Download Sensation, Perception, and Learning

Sensation, Perception, and Learning
PSY 101 – Introduction to Psychology
Week 4
Many slides & activities are adapted from the
Instructor’s Resources for your text or earlier versions
of your text. Other resources used include Huffman’s
(2010) Psychology in Action. Many slides & activities
are adapted from the instructor’s manual.
Images are from Google Images or the Instructor’s
Manual.
THE SENSES
SENSATION
THE PROCESS BY
WHICH OUR SENSORY
RECEPTORS AND
NERVOUS SYSTEM
RECEIVE AND
REPRESENT
STIMULUS ENERGIES
FROM OUR
ENVIRONMENT.
Sensation Cont.
When the sense organs (such as the nose) detect a stimuli
(such as a strong odor), they convert it to a neural impulse,
which is then transmitted to the brain.
This process is called transduction and is necessary,
because the brain only understands these neural impulses
(i.e., action potentials).
Measuring the Senses
One of the first methods to study the relationship between
what we sense and what we actually perceive is
Psychophysics
Key Player  Gustav Fechner
Fechner was interested in the limits of what we are able to
sense or in other words our thresholds for seeing, hearing,
smelling and feeling. For example, we can hear a
policeman’s whistle, but not a dog whistle. A dog whistle is
below our threshold for hearing.
Measuring the Senses Cont.
Fechner wanted to know our precise limitations.
Absolute Threshold: minimum amount of stimuli needed to
produce a sensation (at least 50% of the time)
•
•
For example, what’s the softest sound you can hear (at
least 50 % of the time).
Why the 50%? Because other factors come into play, like
we weren’t paying attention a few times.
Measuring the Senses Cont.
Some examples of our absolute thresholds include:
•
•
•
We can see a candle flame on a dark night from 30 miles
away
We can taste one teaspoon of sugar in 2 gallons of water
We can smell one drop of perfume diffused into an entire
volume of a 6 bedroom apartment
Subliminal Stimulation
1. Yes, we can sense stimuli that is outside of our conscious
awareness (a bit below our absolute threshold).
2. Yes, this can have fleeting, minimal impact on our
behavior.
Sensory Adaptation
Anyone who works or lives near a paper mill, fish market,
or chicken processing center should be grateful for sensory
adaptation.
This is also why men who put on too much cologne don’t
notice it. They’ve already adapted to it.
Sensory adaptation frees up our attention space and allows
us to focus on novel (new) stimuli.
But, we don’t adapt to everything. Intense pain and heat are
examples of warning signals that don’t go away.
Vision
VISION
STIMULUS – Light rays
Lens bends the light rays to focus
Retina converts light rays into
neural activity
•
•
Rods – black, white, and
gray receptors
Cones – detail and color
receptors
Optic nerve sends message to the
visual cortex of the brain
•
Blind spot exists where
optic nerve leaves the eyes
as there are no receptors in
this location
Structure of the Eye
Light enters the eye through
the cornea (“window”)
Then passes through the pupil,
an opening in the …
Iris, which is a muscle that
contracts or dilates to let more
or less light in. The
Lens focuses light by
changing its curvature (called
accommodation) and forms
upside down image on
Structure of the Eye
the Retina, which processes
light into a neural impulse
(transduction), that is then
sent through the optic disk
(hole in retina) to the Brain
Visual Information Processing
Optic nerves connect to the thalamus in the middle of the
brain, and the thalamus connects to the visual cortex.
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.
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, movement, etc.
Theories on Color Vision
Color is a psychological interpretation. It is a perception,
not a physical property of light. Color perception is based
on the dominant wavelength in a mixture of various
wavelengths. But what is dominant can often be a little bit
fuzzy.
So how do we make the transition to perceiving color?
Theories on Color Vision Cont.
1. Trichromatic Theory
•
•
•
•
•
Young and Helmholtz
Humans have 3 receptors
(red, green and blue)
Eye mixes these colors by
varying their proportions
Color television only uses
red, green and blue
But doesn’t explain law of
complementary colors
(pairs of colors that produce
gray when mixed)
Color Blindness
Genetic disorder in which
people are blind to green or
red colors. This supports
the Trichromatic theory.
Ishihara Test
Theories on Color Vision Cont.
