Prologue to Chapter 4
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Human life would be very different without
the ability to sense and perceive external
stimuli
Imagine your world without the ability to
see, hear, smell, touch, and feel
Psychologists are interested in sensation
and perception as inputs to and outputs
from the brain
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Sensation: Receiving messages
about the world
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Sense organs operate through sensory
receptor cells that receive external forms of
energy and translate these external forms
into neural impulses that can be transmitted
to the brain
There are five types of sense organs which
we will examine in this chapter
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Sensation: Receiving messages
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Stimuli: What messages can be received?
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Anything capable of exciting a sensory
receptor cell can be defined as a “stimulus”
Examples include: sound, light, heat, cold,
odor, color, touch, and pressure
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Sensation: Receiving messages
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Transduction: Translating messages into
the brain’s language
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Sense orgrans transduce sensory energy into
neural (bioelectrical) energy
Converting one type of energy into another
type is the process of transduction
Your brain only deals with bioelectrical
impulses so transduction must occur; what
cannot be transduced cannot be a stimulus
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Sensation: Receiving messages
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Sensory limits: How strong must the
message (signal) be for it to be detected by
the sensory receptor?
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Absolute thresholds
Difference thresholds
Sensory adaptation and habituation
Study of these sensory limits and phenomena
is called “Psychophysics”
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Investigating sensory input
devices
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We will now take a closer look at each of
the five sensory input devices
We will look at the eye, the ear, skin
senses, olfaction, and taste
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Vision: Your human camera
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Light: What is it?
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light is constructed of wave/particles packets
of energy called photons
visible light is only a tiny part of the much
broader electromagnetic spectrum
light is measured by its intensity and its
frequency
the visible spectra ranges 390 to 710
nanometers/sec. ossilation
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Vision: Your human camera
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The eye: How does it work?
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The transduction of light wave/particles into
neural energy is carried out by the receptor
cells in the retina of the eye
The retina has 2 general types of cells that
engage in transduction
rods (for transducing black/white light)
 cones (for transducing colored light)
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Vision: Your human camera
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Parts of the eye include:
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cornea, lens, pupil, iris, fovea
vitreous humor, aqueous humor
the optic nerve, blind spot
Here is a picture of the eye
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Vision: Your human camera
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Dark and light adaptation
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How does the eye adjust to seeing in the
dark? How does the eye see in low-light
conditions?
How does the eye adjust to bright-light
conditions?
Rods and cones
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Vision: Your human camera
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Color Vision: What is it and how does it
work?
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Color is the conscious experience that results
from the processing of light energy of
differing frequencies by the eye and the brain
There are two theories as to why we can see
color yet, in truth, no one knows precisely
why we see in color
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Vision: Your human camera
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Theories of color vision
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The “Trichromatic Theory”
3 cone types: red, green, and blue cones
 similar to the RGB setup on your color TV
 red cones detect red, blue detect blue, etc.
 problems exist in this theory however because
there is no known mechanism in the brain for
blending the three colors into the rich hue of color
that we can see
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Vision: Your human camera
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Theories of color vision
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The “Opponent-process Theory”
3 cones types (similar to trichromatic theory) but
each of the three have opponent processes (unlike
trichromatic theory)
 Red-green cones, blue-yellow cones, and blackwhite cones
 After-images and inversions of color, e.g., sunset
after-images, attest to the probability that the
opponent-process theory is correct
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Hearing: Sensing sound waves
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We will now examine hearing and the ear
Sound: What is it?
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hearing is the sense that detects vibratory
changes in the air called sound waves
sound waves are changes in air pressure
throwing a rock into a still lake will give you
a picture of sound waves as they would look
if they were visible to the eye
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Hearing: Sensing sound waves
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Sound: What is it?
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Sound waves are measured by their frequency
and amplitude
frequency: pitch/note
 amplitude: loudness/decibels
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Hearing: Sensing sound waves
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The Ear: How does it work?
