PSYCHOLOGY
(8th Edition)
David Myers
PowerPoint Slides
Aneeq Ahmad
Henderson State University
1
Sensation
Chapter 5
2
Sensation
Sensing the World:
Some Basic Principles
 Threshold
 Sensory Adaptation
Vision
 The Stimulus Input: Light Energy
 The Eye
3
Sensation
Vision
 Visual Information Processing
 Color Vision
Hearing
 The Stimulus Input: Sound
Waves
 The Ear
 Hearing Loss and Deaf Culture
4
Sensation
Other Important Senses
 Touch
 Taste
 Smell
 Body Position and Movement
5
Sensation & Perception
http://dragon.uml.edu/psych/illusion.html
• How do we construct our representations
of the external world?
• Sensation: a process by which our senses must first detect physical
energy (stimulus from the environment) and encode it (called
transduction) into neural signals.
• Perception: a process whereby we select, organize, and interpret
our sensations.
• Transduction: process by which receptor cells from the senses
convert environmental stimuli into neural impulses
6
Light Spectrum
(Electromagnetic energy)
7
Bottom-up Processing
Analysis of the stimulus begins with the sense
receptors and works up to the level of the brain
and mind.
Letter “A” is really a black blotch broken down into
features by the brain that we perceive as an “A.”
8
Bottom-up Processing
(Outside-In)
• Analysis of the stimulus begins with the
sense receptors and works up to the level
of the brain and mind.
Letter “A” is really a black blotch broken
down into features by the brain that we
perceive as an “A.”
9
Top-Down Processing
Information processing guided by higher-level
mental processes as we construct perceptions,
drawing on our experience and expectations.
THE CHT
10
Making Sense of Complexity
Our sensory and perceptual processes work
together to help us sort out complex images.
“The Forest Has Eyes,” Bev Doolittle
11
Sensing the World
Senses are nature’s gift that suit an organism’s
needs.
A frog feeds on flying insects; a male silkworm
moth is sensitive to female sex-attractant odor; and
we as human beings are sensitive to sound
frequencies that represent the range of human
voice.
12
Disorders
• Prosopagnosia: perceptual disorder where an
individual has complete sensation (receives
physical energy to the sensory receptors but
cannot interpret, organize and understand it) no
perception)
• Synesthesia: condition where stimulation of one
sensory system arouses sensations in another
system (sound experienced as colours)
13
Exploring the Senses
1. What stimuli cross our threshold for conscious
awareness?
2. Could we be influenced by stimuli too weak
(subliminal) to be perceived?
3. Why are we unaware of unchanging stimuli,
like a band-aid on our skin?
14
Psychophysics
A study of the relationship between physical
characteristics of stimuli and our psychological
experience with them.
Physical World
Psychological
World
Light
Brightness
Sound
Volume
Pressure
Weight
Sugar
Sweet
15
22nd October 1850
A relative increase in
mental intensity,
[Fechner] realized,
might be measured in
terms of the relative
increase in physical
energy required to
bring it about
(Wozniak, 1999).
Gustav Fechner
(1801-1887)
16
Detection
Absolute
Threshold
Intensity
No
No
No
Yes
Yes
Observer’s Response
Detected
Tell when you (the observer) detect the light.
17
Thresholds
Proportion of “Yes” Responses
1.00
0.50
0.00
Absolute Threshold: Minimum stimulation needed
to detect a particular stimulus 50% of the time.
0
5
10
15
20
Stimulus Intensity (lumens)
25
18
Subliminal Stimulation
Can you perceive stimuli and be unaware of it? Below the absolute threshold?
“DRINK COCOA_COLA EAT POPCORN”
“I am thin, I am smart, I do well on tests”
19
Subliminal Threshold
Subliminal Threshold: When
stimuli are below one’s absolute
threshold for conscious
awareness.
Kurt Scholz/ Superstock
20
Priming
• Priming: often unconscious activation of
associations.
21
Blindsight
If the visual cortex is damaged by stroke or other injury, patients lose the ability to
see things in part of the visual field. The abnormal blind area in the visual field is
called a hemianopia (hem-i-an-NO-pia). Some patients with hemianopias
involving as much as half the visual field can nevertheless reach out and touch
objects in the "blind" area. This is called blindsight.
However, blindsight intrigues investigators because it seems to suggest that
visual information can find its way into the brain through some unconscious
route.
