Perception

Perception Essay, Research Paper



Perception



INTRODUCTION Perception is defined as a process by which organisms interpret and organize

sensation to produce a meaningful experience of the world. Sensation usually refers to the

immediate, relatively unprocessed result of stimulation of sensory receptors in the eyes, ears,

nose, tongue, or skin. Perception, on the other hand, better describes one’s ultimate experience of

the world and typically involves further processing of sensory input. In practice, sensation and

perception are virtually impossible to separate, because they are part of one continuous process.

Our sense organs translate physical energy from the environment into electrical impulses

processed by the brain. For example, light, in the form of electromagnetic radiation, causes

receptor cells in our eyes to activate and send signals to the brain. But we do not understand

these signals as pure energy. The process of perception allows us to interpret them as objects,

events, people, and situations. Without the ability to organize and interpret sensations, life would

seem like a meaningless jumble of colors, shapes, and sounds. A person without any perceptual

ability would not be able to recognize faces, understand language, or avoid threats. Such a person

would not survive for long. In fact, many species of animals have evolved exquisite sensory and

perceptual systems that aid their survival. PRINCIPLES OF PERCEPTUAL ORGANIZATION

Organizing raw sensory stimuli into meaningful experiences involves cognition, a set of mental

activities that includes thinking, knowing, and remembering. Knowledge and experience are

extremely important for perception, because they help us make sense of the input to our sensory

systems. You could probably read the text, but not as easily as when you read letters in their

usual orientation. Knowledge and experience allowed you to understand the text. You could read

the words because of your knowledge of letter shapes, and maybe you even have some prior

experience in reading text upside down. Without knowledge of letter shapes, you would perceive

the text as meaningless shapes, just as people who do not know Chinese or Japanese see the

characters of those languages as meaningless shapes. Reading, then, is a form of visual

perception. Note that in the example above, you did not stop to read every single letter carefully.

Instead, you probably perceived whole words and phrases. You may have also used context to

help you figure out what some of the words must be. For example, recognizing upside may have

helped you predict down, because the two words often occur together. For these reasons, you

probably overlooked problems with the individual letters?some of them, such as the n in down,

are mirror images of normal letters. You would have noticed these errors immediately if the

letters were right side up, because you have much more experience seeing letters in that

orientation. How people perceive a well-organized pattern or whole, instead of many separate

parts, is a topic of interest in Gestalt psychology. According to Gestalt psychologists, the whole

is different than the sum of its GESTALT LAWSparts. Gestalt is a German word-meaning

configuration or pattern. OF GROUPING The three founders of Gestalt psychology were

German researchers Max Wertheimer, Kurt Koffka, and Wolfgang K?hler. These men identified

a number of principles by which people organize isolated parts of a visual stimulus into groups

or whole objects. There are five main laws of grouping: proximity, similarity, continuity, closure,

and common fate. A sixth law, that of simplicity, encompasses all of these laws. Although most

often applied to visual perception, the Gestalt laws also apply to perception in other senses.

When we listen to music, for example, we do not hear a series of disconnected or random tones.

We interpret the music as a whole, relating the sounds to each other based on how similar they

are in pitch, how close together they are in time, and other factors. We can perceive melodies,

patterns, and form in music. When a song is transposed to another key, we still recognize it, even

though all of the notes have changed. 1) PROXIMITY The law of proximity states that the closer

objects are to one another, the more likely we are to mentally group them together 2)

SIMILARITY The law of similarity leads us to link together parts of the visual field that are

similar in color, lightness, texture, shape, or any other quality 3) CONTINUITY The law of

continuity leads us to see a line as continuing in a particular direction, rather than making an

abrupt turn 4) CLOSURE According to the law of closure, we prefer complete forms to

incomplete forms.This tendency allows us to perceive whole objects from incomplete and

imperfect forms. 5)COMMON FATE The law of common fate leads us to group together objects

that move in the same direction . 6) Simplicity Central to the approach of Gestalt psychologists is

the law of pr?gnanz, or simplicity. This general notion, which encompasses all other Gestalt

laws, states that people intuitively FIGUREprefer the simplest, most stable of possible

organizations & GROUND Not only does perception involve organization and grouping, it also

involves distinguishing an object from its surroundings. Notice that once you perceive an object,

