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Perception: Making Sense out of Sensation
Joseph McNair
The “world” of the senses may be described as an “infinite number of discrete impulses . . . in an ever changing pattern. How then does one “make sense” out of the sensory world especially if … no one can ever have the same sensation twice?
“Light hits our eyes; we see. Pressure waves vibrate our ears; we hear . . . “ Bolles, 1991 p. xi.
Perception is defined by some psychologists (Benjamin, Hopkins and Nation, 1990, Rathus 1990, Lefton, 1991) as the process by which an organism selects, stores, organizes and interprets sensory input.
Put another way, perception is the way in which the mechanical or chemical stimulation of our sense organs and the meaning of those sensations are brought together.
Ulric Neisser (1967) described perception as a twofold process:
The practical purpose of human perception is to enable the human being to act quickly and flexibly to survive and function in his or her environment. The mechanical information presented to the senses at any given time is enormous in amount and complex in its detail.
The perceptual apparatus or (in the words of Ornstein) “the mental operating system” (the neuro-mental processes involved in perception) must select, simplify and organize sensory information quickly and efficiently.
The manner in which the mental operating system selects, simplifies and organizes information has been the subject of considerable study. According to Berelson and Steiner (1964):
The facts of raw sensory data are themselves insufficient to produce or to explain the coherent picture of the world as the normal adult experiences it (Berelson and Steiner, 1964, p.99).
The suggestion here is that the “world” of the senses may be described as an “infinite number of discrete impulses . . . in an ever changing pattern” (p. 99). How then do we “make sense” out of the sensory world especially if when reading between the lines of the foregoing no one can ever have the same sensation twice?
Only a fraction of the stimuli actually capable of firing sensory receptors become a part of conscious sensory experience and that fraction is selected. How those stimuli get selected depends on at least three major factors:
With respect to the nature of the stimuli involved, stimuli that most readily compel attention are more likely to be selected than stimuli which do not. For example,
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a loud noise in a relatively quiet environment such as a boisterous sneeze in a library,
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or a bright light in a dark environment like a discharging flash bulb in a darkened movie theater will compel the attention of the perceiver whether the perceiver expects that stimuli or not. The same could be said for the application of “hot” ice on the skin.
Color, movement, size and repetition etc., are also important qualities of stimuli which compel the attention of the perceiver.
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http://www-staff.it.uts.edu.au/~don/graphics/perception/circles.jpg
Thus the differential intensity or quality of stimuli i.e., stimuli which can be readily contrasted with other stimuli in the environment, which more readily draws our attention, will determine whether that sensory information is selected or not.
The expectations of the perceiver e.g., previous experiences or learning, also determine which stimuli will be selected.
…with regard to expectations, other things being equal, people are more likely to attend to aspects of the environment they anticipate than to those they do not, and they are more likely to anticipate things they are familiar with (Berelson et al., 1964, p. 101).
Experience precedes expectation. An initial sensory event or experience, especially an intense one, or one that repeats itself with a fair amount of consistency or regularity sets up the perceiver to “ expect” certain occurrences or “states” under the same or similar conditions in the environment. The perceiver then looks, listens, or feels, etc., for certain stimuli.
Consider the following example:
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It was about five o’clock. Daddy always came home from work at five, driving that old 1951 dynaflow Buick whose engine sounded like the muted rumble of an airplane taking off.
There was a lot of traffic noise outside and a bunch of people on the street outside the house having loud conversations which could have drowned out the sound of anything approaching, but Faye heard the hum of the Buick engine even before it turned onto the street where she lived.
Faye through past experience expected to hear the sound of the car and her perceptual apparatus was “ tuned” to hear its approach even through the other noises outside.
Learning also tunes the mental operating system to be conscious of certain stimuli that other perceivers might not select.
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The exceptional education teacher, when trying to diagnose why a student is having reading problems will be conscious of a student’s inability to discriminate between different sights and sounds, to follow objects with the eyes, to recall images and sounds previously presented and in the order in which they were presented. S/he can do this because s/he has learned to recognize and identify these perceptual cues.