2. Opponent Process Theory
•
•
Hering
3 receptors, which display 1 of
2 colors based on how fast the
neuron is firing
o Red ----- Green
o Yellow ----- Blue
o Black ----- White
Stare at the white dot in the center for a minute
and then look at a blank piece of paper….
Theories of Color Vision:
Reconciliation
Dual Process Theory:
•
Trichromatic at the level of Retina
o Retina contains 3 types of cones
•
Opponent Process at the level of Optic Nerve and Brain
o There are cells in the retina and visual cortex which respond to
colors in the way opponent process predicts
Hearing
HEARING
STIMULUS – Sound waves
Waves go through auditory
canal to eardrum
Eardrum vibrates and sets in
motion the tiny bones in the
middle ear
Inner ear membrane vibrates
and excites fibers in the
auditory nerve
Auditory nerve sends to the
temporal lobe of the brain
Auditory System
Just like light travels in waves, so does sound.
Stimulus: sound (movement of molecules in form of
waves)
Physical  Psychological Perception
•
•
•
Amplitude (height): loudness (dB)
Wavelength (distance bw peaks): pitch (Hz: Hertz)
Purity: Timbre (quality of sound)
Ear Anatomy
Outer Ear (gold)
pinna: receives sound
waves, which travel along the
auditory canal: to the
Middle Ear (blue)
eardrum: which
vibrates the ossicles: hammer,
anvil, & stirrup (movable
bones), which amplify the
sound and send to
Ear Anatomy Cont.
Inner Ear (pink) cochlea:
contains the receptors for
hearing (hair cells)
basiliar membrane: runs along
the cochlea and contains hair
cells
hair cells (our auditory
receptors) transduce sound
into neural impulses that are
sent to
auditory cortex in the
temporal lobe of the brain
Ear Anatomy
The outer ear is essentially an air filled funnel for receiving
sound waves and transporting them inward.
The middle ear is an air filled cavity that contains ossicles.
When sound enters it, it causes the eardrum to vibrate,
which in turn, causes the ossicles to vibrate against the oval
window. The ossicles amplify sound to 30 times greater,
which increases the amount of pressure that sound waves
exert upon the inner ear.
The inner consists of the cochlea, a fluid filled tube, where
transduction takes place
Loudness Perception
The brain interprets loudness from the number of hair cells
activated in the basiliar membrane
Theories of Pitch Perception
Place Theory:
pitch perception  vibration of a particular spot on
the cochlea’s basilar membrane
•
•
Like plucking a harp
Best explains high pitched sounds
Frequency Theory:
pitch perception  rate at which entire basilar
membrane vibrates
•
Best explains low pitched sounds
Smell
Olfaction: Smell
Stimulus: airborne molecules
These are inhaled through the
nose and travel to the olfactory
epithelium (membrane lining of
the roof of the nasal cavity).
Receptors are hair cells on the
olfactory epithelium, which
transduce the molecules to neural
impulses that are sent to the
olfactory bulb located in the
frontal lobe
Messages are sent to both the
temporal lobe and to the limbic
system (which is why smells are
so often linked with memories).
Taste
TASTE
STIMULUS – Chemicals
Chemicals come in contact
with taste buds inside the
mouth
Taste buds trigger neural
impulses
Neural impulses sent to
gustatory portion of the
cortex
Taste
Traditionally, taste sensations consisted of sweet,
salty, sour, and bitter tastes. Recently, receptors for
a fifth taste have been discovered called “Umami”.
Sweet
Sour
Salty
Bitter
Umami
(Savory)
Gustation: Sense of Taste
Major function is to prevent us from eating harmful
substances
•
This is one of the reasons why young children are such
picky eaters. They are more susceptible to falling to food
born illnesses, so evolution has given them more
sensitive taste buds and aversive reactions.
Stimulus: Food molecules
Receptors: taste buds, located in papillae (on surface of
tongue)
Taste and Smell
Food seems bland when you have a cold and can’t smell
very well.
Smell and taste receptors are located close together. Thus,
it’s difficult to separate these sensations.
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.
Touch
TOUCH
STIMULUS – Pressure,
cold, warmth, pain
Nerve endings in the skin
receive the stimulus
Nerve endings send a
message through the
spinal cord and brainstem
into the brain cortex -somatosensory area
Importance of Touch
Infants deprived of the sense of touch can literally waste away.
