The Physics and Psychology of Illusions Essay

We seem either to have to use consciousness to investigate itself, which would sound slightly weird an idea, or to have to disentangle ourselves from the very concept we want to study. Hence, we are now confronted with some tricky questions like- What does consciousness do? Could we have evolved without it? Could consciousness be an illusion? What is consciousness, anyway? What we need to consider is that how could the electric firing of millions of tiny brains produce this- our private, subjective, conscious experience? And if we must understand consciousness, we must solve this problem seriously.

This problem is a modern incarnation of the famous mind-body problem. The trouble while understanding this is that in ordinary human experiences there seem to be two entirely different kinds of thing, with no obvious way to bring the two together. On one hand, we have our own experiences. For example: take a cup of coffee or a pen- and Just look, smell, and feel its texture. Do you believe there is a real objective cup there, with actual tea in it, made of atoms and molecules? Arena you also having a private subjective experience of the cup and the taste of the tea – the ‘what it is like’ for you? What is this experience made of?

It seems to be something completely different from actual tea that I cannot convey to anyone else. I may wonder whether your experience of smelling the coffee is exactly as the smell for me, but I can never really find out. These ineffable (or indescribable) qualities are called “quail. ” Daniel Detente, American philosopher and cognitive scientist, writes that quail is “an unfamiliar term for something that could not be more familiar to each of us: the ways things seem to us. ” On the other hand, I really do believe that there exists a physical world out there that gives rise to these experiences.

We may doubt about what exactly is this physical world made of, or wonder about its deeper nature, but we cannot doubt its existence. When the objective world out there and our subjective experiences of it seem to be such different kinds of thing, how can one be caused by, or arise from, or even depend upon, the other? To solve this mystery, people throughout history have adopted some kind of a dualism: the belief that there exist, indeed, two different realms or worlds. The major religions are almost all dualist: Christians and Muslims believe in an eternal, non-physical soul, and Hindus believe n the Atman or divine self within.

Popular New Age theories invoke the powers of mind, consciousness, or spirit, as though they were an independent force; understanding consciousness. Hence, coming back to the original problem that we previously spotted, we must either actually solve the hard problem (which, indeed, will take a million years or more! ) and explain how subjectivity arises from the material world, or alternatively, if we claim that consciousness is identical to those physical processes, or is an illusion or even that it does now exist at all, we must explain why it appears so strongly to exist.

However, we must deal with a different task here, I. E. To explain why there seems to be such a problem and why we seem to have these ineffable, non-physical, conscious experiences. It is here, that the idea of consciousness as an illusion comes in, for neither consciousness nor the hard problem are what they seem. Also, to understand consciousness, we must consider the aspect of TIME. Detente (1991) formulated this in terms of the Cartesian Theatre – that non-existent place where consciousness happens – where everything comes together and I watch the private show (my stream of experiences) in my own theatre of the mind.

However he uses phrases that imply a show in the non-existent theatre; such phrases as the information in consciousness’, ‘items enter consciousness’, ‘representations become conscious’, or ‘the contents of consciousness’. But consciousness is not a container – whether distributed or not. And, if there is no answer to the question “what is in my consciousness now? ” such phrases imply that people are assuming something that does not exist. Of course it is difficult to write clearly about consciousness and people may write this way when they do not really mean to imply a show in a Cartesian

Theatre. Nevertheless, we should think a little more before using these phrases. If there is an answer to the question ‘what is in my consciousness now? ‘ then it makes sense to speak of things ‘entering consciousness’ and so on. If there is no answer it does not. Dent’s own suggestion is the theory of multiple drafts. Put simply it is this. At any time there are multiple constructions of various sorts going on in the brain – multiple parallel descriptions of what’s going on. None of these is ‘in’ example a question asked or behavior precipitated – a narrative is created.

