Download Sensation

Myers’ PSYCHOLOGY
(6th Ed)
Chapter 5
Sensation
James A. McCubbin, PhD
Clemson University
Worth Publishers
 Sensation- activation of our senses,
receiving energy
 Perception- understanding these sensations,
organizing and interpreting them
 Transduction- information
received by our sensory organs is
transformed into neural impulses
 Travel through the thalamus (except
for smell) to different areas of the brain
7 Senses
Energy
Senses
Sight
Sound
Chemical
Senses
Touch
Taste
Smell
Body
Position
Balance
Kinesthesis
Vestibular
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
Human Absolute Thresholds
Vision
• seeing a candle flame 30 miles away on a
clear night
Hearing
• hearing a watch ticking 20 feet away
Tasting
• tasting one tsp. of sugar dissolved in 2
gallons of water
Smell
• smelling one drop of perfume in a 3-room
house
Touch
• feeling a bee’s wing falling a distance of 1 cm
onto your cheek
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
Thresholds
 Cocktail party phenomenonwhen someone says our name
across a room, we will switch our
attention involuntarily
The Stroop Effect
Sensation- Thresholds
 When stimuli are
detectable less
than 50% of the
100
Percentage
of correct
detections
75
50
Subliminal
stimuli
25
0
Low
Absolute
threshold
Intensity of stimulus
Medium
time (below one’s
absolute
threshold) they
are “subliminal”.
Subliminal Perception
 Brief auditory or visual messages present below
the absolute threshold so that there is a less
that 50% chance that they will be perceived
 False claim that the words “Eat popcorn” and “Drink
Coke” had flashed briefly on a movie screen once
every 4 seconds for 1/3000 of a second and that
sales had risen
 Hysterical reaction- Congress called for FCC,
admitted data was false. But still banned in 1974,
regardless of efficacy
 Even if it is possible for people to perceive info
at low levels of intensity, no clear evidence
that they influence people. But, many believe it
is a powerful advertising tool.
Subliminal Messages???
 Lion King - Disney Subliminal Messages
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
 Senses are more responsive to increases
and decreases and to new events rather
than to ongoing stimulation
 Adapting to a dark movie theater, cold
water, disagreeable odors, street noise
 Eyes quiver to avoid sensory
adaptation
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
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
 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
 Eyeballs too long
 Farsightedness
 faraway objects seen more clearly
 lens focuses near objects behind retina
 Eyeballs too short
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
 Trichromatic (three color) Theory
 Young and Helmholtz
 three different retinal color
receptors
 red
 green
 blue
Color-Deficient Vision
 People who
suffer redgreen
blindness have
trouble
perceiving the
number within
the design
Color Deficiency
 Happens when all or some cones do not
function properly
 Most color deficient people will be able to
see some colors
 Most have problems distinguishing red and
green, others cannot distinguish between
yellow and blue. A few are totally color
deficient and depend only on rods.
 Effects about 8% of men and 1% of
women; a hereditary condition passed on
by women
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
The Pathway of Sound
 Outer ear- receives sound waves, earflap directs
sound down auditory canal. The auditory canal begins
to vibrate, which causes the eardrum to vibrate
The Pathway of Sound
 Middle Ear- air-filled cavity with three tiny bones-
hammer, anvil, and stirrup. Bones vibrate and push
against the cochlea
Pathway of Sound
 Inner Ear- cochlea, a bony tube that contains fluids
and neurons. Pressure makes the liquid inside the
cochlea move and tiny hairs pick up the motion and
turn into neuronal impulses which are sent to the brain
Loudness
 Loudness depends on the amplitude
(height) of sound waves- measured in
decibels
 Sounds over 110 decibels can cause
damage, persistent sounds over 80
decibels cause damage.
Pitch
 Depends on frequency, or the rate of vibration
 Low frequency- deep sounds
 High frequencies- shrill squeaks
The Intensity of Some
Common Sounds
IPods
 More hearing loss in younger people with the use of iPods and




earbud headphones that is similar to that found in aging adults.
Earbuds are placed directly in the ear and can boost the sound
signal by as much as six to nine decibels. It’s enough to cause
hearing loss after only about an hour and 15 minutes.
60 percent/60 minute rule- Using the MP3 devices, including
iPods, no more than about an hour a day and at levels below 60
percent of maximum volume.
To avoid permanent hearing loss in the middle ranges --the
range required to hear conversation in a noisy restaurant, for
example -- they recommend the older style, larger headphones
that rest over the ear opening.
Another option is the use of noise-canceling headphones that
eliminate background noise so listeners don't have to crank the
volume so high.
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
 Sources of sounds are
located when ears
work together. When
a noise occurs on the
right, it reaches the
right ear a fraction of
a second earlier and is
slightly louder in the
right ear.
Deafness
 Conduction- something hinders motion
through the outer or middle ear or
when the bones in the middle ear
become rigid and cannot carry sound
 Help from hearing aids- change sound waves
into vibrations and send to inner ear
Deafness
 Sensorineural-
damage to cochlea
or auditory neurons
 Cochlear implants –
electronic device in
cochlea
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
 sweet
 sour
 salty
 bitter
 umami
 Sensory Interaction
 the principle that one sense may influence
another
 as when the smell of food influences its taste
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
Balance
 Regulated by the vestibular system Semicircular canals (3)- filled with fluid, hair cells
are bent when movement occurs
 Stimuli include spinning, falling, tilting
 Overstimulation results in dizziness and motion
sickness
Body Senses
 Kinesthesis- sense of body movement
and position
 Sensation from receptors in the muscles,
tendons, and joints
 Movements would be jerky and
uncoordinated without