Transcript Document

SENSATION: how we detect physical
energy from the environment and encode it
as neural energy.
Sensation involves transducers-specialized receptor cells.
Transduction – converting stimuli into neural impulses
Stimulation, but
meaningless?
...one great, blooming, buzzing confusion.”-William James,
on a baby’s first perceptual experience.
Can you see what is in this picture?
Perception: how we select, organize, and interpret sensations.
An active process that imposes some organization on
the meaningless sensations.
Perception: Top-Down Processing-analysis based on experience and
expectation (starts with the brain)
Sensation: Bottom-up Processing-analysis that starts with the senses
Perception
Our brains process information
and form schemas so that different
patterns of information seem
distorted.
Absolute Thresholds
• What is the minimum
stimulation necessary
to detect a stimulus
50% of the time?
Vision
On a clear, dark
night you can
see a candle
from 30 miles
away
Intensity 
105
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96
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Y
Y
Y
Y
Y
N
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Y
Y
N
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N
N
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Y
Y
Y
Y
Y
Y
N
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Y
N
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N
N
N
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Y
Y
Y
Y
Y
Y
N
99.5 99.5 98.5 100.5 99.5
Crossover Values
Absolute Thresholds
(Measurements)
Method of Limits
Intensity 
• Stimuli are presented in
ascending or descending
order
• Some stimuli above and
some below threshold
• Ave. crossover from Yes
to No = absolute threshold
105
104
103
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96
Y
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N

Y
Y
N
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
Y
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Y
Y
Y
Y
N
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Y
N
N
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Y
Y
Y
Y
Y
Y
N
99.5 99.5 98.5 100.5 99.5
Crossover Values
GUSTAV: Can measure differences in
the stimulus by recording when the
subject detects differences in a
stimulus.
1801-1887
Example 1: Begin with a minimal stimulus, ask when
subject can detect it. This is the Absolute Threshold.
Example 2: Begin with a standard stimulus, ask subject
when he/she can notice an increase or decrease. This is the
Difference Threshold – or – Just Noticeable Difference
(JND)
Signal Detection Theory
Detecting a weak signal depends on:
1. Signal’s strength
2. Our internal Y state
(experience, motivation & fatigue)
SIGNAL DETECTION THEORY: No single
absolute threshold; it varies with experience,
expectation, motivation, and fatigue.
Difference Threshold (or Just Noticeable Difference):
the minimum difference that a subject can detect between 2 stimuli.
Weber’s Law: to perceive a difference b/w two stimuli, the
two stimuli must differ by a constant %, not a constant amount.
dR=Difference
needed for detection
(perception).
Constant
Original stimulus
amount.
dR=C*R
dR=.10 * 50= 5 If you need to increase 50
decibels to 55 decibels to hear a difference
then,
dR=.10 * 100= 10 you would need to
increase 100 decibels to 110 decibels to hear
a difference
Applying Weber’s Law:
 If a $5.00 per hour worker requires a 50 cent raise to
notice the difference; a $10 per hour worker may need
to receive a _____raise to notice.
SENSORY ADAPTATION: diminished sensitivity as a
consequence of constant stimulation.
Sensory Reason: NERVE CELLS FIRE LESS
FREQUENTLY
Perceptual Reason: SO WE CAN PERCEIVE
WHAT IS USEFUL
Can we a) sense unconsciously stimuli below
threshold and b) can we be influenced by it?
Cited Research:
• 1956: NJ Movie Audiences (Eat Popcorn, Drink
Coca-Cola)-false report!
• By definition we can sense stimuli below absolute
threshold up to 49% of the time.
• What if sense stimuli 0% of the time? Negative &
Positive images (only perceived as a flash of light)
can influence future perceptions.
• Subliminal Priming: subliminal bread allows
detection of butter faster than bottle.
SUBLIMINAL: below
threshold stimuli
Research Conclusions:
subliminal stimuli evoke a
fleeting, subtle effect on
thinking but NOT a powerful,
enduring effect on behavior!
Subliminal Persuasion?
RESEARCH SAYS
NO!!
It was reported that
while this ad was
running, senior
citizens in Florida
were eating dog
food to save money.
Intentional?
Vision
Eyeball is longer,
focused image is
in front of the
retina.
