The Blind Spot  - Part Two

Filling the Holes

In addition to filling the Blind Spot by the completion process, we constantly also fill other holes in our perception. We are, however, always dependent on the context. For example, if one leaves out the letter e in the rst of ths sntnc, you ar still abl to undrstand what th sntnc mans. It isnt' vn ncssary to know wic lttr as bn lft out, or avn't you noticd tat h is also missing?

Completion is usually a very useful mechanism, but it doesn't always function correctly with respect to reality. In the above example of the Blind Spot, we complete a white (black) dot, although a black (white) dot is printed on the paper. It's easy to compare this with a magic trick: in the course of every trick there is one or more "dark" point where the necessary technique must be carried out. In the ideal case, the spectator doesn't notice these techniques; he shouldn't even suspect them, as was so well described by S. W. Erdnase in The Expert at the Card Table, just as we don't even suspect the existence of the Blind spot.

Another form of completion occurs when watching movies or television. Although there are only a certain number of static pictures projected on the screen per second (24 frames per second in a motion picture), we see a fluid moving image. The brain fills the gaps between the pictures and gives us the illusion of motion. Once again the lowest level of the retina is responsible, since after the disappearance of a retinal picture, the receptors continue firing for a moment and transfer the signal to the brain so that we fill out the temporal holes between the individual pictures and are not aware of any flickering. But this does not completely explain the perception of apparent motion.

One can create a simplified version of apparent movement by projecting two light-points situated next to each other on a screen and turning them on and off one after the other. If the physical and temporal conditions are matched, the spectator has the impression that one light moves back and forth on the screen (a phenomena that one often observes in a similar form at construction sites on highways). Although we know that there are two individual lights, we cannot escape the impression of seeing the motion of one single light-point.

The explanation for this lies in the manner in which we perceive real motion. When you move your finger back and forth quickly, the impression will not differ very much from apparent motion even though the finger remains visible between the extremes. In experiments it has been shown that, in fact, only the end points of the finger's motion are important for the perception of this type of movement. If the end points are covered, one does not perceive the movement in the middle. When one covers the middle area so that only the end points are visible, one is aware of the motion. This is due to the characteristics of an apparent movement.

If one considers the apparent movement as a problem of perception—object A disappears at one point, while at a nearby point object B suddenly appears—the assumption (extrapolating from real-world experience) is that the object moved from point A to B.

See: Chapter 7 in Perception by Irvin Rock, W H Freeman & Co., 1995.

So we are again filling a hole—the region between the points—this time with an apparent movement. Yank Hoe's "Sympathetic Coins" is a suitable example of this. The way in which the late Albert Goshman used to vanish a coin also takes advantage of this principle. A coin is apparently thrown from the right hand into the left, however, the hands do not touch during the throwing gesture. The spectator has the impression of having seen the coin in flight. This vanish is more deceptive than many others (anyone who saw Goshman could verify this) for the simple reason that the spectator deceives himself because his brain completes the picture of the coin's apparent flight, a process against which he cannot defend himself any more than against the above mentioned apparent movement of one light-point.

See "The Toss 'Vanish" in Magic by Gosh, Page and Goshman, 1985.

We remain with Goshman and assume the coin disappears from his left hand to reappear under a salt shaker on the table. This effect, which Goshman constantly repeats during his famous close-up-act, is based in an extended way on the solution of a perceptive problem by assumption of movement. In this case there are coins, not lights, which suddenly vanish and reappear. As a "solution," the spectator concludes that the coin has moved. The only difference is the fact that he does not see the coin visually "jump" under the salt shaker (in the way he sees the light jumping back and forth). But this is precisely the reason for the perception of the event as a magical effect. The psychologist, Ernst von Glasersfeld writes the following:

"Here I want to emphasise that this continuity with respect to the existence of an individual object is the result of manipulation carried out by the spectator and can never be a proof for its objective reality. No one uses this abstract possibility more skillfully than the magician. During a performance he asks, for example, for a signet ring from the audience, throws it half way through the room to his helper and lets the baffled spectator find the ring in his own pocket. The magic is to guide the perception of the spectator so that unconsciously, from the first appearance of the ring to the throwing of an object through the room, a continuous identity is constructed. If this succeeds, then in fact only magic can transfer the same ring into the pocket of the spectator."