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Outer ear: external part that helps to collect
sound waves
Middle ear: where sound waves are
transduced into mechanical energy
Inner ear: where mechanical energy is
transduced into neural energy/biolelectrical
impulses
Here is a picture of the ear
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The Middle and Inner Ear
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Body Senses: Messages from
myself about myself
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Orientation and movement senses
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Vestibular organs
located in the inner ear, there are movement
detectors and orientation detectors
 semi-circular canals provide orientation detection
or rotary movement detection
 processes involved in detection of movement in
vestibular organs
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Body Senses
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Kinesthetic senses
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located in the muscles, joints, and skin, they
provide information about your movement in
space, posture, and orientation in space
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Body Senses
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Skin Senses
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located in the epidermis and dermis of the
skin; also some in the superficial fascia of the
skin
pressure sensors
temperature sensors
relative heat-change sensors
 relative cold-change sensors
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Body Senses
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Skin Senses
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Pain sensors
pain is a complex sensation that involves more
than the simple transmission of pain messages to
the brain
 pain sensors are located in the epidermis (called
free nerve endings)
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Phantom limbs
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the “phantom limb experience” reveals that the
brain also influences “sensation”
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Chemical Senses: The flavors
and aromas of life
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Taste: What is it?
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chemical “lock/key” sensation
10,000 taste buds on the tongue
the “taste bud”
the tongue’s map to taste: sweet, sour, bitter,
and salty tastes
here is a picture of the tongue
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Chemical Senses
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Smell/Olfaction: What is it?
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Stereo-chemical theory of smell
Similar to taste sense (lock/key)
Receptor cells for smell located at the top of
the nasal cavity in the olfactory epithelium
Here is a picture of the nasal cavity area
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Perception: Interpreting sensory
messages
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Visual perception
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Perceptual organization: why we see things
the way we do
Gestalt principles of perceptual organization
include: proximity, figure-ground, continuity,
similarity, and closure
 In the following slides, I’ll show you examples of
each Gestalt organizational rule
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Perception
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Gestalt rule of proximity
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BBBB
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Perception
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Gestalt rule of figure-ground
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Perception
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Gestalt rule of continuity
What color is next and
why?
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Perception
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Gestal rule of similarity
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Perception
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The Gestalt rule of closure
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“The itsy-bitsy spider went up the garden
spout… down came the rain and…”
What’s next?
Why did you say “washed the spider out”?
“Shave and a hair cut: two bits”
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Perception
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Perceptual constancy: we perceive objects
as being unchanged although the raw
sensory data changes
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size constancy: a car does not grow when it
comes toward us; we perceive it is getting
closer
shape constancy: a pencil is still a pencil even
though we see it from many different angles
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Perception
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Depth perception
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depth perception permits our twodimensional retinas to perceive a three
dimensional world
binocular depth cues include: convergence
and incongruities in pictures between eyes
monocular depth cues include: haziness,
darkness, interposition, and motion parallax
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Perception
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Visual Illusions
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Illusions provide evidence that what we think
we “see” is not the same as the visual
information entering the eye
there are a number of different visual
illusions, e.g.,
the Mueller-Lyre Illusion
 the “top hat illusion”
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Perception
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The Mueller-Lyre Illusion
Which figure has the
longest central line?
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Perception
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The “Top Hat Illusion”
Is the hat taller or
wider?
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Faces or goblet illusion? Figure vs Ground
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Hole or Hill?
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Notice the Intersection of
the Boxes: Darker?
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Herringbone Illusion
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The Impossible Bolt
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Impossible
Crank
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Impossible Stack
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Impossible Triangle
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Duck or Rabbit?
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Opponent Process
American Flag
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Size -Weight Illusion
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Eternal Stairway
Illusion
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Perception
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Individual and cultural influences on
perception
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characteristics of the perceiver can influence
what is perceived
individual differences and cultural differences
do affect perception
using “projective tests” as a means of
assessing the perceiver’s personality/cultural
experience
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Application of psychology:
Perception, illusion, and art
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Art (a two-dimensional surface) uses many
monocular depth cues to convey a 3dimensional picture
Media advertising is totally directed toward
the goal of influencing your perception
about products
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Vance Packard’s book “Hidden Persuaders”
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Application of psychology
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Subliminal perception and its relationship
to emotion
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studies of subliminal perception have shown
that its use can affect the perceiver’s
emotions without their awareness
all propaganda is designed to affect your
emotions using subliminal perceptual
techniques
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Questions?
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Do you have any questions about Chapter
4?
Test #1 will cover information presented in
lecture, the book, and study guide over
these four chapters.
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How to prepare for my tests?
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You must read the book!
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read the chapters at least twice and take good
notes
quiz yourself with another student to see how
much you’ve retained
You can use the studyguide for extra credit
Be sure to bring a #2 pencil to tests!
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How to prepare for my tests
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Any questions about testing?
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