Presentation Plus! Understanding Psychology
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CHAPTER FOCUS
SECTION 1 Sensation
SECTION 2 The Senses
SECTION 3 Perception
CHAPTER SUMMARY
CHAPTER ASSESSMENT
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Chapter Objectives
Section 1: Sensation
• Understand that sensations occur anytime
a stimulus activates a receptor and
discuss how sensations allow humans to
understand reality. 
Section 2: The Senses
• Describe how the sense organs are the
receptors of sensations.
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the information.
Chapter Objectives (cont.)
Section 3: Title
• Define perception as the way we interpret
sensations and organize them into
meaningful experiences.
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Reader’s Guide
Main Idea
– Sensations allow humans to understand reality.
Sensations occur anytime a stimulus activates
a receptor. 
Objectives
– Describe the field of study known as
psychophysics. 
– Define and discuss threshold, Weber’s law,
and signal detection.
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information. Section 1 begins on page 207 of your textbook.
Reader’s Guide (cont.)
Vocabulary
– sensation 
– perception 
– psychophysics 
– absolute threshold 
– Weber’s law 
– signal-detection theory
Click the Speaker button
to listen to Exploring
Psychology.
8
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information. Section 1 begins on page 207 of your textbook.
Introduction
• Your success in gathering information
from your environment, interpreting this
information, and acting on it depends
considerably on its being organized in
ways you expect. 
• In this chapter you will learn more about
sensation and perception, both of which
are necessary to gather and interpret
information in our surroundings.
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What Is Sensation?
• The world is filled with physical changes.
• Any aspect of or change in the
environment to which an organism
responds is called a stimulus. 
• An alarm, an electric light, and an aching
muscle are all stimuli for human beings.
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
What Is Sensation? (cont.)
• A stimulus can be measured in many
physical ways, including its size,
duration, intensity, or wavelength. 
• A sensation occurs anytime a stimulus
activates one of your receptors. 
• The sense organs detect physical
changes in energy such as heat, light,
sound, and physical pressure.
sensation
what occurs when a stimulus
activates a receptor
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What Is Sensation? (cont.)
• A sensation may be combined with other
sensations and your past experience to
yield a perception. 
• A perception is the organization of sensory
information into meaningful experiences.
perception
the organization of sensory
information into meaningful
experiences
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Fraser’s Spiral
Fraser’s spiral
illustrates the
difference
between
sensation and
perception. Our
perception of
this figure is
that of a spiral,
but it is actually
an illusion.
Trace the circle
carefully. Your
finger will
always come
back to its
starting point.
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What Is Sensation? (cont.)
• What is the relationship between color
and wavelength? 
• How does changing a light’s intensity
affect your perception of its brightness? 
• The psychological study of such questions
is called psychophysics.
psychophysics
the study of the relationships
between sensory experiences
and the physical stimuli that
cause them
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Threshold
• In order to establish laws about how
people sense the external world,
psychologists first try to determine how
much of a stimulus is necessary for a
person to sense it at all. 
• Experiments can detect the absolute
threshold–the weakest amount of a
stimulus required to produce a sensation.
absolute threshold
the weakest amount of a
stimulus that a person can
detect half the time
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The Human Senses
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Sensory Differences and Ratios
• Another type of threshold is the
difference threshold. 
• The difference threshold refers to the
minimum amount of difference a person
can detect between two stimuli. 
• A related concept is the just noticeable
difference, or JND.
difference threshold
the smallest change in a
physical stimulus that can be
detected between two stimuli
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Sensory Differences and Ratios (cont.)
• Weber’s law states that the larger or
stronger a stimulus, the larger the
change required for a person to notice
that anything has happened to it. 
• By experimenting with variations in
sounds, temperatures, pressures, colors,
tastes, and smells, psychologists are
learning more about how each sense
responds to stimulation.
Weber’s law
the principle that the larger or
stronger a stimulus, the larger
the change required for an
observer to notice a difference
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Sensory Differences and Ratios (cont.)
• People who can detect minute changes
in sensation are called experts. 
• Experts who can detect small differences
work as food tasters, wine tasters, smell
experts, perfume experts, and so on.
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Sensory Adaptation
• Psychologists have focused on people’s
responses to changes in stimuli because
they have found that the senses are tuned
to change. 
• Senses are most responsive to increases
and decreases, and to new events rather
than to ongoing, unchanging stimulation. 
• A good example of this sensory adaptation
is the increase in visual sensitivity that you
experience after a short time in a darkened
movie theater.
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Sensory Adaptation (cont.)
• Sensory adaptation allows us to
notice differences in sensations and
react to the challenges of different or
changing stimuli. 
• This principle is helpful when performing
many activities, such as the work of police,
security guards, and home inspectors. 
• These people may notice minute changes
and act appropriately.
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The Disappearing Circle
Sensation depends on change and contrast in the
environment. Hold your hand over one eye and stare at the
dot in the middle of the circle on the right. You should have no
trouble maintaining the image of the circle. If you do the same
with the circle on the left, however the image will fade. The
circle reappears only if you close and reopen your eye or you
shift your gaze to the X.