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
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
Dark & Light Adaptation
Adaptation - process by which the eye becomes
more or less sensitive to 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
RODS & CONES
THE RETINA
The Blind Spot and the Optic Nerve
Visual Information
Processing
• Feature Detectors
– neurons in the visual cortex
respond to specific features:
• shape
• angle
• movement
Cell’s
responses
Stimulus
Visual Information Processing
• Feature Detection + Parallel Processing
•Color
•Motion
•Form
•Depth
All processed separately
but simultaneously
Visual Information Processing
• Parallel Processing
– simultaneous
processing of several
dimensions through
multiple pathways
– color
– motion
– form
– depth
STIMULUS: Light Energy
Wavelength = Hue (blue,
green, red, yellow, orange,
etc.)
Wavelength: Distance from the
peak on one light (or sound)
wave to the peak of the next.
Intensity=Amplitude of light wave (height)=Brightness
Short
Wavelength
Long
Wavelength
Great
Amplitude
Small
Amplitude
STIMULUS: Light Energy
Bluish Colorshigh frequency
Reddish
Colors-low freq.
Bright Colors
Dull Colors
1. All the invisible colors of sunlight shine on the apple.
2. The surface of a red apple absorbs all the colored light
rays, except for those corresponding to red, and reflects
this color to the human eye.
3. The eye receives the reflected red light and sends a
message to the brain.
Trichromatic Theory of Color Vision
Human eye has 3 types of cone
receptors sensitive to different
wavelengths of light.
Short
Helmholtz 1852
Medium
Long
People see colors because the
eye does its own “color mixing”
by varying ratio of cone
neural activity
Color-Deficient Vision
• People who suffer redgreen blindness have
trouble perceiving the
number within the
design
Visual Information Processing
Opponent-Process Theory- opposing retinal processes
enable color vision
“ON”
red
green
blue
yellow
black
white
“OFF”
green
red
yellow
blue
white
black
Opponent Process- Afterimage Effect
Pitch-measured in Hertz
Ex: 440Hz=A in the 4th octave on
piano=440 vibrations per second
Short Waves (Hi f )=High Pitch
Long Waves (Low f )=Low Pitch
Loudnessmeasured in
Decibels
Audition- The Ear
Audition- The Ear
• Outer Ear
– Auditory Canal
– Eardrum
• Middle Ear
– hammer
– anvil
– stirrup
• Inner Ear
– oval window
– cochlea
– basilar membrane
– hair cells
1. Sound waves cause
air pressure changes in
the auditory canal.
4. Fluid moves
hair cells on
the basilar
membrane
generating a
nerve impulse.
2. The eardrum
vibrates and the
vibrations are
transmitted to the
inner ear (hammer,
anvil, stirrup).
3. The stirrup vibrates
the wall of the cochlea,
creating waves in the
fluid inside.
How do we
determine pitch?
PLACE
THEORY
This section of the
cochlea’s basilar
membrane
contains hair cells
sensitive to low
frequencies (long
wavelengths)
This section
contains hair cells
sensitive to high
frequencies (short
wavelengths)
FREQUENCY THEORY
1000 Waves per Second = 1000 Nerve impulses per second
VOLLEY PRINCIPLE: Nerves take turns sending sound waves
over 1000 waves per second.
NERVE
DEAFNESS
CONDUCTION
DEAFNESS
PAIN!!
Touch
• Skin Sensations
– pressure
• only skin
sensation with
identifiable
receptors
– warmth
– cold
– pain
Tickles-adjacent pressure spots?
Itching-repeated stroking of pain spot?
Wetness-adjacent cold & pressure spots?
Hot-nearby cold/warm spots (cold receptors respond
to both extreme hot or cold spots)
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
Small Nerve Fibers
Large Nerve Fibers
SPINAL CORD
Opens when
Tissue is damaged!
Other sensory stimulation
Closes the small nerve fibers
(pain is reduced)
•Rubbing area around pain
•Ice on an injury
•Electrical stimulation
•Acupuncture
GATE-CONTROL THEORY
Endorphins released
-playing with an injury
Pain = Physical Sensation (tissue damage: heat, pressure,
cold, tearing, breaking, etc.) + psychological (perception
of pain in the brain)
TREATMENT FOR PAIN
Treat the physical damage/Treat the psyche
•Drugs
•Surgery
•Exercise
Giving Birth:
Lamaze Method
•Relaxation
•Massage
•Distraction
•Hypnosis
•Relaxation
•Distraction
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
5 million
receptor
cells!!!!!!
