Download Sensation

Myers’ PSYCHOLOGY
(6th Ed)
Chapter 5
Sensation
James A. McCubbin, PhD
Clemson University
Worth Publishers
1
CH. 5: Sensation
 Sensation: process by which sensory receptors
+ nervous system receive & represent stimulus
energy
- stimulation of neurons in sensory nerves,
such as optical & auditory nerves…creating
action potential
 Perception: the way we organize & interpret
sensory info, enabling us to recognize
meaningful objects & events
-helps us to “know” what something is…as
long as we have experience with it
-prosopagnosia: visual condition
-can receive stimulus, but cannot organize it
into recognizable things…so can’t recognize it
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Sensory & perceptual processes work together to
help us sort out complex processes
“The Forest Has Eyes…”
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Sensation
 Bottom-Up Processing: sensory analysis that
begins w/ sense receptors then  brain’s
integration of sensory info
-neural signals  into action potentials
 Top-Down Processing: info processing guided
by higher-level mental processes
 as when we construct perceptions drawing
on our experience & expectations…often
what we are used to seeing…&
---what we expect to see
EX: prosopagnosia: receiving signals (sensory)
& ID facial features, but can’t put it
together& name them…but can feel
emotional reaction…see son, warm emotions,
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but no recognition…
Sensation- Basic Principles
 Thresholds: “How low can you go?”
 Psychophysics
 study of the relationship between physical
characteristics relate to our psychological
experience …how intense? How is it
changing?
 Light- brightness
 Sound- volume
 Pressure- weight
 Taste- sweetness
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Sensation- Thresholds
 Absolute Threshold: minimum stimulation
needed to detect a particular stimulus 50%
of the time
EX: the earphones used in a hearing test…
-vision: if we are on top of a mtn., we can see
a candle flame on another mtn. 30 miles away
(if it is a dark, clear night)
-touch: wing of a bee on our cheek
-smell: 1 drop of perfume in a 3-rm. Apt.
 Difference Threshold (197): minimum
difference between two stimuli required for
detection 50% of the time
 just noticeable difference (JND)
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Sensation- Thresholds
 Signal Detection Theory: predicts how & when
we detect the presence of a faint stimulus (signal)
amid background stimulation (noise…meaning
distracting stuff around you…can be visual)
 assumes that there is no single absolute threshold
 detection depends partly on person’s
 Experience
 expectations
 motivation
 level of fatigue
-soldier’s awareness on guard duty?
-mom’s can hear baby b/c tuned in to it
--how about you & your cell phone?? 
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Sensation- Thresholds
Subliminal: real or
unreal?
100
Percentage
of correct
detections
75
50
Subliminal
stimuli
25
0
Low
Absolute
threshold
Intensity of stimulus
Medium
 When stimuli are just
below one’s absolute
threshold for
conscious
awareness, but can
be perceived
unconsciously
 “EAT POPCORN?”
 Eliminate bad habits,
attain goals?
 Can have fleeting
effect…but not
enduring
 Expectations?(197)
 Now ads put info into
our minds—colors,
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“cool” in smoking…
Sensation- Thresholds
 Weber’s Law- to perceive as different, 2 stimuli
must differ by a constant minimum %…how much
causes a JND?
 light intensity- for avg. person to tell a difference in
2 lights, difference must be at least 8%
 weight- 2% (5 lbs?)
--tone frequency- 0.3%
 NOTE: these are rough approximations
-affected also by expectations & experience: 50 cent
bar  5 cents? How much w/ $40,000 Mercedes?
 Sensory adaptation- diminished sensitivity as a
consequence of constant stimulation
-after constant exposure to a stimulus, nerves fires
less frequently…odors, your watch, sounds…but not
vision b/c eyes continually move just slightly…but if
we held it constant? 
9
Vision- Stabilized Images on the
Retina: If truly constant, vision does fade…
10
Benefit of sensory adaptation: Though it
reduces our sensitivity, it allows us to
focus on new info coming into our
environment
--we notice novelty…the new, the
different…
Why is this important?
“We perceive the world not as it is, but
as it is useful for us to perceive it.”
--Effect of TV…why does it hold our
attention so well?
