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Chapter 3
Sensation and Perception
Ms. Chauvin
I. Sensation
1. Sensation-the process by which the sensory receptor gives rise to
2. History—earliest psychological research on sensation examined
relationship between
 Psychophysics—study of the correlation between physical
stimuli and the behavior or mental experience the stimuli
invoked (oldest field within psychology)
 Gustav Fechner—
3. Absolute Threshold—
 Psychologists measure absolute threshold by recording
 Trying to see a dim light in a dark room, hearing a soft sound
in a quiet room, etc
 If you’ve ever had a hearing test
4. Sensory Adaptation—diminishing responsiveness of sensory
systems to prolonged sensory output
 Sunshine feels
 Hum of A/C
5. Signal Detection Theory—
 Can have life or death consequences—wartime sentry vs.
peacetime sentry fall asleep
6. Difference Threshold—
 Test—use pairs of stimuli—ask observer whether two stimuli
are the same or different
7. Just Noticeable Difference (JND)—
 Ernest Weber—Developed Weber’s Law:
 For the avg. person to perceive their differences,
8. Sensory Physiology:
 Transduction—conversion of one form of energy like light, to
another form, such as neural impulses
9. Vision—your eyes’ ability to respond to light
 Mechanisms: 6 major parts:
Color Blindness—some cones sensitive to _________________, others to
_________________, others to ____________________________. When one type of cones is
missing or deficient ________________________________results. More common in
_______________; thought to be ________________________ passed on to _________________by
__________________.
 Pathways to Brain: destination of much visual information is
the part of the _____________________known as the
_________________________________
1)
2) ganglion cells register
3) cortical neurons called ____________________________respond
to particular features of the scene such as __________________,
______________________, ________________________, ______________________.
From this, the brain assembles the image.
4) The visual cortex passes this info. on to the
 Color Vision—two theories of color vision
1) Young-Helmholtz 3-Color Theory: the retina has 3
types of color receptors, each sensitive to one of three
colors:
. Our perception of color is due
to the
2) Opponent-Process Theory (Hering)—There are
opposing retinal processes (cones
which enable color vision. Cells
stimulated by one would be inhibited by another.
Confirmed by
 Color Constancy—perceiving familiar objects as having
consistent color, even though changing illuminations alter
wavelengths alter
Color will remain roughly constant
****we see color thanks to our brain’s
10. Audition (hearing)—sound wave travels at a rate of 1100 ft/sec. It
has two basic properties:
 Frequency:
 Amplitude:
 3 Dimensions of Sound: pitch, loudness and timbre
1) pitch:
2) loudness: physical intensity; determined by its______________.
(sound waves with large amplitude are experienced as
______________and those with small amplitude as _______________)
Loudness is measured in _____________________. See thermometer
of familiar sounds. Prolonged exposure to sounds louder
than ______________________________can produce permanent hearing
loss.
2) Timbre—reflects the components of a sound’s complex
sound wave. Timber sets apart
 Mechanisms of the auditory system
1) outer ear channels
2) middle ear transmits vibrations through 3 tiny bones (
) to a snail-shaped tube in inner ear (cochlea)
3) inner ear’s (cochlea) membrane
4) basilar membrane bends hair cells;
5) neural messages sent to
 Deafness—two types
1) conduction deafness—
2) nerve deafness—
 Two Theories of Pitch Perception—ability to distinguish the
chirp of a bird from the roar of a truck
1) Place Theory—Hermann von Helmholtz—
2)Frequency Theory—theory that nerve impulses traveling up
to the auditory nerve match the
***frequency theory best explains how we perceive_______________________, place
theory best explains ______________________, volley theory best explains
________________________.
 Location—humans use sound to determine the locations of
objects in space through the use of 2 mechanisms:
1) relative timing—
2) relative intensity—
11. Olfaction (Smell)—in humans, evolved mainly as a mechanism for
_________________________; in some species, ______________________________________.
 Classifications:
 Mechanism:
1)odors react with receptor proteins on the
2) nerve impulses are initiated and convey
3) smell is a lesser sense in humans, but humans do, like
animals, emit pheromones
****smell is the ONLY sense that is NOT routed through the thalamus; for that
reason, it is more tied to emotional memory than any other sense
12. Taste—
 Taste receptors –surface of tongue covered with
1) four primary taste qualities:
2)
3) taste receptors get replaced, but
13. Touch—hidden beneath the skin are __________________________________.
When they are stimulated, they send messages to the brain. What commonly
is called touch is actually three different receptors:
 Pressure receptors—found over different parts of the body in
differing amounts. (
 Pain receptors: respond to a # of intense stimuli cutting or
pricking, twisting, heat or cold, damage to tissue or pressure
(vary in # from 50 per sq. cm on bottom of foot to 230 in same
sized space on neck)
1)pain is body’s response to noxious stimuli—
2)starting at spinal cord—
3)psychology of pain—your emotional responses, context
factors, and your interpretation of the situation can be as
important as the actual physical stimuli in determining how
much pain you experience
***pain can be modified by
4) Gate-Control Theory of Pain—Ronald Melzack—
suggests that cells in the spinal cord act as
***it is the message descending from the brain that
provides the psychological context in which you experience pain
 One aspect of cutaneous sensitivity plays a central role in
_______________________________. Through touch, you communicate your
desire to
1) Erogenous Zones—
14. Vestibular & Kinesthetic Senses
 Vestibular—
(tiny hairs and canals in inner ear inform you how your head is
moving when you turn, nod, or tilt it)
 Kinesthetic—
Notifies the brain of your position and movement of body parts
II. Perception—
 Bottom-up processing—recognition of an object by breaking it
down to its component parts; relies heavily on sensory receptors
 Top-down processing—
1. Selective Attention—
2. Perceptual Illusions—reveal ways that we normally organize and
interpret our sensations
 Muller-Lyer Illusion—
3. Perceptual Organization-Gestalt—emphasis on our tendency to
4. Form Perception—a “top down” process, according to Gestalt
 Figure-ground—
 Grouping—our minds follow certain rules for grouping
stimuli together
1) Proximity—
2) Similarity—
3) Continuity—
4) Connectedness—
5) Closure—
5. Depth Perception—seeing things in 3D enables us to estimate their
distance from us
 Visual Cliff—Gibson and Walk—
 Binocular Cues—rely on both eyes’ images
1) retinal disparity—
2) convergence—
 Monocular Cues—those we need only one eye to see
1)interposition—
2) relative size-3) relative clarity—
4) texture gradient—
5) relative height—
6) relative motion (motion parallax)—
7) linear perspective—
8) light and shadow—
***artists use monocular cues to convey depth on a flat canvas; so do people
with sight in only one eye
6. Motion Perception—brain computes motion partly based on
7. Perceptual Constancy—we now that a stimulus remains the same
even though it does not appear to (airplane on ground vs. in air)
PERCEPTUAL INTERPRETATION—perceptual abilities both nature AND
nurture
8. Sensory Deprivation and Restored Vision—cat experiments—there
seems to be a ________________________for normal sensory and perceptual
development
9. Perceptual Adaptation-10. Perceptual Set—our experiences assumptions, and expectations
greatly influence what we perceive;
11. Extrasensory Perception (ESP)—claim that perception can exist
apart from sensory input; includes telepathy, clairvoyance, and
precognition
 parapsychology—
 telepathy—
 clairvoyance—
 precognition—
 ESP has yet to be scientifically validated
 Testing ESP--