the area around that object becomes the background. For example, when you look at your

computer monitor, the wall behind it becomes the background. The object, or figure, is closer to

you, and the background, or ground, is farther away. Gestalt psychologists have devised

ambiguous figure-ground relationships?that is, drawings in which the figure and ground can be

reversed?to illustrate their point that the whole is different from the sum of its parts. Consider the

accompanying illustration entitled “Figure and Ground.” You may see a white vase as the figure,

in which case you will see it displayed on a dark ground. However, you may also see two dark

faces that point toward one another. Notice that when you do so, the white area of the figure

becomes the ground. Even though your perception may alternate between these two possible

interpretations, the parts of the illustration are constant. Thus, the illustration supports the Gestalt

position that the whole is not determined solely by its parts. The Dutch artist M. C. Escher was

intrigued by ambiguous figure-ground relationships. Although such illustrations may fool our

visual systems, people are rarely confused about what they see. In the real world, vases do not

change into faces as we look at them. Instead, our perceptions are remarkably stable.

Considering that we all experience rapidly changing visual input, the stability of our perceptions

is more amazing than the occasional tricks that fool our perceptual systems. How we perceive a

stable world is due, in part, to a number of factors that maintain perceptual constancy.

PERCEPTUAL CONSTANCY As we view an object, the image it projects on the retinas of our

eyes changes with our viewing distance and angle, the level of ambient light, the orientation of

the object, and other factors. Perceptual constancy allows us to perceive an object as roughly the

same in spite of changes in the retinal image. Psychologists have identified a number of

perceptual constancies, including lightness constancy, color constancy, shape constancy, and size

constancy. LIGHTNESS CONSTANCY Lightness constancy means that our perception of an

object’s lightness or darkness remains constant despite changes in illumination. To understand

lightness constancy, try the following demonstration. First, take a plain white sheet of paper into

a brightly lit room and note that the paper appears to be white. Then, turn out a few of the lights

in the room. Note that the paper continues to appear white. Next, if it will not make the room

pitch black, turn out some more lights. Note that the paper appears to be white regardless of the

actual amount of light energy that enters the eye. Lightness constancy illustrates an important

perceptual principle: Perception is relative. Lightness constancy may occur because the white

piece of paper reflects more light than any of the other objects in the room?regardless of the

different lighting conditions. That is, you may have determined the lightness or darkness of the

paper relative to the other objects in the room. Another explanation, proposed by 19th-century

German physiologist Hermann von Helmholtz, is that we unconsciously take the lighting of the

room into consideration when judging the COLOR CONSTANCY Color constancy is closely

related tolightness of objects. lightness constancy. Color constancy means that we perceive the

color of an object as the same despite changes in lighting conditions. You have experienced color

constancy if you have ever worn a pair of sunglasses with colored lenses. In spite of the fact that

the colored lenses change the color of light reaching your retina, you still perceive white objects

as white and red objects as red. The explanations for color constancy parallel those for lightness

constancy. One proposed explanation is that because the lenses tint everything with the same

color, we unconsciously “subtract” that color from the scene, leaving the SHAPE CONSTANCY

Another perceptual constancy is shapeoriginal colors. constancy, which means that you

perceive objects as retaining the same shape despite changes in their orientation. To understand

shape constancy, hold a book in front of your face so that you are looking directly at the cover.

The rectangular nature of the book should be very clear. Now, rotate the book away from you so

that the bottom edge of the cover is much closer to you than the top edge. The image of the book

on your retina will now be quite different. In fact, the image will now be trapezoidal, with the

bottom edge of the book larger on your retina than the top edge. (Try to see the trapezoid by

closing one eye and imagining the cover as a two-dimensional shape.) In spite of this trapezoidal

retinal image, you will continue to see the book as rectangular. In large measure, shape

constancy occurs because your visual system takes depth into SIZE CONSTANCY Depth

perception also plays a major role in sizeconsideration constancy, the tendency to perceive

objects as staying the same size despite changes in our distance from them. When an object is

near to us, its image on the retina is large. When that same object is far away, its image on the

retina is small. In spite of the changes in the size of the retinal image, we perceive the object as

the same size. For example, when you see a person at a great distance from you, you do not

perceive that person as very small. Instead, you think that the person is of normal size and far