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
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DETECTED.
The focusing of conscious awareness on a particular stimulus.
MAY I HAVE
YOUR ATTENTION
ADD-a
PLEASE????!!!!
perceptual
problem
Select (decision)
Focus (one thing over others)
Sustain (maintaining focus)
Shift (one task to another)
Alternate (listening/notes)
EXAMPLES OF SELECTIVE ATTENTION
Brands on an upper shelf
received 35 percent greater
attention than did those on a
lower shelf.
Illusions-Why are they useful?
•
•
•
•
•
Reveal organization principles of the brain
Reveal how sensations are interpreted
Muller-Lyer
Ames Room
St.Louis Gateway Arch
Gestalt: The tendency of the brain to integrate parts into a whole
Similarity
Continuity
Gregory: Illusory figures
Can you see the triangle?
• Most of the triangle boundary is
not black/white contrast. i.e. most
of the boundary isn’t there!
• The triangle (foreground) looks
brighter than the rest
• When you outline the triangle, the
perceived brightness disappears
The brain enhances reality
Kanizsa’s triangle
Proximity
Closure-fill in gaps
to create a whole
object.
Visual Cliff Experiment:
Depth perception is an inborn ability.
Cues to Depth
MONOCULAR CUES (8)
• Relative size
• Interposition
• Relative clarity
• Texture gradient
• Relative height
• Relative Motion
• Linear perspective
• Relative brightness
BINOCULER CUES
• Retinal disparitycomparison of 2
images sent to the
brain
• Convergence-inward
turn of the eye when
looking at near objects
MONOCULAR CUES-Depth cues requiring only
one eye.
When 2
objects of the
same size are
2 different
distances
from our
retina, the
object casting
the smaller
retinal image
is perceived as
farther away.
RELATIVE
HEIGHT
Above eye level-distant
EYE LEVEL
Below eye
level-close
RELATIVE CLARITYatmosphere causes
distant objects to appear
hazy.
TEXTURE GRADIENTdistinct texture (close) to
indistinct texture (distant)
RELATIVE BRIGHTNESS-nearby objects reflect
more light to eyes. Example: cars in fog seem farther
away than they are because of limited light.
INTERPOSITION-when one
object blocks out another object,
we perceive it as closer.
LINEAR
PERSPECTIVE- parallel
lines appear to converge
with distance, the more
convergence-the greater
the distance.
Distant objects move
with you. Objects farther
away move more slowly.
Fixation Point
Closer objects move
backward, the closer the
object the faster the motion
RELATIVE MOTION
BINOCULAR CUES
STROBOSCOPIC MOVEMENT
PHI PHENOMENON
SHAPE CONSTANCY- objects have a constant
form even though the shape on the retina changes
Nature
?
• Kant-Inborn: We come already
equipped with sense organs.
• “I was blind but now I can see.”
Blind people with restored
vision could see colors and
figure/ground.
Nurture
• Locke-we learn to link size and
distance
• Blind with restored vision could
not recognize objects that were
familiar by touch.
• Critical Period for visual
development (kitten/monkey
goggle experiments). Need
experience (nurture) for neural
development.
• Cat vertical/horizontal line
experiment.
Perceptual Adaptation
Adaptability:
Fish, frogs, salamanders: No—didn’t
do well after their eyes turned upside
down.
Kittens, Monkeys, Humans: YesStratton’s upside/down left/right
goggles!
Perceptual Set Demonstration
(½ the class look @ the next image)
Influences on Perceptual Setmental predispositions
• Schemas: Concepts formed through
experience.
• Context Effects: Need background
information (context) to understand.
ex: -eel (peel or wheel)
-attacks or a tax
E.S.P.
Is the sportscaster
demonstrating:
•Telepathy?
•Clairvoyance?
•Precognition?
A psychic is an actor playing the
role of a psychic.
Psychologist-magician Daryl Bem
(1984)