22
Difference Threshold
Difference Threshold: Minimum difference
between two stimuli required for detection 50%
of the time, also called just noticeable difference
(JND).
Difference
Threshold
No
No
Yes
Observer’s Response
Tell when you (observer) detect a difference in the light.
23
Weber’s Law
Two stimuli must differ by a constant minimum
percentage (rather than a constant amount), to be
perceived as different. Weber fraction: k = dI/I.
Stimulus
Constant (k)
Light
8%
Weight
2%
Tone
3%
24
Signal Detection Theory (SDT)
Predicts how and when we detect the presence
of a faint stimulus (signal) amid background
noise (other stimulation). SDT assumes that
there is no single absolute threshold and
detection depends on:
Ex. Soldier during wartime
hearing a twig break in the woods.
Carol Lee/ Tony Stone Images
Person’s experience
Expectations
Motivation
Level of fatigue
25
SDT Matrix
The observer decides whether she hears the tone
or not, based on the signal being present or not.
This translates into four outcomes.
Decision
Yes
No
Present
Hit
Miss
Absent
False
Alarm
Correct
Rejection
Signal
26
Sensory Adaptation
Diminished sensitivity as a consequence of
constant stimulation.
Put a band aid on your arm and after awhile
you don’t sense it.
27
Sensory Adaptation
• Diminished sensitivity as a consequence
of constant stimulation.
• Our eyes are being constantly stimulated
by electromagnetic wavelengths..why
doesn’t our vision become less sensitive
and our ability to see diminish?
28
Now you see, now you don’t
29
Sensory Perception
seeing, hearing, smelling, tasting, touching
https://www.youtube.com/watch?v=TAzTFg
PSPiU
30
Vision
31
Vision
• Does a flower or tomato itself
have colour?
32
Both Photos: Thomas Eisner
The Stimulus Input: Light Energy
Visible
Spectrum
33
Why We See Colour
Ripe tomatoes contain
a carotenoid known as
"Lycopene".
• Lycopene is a bright red carotenoid pigment, a phytochemical
found not only in tomatoes but also other red fruits.
• Lycopene absorbs most of the visible light spectrum, and being
red in colour, Lycopene reflects mainly red back to the viewer.
• A ripe tomato is red because it reflects rays from the red end
of the spectrum and absorbs rays from the blue end.
34
PsychSim5: activities
• http://bcs.worthpublishers.com/gray/conte
nt/psychsim5/launcher.html
35
Transduction and vision
• http://www.youtube.com/watch?v=ARNtUd
uVI4M
36
Light Characteristics
1. Wavelength (hue/color)
2. Intensity (brightness)
3. Saturation (purity)
37
Light Spectrum
(Electromagnetic energy)
38
Wavelength
Color (hue) and Pitch (sound)
Color (hue) is the
dimension of
color determined
by the
wavelength of the
light.
Wavelength is the
distance from the
peak of one wave
to the peak of the
next.
39
Wavelength (Hue)
Violet
Indigo
400 nm
Short wavelengths
Blue
Green
Yellow
Orange
Red
700 nm
Long wavelengths
Different wavelengths of light result
in different colors.
40
Intensity (Brightness)
Intensity
Amount of
energy in a
wave
determined by
the amplitude.
It is related to
perceived
brightness.
41
Intensity (Brightness)
Blue color with varying levels of intensity.
As intensity increases or decreases, blue color
looks more “washed out” or “darkened.”
42
Purity (Saturation)
Saturated
Saturated
Monochromatic light added to green and red
makes them less saturated.
43
Color Solid
Represents all
three
characteristics of
light stimulus on
this model.
http://www.visionconnection.org
44
The Eye
45
Parts of the eye
1. Cornea: Transparent tissue (glossy) where
light enters the eye.
2. Iris: Muscle that expands and contracts to
change the size of the opening (pupil) for light.
3. Lens: Focuses the light rays on the retina.
4. Retina: Contains sensory receptors that process
visual information and sends it to the brain.
46
Acuity
• http://www.youtube.com/watch?v=g1Krps
V3-_Y
47
The Lens
Lens: Transparent structure
behind the pupil that
changes shape to focus
images on the retina.
Accommodation: The
process by which the eye’s
lens changes shape to help
focus near or far objects on
the retina (aging impacts this
ability).