In the 19th century, close to 100% of infants who had been
placed in orphanages died before the age of 2. Overworked staff
seldom found time to touch or caress the babies. After a
systematic introduction of touch in which the babies were held
several times a day, the mortality rate dropped to 10%.
In one study, premature infants who were held went home 6
days earlier than those who were not.
So, give that baby an extra cuddle. It’s essential for their health.
Pain
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.
Pain Cont.
So, pain is important for our survival, but when it becomes
chronic it hinders our performance.
There are also people who feel pain when they shouldn’t
(phantom limb pain)
And those who don’t feel pain when they should (people
who walk over coals)
There’s also the phenomena of ….
Pain Cont.
Stress Induced Analgesia
o pain isn’t felt because animal is faced with
threat
o For example, soldiers severely wounded
in battle often don’t notice until the battle
is over. This is partly dependent on our
body’s natural pain killers, endorphins
Biopsychosocial Influences
PERCEPTUAL
ORGANIZATION
Visual Organization
Gestalt psychologists examined top down processing to
demonstrate that perception is mainly reliant on responding
immediately to the whole.
GESTALT PRINCIPLES
FIGURE-GROUND -- organization of the visual field into
objects (figures) that stand out from their surroundings
(ground).
FIGURE-GROUND
GESTALT PRINCIPLES
GROUPING
•
•
•
•
•
PROXIMITY
SIMILARITY
CONTINUITY
CONNECTEDNESS
CLOSURE
Proximity
SIMILARITY
CONNECTEDNESS/
SIMPLICITY
Visual Organization: Depth Perception
Depth perception: The ability to see objects in 3-D, even though
the images that strike the retina are 2-D
Binocular cues: involve both eyes
o Retinal Disparity: separation of the eyes causes different
images to fall on each retina
o Convergence: the closer the object the more the eyes
converge, or turn inward
MONOCULAR DEPTH CUES
Relative Image Size
Texture Gradient
Linear Perspective
Interposition
Atmospheric Perspective
Relative Elevation
Familiarity
Monocular Cues
Relative Size: If two
objects are similar in size,
we perceive the one that
casts a smaller retinal
image to be farther away.
Monocular Cues Cont.
Rene Magritte, The Blank Signature, oil on canvas,
National Gallery of Art, Washington. Collection of
Mr. and Mrs. Paul Mellon. Photo by Richard Carafelli.
Interposition: Objects that
occlude (block) other
objects tend to be
perceived as closer.
Monocular Cues Cont.
Image courtesy of Shaun P. Vecera, Ph. D.,
adapted from stimuli that appered in Vecrera et al., 2002
Relative Height: We
perceive objects that are
higher in our field of
vision to be farther away
than those that are lower.
Monocular Cues Cont.
Relative motion: Objects
closer to a fixation point
move faster and in
opposing direction to
those objects that are
farther away from a
fixation point, moving
slower and in the same
direction.
Monocular Cues Cont.
© The New Yorker Collection, 2002, Jack Ziegler
from cartoonbank.com. All rights reserved.
Linear Perspective:
Parallel lines, such as
railroad tracks, appear to
converge in the distance.
The more the lines
converge, the greater their
perceived distance.
Monocular Cues Cont.
From “Perceiving Shape From Shading” by Vilayaur
S. Ramachandran. © 1988 by Scientific American, Inc.
All rights reserved.
Light and Shadow: Nearby
objects reflect more light
into our eyes than more
distant objects. Given two
identical objects, the
dimmer one appears to be
farther away.
Visual Organization
Perceptual Constancy: perceiving the environment as remaining
the same even with changes in sensory input
•
Allows us to identify people and things in less time
Four best-known constancies:
• Size
• Shape
• Color
• Brightness
Size Constancy
We know that the people in the back of the picture are roughly the same size
as the people in the front. However, when we take one of these people and
put them in the front (see left hand side, man in shirt), we see that he is
actually much smaller.
Shape Constancy
We perceive the shape of the door as constant, which helps us identify it as
a door, even when the shape is actually changing.
Ames Room Illusion
This distorted room appears to have a normal rectangular shape when viewed
through a peephole with one eye. The person on the right seems
disproportionally large because we judge his/her height based on the false
assumption that he/she is the same distance away as the individual in the
other corner. This is where our perceptual shortcuts can lead us astray.
Ames Room
The Ames room is designed to demonstrate the sizedistance illusion.
