第36章
’ (Sullivan, 1908, p. 295). During a hearing test, Helen
astonished a roomful of people when “she would turn her head, smile, and act as though she had
heard what was said.” However, when Annie let go of Helen’s hand and moved to the opposite
side of the room, Helen remained motionless for the rest of the test. Although she could neither see
nor hear, Helen Keller extracted a great deal of sensory information from the world. She did not
perceive color, light, and sound through ordinary channels. Instead, she “heard” symphonies by
placing her hands on a radio to feel the vibrations, and she “saw” where a person had been by
picking up the scent of his or her clothes. Her ability to compensate for her sensory disabilities hints
at the intricate coordination within human sensory systems and the interaction of sensory and
brain processes. It also makes us aware of the extent to which our senses work in unison to weave
experience of the world around us into the fabric of our very being.
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LEARNING OBJECTIVES
On completion of this chapter, students should be able to:
1. Understand the relationship between sensation and perception
2. Explain the perceptual concepts of reality, ambiguity, and illusion
3. Describe the roles(s) played by attention in the processes of perception
4. Define the concepts of preattentive processing and guided search
5. Explicate the Gestalt principles of figure, ground, and closure, and be able to give examples
of each
6. Describe the principles of perceptual grouping
7. Define the concepts of motion and depth perception
8. Explain the importance of perceptual constancy in perceptual processes
9. Describe the significance of identification and recognition in the overall process of
perception
CHAPTER OUTLINE
I. Sensing, Organizing, Identifying, and Recognizing
A. The Proximal and Distal Stimulus
1. Perception is the set of processes that organize information in the
sensory image and interpret that information as having been
produced by objects or events in the external world
2. Perceptual organization refers to the internal representation of an
object
3. A distal stimulus is a physical object in the world
4. A proximal stimulus is the optical image of a distal stimulus that
appear on the retina
B. Reality, Ambiguity, and Illusions
1. Ambiguity means that a single image at the sensory level can result inr />
multiple interpretations at the perceptual and identification levels
2. When your perceptual systems deceive you into experiencing a
stimulus pattern in a manner that is demonstrably incorrect, you are
experiencing an illusion
C. Approaches to the Study of Perception
1. Helmholtz argued for the importance of experience, or nurture, in
perception
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2. Gestalt psychology put greater emphasis on the role of innate
structures, or nature, in perceptual experience
3. The Gibsons suggested that perception could be better understood
through an analysis of the immediately surrounding environment
a) Gibson’s theory of ecological optics focused attention on
properties of external stimuli rather than on the mechanisms
by which you perceive the stimuli
II.Attentional Processes
A. Selective Attention
1. In 1958 Donald Broadbent proposed that the mind functions as a
communications channel, like a telephone line or computer modem,
that has a limited capacity to process information
2. The brain’s limited processing capacity makes it impossible to attend
to everything and makes the filtering of information to the brain
necessary
3. Broadbent’s Filter Theory of Attention asserted that this filtering
occurs early in the process, before the input’s meaning is assessed
4. Dichotic listening tasks were used to test filter theory, and it was
found that not all information is filtered
5. The cocktail party phenomenon occurs when an individual hears
their own name mentioned across a noisy room although the
individual is participating in an unrelated conversation. Thus, even
information to which an individual is not attending is processed to
some extent.
6. As a general rule, information that is not attended to will not make its
presence known, unless it is very distinct or personally relevant
B. Attention and Objects in the Environment
1. One of the main functions of attention is to help you find particular
objects in a noisy visual environment
2. Complex processing occurs without attention or awareness
3. Preattentive processing operates on sensory inputs before you attend to
them, as they first enter the brain from sensory receptors
a) Is skilled at finding objects that can be defined by a single
feature
b) Allows parallel search of the environment for a single
prominent feature
(i) Parallel search allows the consideration of many
objects at once
(ii) Serial search allows the consideration of only one
object at a time
c) Allows guided search of the environment and provides
relatively sophisticated assistance in finding objects in the
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environment
III. Organizational Processes in Perception
A. Perceptual Organization refers to the processes that put sensory information together to
give you the perception of coherence. What a person experiences as a result of these
processes is called a percept.