The rest f the time there are lots of contenders in various stages of revision in different parts of the brain, and no final version. As he puts it “there are no fixed facts about the stream of consciousness independent of particular probes”. “Just what we are conscious of within any particular time duration is not defined independently of the probes we use to precipitate a narrative about that period. Since these narratives are under continual revision, there is no single narrative that counts as the canonical version, the events that happened in the stream of consciousness of the subject. Detente 1991 p 136) However, I would put it slightly differently. I want to replace our familiar idea of a stream of consciousness with that of illusory backwards streams. At any time in the brain a whole lot of different things are going on. None of these is either ‘in’ or ‘out’ of consciousness, so we don’t need to explain the ‘difference’ between conscious and unconscious processing. Every so often something happens to create what seems to have been a stream. For example, we ask “Am I conscious now? At this point a retrospective story is invented about what was in the stream of unconsciousness a moment before, together with a self who was apparently experiencing it. Of course there was neither a conscious self nor a stream, but it now seems as though there was. This process goes on all the time with new stories being invented whenever required. At any time that we bother to look, or ask ourselves about it, it seems as though there is a stream of consciousness going on. When we don’t bother to ask, or to look, it doesn’t, but then we don’t notice so it doesn’t matter.

This way the grand illusion is invented. ‘What is all this? What is all this stuff – all this experience that I seem to be having, all the time? ‘ I have now arrived at the answer that all this stuff is a grand illusion. This has not solved the problems of consciousness, but at least it tells us that there is no point trying to explain the difference between things that are in consciousness and those that are not because there is no such difference. And it is a waste of time trying to explain the contents of the stream of consciousness because the stream of consciousness does not exist. . PERCEPTION: * Meaning and definition: There are several definitions of Perception. Some of them are as follows: According to Chatter, Perception is the organization, identification and interpretation of sensory information in order to represent and understand the environment. McGraw-Hill Science ; Technology Encyclopedia defines perception as: Those subjective experiences of objects or events that ordinarily result from stimulation of the receptor organs of the body.

This stimulation is transformed or encoded into neural activity (by specialized receptor mechanisms) and is relayed to more central regions of the nervous system where further neural processing occurs. Most likely, it s the final neural processing in the brain that underlies or causes perceptual experience, and so perception-like experiences can sometimes According to Carline and Meyer, perception is the method by which the sensations experienced at any given moment are interpreted and organized in some meaningful fashion.

Galoots, K. (2007) defines perception as the process of taking sensory input and interpreting it meaningfully. * Process of Perception: There are two main processes involved in perception as stated by Psychologists namely, bottom-up processing and top-down processing. We shall now study both these processes in details. The term bottom-up (or data driven) essentially means the perceiver starts with the small bits of information from the environment that he combines in various ways to form a percept.

A bottom-up model of perception and pattern recognition might describe your perception of edges, rectangular and other shapes, and certain lighted regions and putting this information together to “conclude” that you are perceiving doors and a hallway. The idea here is that the system works in one direction, starting from the input and proceeding to a final interpretation. Whatever happens at a given point, is unaffected by later processing; he system has no way of going back to an earlier point so as to make changes or adjustments.

When we speak of bottom-up processing, we typically have in mind something that takes information about a stimulus (by definition a “lower” level of processing) as an input. Bottom-up processes are relatively uninfluenced by our experiences, expectations or previous learning (the so-called “higher” level processes). Poster and Rachel (1984) argued that bottom-up processes involve automatic, reflexive processing that takes place even when the perceiver is passively regarding the information.

In top-down processing (also called the theory-driven or conceptually driven processing), in contrast, the perceivers expectations, theories, or previous experiences guide the selection and combination of the information in the process of recognizing a pattern. For example, a top-down description of hallway example would go something like- You knew you were in your dorm, and you had information from your past experience about how close to the window were the trees, Walkways, street with cars, etc were. So now, when you look out the window, you expect to see those walkways, street with cars, trees, etc.

These expectations thus guide where you looked, what you looked at, and how you put this gathered information together. Another example could be this: If someone asked you that there was a bird in the room, where would you look? It is interesting to notice here how this “looking” would change if you were told to look for a rat or a cockroach in the room. Here, your past experiences with these creatures guided you to first look above to the ceiling in the case of the bird or otherwise to look at the ground in case of the rat or the cockroach.