Acuity: sharpness of vision
48
The Lens
Nearsightedness: A
condition in which
nearby objects are seen
more clearly than
distant objects.
Farsightedness: A
condition in which
faraway objects are
seen more clearly than
near objects.
49
Retina
Retina: The lightsensitive inner
surface of the eye,
containing receptor
rods and cones in
addition to layers of
other neurons
(bipolar, ganglion
cells) that process
visual information.
50
Retina
51
Transduction
• Receptor cells for vision:
Cones and Rods
52
Rods and Cones
• http://www.youtube.com/watch?v=QkZn_y
turdI&list=PL9502746727159FA8
53
Optic Nerve, Blind Spot & Fovea
Optic nerve: Carries neural impulses from the eye to the
brain. Blind Spot: Point where the optic nerve leaves the
eye because there are no receptor cells located there. This
creates a blind spot. Fovea: Central point in the retina
around which the eye’s cones cluster.
http://www.bergen.org
54
Test your Blind Spot
Use your textbook. Close your left eye, and fixate
your right eye on the black dot. Move the page
towards your eye and away from your eye. At
some point the car on the right will disappear due
to a blind spot.
55
Photoreceptors
(cones & rods)
E.R. Lewis, Y.Y. Zeevi, F.S Werblin, 1969
56
Bipolar & Ganglion Cells
Bipolar cells receive messages from
photoreceptors and transmit them to ganglion
cells, which are for the optic nerve.
57
Visual Information Processing:
Pathways
Optic nerves connect to the thalamus in the
middle of the brain, and the thalamus connects to
the visual cortex.
58
Ganglion & Thalamic Cells
Retinal ganglion cells and thalamic neurons
break down visual stimuli into small
components and have receptive fields with
center-surround organization.
ON-center OFF-Surround
Action Potentials
59
Feature Detection
Ross Kinnaird/ Allsport/ Getty Images
Nerve cells in the visual cortex respond to
specific features, such as edges, angles, and
movement.
60
Shape Detection
Ishai, Ungerleider, Martin and Haxby/ NIMH
Specific combinations of temporal lobe activity
occur as people look at shoes, faces, chairs and
houses.
61
Perception in Brain
Our perceptions are a combination of sensory
(bottom-up) and cognitive (top-down) processes.
62
Visual Information Processing
Processing of several aspects of the stimulus
simultaneously is called parallel processing. The
brain divides a visual scene into subdivisions such
as color, depth, form and movement etc.
63
Tim Bieber/ The Image Bank
From Sensation to Recognition
64
Addition of Colors
If three primary colors (from light) are mixed, the
wavelengths are added and the color white is the
result. (sunlight is white because all wavelengths
are blended together)
Fritz Goro, LIFE magazine, © 1971 Time Warner, Inc.
65
Subtraction of Colors
If three primary
colors (pigments) are
mixed, subtraction
of all wavelengths
occurs and the color
black is the result.
66
Theories of Color Vision
1. Trichromatic theory (three color theory):
Based on behavioral experiments, Young-Helmholtz
suggested that the retina should contain three
receptors that are sensitive to red, blue and green
colors and in combination produce the perception of
colour.
Standard stimulus
Comparison stimulus
Max
Medium
Low
Blue
Green
Red
67
Photoreceptors
Blue
Cones
MacNichol, Wald
and Brown (1967)
measured directly
the absorption
spectra of visual
pigments of single
cones obtained from
the retinas of
humans.
Short
wave
Green
Cones
Medium
wave
Red
Cones
Long
wave
68
Color Blindness
Genetic disorder in which people are blind to
green or red colors. This supports the
Trichromatic theory.
Ishihara Test
69
Color Blindness
H:\Courses\AP psychology\AP
Psychology\Ch 5 & 6 Sensation and
Perception\Vischeck Examples.mht
70
2. Opponent Process Theory
Hering proposed that we process four primary
colors combined in pairs of red-green, blueyellow, and black-white.
Cones
Retinal
Ganglion
Cells 71
Opponent Colors
Gaze at the middle of the flag for about 30
Seconds. When it disappears, stare at the dot and report
whether or not you see Britain's flag.
72
After Image supports opponent=process theory of colour.
*
73
Two Stage Theory of Colour
• Trichromatic (3 colour) Theory is first
stage of colour processing and then the
Opponent processing theory is the second
stage.
74
Color Constancy
Color of an object remains the same under
different illuminations. However, when context
changes the color of an object may look different.