An even more complex example of this is the case of the “black and white” photographer:
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When a “black and white” photographer assesses a color image which s/he intends to convey in black and white, s/he must previsualize that image in blacks, whites and shades of gray to render it dramatically in the desired medium.
The photographer who has learned to see in “black and white” can see colors in terms of their grayscale equivalents, can select out of a colorful environment those hues, shades and textures which can be rendered most effectively in blacks, whites and grays.
Classical research has shown repeatedly that“ motive-relevant” stimuli e.g., stimuli associated with the personal needs and values of the perceiver, are more readily selected than motive-neutral stimuli.
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The hungry person is more likely to select out of the environment stimuli associated with food.
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The shopper with a preference for the color red will select out red items before items of other colors.
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A person in a crowd of people can “tune” into conversations for which s/he has some interest.
In some instances, the need will not only select out the stimuli, but relatively speaking, will alter the “percept” according to the need:
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When shown a certain coin, children from poor homes experienced it as larger than did the richer children, a finding that has been repeated in other cultures such as in Hong Kong.
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In another study students in a class were asked to draw a picture of the teacher. The majority of the honor students drew the teacher slightly smaller than the students in the picture. But the pictures by less-than-average students depict the teacher as much taller than the students (Ornstein p. 35).
According to Berelson et al., the perceiver will seek out pleasant or sympathetic stimuli to select while avoiding noxious or threatening ones.
http://schatz.sju.edu/introlec/blacky/blacky.html
They describe the “Blacky Pictures Test” to illustrate how threatening pictures or words are found to have higher thresholds of recognition and/or are described less accurately at given levels of exposure than are neutral materials.
Pictures of a small black dog are flashed in a darkened room on a screen by a tachistoscope. A tachistoscope is a projector that exposes (flashes) visual images (pictures) for very brief, controlled periods (seconds and milliseconds). “ Blacky” the dog, is shown in a variety of situations, some rich in sexual significance.
When two threatening scenes and two neutral ones were flashed at near threshold speeds, the subjects took longer locating the threatening pictures than the neutral controls.
Moreover, threatening pictures also made more of an impression (i.e., were reported to “stand out more”) when exposure time was far beneath threshold (adapted from Berelson, et al, 1964, p. 102).
Culture, even at the selection stage of perception, may determine the sensory modalities (channels) a group of people may prefer in selecting stimuli from the environment. R.H. Barsch (1971) suggests that the human being learns to prefer certain sensory channels in the selection of sensory cues (stimuli) but moves through various developmental stages before that preferential channel is established and used efficiently. (Barsch, R. H. cited in Shade, B. in Jones, 1994, p. 235).
He suggests that the young child initially uses the sense of taste (gustatory), smell (olfactory) and touch (tactile) to explore his or her environment far more efficiently than seeing (visual), hearing (auditory) or bodily position, presence or movement (kinesthetics).
As the child develops language and concepts through cultural training e.g., child-rearing practices, formal and informal education, the kinesthetic, auditory and visual channels become the sensory modalities most heavily used. (Barsch, R. H. cited in Shade, B. in Jones, 1994, p. 235).
African American psychologist Barbara J. Shade (1994) cites the observation made by Charles Keil regarding the perceptual modes characteristic of the African American community in the United States:
…its modes of perception and expression, its channels of communication are predominantly auditory and tactile rather than visual and literate …the prominence of the aural perception, oral expression and kinesic codes…sharply demarcate the culture from the white world (Shade in Jones, 1994, p. 235).
Shade’s own findings, however, lead her to believe that the sensory modality of preference for African Americans is the kinesthetic mode:
Although the aural (hearing) mode is undoubtedly a very important channel in African American culture, it seems probable that the kinesthetic mode is the primary mode of information induction for the majority of the members of the [African American] community (p. 235).
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Knowledge of sensory modalities of preference impact greatly on decisions a teacher must make with respect to determining learning styles of students. They also impact the selection of teaching style or styles to employ with maximum effect. Such knowledge is of fundamental importance to meeting the needs of a diverse student population.
