garner funereal attendance by the whole clan. The people behind Susana are in an unhappy marriage. To Steve's right a group of coworkers are celebrating someone's achievement; Eric's not yet sure what it is. The man over there is having a good time. That woman is in a bad mood. The birthday couple are making bedroom eyes at each other and do not want to be disturbed.

Eric says that he needs this kind of information when choosing subjects for his mentalism performances and he gathers it by practicing situational awareness-the deliberate perception of everything happening in the immediate s.p.a.ce and time, the comprehension of its meaning, and the prediction of what may happen next. As we entered the restaurant, sat down at the table, ordered from the menu, and dug in, Eric casually cast his spotlight of attention onto all of the people around us, out of habit.

Eric never stops a.s.sessing his surroundings. You never know when you're going to need information for an impromptu display of magic, he says. By moving his attentional focus like a searchlight in the night sky, Eric has learned to avoid getting too absorbed by any individual aspect of what is happening around him and, for this reason, he says that he no longer experiences magic the same way most people do. He's not impervious to misdirection but he's resistant to it. Nor by his own admission is he any good at mult.i.tasking. The skill he describes involves serial attention.

We wondered how difficult it would be to learn situational awareness skills and attended a training course at the Marine Corps' Aviation Survival Training Center in Miramar, California. The navy teaches its aviators about situational awareness-how to optimize perception and cognition in demanding environmental and mental workload conditions. It does not matter if you are ordering from a menu while maintaining conversation or recovering from a flat spin in a fixed-wing jet, some optimal pattern of attentional scanning will maximize your success at whatever you are trying to achieve.

We experienced the challenge firsthand when we strapped in and flew a multimillion-dollar simulator of one of the largest helicopters in the U.S. military inventory, the CH-53 Super Stallion. Seated in the c.o.c.kpit, we tried to allocate our attentional systems and scan our instruments while flying the huge beast. Our instructor, marine pilot Captain Vincent "Fredo" Bertucci, explained that your ability to scan your surroundings breaks down when your attention gets stuck in a rut. The world outside your windscreen beckons while your sensations give you the wrong information. Problems arise with the engines, with the s.h.i.+p you're landing on, with the load you're trying to lift with your chopper, with your communication systems inside and outside the aircraft. All of these events call for your attention, and will do so for too long if you're not careful. While your attention spotlights the one problem without scanning the other potential problems-for instance, you stare at a single broken gauge-you can unwittingly fly the helicopter into the drink.

Magicians use overt and covert misdirection to produce effects similar to these flight conditions. They split your attention and lead you to cognitive disaster. If we can reverse-engineer how magicians do it and apply those principles to developing methods to counteract attentional slips, we may be able to reduce the failures of attention that take place under conditions of high mental workload.

Two years after the Magic of Consciousness symposium in Las Vegas, we are in the quaint Pyrenees village of Benasque, Spain, attending an international conference on art and science. It is an eclectic group of experts who have come to explore the limits of human perception. Chefs are paired with scientists who study the sense of smell, architects are teamed with experts on human spatial perception, painters are linked up with visual neuroscientists, and the two of us are paired with one of Spain's premier young magic talents.

While we tackle the more academic aspects of overt and covert misdirection and their relations.h.i.+p to the brain's mechanisms of attention, Miguel Angel Gea cuts to the chase by performing tricks that dazzle the a.s.sembled cognoscenti, proving their grasp on reality is ever so frail.

Miguel Angel is a big young man with a long mane of brown hair cinched up in a ponytail. With his cargo pants and gauze s.h.i.+rt, he exudes casual good humor, which is not surprising, given that he was trained by Juan Tamariz himself. Miguel Angel is such a fun-loving soul that, despite his original intention to join us in Benasque for less than twenty-four hours, he ends up staying for four days-all due to the warm reception he receives from the conference partic.i.p.ants and villagers. Our joint conference presentation begins at 9:00 p.m. and runs, by popular demand, until midnight, after which Miguel Angel repairs to the bars and restaurants of the village, regaling locals (who know him from Spanish television) with more tricks until the wee hours of the morning. He does this each night, ending the revelry only when he announces that he is completely exhausted and can no longer hold a coin or deck of cards.

