Myers’ PSYCHOLOGY
(8th Ed)
Chapter 5
Sensation
AP Psychology
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
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 higherlevel mental processes
as when we construct perceptions drawing
on our experience and expectations
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
usually defined as the stimulus needed for
detection 50% of the time
Difference Threshold
minimum difference between two stimuli that
a subject can detect 50% of the time
just noticeable difference (JND)
increases with magnitude
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
100
Percentage
of correct
detections
75
50
Subliminal
stimuli
25
0
Low
Absolute
threshold
Intensity of stimulus
Medium
When stimuli are
detectable less than
50% of the time
(below one’s
absolute threshold)
they are
“subliminal”.
Sensation- Thresholds
Weber’s Law- to perceive a difference
between two stimuli, they must differ by
a constant proportion
light intensity- 8%
weight- 2%
tone frequency- 0.3%
Sensory adaptation- diminished
sensitivity with constant stimulation
Vision- Stabilized
Images on the Retina
Vision
Transduction- conversion of one form of
energy to another
Wavelength- the distance from the peak of
one wave to the peak of the next
Hue- dimension of color determined by
wavelength of light
Intensity- amount of energy in a wave
determined by amplitude
brightness
loudness
Vision-
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 the 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
change in shape of lens
focus near objects
Retina
inner surface of eye
light sensitive
contains rods and cones
layers of neurons
beginning of visual information
processing
Vision
Acuity- the sharpness of vision
Nearsightedness
nearby objects seen more clearly
lens focuses image of distant objects in front
of retina
Farsightedness
faraway objects seen more clearly
lens focuses near objects behind retina
Vision
Normal
Vision
Nearsighted
Vision
Farsighted
Vision
Retina’s Reaction
to Light- Receptors
Cones
near center of retina (fovea)
fine detail and color vision
daylight or well-lit conditions
Rods
peripheral retina
detect black, white and gray
twilight or low light
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
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
neurons in the
visual cortex
respond to specific
features
shape
angle
movement
Cell’s
responses
Stimulus
How the Brain
Perceives
Illusory Contours
Visual Information
Processing
Parallel Processing
simultaneous processing of several
dimensions through multiple
pathways
color
motion
form
depth
Visual Information
Processing
Abstraction:
Brain’s higher-level cells
respond to combined
information from
feature-detector cells
Feature detection:
Brain’s detector cells
respond to elementary
features-bars, edges, or
gradients of light
Retinal processing:
Receptor rods and
conesbipolar cells
 ganglion cells
Recognition:
Brain matches the
constructed image with
stored images
Scene
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 ProcessAfterimage Effect
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
Outer Ear
Auditory Canal
Eardrum
Middle Ear
hammer
anvil
stirrup
Inner Ear
oval window
cochlea
basilar membrane
hair cells
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
Audition
 Older people tend to hear low
frequencies well but suffer hearing los
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
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
Taste
Taste Sensations- biological wisdom, 200
sweet
sour
salty
bitter
UMAMI
Sensory Interaction
one sense may influence another
as when the smell of food influences its taste
Synaesthesia- one sense triggers another???
Smell Illustration p. 231
Olfactory
nerve
Olfactory
bulb
Nasal
passage
Receptor cells in
olfactory membrane
Smells evoke memories!
20,000 breaths a day, OLFACTION
Just like taste, smell is a chemical sense.
5 million receptor cells at the top of each
nostril. Babies recognize Mom’s scent!
We can detect smell but it is hard to
describe them. Easier to explain sounds.
We have our own chemical smell
signature except for identical twins…
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
th
Movement- the real 6 Sense
Kinesthesis- 200 muscles for 1 step!
the system for sensing the position and
movement of individual body parts
Vestibular Sense
the sense of body movement and positionbiological gyroscope.
including the sense of balance- inner ear,
semicircular canals- vestibular sacs, cochlea,
cerebellum- helps you maintain balance.