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Signal-Detection Theory
• There is no sharp boundary between
stimuli that you can perceive and stimuli
you cannot perceive. 
• The signal-detection theory studies the
relations between motivation, sensitivity,
and decision making in detecting the
presence or absence of a stimulus (Green
& Swets, 1966).
signal-detection theory
the study of people’s
tendencies to make correct
judgments in detecting the
presence of stimuli
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Signal-Detection Theory (cont.)
• Detection thresholds involve recognizing
some stimulus against a background of
competing stimuli. 
• In studying the difficulties faced by radar
operators, psychologists have reformulated
the concept of absolute threshold to take
into account the many factors that affect
detection of minimal stimuli. 
• As a result, signal-detection theory
abandons the idea that there is a single
true absolute threshold for a stimulus.
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Signal-Detection Theory (cont.)
• Psychologists have identified two different
types of processing stimuli, or signals. 
• Preattentive process is a method for
extracting information automatically
and simultaneously when presented
with stimuli. 
• Attentive process is a procedure that
considers only one part of the stimuli
presented at a time.
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The Stroop Effect
Name the color of the squares.
26
The Stroop Effect (cont.)
Name the color of the words in the figure below. 
Why was it
more difficult
to name the
color of the
words?
27
Section Assessment
Review the Vocabulary What is
the difference between sensation
and perception?
A sensation is the activation of a
sensory receptor by a stimulus. A
perception is the organization of
sensation into meaningful experiences.
28
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Section Assessment (cont.)
Visualize the Main Idea Complete
the chart shown on page 213 of your
textbook by listing the fives senses
and their absolute thresholds.
Sight: a candle flame from 30 miles
away on a clear night; sound: a
watch ticking 20 feet away; taste: 1
teaspoon of sugar dissolved in 2
gallons of water; smell: 1 drop of
perfume in a 3-room house; and
touch: a bee’s wing falling 1
centimeter onto your cheek.
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Section Assessment (cont.)
Recall Information How does the
signal-detection theory explain
how you may be able to study while
others are watching television in
the same room?
The signal-detection theory assumes
that humans can choose what stimuli
to attend to and block out other
surrounding stimuli. Your motivations,
sensitivity, and decision making affect
your concentration.
30
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Section Assessment (cont.)
Think Critically Why do you think
we do not respond to all stimuli
present in our environment?
We do not respond to all stimuli
present in our environment because
our bodies would be overloaded
with stimuli. Our bodies would
soon be unable to process more
sensory information.
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Section Assessment (cont.)
What would happen if you asked a
four-year-old child who knew his
colors but could not read to complete
the Stroop effect activity? What if you
tried this experiment with someone
who did not speak English? What if
you used noncolor words?
32
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Reader’s Guide
Main Idea
– The sense organs–the eyes, ears, tongue,
nose, skin, and others–are the receptors
of sensations. 
Objectives
– Describe the nature and functioning of the
sense organs. 
– Identify the skin and body senses and explain
how they work.
34
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information. Section 2 begins on page 214 of your textbook.
Reader’s Guide (cont.)
Vocabulary
– pupil 
– lens 
– retina 
– optic nerve 
– binocular fusion 
– retinal disparity 
– auditory nerve 
– vestibular system 
– olfactory nerve 
– kinesthesis
35
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information. Section 2 begins on page 214 of your textbook.
Click the Speaker button
to listen to Exploring
Psychology.
Introduction
• Why can you see your hand moving
even in total darkness? 
• You have just experienced kinesthesis–
one of the senses. 
• Although people are thought to have five
senses, there are actually more. 
• In addition to vision, hearing, taste,
smell, and touch, there are several skin
senses and two “internal” senses:
vestibular and kinesthetic.
36
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Introduction (cont.)
• Each type of sensory receptor takes
some sort of external stimulus and
converts it into a chemical-electrical
message that can be understood by
the brain. 
• So far, we know most about these
processes in vision and hearing. 
• The other senses have received less
attention and are more mysterious in
their functioning.
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Vision
• Vision is the most studied of all the
senses, reflecting the high importance
we place on our sense of sight. 
• How does vision occur? 
• Light enters the eye through the pupil and
reaches the lens, a flexible structure.
pupil
the opening in the iris that
regulates the amount of light
entering the eye
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lens
a flexible, transparent
structure in the eye that
changes its shape to focus
light on the retina
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Vision (cont.)
• The lens then focuses light on the retina. 
• The retina contains two types of lightsensitive receptor cells: rods and cones. 
• These cells are responsible for changing
light energy into neuronal impulses,
which then travel over the optic nerve
to the brain, where it is routed to the
occipital lobe.
retina
the innermost coating of
the back of the eye,
containing the light-sensitive
receptor cells
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optic nerve
the nerve that carries
impulses from the retina
to the brain
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Vision (cont.)
• Cones require more light to respond than
rods and work best in daylight. 
• Since rods are sensitive to much lower
levels of light than cones, they are
particularly useful in night vision.
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The Human Eye
41
Light
• Light is a form of electromagnetic
radiation. 
• Other forms of electromagnetic radiation
include radio waves, microwaves, infrared
radiation, ultraviolet rays, X rays, and
gamma rays. 