away. Similarly, when we view a skyscraper from far away, its image on our retina is very

small?yet we perceive the building as very large. Psychologists have proposed several

explanations for the phenomenon of size constancy. First, people learn the general size of objects

through experience and use this knowledge to help judge size. For example, we know that insects

are smaller than people and that people are smaller than elephants. In addition, people take

distance into consideration when judging the size of an object. Thus, if two objects have the

same retinal image size, the object that seems farther away will be judged as larger. Even infants

seem to possess size constancy. Another explanation for size constancy involves the relative

sizes of objects. According to this explanation, we see objects as the same size at different

distances because they stay the same size relative to surrounding objects. For example, as we

drive toward a stop sign, the retinal image sizes of the stop sign relative to a nearby tree remain

constant?both images grow larger at the same rate DEPTH PERCEPTION Depth perception is

the ability to see the world in three dimensions and to perceive distance. Although this ability

may seem simple, depth perception is remarkable when you consider that the images projected

on each retina are two-dimensional. From these flat images, we construct a vivid three-

dimensional world. To perceive depth, we depend on two main sources of information: binocular

disparity, a depth cue that requires both eyes; and monocular cues, which allow BINOCULAR

DISPARITY Because our eyesus to perceive depth with just one eye are spaced about 7 cm

(about 3 in) apart, the left and right retinas receive slightly different images. This difference in

the left and right images is called binocular disparity. The brain integrates these two images into

a single three-dimensional image, allowing us to perceive depth and distance. For a

demonstration of binocular disparity, fully extend your right arm in front of you and hold up

your index finger. Now, alternate closing your right eye and then your left eye while focusing on

your index finger. Notice that your finger appears to jump or shift slightly?a consequence of the

two slightly different images received by each of your retinas. Next, keeping your focus on your

right index finger, hold your left index finger up much closer to your eyes. You should notice

that the nearer finger creates a double image, which is an indication to your perceptual system

that it is at a different depth than the farther finger. When you alternately close your left and right

eyes, notice that the nearer finger appears to jump much more than the more distant finger,

reflecting a greater amount of binocular disparity. You have probably experienced a number of

demonstrations that use binocular disparity to provide a sense of depth. A stereoscope is a

viewing device that presents each eye with a slightly different photograph of the same scene,

which generates the illusion of depth. The photographs are taken from slightly different

perspectives, one approximating the view from the left eye and the other representing the view

from the right eye. The View-Master, a children’s toy, is a modern type of stereoscope.

Filmmakers have made use of binocular disparity to create 3-D (three-dimensional) movies. In 3-

D movies, two slightly different images are projected onto the same screen. Viewers wear special

glasses that use colored filters (as for most 3-D movies) or polarizing filters (as for 3-D IMAX

movies). The filters separate the image so that each eye receives the image intended for it. The

brain combines the two images into a single three-dimensional image. Viewers who watch the

film without the glasses see a double image. Another phenomenon that makes use of binocular

disparity is the autostereogram. The autostereogram is a two-dimensional image that seemingly

becomes three-dimensional when the viewer relaxes or defocuses the eyes, as if focusing on a

point in space behind the image. The two-dimensional image usually consists of random dots or

lines, which, when viewed properly, coalesce into a previously unseen three-dimensional image.

Most autostereograms are produced using computer software. The mechanism by which the

autostereogram works is complex, but it employs the same principle as the stereoscope and 3-D

movies. That is, each eye receives a slightly different image, which the brain fuses into a single

three-dimensional image. The autostereogram was first popularized in the Magic Eye series of

books in the early 1990s, although its invention traces back to 1979. Although binocular

disparity is a very useful depth cue, it is only effective over a fairly short range?less than 3 m (10

ft). As our distance from objects increases, the binocular disparity decreases?that is, the images

received by each retina become more and more similar. Therefore, for distant objects, your

perceptual system cannot rely on binocular disparity as a depth cue. However, you can still

determine that some objects are nearer and some MONOCULAR CUES Close onefarther away

because of monocular cues about depth. eye and look around you. Notice the richness of depth

that you experience. How does this sharp sense of three-dimensionality emerge from input to a

single two-dimensional retina? The answer lies in monocular cues, or cues to depth that are

effective when viewed with only one eye. The problem of encoding depth on the two-