See "Introduction to Radical Constructivism" in Radical Constructivism by Ernst von Glasersfeld, published by Falmer Press, July 1996.

Our task as performers is to leave the spectator only one possible interpretation. We give him beginning and end points and he himself constructs, by an unconscious automatic functioning process of his perception, a reality (the traveling of a coin), which simultaneously contradicts his conscious perception. The stronger this contradiction, the more powerful the magic.

Why doesn't the spectator interpret his perception as the appearance and disappearance of two objects? He doesn't see the coin in motion as in the case of the light. The performance helps here, but one can also say that we have simply learned incorrectly. In the course of growing up, we learn hrough experience that objects don't simply appear and disappear. Gradually we create more and more categories and judgments about how the world looks. For example, we learn that objects still exist when they are lost from view for a short time or when we turn away. In addition to cause and effect thinking, the concept of object permanence, as the psychologists call it, is one of the learned schemes which help us to order the "outer" world. We give the incoming sense stimulations a structure which is bound inseparably with our physiological perception apparatus, but which is learned. Division and ordering of objects in the learning process occurs in the first two years of life. The development psychologist Jean Piaget spent his entire life studying this. In his book The Construction of Reality in the Child he writes:

The child's world is a word of pictures, of which each individual is known to a greater or lesser extent and can be analyzed, but which all disappear in an unpredictable way and appear again (. . .) Observation and experiment seem to demonstrate that the concept of an object is far from being instinctive or pre-programmed through experience, but is slowly built up. Six individual phases can be distinguished, which correspond to the general psychological development.

See: Construction of Reality in the Child by Jean Piaget, Ballantine Books, 1986.

Piaget studied and documented the individual phases in innumerable experiments. He established that a two month old baby appears to consider objects to be permanent when he can grasp them:

Permanence is only the action of grasping. When I hide the clock behind my hands before Jacqueline's eyes, she doesn't react and immediately forgets everything: when there is no physical contact, the visual pictures appear to blend into one another without materializing. Here is a further proof: I lay the eraser that Jacqueline just had in her hand on her knee. The instant that she wants to grasp it again, I place my hand between her eyes and the eraser: she gives up immediately as if the object doesn't exist any more."

As simple as it might be to let an eraser disappear for a child in this age—a false transfer isn't even necessary—it's useless for the performer because no magic takes place in the child's head since there is no contradiction to reality. Reality is magic and consists of pictures which appear and disappear. The child doesn't even look for the eraser, but gives up immediately when she doesn't see it anymore. Only when the child is many months older does she look for it:

"Jacqueline looks at a ring which I place in my hand. She opens my hand by lifting the fingers and finds the object with ecstasy. Now I place the ring visibly in my left hand. Then I place the left hand against the right hand and show both closed hands (the ring passed to the right hand). Jacqueline, who is astonished, says 'Ring, ring, where is it?', but doesn't come up with the idea of looking in my right hand."

In the course of the first years, we construct concepts such as object, permanence, causality, etc. The existence of these concepts is absolutely necessary to allow the magic trick to work. This means that these higher order processes of perception are the basis for experiencing a magical effect, the performer works with and against them at the same time. With the magic trick we create a contradiction to the experienced values of our perception on one hand, but on the other hand we use precisely these special effects for its realization.

Higher Perception

A further decisive characteristic of perception is that our experience and knowledge influence how we process incoming stimulations. This process is termed "top-down" because higher brain functions exert a dominant influence over stimulation processing. In this case, knowledge wins over pure perception. The reverse is true of the "bottom-up" processes which we have considered up to this point. In figure 1, perception wins out over knowledge. Although we know that both table areas are the same size, our perception of them differs. Almost all visual effects of magic fall into this category. Consider, for example, Francis Tabary's rope trick. Even though one knows how it works, one is deluded at certain points. The same goes for visual card changes (see "Instant Camera Card" or "Sympathetic Ten" earlier in this book). Knowledge about the trick technique does not prevent us from perceiving a transformation as magic.

See chapter 4 in Psychology (2nd edition) by Philip G. Zimbardo, Ann L. Weber, Longman Publication Group, 1997 Effects which are less visual and take place on an intellectual level, for example, mental effects, tend to be based on the "top-down" principles of perception by using mental distractions to disrupt the audience's perception. These take advantage of the fact that we constantly create hypotheses based on our knowledge and experience, and within this frame interpret incoming sensual data.