Even the simplest sensory experiences are organized by each individual perceiver. In fact, it is accurate to say that our mental operating system imposes form on the sensory stimuli that we select from the environment. According to Ornstein
…the mental operating system is so specialized for organizing sensory information that it attempts to organize things into a pattern even when there is none… The rules of mental organization are the basis of the Gestalt approach to psychology.
Gestalt is a German word with no direct English equivalent but it roughly means to create a form. A gestalt is the immediate organization of the form of an object. You will instantly perceive stimuli as complete forms, not disconnected (p. 33).
Beginning with the original work of Max Wertheimer in 1912, Gestalt psychologists argued that the human perceptual organization ability is innate, that the way the human being organizes the perceptual world is the same for everyone.
Notwithstanding the role of culture in determining the way we perceive our world, modern research tends to support a number of innate general organizing tendencies. We examine below examples of those organizing tendencies known as perceptual constancy, specifically size, shape and space constancy; monocular cues, including relative size, interposition, and shadow; and binocular cues. We will then examine examples of the Gestalt laws of organization.
PERCEPTUAL CONSTANCY
Perceptual constancy is our tendency to see properties of objects as unchanging despite perpetually changing retinal stimuli. According to Daniel Chandler:
Our perception of objects is far more constant or stable than our retinal images. Retinal images change with the movement of the eyes, the head and our position, together with changing light. If we relied only on retinal images for visual perception we would always be conscious of people growing physically bigger when they came closer, objects changing their shapes whenever we moved, and colors changing with every shift in lighting conditions. Counteracting the chaos of constant change in retinal images, the visual properties of objects tend to remain constant in consciousness. We are not usually conscious of people appearing to get bigger as they approach us or of things appearing to change shape according to the angles from which we view them. Chandler, D. 2003, Visual Perception 2, [online][URL http://www.aber.ac.uk/media/Modules/ MC10220/visper02.html
The following examples illustrate three of the most prominent constancy phenomena.
SIZE CONSTANCY
Size constancy refers to the fact that our perceptions of the size of objects are relatively constant despite the fact that the size of objects on the retina vary greatly with distance.
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In the above image, the man in the background is about the same size as the man in the foreground. If we take the image of the man in the background and place it beside the man in the foreground, it would seem that either the man in foreground is a giant, or the man in the back ground is a dwarf.
Shape constancy refers to those perceptual experiences where the perceived shape of an object remains constant despite changes in the shape of its retinal projection caused by the movement of the object relative to the observer.
Consider a round object, a ball, for example. Place the ball in front of you on a table. Now look at the ball from several different angles. The ball is round regardless of the angle you view it. When you look at it from some distance away from the table, the shape of the ball is elliptical on your retina. The only time that image is approximately round on the retina is when you look at it straight on.
Look at the following illustration of a door closed, slightly open and nearly half-way open:
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The door appears to change shape as it is opens. Shape constancy ensures that we are not conscious of this shapeshifting.
The visual world appears to us as stable and unmoving despite continuing movement of the retinal image, caused by the movement of the eyes, as in visual tracking and saccades [A rapid intermittent eye movement, as that which occurs when the eyes fix on one point after another in the visual field], the head and the entire body.
Other perceptual constancies include:
· Light or brightness constancy or the perception that an object’s brightness remains constant even when the amount of light hitting changes, and
· color constancy or the perception that the color of an object remains constant even when the light illuminating the object changes.
The relative distance of objects can be determined because of two major types of visual depth cues – monocular and binocular. Binocular cues require the use of both eyes, while monocular cues only need one eye. Let us begin with some examples of monocular cues.
