FREE ESSAY ON PERCEPTION

PERCEPTION

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 Kohler. 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 pragnanz, 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 fartherservationist theme of
ruling nature highly contrasts the ecofeminist view.  Ecofeminists are disturbed by the
idea that the earth has no intrinsic value.   They believe that man should not try to be
the ruler of "mother earth" and that women have the strongest ties to nature. 
Environmentalists seek to understand why nature is viewed as inferior to humans
(considering that humans are a part of it) while feminists strive to understand why women
are devalued in the same way by society.  Together, in the paradigm of ecofeminism, these
two issues are combined to try to understand and resolve women and the earth being
dominated, abused, and repressed by man who is given ultimate power in our western
culture.    Under the ecofeminist view, women are closest to the earth and have the
strongest interest in preserving it for the future generations.  Being natural
caretakers, women belong on the frontline in the war to save the earth and protect
humanity.  
Perhaps the strongest tie between conservationism and ecofemiugh 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