This top-down processing is also the basis for our stereotypes ND Judgmental heuristics which lead us to the “false perceptions” or “illusions” about our social stimuli. These are discussed in details later in this paper. We shall consider two important theories of perception as stated by Galoots, K. (2007). The first theory is called the ‘Feature Integration theory by Trainman(FlT: Trainman, 1986) : According to this theory, the first stage of perception is the pre-attentive stage. This stage occurs automatically and usually doesn’t require any effort or attention by the perceiver.

It is in this stage, that the object is analyzed in to its features. However, this idea that an object is automatically broken into features proves to be counterintuitive because when we look at an object, we usually see the object as a whole, and not an object that has been divided into its individual features. The reason we are not aware of this process of feature analysis is that it often occurs early in the perceptual process, even before we actually become conscious of the object and of the fact that we are perceiving it.

To provide some perceptual evidence that object are, in fact, analyzed into features, Trainman and Schmidt conducted an experiment to show that early in the process features may exist independently of one another. In this experiment, the above two figures were flashed on screen for one-fifth of a second, followed by a random dot masking field designed to eliminate any residual perception that may remain after the stimuli are turned off. Participants were asked to report the object displayed initially and then to report what they saw after both the images were flashed alternatively.

It was found that that a small brown circle and a large green rectangle may be seen as a small green circle and a large brown rectangle. These combinations of features from different stimuli are called illusory conjunctions. Illusory conjunctions could also be explained with an example. When one perceives a cell-phone, one in the preventative stage first perceives the tilted lines of the phone, the curvature of the phone, the surface and the color, all independently. This perception of independent features is what causes illusory conjunctions.

They are, in Trainman’s words, “free floating” and can therefore be incorrectly combined in laboratory situations when briefly flashed stimuli are followed by a masking field. According to Trainman’s model, these individual features are combined in the second stage, which is called the focused-attention stage. Once these individual features like the tilted lone, curvature, color of the cell-phone are combined together, we actually perceive the object and recognize it as being a “cell- phone. The second theory of perception is the Recognition-sys-components theory (RFC: Irving Epidermal, 1987) : According to this theory, the features are not lines, curves, or colors, but are three dimensional volumes called goons. These could be shapes such as cylinders, rectangular solids, and pyramids. Irving who proposed this theory proposed that there are 36 different goons, and that this number of goons is enough to enable us to construct a large proportion of the objects that exist in the environment. These goons have three main properties.

First is the property of view invariance. This is an important property of goons that they can be identified when viewed from different angles. This property occurs because goons contain view invariant properties- properties such as the three parallel edges of a rectangular solid figure remain visible even when the goon is viewed from many different angles. The second property is the property of discriminatingly. This means that each goon peculiar, individualistic character. The third property is the property of Resistance to visual noise.

This means that you can identify and perceive goons even under “noisy’ conditions, even when over half of the contour of a goon is obscured. The basic message of the RFC theory is that if enough information is available to enable us to identify an object’s basic goons, we will be able to identify the object. Both Feature- Integration theory and Recognition By Components theory are based on the idea of early analysis of objects into parts. The difference is that the FIT theory is more concerned with features like lines, curves, colors and the RFC hero is more unconcerned about how we perceive three-dimensional shapes.

There is, however, much more to perception than Just analyzing objects into features. We will now go to consider other aspects of perception, which focus not on only the early analysis of features, but on how we organize elements of the environment in to separate objects. * The Gestalt Approach of Perception: Gestalt psychology attempts to understand psychological phenomena by viewing them as organized and structured wholes rather than the sum of their constituent parts.