• All of these are known collectively as the
electromagnetic spectrum. 
• The colors we see are actually different
wavelengths of light.
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The Electromagnetic Spectrum
43
Color Deficiency
• When some or all of a person’s cones do
not function properly, he or she is said to
be color-deficient. 
• There are several kinds of color deficiency,
and most color-deficient people do see
some colors. 
• Very few people are totally color-deficient. 
• Color deficiency affects about 8 percent
of American men and less than 1
percent of American women and is a
hereditary condition.
44
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Binocular Fusion
• Because we have two eyes, located
about 2.5 inches (6.4 cm) apart, the
visual system receives two images. 
• Instead of seeing double, however, we
see a single image, probably a composite
of the views of two eyes. 
• The combination of the two images into
one is called binocular fusion.
binocular fusion
the process of combining the
images received from the two
eyes into a single, fused image
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Binocular Fusion (cont.)
• Not only does the visual system receive
two images but there is also a difference
between the images on the retinas. 
• This difference is called retinal disparity. 
• Retinal disparity is essential to your sense
of depth perception.
retinal disparity
the differences between the
images stimulating each eye
46
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Binocular Fusion (cont.)
Nearsightedness and Farsightedness
• Some of us are born with perfectly shaped
eyeballs and have almost perfect vision. 
• If your eyeball is a little too long, however,
you are nearsighted. 
• If your eyeball is too short, you are
farsighted.
47
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A Changing Flag
Proceed to the next slide and stare
steadily at the image of the flag for about
1 minute. Then go to the next slide and
note what you see on that slide.
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49
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A Changing Flag
What did you notice when the screen
appeared? What happens when you shift
your glance to a blank wall some distance
away? Why?
51
Hearing
• Hearing depends on vibrations of the air,
called sound waves. 
• Hair cells change sound vibrations into
neuronal signals that travel through the
auditory nerve to the brain. 
• Loudness of sound is determined by the
amplitude, or height, of sound waves.
auditory nerve
the nerve that carries
impulses from the inner ear to
the brain, resulting in the
sensation of sound
52
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Hearing (cont.)
• Pitch depends on sound-wave frequency,
or the rate of the vibration of the medium
through which the sound wave is
transmitted. 
• Sources of sounds can be located when
your ears work together. 
• When a noise occurs on your right, the
sound wave comes to both ears, but it
reaches your right ear a fraction of a
second before it reaches the left; it is also
slightly louder in the right ear.
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Decible Levels
54
The Pathway of Sound
• The ear is designed to capture
sound waves. 
• The outer ear receives sound waves, and
the earflap directs the sounds down a
short tube called the auditory canal. 
• The middle ear is an air-filled cavity, and
its main structures are three tiny bones–
the hammer, anvil, and stirrup. 
• The cochlea–a bony tube containing fluids
and neurons–makes up the inner ear.
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The Human Ear
56
Deafness
• There are two types of deafness. 
• Conduction deafness occurs when
anything hinders physical motion through
the outer or middle ear or when the bones
of the middle ear become rigid and cannot
carry sounds inward. 
• Sensorineural deafness occurs from
damage to the cochlea, the hair cells, or
the auditory neurons.
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Balance
• The body’s sense of balance is regulated
by the vestibular system inside the
inner ear. 
• Its prominent feature is the three
semicircular canals. 
• The stimuli for vestibular responses
include movements such as spinning,
falling, and tilting the body or head.
vestibular system
three semicircular canals that
provide the sense of balance,
located in the inner ear and
connected to the brain by a nerve
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Smell and Taste
• Smell and taste are known as the
chemical senses because their receptors
are sensitive to chemical molecules rather
than to light energy or sound waves. 
• Smell receptors in the nose send
messages about smells through the
olfactory nerve to the brain.
olfactory nerve
the nerve that carries smell
impulses from the nose to
the brain
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The Human Tongue
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Smell and Taste (cont.)
• Studies show that four primary sensory
experiences–sour, salty, bitter, and sweet–
make up taste. 
• Much of what is referred to as taste is
actually produced by the sense of smell. 
• Sensations of warmth, cold, and pressure
also affect taste. 
• The chemical senses seem to play a
relatively unimportant role in human
life when compared to their functions in
lower animals.
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The Skin Senses
• Receptors in the skin are responsible for
providing the brain with at least four kinds
of information about the environment:
pressure, warmth, cold, and pain. 
• Some skin receptors (such as neurons) are
particularly sensitive to hot or cold stimuli. 
• Many kinds of stimuli–scratches, punctures,
severe pressure, heat, and cold–can
produce pain.
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Perceptions of Pain
• Whereas other senses rely primarily on a
single stimulus, pain results from many
different stimuli. 
• Have you ever stubbed your toe and then
rubbed it to reduce the pain? 
• According to the gate control theory of
pain, we can lessen some pains by
shifting our attention away from the pain
impulses or by sending other signals to
compete with the pain signals.
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The Body Senses
• The sense of movement and body position
is kinesthesis. 
• It cooperates with the vestibular and visual
senses to maintain posture and balance. 