Color Constancy
Perceiving familiar objects as having consistent color even
when changing illumination filters the light reflected by the
object.
Color Constancy
PERCEPTUAL
SET
We perceive based on past experience
We perceive based on context of stimulus
LEARNING
LEARNING IS A RELATIVELY PERMANENT CHANGE IN
BEHAVIOR DUE TO EXPERIENCE
THREE LEARNING THEORIES
CLASSICAL CONDITIONING
OPERANT CONDITIONING
OBSERVATIONAL LEARNING
Classical Conditioning
Classical conditioning is a basic form of learning in which
one stimulus (event) predicts the occurrence of another
stimulus (event)
Key Player: Ivan Pavlov
•
also called Pavlovian Conditioning
Classical Conditioning Cont.
Before Conditioning/Learning
•
•
At the core of classical conditioning is reflexive
responding.
Reflex: is an unlearned response
o Such as salivating to food, blinking when a puff of air goes in
our eye, or a loud, unexpected noise startling us
o Reflexes naturally happen in response to stimulation that is
biologically relevant
o (Myers, 2013).
Classical Conditioning Cont.
Before conditioning (i.e., learning)
•
•
Any stimulus that naturally causes a reflexive response is
called an unconditioned stimulus (UCS) (i.e., an
unlearned stimulus).
The unlearned, reflexive response to the unconditioned
stimulus is called the unconditioned response (UCR).
(Myers, 2013)
Classical Conditioning Cont.
During Conditioning/ Learning
•
•
During conditioning, a neutral stimulus such as a tone is
paired with the unconditioned stimulus (UCS) such as
meat powder.
After a number of pairings, the subject learns to associate
the two together
Classical Conditioning
After Conditioning/ Learning
•
•
•
•
•
Now, the tone causes the dog to salivate as well.
This previously neutral stimulus (tone) has through
conditioning gained the ability to cause a learned
response. It is called the conditioned stimulus (CS) (i.e.,
learned stimulus).
Salivating to the tone is the Conditioned Response (CR):
learned response that occurs because of conditioning
Notice that in most cases, the conditioned response is the
same as the unconditioned response. The intensity may
be different.
(Myers, 2013)
SUMMARY - HOW CLASSICAL
CONDITIONING WORKS
LEARN TO
ASSOCIATE
TWO STIMULI
PAVLOV’S EXPERIMENT
Before Conditioning
UCS (food
in mouth)
UCR
(salivation)
During Conditioning
Neutral
stimulus
(tone)
No
salivation
After Conditioning
UCS (food
in mouth)
Neutral
stimulus
(tone)
UCR
(salivation)
CS
(tone)
CR (salivation)
Basic Processes in Classical Conditioning
1. Acquisition: initial stage of learning
•
A. Contingency: generally, the CS needs to be presented
before the UCS
o Would presenting the tone after the dog had eaten caused learning to
occur? Probably not
•
B. Timing: pairing needs to be done close in time for learning
to occur
o What if the tone was presented an hour before the food? The dog
would have forgotten about it by the time the food arrived.
•
C. Salience of CS: the more novel or unusual the CS is, the
more likely learning will occur
o A loud tone will catch the dog’s attention more than a barely audible
tone.
(Myers, 2013)
Acquisition
(Myers, 2013)
The CS needs to come half a second before the US
for acquisition to occur.
Basic Processes in Classical Conditioning Cont.
2. Extinction: gradual weakening and disappearance of the
conditioned response
•
•
Occurs when Conditioned Stimulus (Tone) is presented
without the Unconditioned Response (Food) for several
trials
After a while, the dog stops salivating to the tone. The
conditioned response has been extinguished.
(Myers, 2013)
Basic Processes in Classical Conditioning Cont.
3. Spontaneous Recovery: If after extinction, Pavlov
stopped sounding the tone for a while and then did it again,
the salivation response to the tone would reappear briefly,
demonstrating that the dog had not forgotten about it. This
is called spontaneous recovery
Basic Processes in Classical Conditioning Cont.
4. Stimulus Generalization: after learning to respond to
specific conditioned stimulus (such as a tone), subject also
responds to similar stimuli (similar tones)
•
•
Example: Case of Little Albert
http://www.youtube.com/watch?v=FMnhyGozLyE
Basic Processes in Classical Conditioning Cont.