In reading, for example, we not only register letters and words (bottom-up), but we also perceive the letters independently of our expectations and the particular context (top-down). In figure 5 you probably read "The Cat." If one compares the middle letter in each word, one finds that they are identical in form. The context, given through knowledge of the English words, causes us to perceive the same object differently.

An example of the influence of experience on perception is shown in figure 6a and b. Usually we can easily identify the faces of fellow-creatures and quickly notice small differences. Since we very seldom turn a face upside-down, the interpretation of the expression breaks down at the position of the eyes and angle of the mouth. We notice a small difference between the two photos of Margaret Thatcher, but only see the extent of the distortion when we turn the book around and view the faces in the usual position.

In a further example of a "top-down" process, figure 7 shows the influence of experience on grouping objects, an internal step in perception, which serves to order the individual areas of a retinal picture to geometric objects and structures which belong together.

On the left side we see the two branches behind the tree as two crossed branches. Although the configuration of the two bent branches on the right could also be possible (or four individual branches), this interpretation is apparently not as easy for us to grasp. We chose instead the simplest solution and connect the opposite branches together since this completion gives a straight line.

From experience we know that lines and forms of objects in our surroundings usually do not exhibit abrupt changes of direction. This fact influences the processes of grouping and organizing pictures from the retina so that we prefer straight or steady constructions.

Comment: This "Principle of Good Form" was first formulated by the Gestalt psychologist Max Wertheimer: We connect those parts of a pattern, the way we assume continuity, because these lie on a line or deviate from it only by a small angle. In contrast, we consider contours with abrupt changes in direction to be unrelated. It's interesting that the completion mechanism of the Blind spot creates two crossing branches. Look at the picture so that the bend in the branches on the right falls in your Blind spot.

There are a number of examples of tricks whose technique is based on this principle, in particular Bob Carver's "Professor's Nightmlare," Jay Sankey's "Cardboard Contortionists," and Paul Harris' "Immaculate Connection."

In an extended connection, one can certainly say that perception of a magic trick by which the spectator influences the trick himself are usually "bottom-up" processes, though the presentation works from "top-down" processes. In the latter, the lecture (or the music) arouses certain associations, expectations and feelings, which have an influence on the ordering of the sensual stimulants.

Experience and knowledge lead us to choose one from more than one possible interpretation of the incoming stimulations while perception is in process. In an extended sense, this means that our knowledge, our expectations, and our feelings determine what we perceive and what we consider to be "real." Just as the limitations determine which of the incoming data we process through the construction of our nervous system, the receptors of the retina, for example, are only sensitive to a certain region of the electromagnetic spectrum which we perceive as light in different colors. Similarly, we can only hear sound waves as a tone in a limited frequency region.

We are not aware that our perception, that we consider to be the end picture of an objective reality, is subject to so many limitations and automatic mechanisms. More precisely, we construct only one model from the information content of the incoming sensual stimulants, and it's this model of reality that we perceive. In transforming the sentence "seeing is believing," one could also say "believing is seeing," or as Heinz von Foerster, a biophysicist expressed it: "The world, as we perceive it, is our own invention."

Comment: Heinz von Foerster, "Das Konstruieren einer Wirklichkeit" (The Construction of a Reality) in The Invented Reality; How Do We Know What We Believe We Know?: Contributions to Constructivism by Paul Watzlawick, W. W. Norton & Co., 1984.

Magic and Constructed Reality

There have been a number of scientific experiments and daily incidents which support von Foerster; one only needs to think of the "invention" of the perception apparatus which eliminates the blind spot from our experience by constructing a substitute. Another impressive example comes from neurobiology and has to do with color perception.

See: "The Retinex Theory of Color Vision" by Edwin Landon, p.108 in Scientific American, September, 1968.

By 1672 the phenomenon of colored shadows, which can easily be demonstrated, had already been described. If an object, such as your hand, is illuminated by two light sources, one red and the other white, they throw two different shadows in the actual light circle. One is red and the other is green. But where does the green color come from, when all that one could expect was red, white or a rose mixture of the two? This happens because what we perceive as color and consider in the above case to be green is not necessarily a property of the observed object, but represents a pattern of arousal of the nerve cells of our retina. This pattern can be caused by a chance combination of light waves of wavelengths other than green. Humberto Maturana, a neurobiologist from Chile, was one of the first to discover this and wrote at the end of his study:

"The result is that the activity of nerve cells from living cells do not reflect a non dependent environment and, therefore, do not make it possible to construct an absolute existing outer world."