• Without kinesthetic sensations, your
movements would be jerky and
uncoordinated.
kinesthesis
the sense of movement and
body position
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Section Assessment
Review the Vocabulary What are
the five basic senses? Describe
two additional senses that
humans have.
The five basic senses are vision,
hearing, taste, smell, and touch. The
sense of balance (vestibular system)
and sense of movement and body
position (kinesthesis) are two
additional senses humans have.
65
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Section Assessment (cont.)
Visualize the Main Idea Use a
flowchart similar to the one shown
on page 222 of your textbook to
describe the pathway of sound.
The outer ear receives sound waves. The
earflap directs the sound down the auditory
canal to the eardrum. The eardrum’s
vibration causes the bones in the middle ear
to vibrate, pushing them against the cochlea.
The hairs inside the cochlea have sensory
cells that turn sound vibrations into neural
impulses. The auditory nerve sends the
impulses to the cerebral cortex of the brain.
66
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Section Assessment (cont.)
Recall Information What is the
electromagnetic spectrum and
why do we see only a portion of it?
The electromagnetic spectrum
includes radio waves, microwaves,
light, infrared radiation, ultraviolet rays,
E rays, and gamma rays. The
receptors in our eyes allow us to see
only certain wavelengths.
67
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Section Assessment (cont.)
Think Critically Why can we see
steadily and read street signs
even though we may be walking
or running?
The vestibular system regulates the
body’s sense of balance. The fluid in
the semicircular canals moves as our
bodies move, which allows our eyes to
stay focused and keeps us from
getting dizzy.
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Section Assessment (cont.)
Now that you have studied the
various sense organs, review the
brain functions and to which areas
of the brain the neuronal impulses
for each sense are transmitted.
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Reader’s Guide
Main Idea
– The way we interpret sensations and
organize them into meaningful experiences
is called perception. 
Objectives
– Outline the principles involved in perception. 
– Describe how we learn to perceive and what
illusions are.
71
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Reader’s Guide (cont.)
Vocabulary
– Gestalt 
– subliminal messages 
– motion parallax 
– constancy 
– illusions 
– extrasensory
perception (ESP) 
Click the Speaker button
to listen to Exploring
Psychology.
72
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information. Section 3 begins on page 223 of your textbook.
Introduction
• Perception goes beyond reflexive
behavior and allows us to confront
changes in our environment. 
• Perceptual thinking is essential for us to
adapt to change. 
• People do not usually experience a
mass of colors, noises, temperatures,
and pressures. 
• Rather, we see cars and buildings, hear
voices and music, and feel pencils, desks,
and physical contact.
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Introduction (cont.)
• People do not merely have sensory
experiences; we perceive objects. 
• The brain receives information from the
senses and organizes and interprets it into
meaningful experiences–unconsciously. 
• This process is called perception.
74
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Principles of Perceptual Organization
• Through the process of perception, the
brain is always trying to make sense out
of the confusion of stimuli. 
• The brain makes sense of the world by
creating “wholes” out of bits and pieces of
information in the environment. 
• Each “whole” that is organized by the
brain is called a Gestalt.
Gestalt
the experience that comes
from organizing bits and
pieces of information into
meaningful wholes
75
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Principles of Perceptual
Organization (cont.)
• Gestalt psychologists have tried to
identify the principles the brain uses in
constructing perceptions (Koffka, 1963). 
• Principles that people use in organizing
patterns are proximity, continuity,
similarity, simplicity, and closure. 
• The Gestalt principles of organization help
explain how we group our sensations and
fill in gaps to make sense of our world.
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Gestalt Principles
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Figure-Ground Perception
• One form of perceptual organization
is the division of experience into figure
and ground. 
• Figure-ground perception is the ability to
discriminate properly between a figure
and its background. 
• Figure and ground are important in
hearing as well as in vision.
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What Is It?
What did you see the first time
you looked at this illustration–a
vase or two profiles? People
invariably organize their
experience into figure and
ground.
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Perceptual Inference
• Often we have perceptions that are
not based entirely on current
sensory information. 
• The phenomenon of filling in the gaps in
what our senses tell us is known as
perceptual inference (Gregory, 1970). 
• Perceptual inference is largely automatic
and unconscious; thus, it often depends
on experience. 
• On the other hand, we are probably born
with some of our ability to make
perceptual inferences.
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Learning to Perceive
• In large part, perceiving is something that
people learn to do. 
• Experiments with human beings have
also shown that active involvement in
one’s environment is important for
accurate perception. 
• Learning to perceive is influenced by our
needs, beliefs, and expectations.
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Defying Basic Geometric Laws
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Subliminal Perception
• In 1957, Vance Packard divulged that
advertisers were using a revolutionary
breakthrough in marketing techniques:
subliminal advertising. 
• This concept used subliminal messages,
brief auditory or visual messages
presented below the absolute threshold
so that there is less than a 50 percent
chance that they will be perceived.
subliminal messages
brief auditory or visual
messages that are presented
below the absolute threshold
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Subliminal Perception (cont.)
• The idea for subliminal ads was a natural
outgrowth of a long series of
controversial studies on subliminal
perception–the ability to notice stimuli
that affect only the unconscious mind. 