RELATIVE SIZE
David Gershaw (2001) explains how we interpret distance through the monocular cue called relative size:
One monocular cue is relative size. If a familiar object casts a smaller image in our eye, we assume it has not merely shrunken. It is merely farther away. In the … illustration…[below], you assume the man is aiming the spear at the antelope rather than a tiny elephant. This is because you are familiar with elephants, allowing you to interpret the smaller image as an indication of greater distance. Kersaw, D, 2002, Aline On Life, [online][URL]http://www3.azwestern.edu/psy/dgershaw/lol/ VisualDepth1.html
http://www3.azwestern.edu/psy/dgershaw/lol/images/spear.jpg
Interposition (also called occlusion, superimposition or overlay) refers to the perceptual experience where one object is interpreted as obscuring part of another one. The object which seems to be obscured is seen as being further away. This cue is stronger with shapes with which we are familiar, when a familiar outline is broken by the obscuring shape –the one which is seen as in front of it. Consider the following example
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The darker blue rectangle is perceived to be farther away than the lighter blue rectangle.
SHADOW
In the following illustration, we see how shadow is a cue for depth perception. The figure consists of several rows and columns of shadowed circular shapes. Some shapes seem to be bumps, and others seem to be hollows. The location of the shadow on the shape is the only cue to whether it is a bump or a hollow. Those shapes which are shadowed in the lower portion seem to be bumps, while those shadowed at the top seem to be hollows. Reversing the image changes the location of the shadows and thus changes the perception.
http://www.aber.ac.uk/media/Modules/MC10220/visper02.html
Binocular cues help us perceive depth when viewing close objects. Because our eyes are several centimeters apart, we get a different view of the world from each eye. This different view is called binocular disparity. Close your left eye. Now, hold your right index finger about twelve (12) inches in front of your nose. Hold your left index finger about six (6) inches in front of your nose. Look at the right finger first with each eye, first the right, and then the left. Your left finger, the nearer one, will appear to be in different places when seen by each eye. Now, look at the two fingers with both eyes open. The left finger will appear as a double image.
Stereopsis (stereoscopic vision) is the process in which an impression of depth is created when the two eyes view the same scene. Since the images drawn on the retinas differ by a small degree, the two corresponding images (and the position of the eyes) are processed by the brain to create a sensation of depth.
We owe our knowledge of the organization of visual perception directly to the Gestaltists, Max Wertheimer (1880-1943), Wolfgang Köhler (1887-1967) and Kurt Koffka (1886-1941) who proposed that perceptual organization could be seen to consist of two basic principles:
Taking the latter of the two foregoing principles first, we have the organizing idea used by Gestaltists to develop their principles of perceptual organization, especially with respect to “figures.” According to Lester A. Lefton (1991):
The early Gestaltists believed that people organize a complex visual field into a coherent whole rather than seeing individual, unrelated elements (Lefton, 1991, p. 97).
Put another way, visual stimuli that can be grouped together and seen as a whole or as a form will be seen as exactly that. This is called the Law of Simplicity or Pragnanz.
J. E. Hochberg (1979) described the series of laws developed by the Gestalt psychologists for predicting how an array of visual stimuli would be seen as a particular whole or form. The first of these general principles of perceptual organization involve a “figure” as distinct from a background. According to Chandler:
Confronted by a visual image, we seem to need to separate a dominant shape (a 'figure' with a definite contour) from what our current concerns relegate to 'background' (or 'ground'). An illustration of this is the famous ambiguous figure devised by the Danish psychologist Edgar Rubin.
http://www.aber.ac.uk/media/Modules/MC10220/visper06.htm
Images such as this are ambiguous concerning figure and ground. Is the figure a white vase (or goblet, or bird-bath) on a black background or silhouetted profiles on a white background? Perceptual set operates in such cases and we tend to favor one interpretation over the other (though altering the amount of black or white which is visible can create a bias towards one or the other). When we have identified a figure, the contours seem to belong to it, and it appears to be in front of the ground.Chandler, D. 2001, Visual Perception 6,[online][URL]http://www.aber.ac.uk/media/Modules/ MC10220/visper06.htm
Images created by author
Elements close to another in space or time will be perceived as groups. The first figure because of this principle seems to be columns. The second seems to be rows.