R. Beau Lotto at University College, London
75
Audition
76
Audition
• If a tree falls in the forest and
there is no ear there to hear it, is
there sound?
77
• NO!
• Sound is a human psychological
phenomenon. The tree falling will produce
vibrations but only an “ear” can hear it.
78
The Stimulus Input: Sound Waves
Sound waves are composed of compression and
rarefaction of air molecules.
Acoustical transduction: Conversion of sound
waves into neural impulses in the hair cells of the
inner ear.
79
Sound Characteristics
1. Frequency (pitch)
2. Intensity (loudness)
3. Quality (timbre)
80
Frequency (Pitch)
Frequency (pitch):
The dimension of
frequency
determined by the
wavelength of
sound.
Wavelength: The
distance from the
peak of one wave
to the peak of the
next.
81
Intensity (Loudness)
Intensity
(Loudness):
Amount of energy
in a wave,
determined by the
amplitude, relates
to the perceived
loudness.
82
How do we hear sound?
• http://www.youtube.com/watch?v=46aNG
GNPm7s
• http://www.youtube.com/watch?v=dCyz8eAs1I
83
Loudness of Sound
Richard Kaylin/ Stone/ Getty Images
120dB
84
70dB
Quality (Timbre)
Quality (Timbre): Characteristics of sound from
a zither and a guitar allows the ear to distinguish
between the two.
http://www.1christian.net
www.jamesjonesinstruments.com
Zither
Guitar
85
Overtones
Overtones: Makes the distinction among musical
instruments possible.
86
The Ear
Outer Ear: Pinna. Collects sounds.
Middle Ear: Chamber between eardrum
(tympanic membrane) and cochlea
containing three tiny bones or ossicles
(hammer, anvil, stirrup) that concentrate the
vibrations of the eardrum on the cochlea’s
oval window.
*(Malleus-hammer, Incus-anvil, Stapes-stirrup)
Inner Ear: Innermost part of the ear,
containing the cochlea (basilar membrane,
hair cells), semicircular canals, and vestibular
87
Cochlea
Cochlea: Coiled, bony, fluid-filled tube in the
inner ear that transforms sound vibrations to
auditory signals.
88
The Ear
Dr. Fred Hossler/ Visuals Unlimited
89
Audition Theories
• http://www.youtube.com/watch?v=IdLO_7e9BI
90
Theories of Audition
1.
Place Theory suggests that sound frequencies stimulate the
basilar membrane at specific places resulting in perceived
pitch (place of maximum vibration = pitch discrimination)
Great for high frequencies but not so good for low
frequencies
http://www.pc.rhul.ac.uk
91
Theories of Audition
2. Frequency Theory states that the rate ( speed) of nerve impulses
traveling up the auditory nerve matches the frequency of a tone, thus
enabling us to sense its pitch (when whole basilar membrane vibrates
& triggers neural signal to the brain at the same rate as the sound
wave).
Great for low frequencies but not so good for high frequencies
because neurons can’t fire > 1000 pulses/sec.
Sound
Frequency
Auditory Nerve
Action Potentials
100 Hz
200
92
Theories of Audition
• Volley Theory: Alternate place and
Frequency
93
Localization of Sound
1. Intensity differences
2. Time differences
Time differences as small as 1/100,000 of a second
can cause us to localize sound. The head acts as a
“shadow” or partial sound barrier.
94
Hearing Loss
Conduction Hearing Loss: Hearing loss caused by
damage to the mechanical system that conducts
sound waves to the cochlea (hearing aid)
Sensorineural Hearing Loss: Hearing loss caused
by damage to the cochlea’s receptor cells or to the
auditory nerve, also called nerve deafness
(cochlear implant)
95
Hearing Aid
96
Deaf Culture
Cochlear implants are electronic devices that
enable the brain to hear sounds (damage at hair
cell/nerve)
Wolfgang Gstottner. (2004) American
Scientist, Vol. 92, Number 5. (p. 437)
EG Images/ J.S. Wilson ©
Deaf Musician
Cochlear Implant
97
Hearing Deficits
Older people tend to hear low frequencies well but suffer
hearing loss when listening for high frequencies.
98
Other Important Senses
Touch
The sense of touch is a mix of four distinct skin
senses—pressure, warmth, cold, and pain.