• Even if it is possible for people to perceive
information at very low levels of intensity,
there is no clear evidence that these
weak, often limited messages would be
more powerful in influencing people than
would conscious messages.
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Depth Perception
• Depth perception, which is the ability
to recognize distances and threedimensionality, develops in infancy. 
• Psychologists have placed infants on
large tables and found that they most
likely will not crawl over the edge. 
• Infants seem able to perceive that it is a
long distance to the floor.
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The Necker Cube
The Necker cube is an ambiguous figure. You
can will yourself to see it as if you were looking
down on it, with corner X closest to you, or as if
you were looking up at it, with corner Y closest
to you.
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Monocular Depth Cues
• People use many monocular depth cues
to perceive distance and depth. 
• Monocular depth cues are cues that can
be used with a single eye. 
• Four of the monocular cues external to us
that we use are: 
– relative height 
– interposition 
– light and shadows 
– texture-density gradient
87
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Monocular Depth Cues (cont.)
• Another cue is motion parallax–the
apparent movement of objects that
occurs when you move your head from
side to side or when you walk around. 
• Two other distance cues are linear
perspective and relative motion.
motion parallax
the apparent movement of
stationary objects relative to
one another that occurs when
the observer changes position
88
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Binocular Depth Cues
• Binocular depth cues depend upon the
movement of both eyes. 
• For example, convergence is the process
by which your eyes turn inward to look at
nearby objects. 
• Another cue is the information provided by
retinal disparity. 
• Because each of your eyes occupies a
different position, each eye receives a
slightly different image. That difference is
retinal disparity.
89
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Constancy
• When we have learned to perceive
certain objects in our environment, we
tend to see them in the same way,
regardless of changing conditions. 
• Despite changing physical conditions,
people are able to perceive objects as the
same by the processes of size, shape,
brightness and color constancy.
constancy
the tendency to perceive
certain objects in the same
way regardless of changing
angle, distance, or lighting
90
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Constancy (cont.)
• An example of size constancy will
illustrate how we have an automatic
system for perceiving an object as being
the same size whether it is far or near. 
• Distance information compensates for
the enlarging eye image to produce
size constancy. 
• If information about distance is eliminated,
your perception of the size of the object
begins to correspond to the actual size of
the eye image.
91
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Shape Constancy
We perceive the opening door as being
rectangular in shape, although our view of the
shape of it changes as it opens.
92
Illusions
• Illusions are incorrect perceptions. 
• Illusions can be useful in teaching us
about how our sensation and perceptual
systems work. 
• Illusions are created when perceptual
cues are distorted so that our brains
cannot correctly interpret space, size,
and depth cues.
illusions
perceptions that misrepresent
physical stimuli
93
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Extrasensory Perception
• We are fascinated by things that cannot
be seen, easily explained, or often even
verified, such as flying saucers, atoms,
genes, and extrasensory perception. 
• Extrasensory perception (ESP)–
receiving information about the world
through channels other than the normal
senses–is a hotly debated topic.
extrasensory perception (ESP)
an ability to gain information
by some means other than
the ordinary senses
94
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Extrasensory Perception (cont.)
• There are four types of ESP: 
– Clairvoyance is perceiving objects or
information without sensory input. 
– Telepathy involves reading someone else’s
mind or transferring one’s thoughts. 
– Psychokinesis involves moving objects
through purely mental effort. 
– Precognition is the ability to foretell events. 
• Many people are convinced that ESP exists
because of an intense personal experience
that can never be scientifically validated.
95
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Extrasensory Perception (cont.)
• Many scientists do not accept the results
of experiments supporting ESP because
the findings are highly unstable. 
• One basic principle of scientific research
is that one scientist should be able to
replicate another scientist’s results. 
• Not only do different ESP experiments
yield contradictory findings but also the
same individual seems to show ESP on
one day but not on the next.
96
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Section Assessment
Review the Vocabulary Describe
the Gestalt principles of
organization. How do these
principles help us organize reality?
Gestalt principles of organization are
proximity, similarity, closure, continuity,
and simplicity. They help us organize
perceptual information in a way that
allows us to create a whole.
97
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Section Assessment (cont.)
Visualize the Main Idea Use a
graphic organizer similar to the
one shown on page 231 of your
textbook to list and briefly
describe monocular depth cues.
Answers should reflect an
understanding of monocular depth
cues, which include relative height,
interposition, light and shadows,
texture-density gradient, motion
parallax, linear perspective, and
relative motion.
98
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Section Assessment (cont.)
Recall Information What are the
binocular depth cues? How do
they help us judge reality?
Binocular depth cues depend on the
movement of both eyes.
Convergence is when our eyes turn
inward to view objects that are close.
Large retinal disparity means the
object is close; small retinal disparity
means the object is farther away.
These cues help us judge distance.
99
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Section Assessment (cont.)
Think Critically How do illusions
demonstrate the difference between
sensations and perceptions?
Sensations are the sensory input;
perceptions are the sometimes
inaccurate processing of the stimuli.
The illusion is created when our brain
misinterprets the sensory stimuli.
100
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Section Assessment (cont.)
