Transcript Chapter 5 Sensation - Mercer Island School District

Myers’ PSYCHOLOGY
(6th Ed)
Chapter 5
Sensation
James A. McCubbin, PhD
Clemson University
Worth Publishers
Sensation
Sensation
a process by which our sensory receptors
and nervous system receive and represent
stimulus energy
Perception
a process of organizing and interpreting
sensory information, enabling us to
recognize meaningful objects and events
Sensation
Our sensory
and
perceptual
processes
work
together to
help us sort
out complex
processes
Sensation
Bottom-Up Processing
analysis that begins with the sense receptors and
works up to the brain’s integration of sensory
information
Top-Down Processing
information processing guided by higher-level
mental processes
as when we construct perceptions drawing on our
experience and expectations
Making sense of the world
What am I
seeing?
Bottom-up
processing:
taking sensory
information and
then assembling
and integrating it
Top-down
processing:
using models,
ideas, and
expectations to
interpret sensory
information
Is that
something I’ve
seen before?
5
Do you see a
painting or a 3D
bottle?
What’s on the
bottle?
Kids see eight to
ten dolphins.
Why do you think
kids see
something
different from
what adults see?
6
Top-down
Processing
You may start
to see
something in
this picture if
we give your
brain some
concepts to
apply:
“tree”
“sidewalk”
“dog”
“Dalmatian”
7
From Sensory Organs to the Brain
The process of sensation can
be seen as three steps:
Reception-the stimulation
of sensory
receptor cells by
energy (sound,
light, heat, etc)
Transduction-transforming
this cell
stimulation into
neural impulses
Transmission-delivering this
neural
information to
the brain to be
processed
8
Sensation- Basic Principles
Psychophysics
study of the relationship between physical
characteristics of stimuli and our
psychological experience of them
Light - brightness
Sound - volume
Pressure - weight
Taste - sweetness
Sensation- Thresholds
Absolute Threshold
minimum stimulation needed to detect a
particular stimulus 50% of the time
Difference Threshold
minimum difference between two stimuli
required for detection 50% of the time
just noticeable difference (JND)
Sensation- Thresholds
Signal Detection Theory
predicts how and when we detect the
presence of a faint stimulus (signal) amid
background stimulation (noise)
assumes that there is no single absolute
threshold
detection depends partly on person’s
experience
expectations
motivation
level of fatigue
Sensation- Thresholds
 Subliminal
100
Percentage
of correct
detections
 When stimuli are below one’s
absolute threshold for conscious
awareness
75
50
Subliminal
stimuli
25
0
Low
Absolute
threshold
Intensity of stimulus
Medium
Subliminal Stimulation
Priming—The activation, often
unconsciously, of certain associations, thus
pre-disposing one’s perception, memory, or
response.
“masking” stimulus that interrupts the brain’s
processing
Ex. Back-masking of music
http://jeffmilner.com/backmasking/
Sensation- Thresholds
Weber’s Law- to perceive as different, two
stimuli must differ by a constant minimum
percentage
light intensity- 8%
weight- 2%
tone frequency- 0.3%
Sensory adaptation- diminished sensitivity as
a consequence of constant stimulation
Sensory Adaptation
 To detect novelty in our
surroundings, our senses
tune out a constant stimulus.
 The rock in your shoe or the
ticking of a clock are more
difficult to sense after a
while.
 We don’t notice this visually
because normally our eyes
are constantly moving.
 However, if you concentrate
on keeping your eyes in one
spot, you’ll see the effects,
as your eyes adjust to stimuli
in the following slides.
15
16
Sensory Adaptation
Sensory adaptation- diminished sensitivity
as a consequence of constant stimulation
*try it: move your watch up your wrist an
inch…
*try it: try working in a noisy cafe
*try it: fart in a car, and after the smell has
disappeared, invite a friend to join you.
Now, consider, why do our senses diminish
in their sensitivity?
(Informative changes in environment)
Vision- Stabilized Images on the
Retina
Vision
Transduction
conversion of one form of energy to
another
in sensation, transforming of stimulus
energies into neural impulses
Wavelength
the distance from the peak of one wave to
the peak of the next
Vision
Hue
dimension of color determined by
wavelength of light
Intensity
amount of energy in a wave determined by
amplitude
brightness
loudness
The spectrum of
electromagnetic
energy
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)
Vision
 Pupil- adjustable opening in the center of the eye
 Iris- a ring of muscle that forms the colored portion of the eye
around the pupil and controls the size of the pupil opening
 Lens- transparent structure behind pupil that changes shape to
focus images on the retina
Vision
Vision
 Accommodation- the process by which 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
Vision
 Acuity- the sharpness of vision
 Nearsightedness- condition in which nearby objects are seen more
clearly than distant objects because distant objects in front of retina
 Farsightedness- condition in which faraway objects are seen more
clearly than near objects because the image of near objects is focused
behind retina
Vision
Farsighted
Vision
Nearsighted
Vision
Normal
Vision
Retina’s Reaction
to Light- Receptors
Rods
peripheral retina
detect black, white and gray
twilight or low light
Cones
near center of retina
fine detail and color vision
daylight or well-lit conditions
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
Rods and Cones
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
Pathways from the Eyes to the Visual
Cortex
Visual Information Processing
 Feature Detectors
 nerve cells in the brain that
respond to specific features
 shape
 angle
 movement
Cell’s
responses
Stimulus
Visual Information Processing
oThe motion aftereffect (MAE) is a visual illusion experienced
after viewing a moving visual stimulus for a time (tens of
milliseconds to minutes) with stationary eyes, and then
fixating a stationary stimulus. The stationary stimulus
appears to move in the opposite direction to the original
(physically moving) stimulus. The motion aftereffect is
believed to be the result of motion adaptation.