B. Figure, Ground, and Closure
1. A figure is an object in the foreground of the visual field
2. The ground is the background against which the object is seen
3. There is a strong tendency to perceive a figure as being in front of a
ground
4. Illusory contours are divisions or regions that do not exist in the distal
stimulus, but do exist in the proximal experience of the stimulus
5. Closure is a powerful organizing process that fills in missing areas
and makes incomplete figures or patterns appear complete
C. Principles of Perceptual Grouping
1. The Law of Proximity states that all else being equal, the nearest
elements are grouped together
2. The Law of Similarity states that all else being equal, the most similar
elements are grouped together
3. The Law of Common Fate states that all else being equal, elements
moving in the same direction and at the same rate of speed are
grouped together
4. The Law of Pragnanz is a general law that states that individuals
perceive the simplest organization that fits the stimulus pattern
D. Spatial and Temporal Integration
1. Individuals are often unable to detect when a whole object has
changed from one fixation to another
2. A fixation is one glance or brief glimpse
E. Motion Perception
1. Motion perception requires comparison across different fixations of
the world and is dependent on reference frame
2. Induced motion occurs when a stationary object appears to be moving
because a reference frame to which it is being compared is moving.
There is a tendency for the visual system to take a larger, surrounding
figure as the reference frame for a smaller figure inside it.
3. The simplest form of apparent motion is the phi phenomenon, which
occurs when two stationary spots of light are turned on and off
alternately very quickly. It appears that a single light is moving back
and forth between the two spots of light.
F. Depth Perception
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1. Depth perception requires that the visual system extract three-
dimensional representations from two-dimensional information
2. Vision relies on depth cues that allow the interpretation of sensory
input
G. Binocular and Motion Cues
1. Binocular disparity is the displacement between the horizontal
positions of corresponding images in the two eyes
2. Convergence is the turning in of the eyes when they fixate on a single
object. The eyes must converge more for objects that are near than for
objects that are distant.
3. Relative motion parallax provides information about depth as an
individual moves because objects that are close appear to move more
than objects that are farther away
H. Perceptual Constancies
1. Perceptual constancy refers to the tendency to see the world as invariant,
constant, and stable, despite changes in the stimulation of sensory
receptors
2. Size and shape constancy
a) Size constancy refers to the ability to perceive the true size of an
object despite variations in the size of its retinal image
b) Shape constancy refers to the ability to perceive correctly an
object’s actual shape, even when the object is slanted away
from the viewer, making the shape of the retinal image
substantially different from that of the object itself
c) Orientation constancy refers to the ability to recognize the true
orientation of the figure in the real world, even though its
orientation in the retinal image is changed
d) Lightness constancy is your tendency to perceive the whiteness,
grayness, or blackness of objects as constant across changing
levels of illumination
IV. Identification and Recognition Processes
A. Bottom-Up and Top-Down Processes
1. Bottom-up processing is taking sensory data into the system and
sending it upward for extraction and analysis of relevant information.
It is anchored in empirical reality and deals with bits of information
and the transformation of concrete, physical features of stimuli into
abstract representations. Also called data-driven processing.
2. Top-down processing is when past experiences, knowledge,
motivations, cultural background, and expectations affect perception,
as higher mental functioning influences how objects and events are
understood. Also called hypothesis-driven processing.
3. Phonemic restoration occurs when there are gaps in physical signals
and perception replaces part of a word that was obscured by noise in
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a very loud environment
B. Object Recognition
1. Irving Biederman has proposed that all objects can be assembled from
a set of geometrical ions, or geons. From a set of 36 geons, Biederman
believes that perception can make a strong guess at the nature of an
object.
C. The Influence of Contexts and Expectations
1. Expectations can influence hypotheses about what is out there in the
world and can influence what is actually perceived
2. It takes longer to recognize an object when it is seen in the wrong
context, not in a familiar place
3. Object identification is a constructive, interpretive process
4. Set is a temporary readiness to perceive or react to a stimulus in a
particular way. There are three types of sets: motor, mental, and
perceptual.
a) A motor set is a readiness to make a quick, prepared response
b) A mental set is a readiness to deal with a situation, such as a
problem-solving task or game, in a way determined by learned
rules, instructions, expectations, or habitual tendencies.
Mental sets can actually prevent problem-solving when old
rules do not fit new situations.
c) A perceptual set is a readiness to detect a particular stimulus
in a given context
D. Creatively Playful Perception
1. Perceptual creativity involves experiencing the world in ways that are
imaginative, personally enriching, and fun
E. Final Lessons
1. A perceptual experience in response to a stimulus event is determined
not only by the stimulus but also by the person experiencing it. In
addition to sensation, final perception depends on past experience,
expectations, wants, goals, values, and imagination.
2. A proper balance of top-down and bottom-up processing achieves the
basic goal of perception: to experience what is out there in a way that
maximally serves your needs as a biological and social being, moving
about and adapting to your physical and social environment.
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DISCUSSION QUESTIONS
1. Why are there separate chapters on sensation and perception?