Thus, Gestalt psychology dissociates itself from the more ‘element’s’/ educationists/decomposition approaches to psychology like structuralism (with its tendency to analyses mental processes into elementary sensations) and it accentuates concepts like emergent properties, holism, and context. In the ass and ass Gestalt psychology was applied to visual perception, most notably by Max Worthwhile, Wolfgang KГ¶heeler, and Kurt Kafka who founded the so-called gestalt approaches to form perception.

Their aim was to investigate the global and holistic processes involved in perceiving structure in the environment (e. G. Sternberg 1996). More pacifically, they tried to explain human perception of groups of objects and how we perceive parts of objects and form whole objects on the basis of these. There are 6 main principles of Gestalt Approach as follows: 1 . Principle of Proximity: The law of proximity posits that when we perceive a collection of objects, we will see objects close to each other as forming a group.

When the circles are placed in a close distance, they are perceived to be in a group together. 2. Principle of Similarity: Similarity means there is a tendency to see groups which have the same characteristics so in this example, there are two groups f black circles and two groups of white circles arranged in lines. The principle of similarity states that things which share visual characteristics such as shape, size, color, texture, value or orientation will be seen as belonging together. 3.

Principle of Continuity: The principle of continuity predicts the preference for continuous figures. We perceive the figure as two crossed lines instead of 4 lines meeting at the center. In our example, the eye naturally follows the two lines and perceives them to exist in a continuum. 4. Principle of Closure: Closure occurs when an object is incomplete or a space is not completely enclosed. If enough of the shape is indicated, people perceive the whole by filling in the missing information.

Thus, in the example, we perceive a triangle to exist in between the three apparent circles instead of viewing them separately as three incomplete circles. 5. Principle of figure silhouette, or shape is naturally perceived as figure(object), while the surrounding area is perceived as ground(background). Balancing figure and ground can make the perceived image more clear. Using unusual figure/ground relationships can add interest and subtlety to an image. Thus, in our example, the small square is seen to e a figure which is placed above the ground of the larger square. . Principle of Symmetry: The principle of symmetry describes the instance where the whole of a figure is perceived rather than the individual parts which make up the figure. Thus, the figure is perceived as a whole consisting of two overlapping diamond shapes rather than perceiving them as one diamond in the middle and two irregular figures each on the top and bottom respectively. 3. PHYSICS AND ILLUSIONS: It was the German Physicist, Hermann von Hellholes (1821-1894) who introduced the notion that visual perceptions are unconscious inferences (von Hellholes 1866).

For von Hellholes, human perception is but indirectly related to objects, being inferred from fragmentary and often hardly relevant data signaled by the eyes, so requiring inferences from knowledge of the world to make sense of the sensory signals. Following von Hellhole’s lead we may say that knowledge is necessary for vision because retinal images are inherently ambiguous (for example for size, shape and distance of objects), and because many properties that are vital for behavior cannot be signaled by the eyes, such as hardness and weight, hot or cold, edible or poisonous.

For von Hellholes, ambiguities are usually resolved, and non-visual object properties inferred, from knowledge by unconscious inductive inference from what is signaled and from knowledge of the object world. It is extraordinarily hard to give a satisfactory definition of an ‘illusion’. It may be the departure from reality, or from truth; but how are these to be defined? There are two clearly very different kinds of illusions: those with a physical cause and cognitive illusions due to misapplication of knowledge.

Although they have extremely different kinds of causes, they can produce mom surprisingly similar phenomena (such as distortions of length or curvature), so there are difficulties of classification that require experimental evidence. Illusions due to the disturbance of light, between objects and the eyes, are different from illusions due to the disturbance of sensory signals of eye, though both might be classified as ‘physical’. Extremely different from both of these are cognitive illusions, due to misapplied knowledge employed by the brain to interpret or read sensory signals.

For cognitive illusions, it is useful to distinguish specific knowledge of objects, from general knowledge embodied as rules. These can be misleading in unusual conditions, and so can be revealed by observation and experiment. We will be viewing both these types of illusions in this paper. * MГјleer-Lyre Illusion: In the image below, which line appears the longest? For most people, the line with the fins of the arrow protruding outward appears to be the longest while the line with the arrow fins pointing inwards appears shorter . In reality, the shafts of both lines are exactly the same length.

