Notebook, 1993-

Return to - Notes for a Perspective on Art Education -- NOTES on Child Development

Notes from: Coon, Dennis. Introduction to Psychology, Exploration and Application. St. Paul: West Publishing Company, 1989.

The Brain, Biology, and Behavior - Sensation & reality - Perceiving the World - States of Consciousness

Conditioning & Learning - Cognition & Creativity - Artificial Intelligence - Enhancing Creativity

Emotion - Health, Stress & Coping - ANS Effects

Theories of Personality - Dimensions of Personality - From Birth to Death - Child Development

Perceiving the World

(From basic perception of form to the complexities of perceiving people and events)

Have you ever seen the sun set? You may think you have. Yet, in reality, we know that the sun does not "set." Instead, our viewing angle changes as the earth turns, until the sun is obscured by the horizon. Want to try the alternative? This evening stand facing the west. With practice, you can learn to feel yourself being swept backward on the rotating surface of the earth as you watch an unmoving sun recede in the distance (Fuller, 1969).

Perception, the process of meaningfully organizing sensation --or how we assemble sensations into a usable "picture" or model of the world. As we perceive events, the brain actively selects, organizes, and integrates sensory information. These mental processes are so automatic that we are rarely aware of them.

I. PERCEPTUAL CONSTANCIES. The energy patterns reaching our senses are constantly changing, even when they come from the same object. Size, shape, and brightness constancy rescue us from a confusing world in which objects would seem to shrink and grow, change shape as if they were made of rubber, and light up or fade like neon lamps. Using size to judge distance requires familiarity with the appearance of objects. What would it be like to have your vision restored after a lifetime of blindness? A newly sighted person must learn to identify objects, to read clocks, numbers, and letters, and to judge sizes and distances. Some perceptions--like seeing a line on a piece of paper--are so basic they seem to be native (inborn). But much perception is empirical, or based on prior experience. [Colin Turnbull's story of the Pygmy from the dense rain forests of Africa experiencing the vast African plains for first time and seeing a herd of buffalo grow from "insects" to buffalo in front of his eyes, like witchcraft.]

William James said, "To the infant the world is just a big, booming, buzzing confusion." Like an infant, Mr. S. B. (the man who got vision at 51) had to find meaning in his visual sensations. He was soon able to tell time from a large wall clock and to read block letters he had known before only from touch. At a zoo, he recognized an elephant from descriptions he had heard. However, handwriting meant nothing to him for more than a year after he regained sight, and many objects remained meaningless until he touched them. Thus, while Mr. S. B. had visual sensations, his ability to perceive remained limited.

A. How are sensations organized into meaningful perceptions?
Figure-ground organization. The simplest organization involves grouping some sensations into an object, or figure, that stands out on a plainer background. It is probably inborn, since it is the first perceptual ability to appear after cataract patients regain sight. In normal figure-ground perception, only one figure is seen.

Reversible figures: Figure and ground can be switched. As you shift from one pattern to the other, you should get a clear sense of what figure-ground organization means.

Gestalt psychologists conclude a number of factors would bring some order to your perceptions causing the formation of a figure:

In addition to these principles, Learning and past experience greatly affect perceptual organization. One can have an immediate recognition of letters and not be able to read handwriting. Camouflage patterns break up figure-ground organization. If you had not seen a similar camouflaged animal in a scene, for example, would you recognize it? In a way we are all detectives, seeking patterns in what we see. In this sense a meaningful pattern represents a perceptual hypothesis, or guess held until the evidence contradicts it. The active nature of organizing perceptions is perhaps most apparent for ambiguous stimuli (patterns allowing more than one interpretation). If you look at a cloud, you may discover dozens of ways to organize its contours into fanciful shapes and scenes. Even clearly defined stimuli may permit more than one interpretation. In some instances, a stimulus may offer such conflicting information that perceptual organization becomes impossible. A tendency to make a three-dimensional object out of a drawing is frustrated by the "three-pronged widget", an impossible figure.

B. Is the ability to understand drawings learned? Humans almost always appear to understand lines that represent the edges of surfaces. We also have no problem with a single line used to depict the parallel edges of a narrow object, such as a rope. One thing that we do not easily recognize is lines showing color boundaries on the surface of an object.

To illustrate the last point, let's pay a brief visit to the Songe, a small tribe in Papua New Guinea. Before they were tested, the Songe had never made or seen line drawings--not even doodles scratched on the ground. As a test, the Songe were shown drawings of a hand and a parrot. They easily recognized the hand and the parrot from simple outlines, but lines showing color boundaries confused them. The half-moons on the fingernails, for example, made them think that the nails had been damaged and new ones were growing in. Similarly they thought that the parrot must have been cut repeatedly. They thought this even though the lines in the drawing match color markings of parrots found in Songe territory (Kennedy, 1983).

Depth perception is the ability to see three-dimensional space and to accurately judge distances. Without depth perception, you would be unable to successfully drive a car or ride a bicycle, play catch, shoot baskets, thread a needle, or simply navigate around a room. The world would look like a flat surface.

A. Is depth perception learned? Some psychologists (nativists) hold that depth perception is inborn. Others (the empiricists) view it as learned. Most likely, depth perception is partly learned and partly innate. Some evidence on the issue comes from work with the visual cliff. The visual cliff is basically a glass-topped table. On one side a checkered surface lies directly beneath the glass. On the other side, the checkered surface is 4 feet below. This makes the glass look like a tabletop on one side and a cliff, or drop-off, on the other. To test for depth perception, 6- to 14-month-old infants were placed in the middle of the visual cliff. This gave them a choice of crawling to the shallow side or the deep side. (The glass prevented them from doing any "sky-diving" if they chose the deep side.) Most infants chose the shallow side. In fact, most refused the deep side even wen their mothers tried to call them toward it (Gibson & Walk, 1960). Other tests have shown that human depth perception consistently emerges at about 4 months of age (Aslin & Smith, 1988). And tests show that babies first become aware of "3-D" designs at age 4 months. The nearly universal emergence of depth perception at this time suggests that it depends more on brain development than it does on individual learning. It is very likely that at least a basic level of depth perception is innate. A number of depth cues combine to produce our experience of three-dimensional space. Depth cues are features of the environment and messages from the body that supply information about distance and space. Some cues will work with just one eye (monocular cues), while others require two eyes, (binocular cues).

If disparity is so important, can a person with one eye perceive depth? A one-eyed person lacks convergence and retinal disparity, and accommodation is helpful mainly for judging short distances. This means that a person with only one eye will have limited depth perception. Try driving a car or riding a bicycle some time with one eye closed. You will find yourself braking too soon or too late, and you will have difficulty estimating your speed.


[Notes from: Coon, Dennis. Introduction to Psychology, Exploration and Application. St. Paul: West Publishing Company, 1989.]



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