Without consulting your textbook,
write down five new things that
you learned from this chapter.
Share your answers.
101
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Section 1: Sensation
• The absolute threshold is the weakest
amount of a stimulus required to produce
a sensation; the difference threshold is the
minimum amount of distinction a person
can detect between two stimuli. 
• Senses are most responsive to increases
and decreases rather than to ongoing
stimulation. 
• Sensory adaptation allows people to notice
differences in sensations and react to the
challenges of different or changing stimuli.
103
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Section 2: The Senses
• Vision provides people with a great deal of
information about the environment and the
objects in it. 
• Hearing depends on vibrations of the air,
called sound waves. 
• The body’s sense of balance is regulated
by the vestibular system inside the
inner ear. 
• Smell and taste are known as the chemical
senses because their receptors are
sensitive to chemical molecules.
104
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Section 2: The Senses (cont.)
• Receptors in the skin are responsible for
providing the brain with information about
pressure, warmth, cold, and pain. 
• Kinesthesis cooperates with the vestibular
and visual senses to maintain our sense of
movement and body position.
105
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Section 3: Perception
• The Gestalt principles of organization help
explain how we group our sensations and
fill in gaps to make sense of our world. 
• Figure-ground perception is the ability to
discriminate properly between figure
and ground.
• Perceptual inference is the phenomenon of
filling in the gaps in what our senses tell us.
• Learning to perceive is influenced by our
needs, beliefs, and expectations.
106
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Section 3: Perception (cont.)
• People use monocular depth cues and
binocular depth cues to perceive distance
and depth. 
• Incorrect perceptions, created when
perceptual cues are distorted, are
called illusions.
107
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Click the mouse button to return to the Contents slide.
Reviewing Vocabulary
Use the correct term or concept to complete the following
sentences.
1. The organization of sensory information into
perception .
meaningful experiences is __________
2. The psychological study of questions such as the
relationship between color and wavelength is
psychophysics
called ____________.
3. The minimum amount of difference a person can
difference
detect between two stimuli is the ________
________.
threshold
4. __________
Illusions are incorrect perceptions.
5. __________
Kinesthesis is the sense of movement and
body position.
109
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to display the answers.
Reviewing Vocabulary (cont.)
Use the correct term or concept to complete the following
sentences.
6. The combination of two images into one is
_____________
binocular fusion .
7. A(n) __________
sensation happens when a stimulus
activates a receptor.
subliminal messages
8. Advertisers sometimes use _________________,
which are brief auditory or visual messages
presented below the absolute threshold so that
there is less than a 50 percent chance that they
will be perceived.
110
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to display the answers.
Reviewing Vocabulary (cont.)
Use the correct term or concept to complete the following
sentences.
9. The weakest amount of stimuli required to
produce a sensation is called the _________
absolute
________.
threshold
10. A body’s sense of balance is regulated by the
_______________
vestibular system inside the inner ear.
111
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Recalling Facts
Using a graphic organizer similar
to the one on page 234 of your
textbook, define stimulus and
give at least four examples
of stimuli.
112
Recalling Facts
What is the psychological principle
that explains why you are more likely
to notice when a single lightbulb
burns out in a room with three lamps
than when a single lightbulb burns
out in a sports arena?
Weber’s law suggests that the larger or
stronger a stimulus, the larger the change
required for an observer to notice that
anything has happened to it. In other words,
in a larger arena, it would take a larger
change, such as 100 lightbulbs burning out,
for the observer to notice it.
113
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Recalling Facts
What is our vestibular system? Why
do we need it?
The vestibular system is our sense of
balance located in the inner ear. We
need it to maintain balance.
114
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to display the answer.
Recalling Facts
List four kinds of information we
receive from our skin.
Information includes warmth, cold,
pain, and pressure.
115
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to display the answer.
Recalling Facts
Define figure-ground perception
and provide an example of it.
It is the ability to discriminate
properly a figure from the
background around it. An example is
when you hear your name spoken in
a noisy room–you have discriminated
the sound of your name from all the
surrounding sounds.
116
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to display the answer.
Building Skills
Interpreting a Graph
Review the graph, and then answer the questions that follow.
117
The graph appears on page 235 of your
textbook.
Building Skills
Interpreting a Graph
What three
body parts are
the least
sensitive to
touch?
The shoulder,
the calf, and the
thigh are the
least sensitive
to touch.
118
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to display the answer.
Building Skills
Interpreting a Graph
Why are
certain parts of
the body more
sensitive to
touch than
others?
Sensitivity to
touch varies
because some
places on the
body have more
receptors than
others. Your fingertips for example have more
receptors and are therefore more sensitive.
119
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to display the answer.
Building Skills
Interpreting a Graph
How does the
information in
the graph help
explain why
people reading
in Braille use
their fingertips?
The graph shows
that the fingertips
are the most
sensitive part of
the body. The
ability to sense the sometimes subtle changes in
Braille is best achieved through the finger tips.
120
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to display the answer.
I am the theory that pain can be
lessened by sending signals that
compete with the pain signals.
What am I?
I am the gate control theory of pain.
121
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to display the answer.