See: Humberto Maturana, et. al., "A Biological Theory of the Relativistic Color Coding in the Primate Retina " in Arch. Biologia y Med.. Exp., Suplemento No.1, Santiago: University of Chile, 1968.

This is somewhat easier to understand when one considers a further functional principal of the retina and the entire nervous system. The receptors of the retina absorb impinging electromagnetic rays of a certain wavelength ("light") and are excited by it. They transmit this excitement to the brain in the form of periodic electric charges (action potentials, see figure 8). The only source of information for the brain is the frequency of these periodic charges, which is higher when the stimulating intensity is greater.

This means that the nerve cells which are connected to the receptors only transmit the quantity, but not the quality, of the stimulation. For further processing in the brain the only information available is about the amount of stimulation but not about its type. This makes it all the more astonishing that we are able to construct the colored, three dimensional word that we perceive. The necessity of construction is preprogrammed at the lowest level of perception and continues through the highest levels. We constantly construct or invent patterns and meanings from actual neutral stimulation. Who has never, lying in the meadow and watching the random forms of clouds in the sky, seen the face of a man wearing a hat, a lion, or a tree? The recognition of order and causality are processed similarly, as Paul Watzlawick described using a deck of cards:

"When we mix the cards and then find them ordered in the four colors from Ace to King, this would appear too orderly to be believed. If a statistician teaches us that this order is exactly as probable as every other, we would probably not understand him at first, until we realize that in fact every order (or disorder) obtained by mixing the cards is as probable or improbable as every other. The only reason why this order appears so unusual is that for reasons that have nothing to do with probabilit,y but only with our definition of order, we attribute meaning, importance and prominence to this result and discard all others as lacking order."

See How Real Is Real?: Confusion, Disinformation, Communication by Paul Watzlawick, Random House, 1977.

One immediately thinks of "Out of this World" by Paul Curry or the end effect of Lennart Green's world championship card routine: After he has mixed cards for ten minutes, thrown them around and in his inimitable way otherwise mutilated them, at the end they are all in "new pack order," cleanly separated according to color from Ace to King. We offer the audience a few cornerstones, a scaffold on which he can hang his perceptive mechanisms so that he can fill in the holes between them to build reality. The spectator constructs the magic himself in the act of filling in the holes. Less cornerstones are necessary than one would think. In the attempt to distract the spectator, we often give too much information, we verbalize things that don't need any explanation and fall into one of the holes that the spectator will fill himself. Sentences such as "I have here a completely normal pack of cards . . ." causes the opposite of what you intend by giving too much information. In the book The Secrets of Brother John Hamman, Richard Kaufman writes:

"Every word you say limits what the spectator will think about what he sees. If you say nothing, his thoughts are limited only by his imagination—and that's far more powerful than any measly trick you can do. Brother Hamman discovered that if you say less about what you're doing, the spectator will be forced to think more. The more he thinks, the greater his self deception will be (. . .) Brother John says less, makes fewer claims, leads people to fewer conclusions verbally. He lets them imagine magical things happen because he doesn't say anything to the contrary." See: "Double-Deal Card to Pocket" on p.19 in The Secrets of Brother John Hamman, Kaufman, 1989..

This must not be limited to close-up tricks or general performances. Jim Steinmeyer, one of the most creative designers of great illusions, said basically the same thing when he compared the magical effect to a caricature:

"An effective caricature manages to tell you more about a subject than the best photographs. It does it with a simplicity of line. Every magic trick is as deceptive and illusory as is a caricature. It needs to convey the essence of an effect quickly, but in an understandable manner: the simplicity of a few lines. Understanding an effect in this way is a key toward solving it and creating the illusion."
See Strange Powers, Steinmeyer, 1992.

If we assume we are a successful artist and the audience recognizes the caricature (the effect) on the basis of the "simple lines" which we give him, we run immediately into the limits of the comparison: As artists, we were immediately able to recognize the caricature with the spectator. As magicians, this is denied us, we do not experience the effect ourselves, we do not recognize our own drawing.