Image created by author
Similar items will be perceived in groups. Since the objects are spaced equally in rows and in columns, the proximity principle is not in effect. We can, clearly, group circles with circles and squares with squares.
LeFrancois, 1980, Psychology, p.155
Perceptual phenomena tend to be perceived as continuous. This figure is perceived to be a circle within a five-pointed star, not as five quasi-triangular figures.
Image created by author
Items that move or change together will be seen as whole. Here the arrows pointing in a common direction tend to be grouped.
LeFrancois, 1980, Psychology, p.155
Parts of a figure that are not presented will be filled in by the perceptual system.
The use of the terms figure and (back) ground betrays a bias toward the visual perceptual experience or explaining the world in visual terms. Characteristically, most of the devices used to demonstrate these properties of perception are visual. In fact, figure refers to a target stimulus, one selected out of an array of different stimuli.
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The smell of “chitlins” (chitterlings—the intestines of a pig) would attract the olfactory attention of the perceiver in many African American kitchens over the other smells of “blackeyed peas,” collard greens, corn bread or the sweet potato pie cooking and baking at the same time.
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Wasabi, the spicy hot, green Japanese horseradish served with sushi or sashimi (or duck breast) can take the attention of the perceiver away from any other gustatory stimuli.
A melody line in a European classical piece or a jazz improvisation can be distinguished by the listener from the harmony; the pop vocal solo from the background vocal arrangement.
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A blemish in the texture of normally smooth skin can be easily detected by fingers of average tactile sensitivity.
There is little doubt that the environmental (and hence cultural) factors determining (what figure and) how the figure is selected out of the perceptual environment are defined by the nature of the stimuli involved, what the perceiver expects or is prepared to perceive and/or what the perceiver needs or needs not to perceive. Expectations, preparation, and need assessments are culturally determined.
The miracle of perception provides the proverbial “grist” for the cultural mill. When the mental operating system routinely changes sensory stimuli into the language of the brain, sensory information embellished by the meanings derived from culture is transformed into symbols and abstractions, perceptual correlates and propositional representations, mental images and mental models – the miracle of mental representation.
REFERENCES
Ani, Marimba. Yurugu: An African-Centered Critique of European Cultural Thought and Behavior. Trenton, N.J.: Africa World Press, 1994.
Barsch, R.H. and J. Helmuth, ed. The Processing Mode Hierarchy as a Potential Deterrent to Cognitive Efficiency in Cognitive Studies: 2: Deficits in Cognition New York: Brunner/Mazel, 1971.
Belenky, Mary Field, Clinchy, Blythe McVicker, Goldberger, Nancy Rule and Tarule, Jill Mattuck. Women’s Ways of Knowing: The Development of Self, Voice and Mind. USA: Basic Books/Harper Collins, 1986.
Berelson, Bernard and Steiner, Gary A. Human Behavior: An Inventory of Scientific Findings. New York: Harcourt Brace & World, 1964.
Bolles, Edmund B. A Second Way of Knowing: The Riddle of Human Perception New York: Prentice Hall, 1991.
Capra, Fritjof. The Tao of Physics. Boston: Shambala, 1991.
Chopra, Deepak. Ageless Body, Timeless Mind. New York: Harmony Books, 1993.
Gardner, Howard. The Unschooled Mind: How Children Think & How Schools Should Teach. New York: Basic Books, HarperCollins, 1991.
Group Oppression Berkeley, California: Two Writers Press, 1975.
Lefton, Lester A. Psychology. Fourth Edition Needham Heights, Ma.: Allyn and Bacon, 1991.
Ornstein, Robert The Psychology of Consciousness. Second Edition. New York.: Penguin Books, 1986.
Shade, Barbara J. and Reginald L. Jones, ed. African AmericanPatterns of Cognition in Black Psychology. Third Edition. Berkeley, Ca.: Cobb & Henry, 1991.
Weiten, Wayne. Psychology Applied to Modern Life: Adjustment in the 80s. Second Edition. Pacific Grove, Ca.: Brooks/Cole Publishing Company, 1986.