Click the mouse button to return to the Contents slide.
Explore online information about the
topics introduced in this chapter.
Click on the Connect button to launch your browser and go to the
Understanding Psychology Web site. At this site, you will find
interactive activities, current events information, and Web sites
correlated with the chapters and units in the textbook. When you
finish exploring, exit the browser program to return to this
presentation. If you experience difficulty connecting to the Web
site, manually launch your Web browser and go to
http://psychology.glencoe.com
Think about an occasion in which you were
in a crowded and noisy setting. Did you find
yourself listening to or picking up part of
another conversation? Write an explanation
for this occurrence in your journal.
Select one of the senses and write an
essay about what life would be like without
that sense.
Use an eye patch or gauze taped over one
eye and walk around in familiar surroundings.
What differences do you notice? Write a few
paragraphs about your experiences.
Keep a log for 24 hours of the perceptual
inferences you make. For example, you
might hear the sound of the school bus
before actually seeing it. Yet, based on
past experience, you will perceive this
auditory stimulus as a school bus. At the
end of the 24-hour period, describe how
perceptual inferences help people function
more effectively.
Seeing Is
Believing
Read the case study presented on
page 232 of your textbook. Be
prepared to answer the questions that
appear on the following slides. A
discussion prompt and additional
information follow the questions.
Continued on next slide.
This feature is found on page 232 of your textbook.
Seeing Is
Believing
Why did some images seem
confusing to Kenge?
Kenge had been isolated from views of great
distances his entire life. Since he lived in thick
forests, Kenge had never experienced the view of
distant objects. His brain had not stored information
in memories about size constancy. Therefore, his
brain did know how to interpret the stimuli correctly.
His perceptual development was limited.
Continued on next slide.
Click the mouse button or press the Space Bar to display the
answer. This feature is found on page 232 of your textbook.
Seeing Is
Believing
According to Turnbull, how do we
learn size constancy?
According to Turnbull, size constancy is learned
as we perceive the world around us. It is learned
through experience.
Continued on next slide.
Click the mouse button or press the Space Bar to display the
answer. This feature is found on page 232 of your textbook.
Seeing Is
Believing
Critical Thinking Do you think that Kenge
could adjust to life in your city or town?
Explain the difficulties he might encounter.
Answers will vary. He might survive well in a
large city like New York where the tall buildings fill
the landscape and vistas are uncommon.
Students may also argue that Kenge’s perception
will improve with experience.
Continued on next slide.
Click the mouse button or press the Space Bar to display the
answer. This feature is found on page 232 of your textbook.
Seeing Is
Believing
Discuss the following:
Do you think that Kenge could learn size
constancy if exposed to open spaces
regularly? What reactions would you expect
from Kenge’s village when he explains the
strange things he saw? Do you think Kenge
and the other villagers simply did not pay
attention to visual clues about distance and
size constancy?
Continued on next slide.
This feature is found on page 232 of your textbook.
Seeing Is
Believing
Does perception occur when we are not
paying attention? Recent studies in
cognitive psychology suggest that we
must be paying attention in order to
perceive sensory stimuli. In one
experiment, participants were shown a
series of “+” signs, some with the
horizontal bar longer and some with the
vertical bar longer.
Continued on next slide.
This feature is found on page 232 of your textbook.
Seeing Is
Believing
– As the signs were flashed on the screen, participants
were asked to indicate which bar was longer. 
– After several trials, another object was shown on the
screen at the same time. 
– Objects that were placed away from the point where
the “+” sign appeared were not noticed by 25 percent
of the participants.
Continued on next slide.
Click the mouse button or press the Space Bar to display the
information. This feature is found on page 232 of your textbook.
Seeing Is
Believing
– When the “+” sign was moved to a new location and
the distracting object was placed where the previous
“+” sign had been, 75 percent of the participants did
not see the distracting object. 
– These findings are simply a starting point in the
research of attention and perception. 
– The findings do, however, seem to indicate that what
we perceive is largely affected by what we choose to
pay attention to.
Click the mouse button or press the Space Bar to display the
information. This feature is found on page 232 of your textbook.
Continued on next slide.
Continued on next slide.
Answers:
1. The sense of taste
will be stimulated. 
2. The woman salting
the apple because
the sweetness of
the apple will make
the salt more
noticeable. 
3. Possible answers
include: changing
the volume of the
car stereo
compared to a rock
concert, increasing
the weight of a
backpack from 5 to
7 lbs. compared to
changing the weight
from 40 to 42 lbs.
Click the mouse button or press the Space Bar to
display the answers.
Continued on next slide.
Answers:
Answers will vary for each item.
We do not experience some items
through certain senses. For
example, you may say that we
learn nothing about a watering
can from our sense of taste.
Click the mouse button or press the Space Bar to
display the answers.
Continued on next slide.
Answers:
1. No; the fish on the
left appears larger. 
2. Perception is
affected by its
relationship to the
other objects in
the picture. 
3. You perceive size in
relation to distance.
The fish on the left
is closer.
Click the mouse button or press the Space Bar to
display the answers.