It was devised by Franz Carl MГјleer-Lyre (1857 – In the three-dimensional world, depth perception concerns Judging distance. The closer an object is to the retina, the larger it is on the retina. However, in the two- dimensional world of the MГјalley-Lyre illusion, our brain makes assumptions about the relative depths of the two shafts based on monocular (pictorial) cues. We are used to seeing outside corners of buildings as near to us with the top and bottom of the corner sloping out and away (like the outward slanting fins of the MГјalley-Lyre illusion).

We are used to seeing inside corners of buildings as farther from us with the top and bottom of the corner sloping in somewhat towards us (like the inward landing fins of the MГјalley-Lyre illusion). The retina is saying that the two shafts are the same length but the brain is interpreting the MГјleer-Lyre as a depth issue, with the shaft that looks like an outside corner being closer and the shaft that looks like an inside corner being farther away. In other words, the retina is saying “two shafts equal” and the brain is saying “outside shaft shorter than inside shaft”.

The brain usually wins differences like this. Thus, the brain assess longer than. Psychologists have attempted to support this theory that the MГјalley-Lyre illusion is caused by our experiences with outside and inside corners, by showing the illusion to an African tribe that lived in circular huts and therefore had no perceptual experiences with corners. People in this tribe didn’t seem to be fooled by the illusion thus supporting the “experience with corners” explanation of the illusion. An alternative explanation proposed by R. H. Day suggests that the MГјleer-Lyre illusion occurs because of conflicting cues.

Our ability to perceive the length of the lines depends upon the actual length of the line itself and the overall length of the figure. Since the total neigh of one figure is longer than the length of the lines themselves, it causes the line with the outward facing fins to be seen as longer. This explanation suggests that the shaft ending in the inward slanting fins causes people to perceive it as shorter because the perception of the shaft is pulled back by the “turning back” of the fins. In other words, our eyes go out toward the point and then come back as they follow the fin shafts back.

This turning back of our eyes (or perception) makes the shaft seem shorter. Conversely, the outward slanting fins draw our perception on farther making that shaft seem longer. Motion Illusions: (Waterfall illusion) Motion is a perceptual attribute I. E. The visual system infers motion from the changing pattern of light in the retinal image. Often the inference is correct. Sometimes it is not. The motion after-effect (MAE) is a visual illusion experienced after viewing a moving visual stimulus for a time (tens of milliseconds to minutes) with stationary eyes, and then fixating a stationary stimulus.

The stationary stimulus appears to move in the opposite direction to the original (physically moving) stimulus. The motion after-effect is believed to be the result of motion adaptation. After viewing continuous motion in the same direction for a long time, if you look at a stationary object, it appears to move in the direction opposite to the one you were viewing. This is sometimes called the “waterfall illusion” – if you look at a waterfall for a while, then look at a tree next to it, the tree appears to move upward.

The where you were looking, you were adapting to rightward motion, to the left you adapted to leftward, and so on). We take this as evidence for the existence of neurons that are sensitive to motion and selective for the direction of motion, which adapt to the stimulus. Another example can be seen when one looks at the centre of a rotating spiral for several seconds. The spiral can exhibit outward or inward motion. When one then looks at any stationary pattern, it appears to be moving in the opposite direction. This form of the motion after-effect is known as the spiral aftereffect. Why does this illusion occur?

Neurons coding a particular movement reduce their responses with time of exposure to a constantly moving stimulus; this is neural adaptation. Neural adaptation also reduces the spontaneous, baseline activity of these same neurons when responding to a stationary stimulus. One theory is that perception of stationary objects, for example rocks beside a waterfall, is coded as the balance among the baseline responses of neurons coding all possible directions of motion. Neural adaptation of neurons stimulated by downward movement reduces their baseline activity, tilting the balance in favor of upward movement.