Bruce Ayers/ Stone/ Getty Images
Remember Tiffany Fields: preemie babies massaged and gained
weight!
99
Different areas of the body have
different sensitivities
100
Skin Senses
Receptors: nerve endings in skin
Only pressure has identifiable receptors. All other
skin sensations are variations of pressure, warmth,
cold and pain.
Pressure
Burning hot
Vibration
Vibration
Cold, warmth and pain
101
• Why do Doctors ask you to rate your pain
on a scale of 1-10? Why can’t they just
measure it using some device?
102
Pain
(Psychological aspect to this experience)
Pain tells the body that something has gone
wrong. Usually pain results from damage to the
skin and other tissues. A rare disease exists in
which the afflicted person feels no pain.
AP Photo/ Stephen Morton
Ashley Blocker (right) feels neither pain
nor extreme hot or cold.
103
Gate-Control Theory
Melzak and Wall (1965, 1983) proposed that our spinal cord
contains neurological “gates” that either block pain or
allow it to be sensed.
Small fiber bundles in spinal cord activates/opens gate
while large fiber bundles closes gate (Ex. Rub large area to
ease pain)
“Pain is increased by attending to it” Charles Darwin
Gary Comer/ PhototakeUSA.com
104
Gate Control Theory
105
Rubber Hand Illusion
(brain’s neuro-plasticity, visual capture)
multisensory connections-senory interactions and changes in the brain due to
experience)
• http://www.youtube.com/watch?v=sxwn1w
7MJvk
106
Touch
• Use your knowledge about brain
development and neural pathways to
explain Phantom Limb sensations.
107
Biopsychosocial Influences
108
Pain Control
Pain can be controlled by a number of therapies
including, drugs, surgery, acupuncture, exercise,
lamaze, hypnosis, and even thought distraction.
What about walking on glass or hot coals?
Todd Richards and Aric Vills, U.W.
©Hunter Hoffman, www.vrpain.com
109
Pain Perception
Firewalking
110
111
Firewalking
Coals are poor conductors of heat-think of a cake baking in
the oven- touch the metal pan and the skin burns - touch
the cake and you don’t burn.
112
Taste/ Gustation
(Chemical sense)
Traditionally, taste sensations consisted of sweet,
salty, sour, and bitter tastes. Recently, receptors for
a fifth taste have been discovered called “Umami”,
(flavour of monosodium glutamate).
Sweet
Sour
Salty
Bitter
Umami
(Fresh
Chicken)
113
Taste/ Gustation
(Chemical sense)
Receptors: Taste buds/papillae (200+) on tongue (each
contain a pore where little hairs send signals to
thalamus)) reproduce every week or so. Taste buds
also exist in back of the throat and sides of mouth.
Alcohol, smoking etc diminish sensitivity
114
Sensory Interaction
• When one sense affects another sense,
sensory interaction takes place. So, the
taste of strawberry interacts with its smell
and its texture on the tongue to produce
flavor.
• Vision can also affect our taste!
• Would you eat green eggs and ham?
115
Smell
(Olfaction)
Like taste, smell is a chemical sense. Odorants enter the nasal cavity to
stimulate 5 million receptors (hair cells in olfactory membrane) to
sense smell. Signals are not routed through the thalamus but to the
limbic system, temporal lobes and other cortex areas. Unlike taste,
there are many different forms of smell.
Pheromones=species specifc
116
Age, Gender, and Smell
Ability to identify smell peaks during early
adulthood, but steadily declines after that. Women
are better at detecting odors than men.
117
Smell and Memories
The brain region for
smell (in red) is closely
connected with the
brain regions involved
with memory (limbic
system). That is why
strong memories are
made through the sense
of smell.
118
Body Position and Movement
Kinesthesis
The sense of our body parts’ position and movement is
called kinesthesis. Receptor cells are found in muscles,
joints & tendons.
http://www.heyokamagazine.com
Whirling Dervishes
119
Vestibular sense
The vestibular sense monitors the head (and body’s) position
influenced by mechanical and gravitational forces. Gives us our sense
of equilibrium . Receptor cells: hair cells in semicircular canals and
vestibular sacs that connect to the cochlea. Receptor cells send
messages to the cerebellum (balance, coordination, memory).
120
Wire Walk
Sensory Restriction
• Restricting the senses seems to help in
small doses (think of relaxation, meditation
etc..) but extreme deprivation is not good.
121
Sensory Restriction
122