dimensional retina is quite similar to the problem faced by an artist who wishes to realistically

portray depth on a two-dimensional canvas. Some artists are amazingly adept at doing so, using a

variety of monocular cues to give their works a sense of depth. Although there are many kinds of

monocular cues, the most important are interposition, atmospheric perspective, texture gradient,

linear perspective, size cues, height cues, and motion parallax. 1) INTER POSITION Probably

the most important monocular cue is interposition, or overlap. When one object overlaps or

partly blocks our view of another object, we judge the covered object as being farther away from

us. This depth cue is all around us?look around you and notice how many objects are partly

obscured by other objects. To understand how much we rely on interposition, try this

demonstration. Hold two pens, one in each hand, a short distance in front of your eyes. Hold the

pens several centimeters apart so they do not overlap, but move one pen just slightly farther

away from you than the other. Now close one eye. Without binocular vision, notice how difficult

it is to judge which pen is more distant. Now, keeping one eye closed, move your hands closer

and closer together until one pen moves in front of the other. Notice how interposition makes

depth perception much easier. 2) ATMOSPHERIC PERSPECTIVE The air contains microscopic

particles of dust and moisture that make distant objects look hazy or blurry. This effect is called

atmospheric perspective or aerial perspective, and we use it to judge distance. In the song

“America the Beautiful,” the line that speaks of “purple mountains’ majesty” is referring to the

effect of atmospheric perspective, which makes distant mountains appear bluish or purple. When

you are standing on a mountain, you see brown earth, gray rocks, and green trees and grass?but

little that is purple. When you are looking at a mountain from a distance, however, water droplets

suspended in the air bend the light so that the rays that reach your eyes lie in the blue or purple

part of the color spectrum. This same effect makes the sky appear blue. 3) TEXTURE

GRADIENT An influential American psychologist, James J. Gibson, was among the first people

to recognize the importance of texture gradient in perceiving depth. A texture gradient arises

whenever we view a surface from a slant, rather than directly from above. Most surfaces?such as

the ground, a road, or a field of flowers?have a texture. The texture becomes denser and less

detailed as the surface recedes into the background, and this information helps us to judge depth.

For example, look at the floor or ground around you. Notice that the apparent texture of the floor

changes over distance. The texture of the floor near you appears more detailed than the texture of

the floor farther away. When objects are placed at different locations along a texture gradient,

judging their distance from you becomes fairly easy. 4) LINEAR PERSPECTIVE Artists have

learned to make great use of linear perspective in representing a three-dimensional world on a

two-dimensional canvas. Linear perspective refers to the fact that parallel lines, such as railroad

tracks, appear to converge with distance, eventually reaching a vanishing point at the horizon.

The more the lines converge, the farther away they appear. 5) SIZE CLUES Another visual cue

to apparent depth is closely related to size constancy. According to size constancy, even though

the size of the retinal image may change as an object moves closer to us or farther from us, we

perceive that object as staying about the same size. We are able to do so because we take

distance into consideration. Thus, if we assume that two objects are the same size, we perceive

the object that casts a smaller retinal image as farther away than the object that casts a larger

retinal image. This depth cue is known as relative size, because we consider the size of an

object’s retinal image relative to other objects when estimating its distance. Another depth cue

involves the familiar size of objects. Through experience, we become familiar with the standard

size of certain objects, such as houses, cars, airplanes, people, animals, books, and chairs.

Knowing the size of these objects helps us judge our distance from them and from objects around

them. 6) HEIGHT CLUES We perceive points nearer to the horizon as more distant than points

that are farther away from the horizon. This means that below the horizon, objects higher in the

visual field appear farther away than those that are lower. Above the horizon, objects lower in

the visual field appear farther away than those that are higher. For example, in the accompanying

picture entitled “Relative Height,” the animals higher in the photo appear farther away than the

animals lower in the photo. But above the horizon, the clouds lower in the photo appear farther

away than the clouds higher in the photo. This depth cue is called relative elevation or relative

height, because when judging an object’s distance, we consider its height in our visual field

relative to other objects. 7) MOTION PARALLAX The monocular cues discussed so

far?interposition, atmospheric perspective, texture gradient, linear perspective, size cues, and

height cues?are sometimes called pictorial cues, because artists can use them to convey three-

