To understand the importance of perception you need only realize that the way you perceive your environment to a great extent determines the way you behave. For example you must see a friend walking across campus before you can walk over to him and ask him to have lunch with you. Seeing is one form of perception. Hearing, smelling, tasting, and feeling are others.
This module discusses the relationship of sensation to perception and details the variables at work in a perceptual experience. As you read the text, keep the following questions in mind.
Most theories treat perception as a process that gives meaning to sensations
During the last century a distinction commonly made between sensation and perception (for example, by William James, 1890) was that sensations (such as the "blueness" of the sky) were less complex than perceptions. Perceptions were regarded as the more complex products of sensations together with the meanings they acquired through past experience. A more recent distinction (Boring, 1942) is that sensation refers to the action of a stimulated receptor, while perception refers to the meaning (interpretation) given the sensation.
This separation has had considerable impact on psychology in that some major theoretical approaches have developed along these lines. Psychological theories are considered sensory or perceptual on the basis of 1 ) the kind of phenomena they are concerned with, and 2) where they look for explanations of the phenomena. Sensory theories deal with phenomena such as color vision, intensity discrimination, and visual acuity; they look for explanations in the anatomy and physiology of the sense organs. Perceptual theories, on the other hand, are concerned with phenomena like the constancies, attention, figural after-effect, and space. They seek explanation in terms of central effects, learning, and motivation. However, for the naming of textbooks and chapter headings most psychologists today do not make a fine distinction between sensation and perception.
No single distinction between sensation and perception is entirely satisfactory
A separation of the various categories of phenomena is illogical, since both central and peripheral mechanisms are necessarily activated in the demonstration of any given phenomenon. For example, some psychologists consider color vision as a sensory phenomenon and attempt to explain it in terms of the structure of the eye. Hurvich and Jameson (1957) have developed a rather sophisticated theory of color vision along these lines. Color vision, however, seems to involve more than the peripheral mechanism of the eye. The data of these researchers consist mostly of psychophysical curves which are generated from the response of experimental subjects. The central nervous system (CNSÄthe brain and spinal cord) enters the picture at least twice in the experimental procedure. The brain receives input from the eye and determines what the response will be. Similarly, a perceptual theory cannot deal exclusively with the CNS, since input to the CNS depends on receptor organs.
With the above qualification in mind, we will group all the phenomena to be dealt with in this module under the general heading of perception.
In general two kinds of variables affect our perception of the world: learning variables and physiological variables. The perceptual experience of seeing an airplane fly across a clear blue sky, for example, involves the physiological condition of the sensory receptorsÄyour eyes. If you were nearsighted or color-blind, you might not be able to see the plane or identify the color of the sky. Learning variables enter the picture in several ways. Attention allows you to focus on the planeÄone of the many things you could look at. From your past experiences you know that the object is an airplane and that the color the sky appears to be is called blue.
Another learning variable in perception is a personal value system, which is culturally conditioned and affected by the immediate conditions of deprivation and satiation. In a study.by Bruner and Goodman (1947), for example, significant differences were observed between wealthy and poor 10-year-old children in estimating the size of coins (see Figure 16). The poor children overestimated the size of the coins more than did the wealthy children. Both groups overestimated the size more than did a control group who judged the size of cardboard discs instead of coins.
Figure 16. Influences of value on perception -- not important (Graph showing amount of overestimation of size of different denominations of coins. Each subject manipulated an adjustable diaphragm until he judged it to be equal in size to a coin. While both groups overestimated the size of all of the coins, the poorer children did so to a greater extent. (After Bruner and Goodman, 1947)
Discrimination is another learning variable. The song you hear over the radio is identified by you as a new release by the "Stones." The tall blonde who passes you in the Student Union and smiles is recognized as the girl you sat next to on the first day of class. From now on it will be even easier to distinguish her from the other girls you see. In each of these hypothetical examples you have gone beyond simple sensory contact with an object -- you have made a discrimination or a discriminative response. Such actions are the crux of perception. Discrimination allows you to make sense out of sensations. Discriminations are learned and are constantly being modified by experience.
As mentioned earlier in this module, perception has historically been considered an important way to investigate the nature of man. An assumption implicit in this statement is that man is separate and distinct from other animals -- not just an evolutionary step above them or more highly developed, but special. The reasons and rationale for such a distinction are best left for discussion in a philosophy class. It is sufficient here to note that it is man himself who makes this distinction, not some unbiased observer.
This special pleading by man, for man, is perhaps the main reason that animals traditionally were not used in perceptual research. Other reasons involve technical problems. It has been assumed, for example, that lower animals are unable to tell us what they see! hear, and feel, or to understand verbal instructions so that they will know what to do in the experiment. Recently, however, many of these technical problems have been solved by the use of procedures developed in operant conditioning research.
A behavioral description of instructions is telling the subject what you want him to do. You know if a human subject has understood the instructions by whether or not he does what you have told him to do. If you have told him "Push the button marked 'yes' if you hear a tone when the light comes on, and push the button marked 'no' if you don't hear a tone when the light comes on," you need only to turn on the light to find out if he understood. Operant conditioning procedures train animals to do the same thing.