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Vision:
 Transduction: conversion of 1 form of energy
to another
 in sensation, transforming stimulus energies into
neural impulses (action potential)
 In vision, light is transduced into neural messages
(action potentials) from optic nerve to the brain
 Wavelength: the distance from the peak of one wave to
the peak of the next
--determines hue or color (lo- or hi- pitch in sound)
 Intensity: amount of energy in a wave determined by
amplitude…the height of the wavelength
 Brightness or dullness in colors
 loudness
Humans can only see part of the electromagnetic
spectrum…Which can we not see?
But bees see ultraviolet (b-199)…snakes see infrared
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The spectrum of
electromagnetic
energy
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Vision- Physical
Properties of Waves
Short wavelength=high frequency
(bluish colors, high-pitched sounds)
Great amplitude…
(bright colors, loud sounds)
Long wavelength=low frequency
(reddish colors, low-pitched sounds)
Small amplitude
(dull colors, soft sounds)
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Vision: How we transform physical energy
into color, etc.:
 Cornea- clear outer covering of the eye where
light 1st enters
 Pupil- adjustable opening in the center of
the eye…light comes in from the cornea to the
pupil…
 Iris- a ring of muscle that forms the colored
portion of the eye around the pupil and controls
the size of the pupil opening by contracting &
expanding
 Lens- transparent structure behind pupil that
changes shape to focus images on the retina
--image comes in upside-down
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Vision
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Vision
 Accommodation- the way the eye’s lens changes
shape to help focus near or far objects on the retina
 Retina- the light-sensitive inner surface of the eye,
containing receptor rods and cones plus layers of
neurons that begin the processing of visual
information
-------------------------------------------------------------
Problems in vision:
 Acuity- the sharpness of vision: how well we see
 Nearsightedness- condition in which nearby objects
are seen more clearly than distant objects because
distant objects in front of retina (can see close, not
far away)
[myopia]
 Farsightedness- faraway objects are seen more
clearly than near objects because the image of near
objects is focused behind retina
(hyperopia… aka hypermetropia)
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Vision: When it doesn’t work…
Farsighted
Vision
(elongated)
Nearsighted
Vision
(squatty)
Normal
Vision
(round)
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Retina’s Reaction to Light- -Receptors:
 Rods
 peripheral retina
 detect black, white and gray
 twilight or low light…use for night vision
 Cones
 near center of retina
 fine detail and color vision
 daylight or well-lit conditions
 Fovea: concentration of cones on retina
 Blind spot: no rods or cones…
 
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Retina’s Reaction to Light
 Optic nerve- nerve that carries neural
impulses from the eye to the brain
 Blind Spot- point at which the optic nerve
leaves the eye, creating a “blind spot”
because there are no receptor cells
located there
 Fovea- central point in the retina, around
which the eye’s cones cluster
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1. Light hits retina (rods/cones) 2. fires bipolar
cells…3. ganglion cells activate optic nerve
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Vision- Receptors
Receptors in the Human Eye
Cones
Rods
Number
6 million
120 million
Location in
retina
Center
Periphery
Sensitivity in
dim light
Low
High
Color sensitive?
Yes
No
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Pathways from Eyes to Visual Cortex:
optic chiasm = cross-over point to opposite
hemispheres
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Visual Info Processing: The work of D. Hubel
& T. Wiesel:
 Feature Detectors
 nerve cells in the visual
cortex of the brain that
respond to specific
features (p. 204-205)
 3 features: Shape…
angle…movement…
Cell’s
responses
 Then info goes to special
areas of temporal or
Stimulus
parietal…faces?
Houses? Chairs?
 Begins w/ simple shapes
& combine into more
complex
 fMRI used to ID where we
look…at what we look
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How the Brain Perceives
Changing cube? (b-205)
Stare at the cube…
It will “change” every few seconds!
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Illusory (illusions) Contours:
areas…Do you see a triangle?
We fill in
Psy not totally sure how all this works…are
new research & theories on-going…
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Visual Info Processing (p. 206)
 Parallel Processing: How our brain processes
 simultaneous processing of several aspects of a
problem simultaneously
 EX: Divides a visual scene into color, depth, mov’t,
form (shapes) & works on each at same time
 Coordinates & combines info into perception
 computers = “serial” processing… step 1,2,3,…
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Visual Information Processing
 2 Theories RE: how we see color:
 1) Trichromatic (three color) Theory: receptors for 3
& they “blend” (Young and Helmholtz) Think paint-mixing!