Comparison with "tip" pictures is the closest to a magic performance. A classical tip picture is shown in figure 9 You see either a grandmother with kerchief or a young woman with a hat, who turns her head to the side, but you probably don't see both pictures at the same time. If you look at the picture together with a second person, it's possible that both pictures can be perceived at the same time. Although perception of the picture constantly shifts back and forth, you perhaps see the young woman while your partner sees the old woman. You both have a different reality in your heads, although both have the same stimulation.

Transferring this to a performance would mean that you as the magician see only the old woman (you know the trick like an old hat) while the spectator sees only the young woman. More specifically, while you draw an old woman, the spectator sees only a young woman. He orders the stimulations differently and forms another reality in his head. The difficulty for the magician is in order to draw a stable picture of the young woman the lines must be drawn very carefully. Each small error lets the picture flip over. The flashing of a palmed coin or thumbtip, the slipping of a double card, or simply wrong timing are enough to break the illusion or prevent it from "jelling." Richard Gregory describes this very clearly from the point of view of the lay spectator and the Indian Rope Trick:

". . . and I virtually saw it all happening although the action was hidden—that the hollow rope rose by being filled with compressed air. Then a pole was pushed up from below the stage, and the conjuror's assistant climbed up. When he descended, the pole was withdrawn but the tube-rope remained vertical, kept up by the compressed air (. . .) When one has an adequate running model of the hidden mechanisms of the trick, the performance looks ridiculous."

See: Richard L. Gregory Odd Perceptions, Routledge, London 1986..

It isn't easy to pull the right "strings" so that the audience experiences the "magic" inherent in an illusion. We help him only by the construction of this perception. The advantage of the constructive view is that we throw a positive light on our deeds. We don't misdirect, but we direct. We don't hide, but we lead the audience on the "magic road" as Tamariz calls it. The above mentioned biophysicist, Heinz von Foerster, an active magician in his youth, said:

"A lady floats in the air. The usual argument is something like this: aha—these magicians try to direct my attention away, try to confuse my thinking so that I don't observe what they are really doing. In fact, the whole magic consists of inviting you to create a world of yourself, creating a new world in which ladies are floating, in which elephants keep disappearing (. . .) Magic is not a question of distracting you, of any kind of a gimmick, rather a way of making you attentive to a particular reality you're creating. Magic is the strategy of constructivism."

Susanne Freund, Heinz von Förster—A Portrait, ORF 1992..

We take the audience on a trip, watch out that they don't think of anything stupid and accompany them to an abyss. In order to reach the other side, they must construct their own bridge. We don't tell them that the discussed perceptive mechanisms (and a few more) help them automatically. At the end, when he stands on the other side, the bridge that he passed over has long since collapsed, and he wonders how he managed to arrive there.

The moment that the spectator realizes he has reached a point that, according to his conscious perception, he should not be (because he can't see a bridge) he has reached the "magical" moment. When the effect succeeds, this is always bound with a feeling that is very special and can only be evoked by a magic performance. Tamariz describes this very pictorially in The Magic Way:

"And on the wings of our imagination, and of fantasy, we cross together through the mirror of the moon and bathe ourselves in the rainbow, and paint ourselves in its colors, as we live and enjoy the spell of the Magical Effect."
The Magic Way, Tamariz, 1988

As magicians, we consciously call for this "Moment of Experience." At the moment of astonishment, we indirectly make visible the limitations of the perception in the heads of the audience. We must, at the same time, be careful that the way back has been obliterated so the spectator doesn't, with "joined powers," discover the illusion. A high aim because it's difficult to construct and perform routines so that the audience cannot find the solution by working backward (see the performances of Juan Tamariz in The Magic Way). When in the moment of the effect, the limitations of the perceptive mechanisms become visible and when one takes Paul Klee's comment "Art doesn't reproduce the visual but makes visible," then magic in this sense is an art. Since we are caught within the natural borders of perception and carry them around with us unnoticed in our daily lives. As magicians we are able to make these borders visible in a most playful way. In an ironic sense Richard Gregory is probably right when he writes at the end of his explanations about perception mechanisms:

"Perhaps most people view the world as one single magic trick."

How fortunate for magicians that most people don't notice this!


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