oNeurons coding a particular movement reduce their
responses with time of exposure to a constantly moving
stimulus; this is neural adaptation
How the Brain Perceives
Illusory Contours
Visual Information Processing
Parallel Processing
simultaneous processing of several aspects of a
problem simultaneously
The brain’s natural mode of information
processing for many functions, including vision.
Contrasts with step-by-step processing (serial)
processing of most computers and of conscious
problem solving.
Visual Information Processing
Trichromatic (three color) Theory
Young and Helmholtz
three different retinal color receptors
 red
 green
 blue
Color-Deficient Vision
People who suffer
red-green blindness
have trouble
perceiving the
number within the
design
Visual Information Processing
Opponent-Process Theory- opposing retinal
processes enable color vision
“ON”
“OFF”
red
green
green
red
blue
yellow
yellow blue
black
white
white
black
Opponent Process- Afterimage Effect
Visual Information Processing
Color Constancy
Perceiving familiar objects as having
consistent color, even if changing
illumination alters the wavelengths
reflected by the object
Visual Information Processing
Color Constancy
Perceiving familiar objects as having consistent
color, even if changing illumination alters the
wavelengths reflected by the object
We perceive objects not in isolation, but in
their environmental context is especially
significant for artists and designers.
Audition
Audition
the sense of hearing
Frequency
the number of complete wavelengths that pass
a point in a given time
Pitch
a tone’s highness or lowness
depends on frequency
The Intensity of Some Common
Sounds
Audition- The Ear
Middle Ear
chamber between eardrum and cochlea containing
three tiny bones (hammer, anvil, stirrup) that
concentrate the vibrations of the eardrum on the
cochlea’s oval window
Inner Ear
innermost part of the ear, contining the cochlea,
semicurcular canals, and vestibular sacs
Cochlea
coiled, bony, fluid-filled tube in the inner ear
through which
Audition
Place Theory
the theory that links the pitch we hear with the
place where the cochlea’s membrane is
stimulated
Frequency Theory
the theory that the rate of nerve impulses
traveling up the auditory nerve matches the
frequency of a tone, thus enabling us to sense its
pitch
How We Locate Sounds
Audition
Conduction Hearing Loss
hearing loss caused by damage to the
mechanical system that conducts sound
waves to the cochlea
Nerve Hearing Loss
hearing loss caused by damage to the
cochlea’s receptor cells or to the auditory
nerve
Subliminal Stimulation
Priming—The activation, often
unconsciously, of certain associations,
thus pre-disposing one’s perception,
memory, or response.
“masking” stimulus that interrupts the
brain’s processing
Ex. Back-masking of music
http://jeffmilner.com/backmasking/
Audition
 Older people tend to hear low frequencies
well but suffer hearing loss for high
frequencies
Amplitude required for
perception relative to
20-29 year-old group
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
Touch
Skin Sensations
pressure
 only skin sensation
with identifiable
receptors
warmth
cold
pain
Two types of skin:
•Hairy skin: contains hair cells, which help
detect movement and pressure.
•Glabrous skin: contains no hair cells, so the
receptors in this type of skin are more
sensitive. Glabrous skin is found mainly on
the palms of the hands, bottoms of the feet,
and on the lips.
Other senses
•Kinesthesis – the system for sensing the
position and movement of individual body
parts
•Vestibular sense – the sense of body
movement and position, including the sense
of balance
• Semicircular canals & vestibular sacs contain
fluid that moves when your head rotates or
tilts. This movement stimulates hair-like
receptors, which send messages to the
cerebellum, enabling you to sense body
position.
Pain
Gate-Control Theory
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
(endorphins)
Rubbing the area around the source of pain will
create competing stimulation that block some
pain messages
Taste
Taste Sensations
Sweet – energy source
Salty – sodium essential to
physiological processes
Sour – potentially toxic acid
Bitter – potential poisons
Umami – proteins to grow and repair
tissue
Consider your preferences and facial
expressions for each of the preceding…
Sensory interaction
Sensory Interaction
the principle that one sense may influence
another
as when the smell of food influences its
taste
 The McGurk Effect is a perceptual phenomenon that
demonstrates an interaction between hearing and
vision in speech perception. The illusion occurs when
the auditory component of one sound is paired with the
visual component of another sound, leading to the
perception of a third sound.
Smell
Olfactory
nerve
Olfactory
bulb
Nasal
passage
Receptor cells in
olfactory membrane
Age, Sex and Sense of Smell
Number
of correct
answers
Women and 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
Body Position and Movement
Kinesthesis
the system for sensing the position and
movement of individual body parts
Vestibular Sense
the sense of body movement and position
including the sense of balance