 3 different retinal color receptors
 red
 green
 Blue
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Color-Deficient Vision
 People who suffer
“red-green color
blindness” have
trouble perceiving
the number within
the design
 BUT…true “color
blind – NO cones to
process color
 What we call C-B is
actually color
deficiency
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Visual Information Processing
2) Opponent-Process Theory- opposing retinal
processes enable color vision
--certain # of each in “balance”…& if one goes on, its
opposite goes OFF…then they fire to come back into
balance
“ON”
“OFF”
red
green
green
red
blue
yellow
yellow
blue
black
white
white
black
This causes an “afterimage”…remember the flag??
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Opponent ProcessAfterimage Effect
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Focus on the 3 dots at the center of the
picture
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Visual Information Processing
 Color Constancy
 Perceiving familiar objects as having consistent
color, even if changing illumination alters the
wavelengths reflected by the object
 Also in vision, have brightness
constancy, shape constancy, &
size constancy
 These aspects depend on their surroundings
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I-D
which is
which type
of
constancy
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Audition: the sense of hearing
 Amplitude: the loudness or intensity of sound,
determined by the height of a sound wave
(hi = bright color)
 Frequency: the number of complete wavelengths
that pass a point in a given time (hi-freq. colors = blue)
 Pitch: a tone’s highness or lowness
 depends on frequency
 Timbre: the quality of sound…how 1 voice differs
from another , or a guitar differs from “C” on a piano
 Decibels: measuring unit for sound energy;
measures the amplitude
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The Intensity of Some Common Sounds:
Decibels: the measure of amplitude
(loudness) in sound
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Writing: p. 213…Read & respond to the
following prompts:
1) 1st paragraph: Explain how sound
waves are processed into sound
2) 2nd paragraph: Describe the cilia that
are on the oval window & the basilar
membrane on which the cilia are located.
-What is the dangers to these cilia?
-What happens if they are damaged?
-How can we protect them?
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Audition- The Ear
 Middle Ear
 chamber between eardrum & cochlea containing
three tiny bones (hammer, anvil, stirrup) that
concentrate the vibrations of the eardrum on the
cochlea’s oval window w/ basilar membrane inside.
 Inner Ear
 innermost part of the ear, continuing the cochlea,
semicircular canals, and vestibular sacs
 Cochlea
 coiled, bony, fluid-filled tube in the inner ear
through which contains the basilar membrane
 Basilar membrane: tissue in the cochlea; hair cells on
the basilar membrane hold cilia…which are moved by
vibrations…& this causes firing into the auditory nerve
endings  goes to auditory nerve to brain…
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How we perceive pitch: 2 theories:
 1) Place Theory: says we hear different pitch b/c
different sound waves trigger activity in different places
along the cochlea’s membrane
-so the brain determines pitch by recognizing the
place on the membrane from which it receives neural
signals… EX: hi freq. = beginning of membrane; lo = end
--good at explaining high pitch, not so good at low
 2) Frequency Theory: the rate of nerve impulses
traveling up the auditory nerve matches the frequency
of a tone, thus enabling us to sense its pitch
--EX: If freq. = 100, then 100 pulses per sec. travel up
the auditory nerve…but above 1000? It can’t do it…
--but volley principle says can alternate firing (like
soldiers reloading)…
-Freq. theory is good for low, not so good for
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high...so both together seem to explain it all…
How We Locate Sounds…& the “sound
shadow”…Brain senses waves faster in
closest ear & senses direction…loss of 1
ear = difficulty locating direction of
sounds
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Audition: Hearing loss
 Conduction Hearing Loss: hearing loss caused
by damage to the mechanical system that
conducts sound waves to the cochlea
 Hearing aids can help; sometimes can be
surgically repaired
 Nerve Hearing Loss (Sensorineural) : hearing loss
caused by damage to the cochlea’s receptor cells or
to the auditory nerve
 Cilia (receptor cells for hearing on basilar
membrane) are damaged…& as of now you
cannot repair this loss, & hearing aids are of
minimal benefit
 Usually caused by exposure to loud sound or to
constant sound …and also by aging
--can be caused by some diseases also
45
 Hearing Loss: Repairing sensori-neural hearing loss:
-hearing aids may help a bit
-regenerating cells in other animals (sharks, birds) led to
in other animals—guinea pigs & rat pups
-scientists hope to be able to do the
same in humans
-can do a cochlear implant, a “bionic ear”, that does get
some sound info to the brain
-can use on adults who lost hearing later & on deaf
kids…but not on adults who lost hearing as a young
child & didn’t learn to process sound
Deaf Culture: some members of Nat. Assoc. of the Deaf
argues you should not do this to kids…that deafness is
NOT a disability…
Read p. 217…make a few notes about this (both sides of
the argument) …what do you think? And we will
discuss this…
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Cochlear implants
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Audition & ages…
Amplitude required for
perception relative to
20-29 year-old group
 Older people tend to hear low
frequencies well but suffer hearing
loss for high frequencies
 navy line = 20-29; red = 30-39; blue =
40-49; green = 50-59; yellow = 60+
1
time
10
times
100
times
1000
times
32
64
128
256
512
1024 2048 4096
8192 16384
Frequency of tone in waves per second
Low
Pitch
High
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Touch: Though vision & hearing = 2 major
senses for humans, others are critical also
 4 Skin Sensations
major
 pressure
 only skin sensation
with identifiable
receptors
 warmth
 cold
 Pain
--these 4 processed w/
specialized nerve
endings for each
-emotional ties thru
touch as well as
survival (babies?)