Miguel Angel's love of life is profound. But so are his insights into human behavior. He uses the latest cognitive science literature as a lamppost for guiding the development of new tricks. For example, our colleague Dan Simons of "gorillas in our midst" fame designed another clever experiment that ill.u.s.trates change blindness. In one version of the experiment, a proverbial absentminded professor is observed crossing a campus courtyard. A student walks up to the professor and says, "Excuse me, sir. Can you tell me where the gymnasium is?" He pulls out a campus map. "I don't know my way around."

The professor, who is happy to oblige, looks down at the map in joint attention with the student and begins to point the way. But just then two workmen carrying a large rectangular object-sometimes a door, sometimes a large painting-approach and endeavor to get by. "Excuse us. Excuse us, please, pa.s.sing through," they say as they carry the object between the professor and the student. It takes but a couple of seconds, during which comes the switcheroo. The student-perhaps dressed in jeans and a red T-s.h.i.+rt, with dark hair-ducks behind the object and moves off. A second student who was crouching and moving behind the object-perhaps with blond hair and several inches shorter, dressed in slacks and a collared s.h.i.+rt-now stands up in his place. He is holding the map as he sidles up to the professor, who, amazingly, fails to recognize the change. Perhaps students are "h.o.m.ogeneous units" in his mind, but still you have to marvel at his change blindness. The experiment has been replicated many times, switching characteristics such as height, accent, and clothing of all kinds.

Change Blindness in Action.

When we first moved to our current inst.i.tute, Susana needed an additional laboratory room in which to conduct perceptual experiments. Her department chair graciously offered the drafting room, as long as Susana didn't mind sharing her s.p.a.ce with a lot of bulky equipment-a slant table, large cabinet with flat drawers to store large drawings, huge paper cutters, and the like. Susana gratefully moved in. She then went to the individual lab heads and asked if they wouldn't mind removing any drawings they had stored in the cabinet, since the piece of furniture simply took up too much s.p.a.ce. Each person graciously agreed to help and Susana got rid of the cabinet. Then, on a different floor of the research building, Susana found another shared equipment room with some counter s.p.a.ce available. She moved the paper cutters and other equipment out of her new lab room. Over the course of a few weeks, the drafting room became a drafting room in name only, as it had been completely transformed into her lab. So Susana called the facilities staff and asked them to change the sign on the door from "Neurobiology Drafting Room" to "Laboratory of Susana Martinez-Conde."

Slowly but surely, Susana had transformed her perceptual testing lab s.p.a.ce from a single corner of a shared drafting room to her own complete unshared lab s.p.a.ce, all by employing the principles of change blindness. The department chair still shakes his head when he's reminded of it, but he's never asked for the room back because the lab s.p.a.ce is very productive and its projects have earned grant money to support the research in the room.

Miguel Angel figures that if you fail to notice two very different people swapping places, then you can miss just about anything. Certainly you can mistake one card for another. One afternoon at the conference he demonstrates how. Dressed in his usual casual attire, Miguel Angel calls for a volunteer from the audience. Once she is onstage, he asks her to pick a card from a deck. It is the eight of clubs. He shuffles it back into the deck. "I like to pull your card from my pocket," says Miguel Angel as he magically pulls the eight of clubs from his right hip pocket. Applause.

He looks at the volunteer. "Did you like that trick? Yes? There are tricks that I don't like." He raises his empty hand toward her and reaches into her hair, and, as he pulls away, the eight of clubs is back in the palm of his hand. "Other magicians like to pull cards from people's hair. But I don't like that trick myself," says Miguel Angel. Snickers emanate from the audience.

Next, Miguel Angel slides the eight of clubs back into the deck and places the deck on a table, holding a few cards out. He then rubs those few cards between the thumb and fingertips of his right hand. "Other magicians prefer to make coins appear," he says, as a large coin slides out from between the rubbed cards into his left palm. The crowd responds with oohs and aahs.

The volunteer shakes her head in disbelief. He looks at her as he deposits the remaining cards on the table-which is now a full deck that obviously includes the eight of clubs-leaving only the coin in his left hand. He tosses it into his right palm. "But me, no. I don't like tricks in which cards are taken from your hair, or even tricks with coins," he says as he tosses the coin back again-but this time it disappears.