Or, in other words, while watching a waterfall, the brain cells that detect downward motion become tired. When our eyes look away, the cells that detect upward motion are more active and a stationary object. Fro example a tree or a rock, appears to be moving upwards. An interesting question is why do we not see a strong motion after-effect after we have been driving for minutes or hours on the freeway. After all, during all this time the movement of the entire world outside our car must have totally fatigued our motion systems.

Yet even if we stop abruptly, we do not perceive that the world around us suddenly moves backwards. (Some people, however, have noticed slight effects). This is because, if the motion covers the entire field of view of the eye, little or no motion after-effect of any kind occurs. The brain is concerned with signaling motion relative o some stationary point or relative to some other part of the image moving in a different direction. Humans are not very good at detecting motion of an object when it is seen with no background or when the entire field of view moves roughly in the same direction. ZöEllen illusion: What happens in this illusion: The ZöEllen illusion is a commonly demonstrated optical illusion. First discovered in 1860 by a German astrophysicist named Johann Karl Frederica ZöEllen, this illusion presents a series of oblique lines crossed with overlapping short lines. The oblique lines look as if they are crooked and will diverge. In reality, all of the oblique lines are parallel. Working of this illusion? It is possible to attribute this effect to the way the brain processes angles. This theory suggests that the brain exaggerates acute angles and underestimates obtuse angles.

The brain then adjusts the angles on the transverse lines to create the illusion that the longer lines are slanted. This hypothesis is supported by the fact that the illusion is most powerful at an angle, as perfectly horizontal and vertical lines are more likely intersecting angle is 10 – 30 deg. Alternatively, the illusion may be caused by an impression of depth. The fact that shorter lines are on an angle to the longer lines may help to create the impression that one end of the longer lines is nearer to the viewer than the other end.

Interestingly enough, if the colors in the illusion are changed to equal values of green and red, the illusion disappears. * Pompon Illusion: The Pompon illusion is a geometrical-optical illusion that was first demonstrated by the Italian psychologist Mario Pompon (1882-1960) in 1911. In the image above illustrating the Pompon illusion, the two yellow lines are the exact same size. Because they are placed over parallel lines that seem to converge in the assistance, the top yellow line actually appears to be longer than the bottom one. Why Pompon suggested that the human mind Judges an object’s size based on its background.

He showed this by drawing two identical lines across a pair of converging lines, similar to railway tracks. The upper line looks longer because we interpret the converging sides according to linear perspective as parallel lines receding into the distance. In this context, we interpret the upper line as though it were farther away, so we see it as longer – a farther object would have to be longer than a nearer one for both to produce retinal images of the same size. This is also referred to as “size constancy’ which is used as an explanation for the Pompon Illusion.

Size constancy provides stability in our perception of the world by giving our conception of particular objects a consistent set or properties despite variations in the retinal image size. This is usually useful, but under special circumstances, it can lead to illusions or errors in perception. In the picture above, although the lines are actually drawn of the same size, the distance cues in the context (perspective, texture and others) indicate that the upper line is more distant. This upper line, appears anger because, no context for depth or distance has been drawn into the figure.

It is caused by the fact that there are registered cues for distance here (the converging perspective lines) that are sufficiently strong to evoke the size constancy mechanism, yet are not sufficiently strong to evoke the conscious apprehension of distance. This same principle is used to explain the moon illusion, where the moon on the horizon appears to be much bigger than the moon when it is high in the sky, despite the fact that it is optically always the same-sized disk. The notion is that the moon is seen as f it were on the “surface” of the sky.

If the sky were a uniform hemisphere, there would be no illusion. However, the sky actually appears to be a flattened bowl, with the horizon farther away than the zenith. This is because, when you look toward the horizon you have many depth cues for distance (texture gradients, familiar objects, etc. ) ; whereas when you look up, there is only the sky. This means that the moon appears farther away when on the horizon than when at zenith and, hence, by the action of size constancy, its apparent size is apprehended as being larger. 4. COLOR AND LIGHT ILLUSIONS:

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