Why can we not tickle
ourselves? 
49
Two different views of the sense of touch:
50
Pain
 Fast pain vs. slow pain receptors: slow = dull,
throbbing; fast = sharp, intense
 Phantom-limb pain: 7 out of 10 amputees feel pain or
movement in a missing limb
-but other senses do this also…phantom sights in
those who have lost sight, phantom hearing in those
who have gone deaf
 Gate-Control Theory: See Side 49
 theory that the spinal cord contains a neurological
“gate” that blocks pain signals or allows them to
pass on to the brain
 “gate” opened by the activity of pain signals
traveling up small nerve fibers
 “gate” closed by activity in larger fibers or by
information coming from the brain
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Notes RE: Pain Control:
Cold or competing stimulus (rubbing) can
help w/ this (b-221)
Distraction lessens pain
Endorphins lessen (feel less pain after
phys. activity, like after a game?)
Strong pain for short time is remembered
as worse than moderate pain for long
time
Lamaze: breathing, relaxation, counterstimulation (massage), distraction
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Taste
 Non-tasters vs. super-tasters:
 Taste Sensations
 --sweet (most = sweet) --sour --salty --bitter
 Bitter warns us of possible poisons
 Sensory Interaction
 the principle that one sense may influence another
 as when the smell of food influences its taste
 Each “bump” (papillae) contains up to 200 tastebuds which contain pores w/ receptors
 Sensory interaction: Taste interacts strongly w/
smell…& BOTH are “chemical senses”
--smell + texture + taste = Flavor
-we also have sensory interaction w/ sight + sound:
”I hear better w/ my glasses on…”
54
Taste:
55
Smell: Olfaction…olfactory nerves
--Other than knowing we do have olfactory
receptors, actual way we smell is a
mystery…It is a chemical sense like taste)
Olfactory
nerve
Olfactory
bulb
Nasal
passage
Receptor cells in
olfactory membrane
56
Smell: Odor molecules
can’t be broken down
like light is in a
spectrum…We
recognize odors
individually
Ability declines w/ age
-Smell is primitive…&
evokes strong
emotion
Less research on smell
& taste b/c it is more
subjective (vs.
objective)
-We tend to give it
“qualities”…spicy,
etc., & these can vary
from person to person
57
Age, Sex and Sense
of Smell
Number
of correct
answers
Women & young adults
have best sense of smell
4
Women
3
Men
2
0
10-19
20-29
30-39
40-49
50-59
60-69
Age Group
70-79
80-89 90-99
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Body Position & Movement
 Kinesthesis (mov’t)
 The system for sensing the position & movement of
individual body parts
 We have position & motion sensors that are part of
our skeletal & muscular systems
 Interacts w/ vision
 Read p. 227, below “kines.” RE: Ian Waterman
 Vestibular Sense: The sense of balance
 Monitors the head’s--& thus the body’s—position
 Interacts w/ kinesthesis
 Hair-like receptors in vestibular sacs sense when
fluid is out of balance
 Semi-circular canals & vestibular sacs in inner ear
 Also aids body positioning & proper mov’t.
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Vestibular
sense
organs:
• Head (& so
body) position
• Balance
• Movement
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