Recently, psychophysical experiments on various perceptual phenomena have been performed with animals. A Bekesy audiometer is a device used to test hearing. It varies the intensity of a tone automatically. A human subject is instructed to say "yes" when he hears the tone. The intensity then decreases until the subject says "no" and then increases again, and so on until a stable threshold is obtained. Though (1956, 1958, 1963) has ingeniously adapted this "yes-no" procedure, previously considered a human prerogative, for use with pigeons and monkeys. He has produced data on vision and hearing comparable to the reports of a trained human observer. He simply trained the animals to peck or press one disc if they heard the tone ("yes") and another if they did not ("no"), and not to do either unless the light was on.
Weitzman etal. (1961) used a similar technique to study pain in monkeys. Herrnstein and van Sommers (1962) have developed a technique to construct a psychophysical scale for the perceptual responses of a pigeon. The fact that these animals can be trained, by the use of operant- discrimination training procedures, to produce results similar to human subjects using verbal instructions, demonstrates that verbal instructions are experimentally equivalent to the training procedures used with animals. The real importance of animal perception, however, is that using animals requires a very careful analysis of the problem being investigated and of the experimental procedures used. The degree of control over all of the variables that might affect responding during the experiment is much greater with animals than with humans. In animal experiments, then, there is much less chance of results being influenced by unknown factors.
Another important aspect of animal perception is that you can compare the procedures and results with those from animal research in other areas such as learning, discrimination, and stimulus control. Many similarities have been found. The main difference seems to be that perceptual experiments concentrate on a different independent variableÄchanges in the stimulus to which the organism responds. Operant procedures make a high degree of experimental control possible in the study of animal perception. This allows us to discover how even small changes in the stimulus affect the perceptual response.
One application of Blough's technique has already made it an invaluable contribution to applied psychology. It is often extremely difficult, using traditional methods, to determine if a mentally retarded or autistic child actually cannot hear or if, in fact, he is not responding for some other (possibly behavioral) reason. Since the treatment in the two cases is likely to be quite different, this is an important question. Meyerson and Michael (1960) adapted the Though procedure to obtain auditory curves from such children with remarkable success. This procedure is currently being used in many treatment centers across the country.
Now test yourself without looking back.
1. A common distinction between sensation and perception in the last century was based on the________________________ of the phenomenon.
2. Which of the following is a basis for classifying a theory as sensory or perceptual?
a. The kind of phenomenon it deals with
b. Where it finds the explanation of the phenomenon
3. Why is there no fine distinction made today between sensation and perception?
4. What are the two kinds of variables that affect perception as we are using the term?
5. The most important specific variable in perception is___________________________
6. Why were animals not used in perceptual research in the past?
7. Which of the following is used in animal perception experiments?
a. Verbal instructions
b. Training or conditioning procedures
c. Discrimination training
8. Perceptual experiments concentrate on:
a. how the same stimulus can produce different responses.
b. how different stimuli can produce the same response.
c. how changes in the stimulus will affect a perceptuallresponse.
ANSWER KEY PAGE 143
7 OR MORE CORRECT PAGE 113
FEWER THAN 7 CORRECT PAGE 110
During the last century sensation and perception were considered
separate entities. William James said that "part of what we
perceive comes through our senses from the object before us,
another part ... always comes ... out of our own head."
a. The part that comes through our senses is______________________________
b. The part that comes through our head is___________________________
c. Which was thought to be more complex___________________________________________________________________________________3
Later methods of classifying theories as sensory or perceptual
were based on the kind of phenomena the theory dealt with and
where the theory found its explanation. A theory that dealt with
the central nervous system, for example, was classified as
perceptual, and one that dealt with receptors was classified as
sensory. Write "sensory" or "perceptual" after each of the
a. Seeing light ________________________
b. Interpreting light as a signal to stop____________________
No fine distinction is made today between sensation and
perception because almost all phenomena involve both the central
and the peripheral systems. The simple sensation of seeing light,
for example, involves:
a. the CNS to receive the stimulus.
b. the peripheral system to receive the stimulus.
c. the CNS to interpret the stimulus as light.
d. the peripheral system to interpret the stimulus as light.
When theories are classified as sensory or perceptual, two criteria are used. They are: ____________________________________2
This unit is treating phenomena as perceptual simply for ease of
discussion. Perception depends upon two types of variables,
learning and physiological. Write learning variable or physiological
variable after each of the following:
a. Normal color vision___________________
c. Recognition of an object as a helicopter_____________________________
d. Ability to see__________________________
The single most important variable in perception is discrimination, which depends on more than simple sensory contact. Discrimination is a ______________________________ variable. ____________________________________________1
In the past it was thought that only man could perceive things. It
was thought that animals could not tell us what they see or
understand. For these reasons early research in perception dealt
a. lower animals.
d. (none of these)
2 the kind of phenomena and where the explanation is found.
3 a. sensation
8 b, c
Verbal instructions are used in experimental perceptual research
with humans. Animals cannot understand the complex verbal
instructions. In experiments with animals, then, researchers use:
b. training in discrimination.
c. operant conditioning techniques.
d. (none of these)
Most perceptual experiments with animals concentrate on
changes in the stimulus that affect the response. This means that
the experimenter will:
a. see how many different responses he can get using the same stimulus.
b. vary the stimulus to see what happens to the response.
Because of our perceptive abilities we can tell the difference between two people of the same height who are dressed alike. This is due to
NOW TAKE PROGRESS CHECK 2
3 b, c
ANSWER KEY PAGE 143
6 OR MORE CORRECT PAGE 113
FEWER THAN 6 CORRECT INSTRUCTOR CONFERENCE
UNIT 6 Table of Contents