dimensional information. Another monocular cue cannot be represented on a canvas. Motion

parallax occurs when objects at different distances from you appear to move at different rates

when you are in motion. The next time you are driving along in a car, pay attention to the rate of

movement of nearby and distant objects. The fence near the road appears to whiz past you, while

the more distant hills or mountains appear to stay in virtually the same position as you move. The

rate of an object’s movement provides a cue to its distance. MOTION PERCEPTION Although

motion plays an important role in depth perception, the perception of motion is an important

phenomenon in its own right. It allows a baseball outfielder to calculate the speed and trajectory

of a ball with extraordinary accuracy. Automobile drivers rely on motion perception to judge the

speeds of other cars and avoid collisions. A cheetah must be able to detect and respond to the

motion of antelopes, its chief prey, in order to survive. Initially, you might think that you

perceive motion when an object’s image moves from one part of your retina to another part of

your retina. In fact, that is what occurs if you are staring straight ahead and a person walks in

front of you. Motion perception, however, is not that simple?if it were, the world would appear

to move every time we moved our eyes. Keep in mind that you are almost always in motion. As

you walk along a path, or simply move your head or your eyes, images from many stationary

objects move around on your retina. How does your brain know which movement on the retina is

due to your own motion and which is due to motion in the world? Understanding that distinction

is the problem that faces psychologists who want to explain motion perception. One explanation

of motion perception involves a form of unconscious inference. That is, when we walk around or

move our head in a particular way, we unconsciously expect that images of stationary objects

will move on our retina. We discount such movement on the retina as due to our own bodily

motion and perceive the objects as stationary. In contrast, when we are moving and the image of

an object does not move on our retina, we perceive that object as moving. Consider what

happens as a person moves in front of you and you track that person’s motion with your eyes.

You move your head and your eyes to follow the person’s movement, with the result that the

image of the person does not move on your retina. The fact that the person’s image stays in

roughly the same part of the retina leads you to perceive the person as moving. Psychologist

James J. Gibson thought that this explanation of motion perception was too complicated. He

reasoned that perception does not depend on internal thought processes. He thought, instead, that

the objects in our environment contain all the information necessary for perception. Think of the

aerial acrobatics of a fly. Clearly, the fly is a master of motion and depth perception, yet few

people would say the fly makes unconscious inferences. Gibson identified a number of cues for

motion detection, including the covering and uncovering of background. Research has shown

that motion detection is, in fact, much easier against a background. Thus, as a person moves in

front of you, that person first covers and then uncovers portions of the background.

APPLICATION OF VISUAL PERCEPTION: Apart from this however there are certain features

of visual perception which are applicable to daily business life as well : SIZE : In size we are

most likely to notice things if they are of a different size from similar objects in the immediate

area . Some advertisers seek attention by erecting billboards that are as large as possible.

CONTRAST: When we speak of contrast , we assume that when an object contrasts with its

surroundings it is more noticeable . For instance in the diagram below one square is shaded while

others are not. When we first look at the diagram our attention is drawn to the dark square

because of its contrast to its surroundings. This can be applied in situations like a manager

interviewing twenty women and one man for a job, he would remember the man first , simply

because he posed such a contrast . INTENSITY: Objects may also vary in their intensity.

Intensity can involve characteristics such as brightness, color, depth or sound. Like we listen

more carefully to some one who is yelling. This principle is applied in some television

commercials, which are louder than regular programming ? to catch attention. MOVEMENT:

We tend to focus out attention on objects that are moving in relation to their surroundings.

REPITITION: Repetition can also increase the awareness of an object, well one can recall the

Bicardi ad since its repeated over and over on television. NOVELTY: Lastly novelty also

influences our perception. For instance looking at part d of the slide. Although the circle is as the

same size and color as the square, its novel shape draws attention. People wearing unusual

clothing, books and magazines that have strange covers attract our attention .



Bibliography



Anderson, John R. CognitiveBIBILOGRAPHY BOOKS Applications from; CONSUMER

BEHAVIOUR ,Psychology and its Implications. Wolman, Benjamin B., ed. The Encyclopedia

of Psych iatry, Psychology,GRIFFIN Definitions from; THE BRITANICA

ENCYCLOPEDIAand Psychoanalysis



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