"No," says Miguel Angel, "I prefer tricks with a single card in my pocket." He dips his empty right hand into his pocket and pulls out a card with its back to the audience. "And this single card is your card," he says as he rotates it forward to miraculously reveal the eight of clubs. Wild applause.23 SPOILER ALERT! THE FOLLOWING SECTION DESCRIBES MAGIC SECRETS AND THEIR BRAIN MECHANISMS!.

Miguel Angel has a sly smile on his face. He turns to the audience. "Would you like to know how that trick worked?" We shout a resounding "Yes!" He stands there for a second, as if contemplating his next move. He seems suddenly awkward. "It's a little difficult for a magician to reveal a trick," he says sheepishly. The audience laughs, sympathetically, as Miguel Angel reaches a decision. Flinging his arms over his head, he p.r.o.nounces, "For science!" and launches into an explanation that fascinates scientists and artists alike. He reveals that the trick starts before the show when he picks two similar-looking cards, in this case the eight of clubs and the eight of spades. He places the club above the spade and puts the deck in his pocket for safekeeping until the show.

When Miguel Angel asks the volunteer to pick a card, he uses a force so that she chooses the eight of clubs without realizing it. Forcing refers to a number of methods used by magicians to make you think you are freely choosing a card whereas they know in advance exactly what card you will take. We'll talk about this in more depth in the next chapter.

When the volunteer puts the eight of clubs back into the deck, it is not randomly inserted. Miguel Angel again forces her to place it where he wants it-directly above the eight of spades. His subsequent moves are stock sleight of hand. He "shuffles" the deck so that the two black eights are on top. He palms them and drops both in his pocket. When he says "I like to pull your card from my pocket," he reaches in for the eight of clubs and leaves the spade behind. (You can probably see where this is going.) He then works it so he "pulls" the eight of clubs from the volunteer's hair and he uses the coin routine as distraction from his main goal, which is change blindness.

When all the cards are on the table, you a.s.sume the eight of clubs is safely somewhere in the pile. That's when Miguel Angel reaches into his pocket and removes the eight of spades. He finishes his routine by saying, "Now, I prefer tricks with a single card in my pocket," and he flips the eight of spades over. But you and everyone else are so eye-rollingly amazed, so completely enthralled by the fact that Miguel Angel has impossibly produced the eight of clubs from his pocket, when it's supposed to be on the table, that you fail to detect that it's not the eight of clubs at all. It's a spade. Even the volunteer, less than three feet away, looks at the spade but fails to see it's the wrong card. Miguel Angel manages to fool one hundred leading scientists and artists with a cla.s.sic example of change blindness.24 END OF SPOILER ALERT.

Change blindness studies show that you will not notice dramatic changes in a visual scene if they occur during a transient interruption-such as a magician reaching behind the ear of a spectator, or two workmen carrying a door between you and the person you are talking to-even when you are looking right at the changes. Change blindness is also common during cuts or pans in movies. A winegla.s.s may be empty in one scene and full the next scene. Chances are you'll miss it.

Slow or gradual changes are also very difficult to see, especially if we are not focusing our attention on the changing object. This has been compellingly demonstrated by Simons: whole buildings, boats, people, and other highly salient objects may appear and disappear unnoticed, right in front of our eyes, if they do so slowly enough. It is tempting to speculate on how many things in our lives may slowly change without our awareness. The small aches, pains, and debilities that colonize our bodies as we age would be intolerable if suddenly imposed on a healthy twenty-year-old, but as we gradually grow older these changes creep in for the most part undetected. Other aspects of our lives, jobs, and relations.h.i.+ps may similarly change, worsening or improving in a very gradual and thus unnoticed fas.h.i.+on.

The Greek philosopher Epicurus knew that we tend to adapt to and thus ignore gradual improvements in our lives. He wrote: "Do not spoil what you have by desiring what you have not; but remember that what you now have was once among the things you only hoped for." It's sage advice, provided your pocket isn't being picked while you're distracted by your grat.i.tude.

The Ventriloquist's Secret.

Multisensory Illusions.

The first thing we notice on arriving at the 24th World Champions.h.i.+p of Magic in Beijing is that the ma.s.sive building where it's being held-the China National Convention Center-is all smoke and mirrors. It's not that there's something wrong with the air handling system, or that a magician used too much dry ice during his act. Rather, the edifice was constructed with mirrored panes of gla.s.s that, in the high heat of July 2009, trap huge shrouds of urban smog. Outside, it's worse. The entire city of Beijing is blanketed in smog so thick that you feel as if everybody and everything around you is an apparition emerging from behind a magician's smoke machine.