Exploring the World
of Senses
From the Classroom of Parran H. Curry-Guy
North Education Center, Columbus, OH
Background: People rarely consider how
their experience of the world is affected by
the coordination of their senses. When
one of those senses is impaired, people
can concentrate on what they experience
through their other senses.
Continued on next slide.
Exploring the World
of Senses
From the Classroom of Parran H. Curry-Guy
North Education Center, Columbus, OH
Directions: For this activity you will need
to find a partner and a blindfold that your
teacher will provide. 
Take turns wearing the blindfold and then
having your partner lead you around the
school and its grounds. 
Concentrate on using your other senses
to learn as much as you can about your
surroundings as you are being guided.
Continued on next slide.
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display the information.
Exploring the World
of Senses
From the Classroom of Parran H. Curry-Guy
North Education Center, Columbus, OH
Conclusion: After everybody has had the
blindfold experience, discuss with the
class what you felt, what sounds you
heard, and what smells you encountered.
You should also discuss how you felt
about not having your sense of sight to
guide you.
Total color deficiency is the inability to see
colors. Everything appears in shades of gray.
This rare condition is known as
monochromatism. Partial color deficiency,
known as dichromatism, is the inability to
distinguish one of the primary colors, usually
red or green.
In 1990 Anthony Greenwald and his
colleagues tested the power of suggestion by
switching the labels on two subliminal tapes–
one aimed at improving the memory, the
other at improving self-esteem. At the end of
one month, participants in the study reported
an improvement in whatever area the label
promised.
When the color preferences of college students in
the United States, Kuwait, Iran, and Lebanon
were studied, red and blue had the highest
preference ranking for Americans only. Red and
blue were the lowest-ranked color preferences in
Kuwait. Green consistently ranked high among
students from all four nations. Studies have been
conducted comparing colors preferred by men
and women, by religion, and by climate.
Sensory Dysfunction
Recent studies suggest that many autistic children
and adults have sensory dysfunction in one or more
of their sensory systems including the hearing,
vision, tactile, vestibular, or proprioceptive (internal)
systems. Autistic children are often over- or underresponsive to sensory input. Specific treatment
addressed to their sensory dysfunction can vastly
improve their quality of life. For one autistic boy,
three weeks of visual training reduced his retinal
disparity and improved his eye-hand coordination.
Sensory Deprivation Tanks
• Sensory deprivation tanks, specifically flotation tanks,
allow you to escape the constraints of gravity. 
• Proponents claim that in the tank you can easily slip
into altered states of consciousness. 
• The release of endorphins into your bloodstream
slows as sensory input diminishes. 
• Roderick Borrie, Ph.D., recommends the flotation
tank as the ideal way to recover from intense
competition since stress is reduced, muscles are
relaxed, and blood pressure and heart rate drop.
Continued on next slide.
Click the mouse button or press the Space Bar to display the
information.
Sensory Deprivation Tanks
• While short periods of sensory deprivation may be
useful, long periods of deprivation decrease the
brain’s efficiency, may cause a partial loss of memory,
lower IQ, and may result in hallucinations and
personality changes. 
• Why are limited periods of deprivation useful? 
• Why are long periods of deprivation harmful? 
• Do you think that the effects of long-term deprivation
can be reversed? Explain.
Click the mouse button or press the Space Bar to display the
information.
• Collect samples of children’s artwork to bring
into class and post around the room (include the
artists age). 
• Many different developmental factors play a role in
shaping children’s art. 
• Examine the pieces of art you have collected and
analyze them to see what these pictures reveal
about children’s perception of the environment.
Continued on next slide.
Click the mouse button or press the Space Bar to display the
information.
• What do proportional sizes, colors, and
shapes tell about how children see
the world? 
• What stimuli capture the children’s attention? 
• How do the children depict depth, if at all?
Click the mouse button or press the Space Bar to display the
information.
Blind Spots
Food and Drink Reactions
Click a hyperlink to choose a topic.
• Read the Psychology and You feature on
page 216 of your textbook. 
• Discuss the following:
In what other instances do people
experience blind spots?
Click the mouse button or press the Space Bar to display the
information.
• Read the Psychology and You feature on
page 222 of your textbook. 
• Discuss the following:
What other reactions between foods
and drinks have you encountered?
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information.
Gustav Theodor Fechner
1801–1887
Click the picture to listen to
a biography on Gustav
Theodor Fechner. Be
prepared to answer
questions that appear on
the next two slides.
This feature is found on page 209 of your textbook.
Gustav Theodor Fechner
1801–1887
Why did the flowers look
brighter after Fechner spent
a long period in a room
painted completely black?
Fechner found that the variation in
perception was caused by
variations in the physical stimuli.
Therefore, the change from total
black to color was perceived as a
greater difference than the change
from the viewing of colors from
day to day.
Click the mouse button or press the Space Bar to display the
answer. This feature is found on page 209 of your textbook.
Gustav Theodor Fechner
1801–1887
How did Fechner
revolutionize experimental
psychology?
He used methods of sensory
measurement to explain the
way the mind perceives the
outside world.
Click the mouse button or press the Space Bar to display the
answer. This feature is found on page 209 of your textbook.
End of Custom Shows
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shows and return to the main presentation.
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