Plenty of venues award magicians for their skills, but the World Champions.h.i.+p of Magic is the preeminent international event. Held every three years in a different country by the Federation Internationale des Societes Magiques (FISM), this compet.i.tion is informally known as the Magic Olympics. The weeklong contest is where magic stars are created. Winning a grand prize here is akin to receiving an Oscar; it's a guarantee of steady work for years to come. Many talented young magicians such as Lance Burton have gone from obscurity to world-cla.s.s fame at the Magic Olympics. We're here to see it happen with our own eyes, and it's quite a scene. Twenty-five hundred amateur and professional magicians, purveyors of magical paraphernalia, and curious onlookers from sixty-six countries amble through the main lobby and corridors on their way to huge festooned halls where the ceremonies and compet.i.tions are being held. Their attire ranges from standard street clothes to wizard's robes and everything in between.

Some people attend lectures given by famous magicians on topics such as "From chaos to order: different methods to secretly arrange the cards into special order," "j.a.panese style on how to study magic," "How to present the same trick three different ways," and "Boldness and magic, or the art of having real nerve." Others roam between booths selling rope and card tricks, fake appendages of all types, magic trick books, special order card decks, stage gimmicks...everything a magician could ever covet.

One hundred performers are competing for the grand prize in the two main categories of stage magic and close-up magic. Stage performances are judged on manipulation, general magic, stage illusions, mental magic, and comedy magic. Close-up performers are rated for card magic, parlor magic, and micromagic (magic tricks done on a very small scale, such as small coin tricks or tricks with toothpicks).

Two days into the event we are thrilled to spot Max Maven, one of the world's greatest living mentalists, sitting in front of the overflow screen in the main hall outside the compet.i.tion rooms. Maven is legendary for his ability to read minds. Onstage he a.s.sumes a sinister Svengali look: thick black eyebrows arched high with disdain, a clipped Fu Manchu mustache, and a meticulously shaved widow's peak. He has an extremely high, heart-shaped forehead, pointy ears, a deep baritone voice, and salt-and-pepper hair pulled back into a taut knot from which a long braid hangs down his back. To complete his look, Maven wears black double-breasted suits, black s.h.i.+rts, and bold silver bracelets and rings.

But today Maven is in his street clothes-black T-s.h.i.+rt, black pants and boots. His samurai hair is loosely braided and almost reaches the floor. It is late afternoon and beams of sunlight are s.h.i.+ning into the convention center's halls like pillars of gold in a cathedral. A large sign-RM 319, RESTAURANT AND MAGIC SALON-hangs on the wall.

Maven is relaxing and watching a twenty-foot-high movie screen where a young magician from Sweden is producing card after card after card from an empty outstretched hand. Our son Iago has fallen asleep in his stroller, so we roll over to Maven. We've got a question ready for him: Does he know any multisensory tricks? That is, can he tell us about tricks that rely on interactions among the different senses such as vision, hearing, and touch? Maven is pleased with the query and responds by telling us a cla.s.sic joke used by generations of magicians to entertain friends and family. It's the Dinner Roll trick.

Here's his description: To begin, the magician is seated at a dinner table covered with a cloth. He makes sure that you are in front of him, unable to see his movements behind and below the cloth. He says something corny like "You know it's rude to play with your food. But I wonder if this soft dinner roll will bounce?" He holds the roll in his hand and flings it to the floor. You hear it bounce with a loud thunk and then fly back up into the air, where he catches it.

SPOILER ALERT! THE FOLLOWING SECTION DESCRIBES MAGIC SECRETS AND THEIR BRAIN MECHANISMS!.

The secret behind this very convincing illusion is simple. The magician sits across the table from you, turned away from the normal eating position. The magician's hand makes the motion to fling the roll to the floor. As soon as his hand and lower arm are out of your view, he turns his hand over, palm up. Using his fingers and wrist, he launches the roll back up into the air, making sure not to move his upper or lower arm. All the action is in his fingers and wrist-and in his foot. Before the roll reappears in midair, the magician taps his foot. You hear the thunk at the same time the roll would have hit the floor.