5. Stimulus Discrimination: when the subject learns to
respond only to specific Conditioned Stimulus, rather than
several similar stimuli
(Myers, 2013)
Biological Predispositions
Key Figure: John Garcia
•
•
Food Poisoning  Nausea
UCS  UCR
•
•
Taste and Odor Stimuli + Food Poisoning
CS
UCS
•
•
Taste and Odor Stimuli  Nausea
CS
CR
•
This quick conditioning makes sense in that it protects us
from eating harmful substances in the future. It is a by
product of our evolutionary history
(Myers, 2013)
Operant Conditioning
Form of learning in which responses are controlled by their
consequences
Key Player: Edward Thorndike
•
At about the same time as Pavlov was working with
drooling dogs, Edward Thorndike was watching cats try
to escape from puzzle boxes. He saw that cats began to
associate their behaviors with certain responses.
Gradually, they increased the frequency of behaviors that
were associated with positive outcomes and decreased
the behaviors associated with negative outcomes.
Thorndike referred to this relationship between behavior
and consequences as the Law of Effect.
Operant Conditioning Cont.
•
•
•
Law of Effect: the probability of a response being
repeated is strengthened if followed by pleasant or
satisfying event
See an example of this in action….
http://www.youtube.com/watch?v=BDujDOLre-8
(Myers, 2013)
HOW OPERANT CONDITIONING WORKS
LEARN TO
ASSOCIATE
A RESPONSE
AND ITS
CONSEQUENCE
Response: Pushing
vending machine button
Consequence: Receiving
a candy bar
Reinforcement of Behavior
Reinforcement: strengthens behavior by
•
•
Positive: adding a positive consequence OR
Negative: taking away an aversive stimulus
(Myers, 2013)
Types of Reinforcers
1. Primary: inherently
reinforcing because they
satisfy biological needs
(food, sex, water)
2. Secondary: acquire
reinforcing qualities by being
associated with primary
reinforcers (money, praise)
Immediate & Delayed Reinforcers
Immediate Reinforcer: A reinforcer that occurs instantly
after a behavior.
A rat gets a food pellet for a bar press.
Delayed Reinforcer: A reinforcer that is delayed in time for
a certain behavior.
A paycheck that comes at the end of a week.
Watching TV vs. Getting an A in a Course
Myers Instructors Resources
Basic Processes
1. Acquisition
•
•
Acquisition in operant conditioning is a little bit
different. It is a more gradual process that requires
shaping.
Shaping: reinforcement of closer and closer
approximations to the desired response
o For example, if you want a rat to push a lever, he’s not going
to automatically perform the desired behavior. Instead, you
have to reinforce him each time he gets closer to the lever
until he finally pushes it. This is how circus animals are
trained
(Myers, 2013)
Basic Processes Cont.
2. Extinction
•
•
Also occurs in operant conditioning. It begins when the
previously available reinforcement is stopped.
A behavior can resist extinction depending upon how
often it was reinforced in the first place. In other words,
it depends upon the schedule of reinforcement.
Schedules of Reinforcement
Continuous Reinforcement: response is rewarded every
time
•
Ex. Every time a child throws a tantrum, she gets a piece
of candy
OR
Partial Reinforcement: response is reinforced only some of
the time
•
•
Ex. Sometimes when a child throws a tantrum, she gets a
piece of candy
More resistant to extinction because the child doesn’t
know if she’ll get candy or not each time.
Myers, 2013
Schedules of Reinforcement Cont.
Types of Partial Reinforcement
•
I. Ratio Schedules: need to make response a certain # of
times to be reinforced
o A. Fixed Ratio: reinforcer is given after a fixed # of
nonreinforced responses
– You have to make 20 gadgets before you are paid.
o B. Variable Ratio: reinforcer is given after a variable # of
nonreinforced responses
– Casino slot machines. You get paid after a variable (usually
random) number of responses (pulls of the lever)
(Myers, 2013)
Schedules of Reinforcement Cont.
Types of Partial Reinforcement Cont.
II. Interval Schedules: require a certain period of time to
pass between reinforcers
•
A. Fixed Interval: reinforcer is given for 1st response
after a fixed time has elapsed
o Checking the oven for cookies when the baking time is known
o Studying for a test when the date of the test is known
•
B. Variable Interval: reinforce a behavior after an
unspecified time period
o Studying for a pop quiz when the date is not known
(Myers, 2013)
Punishment
An aversive event that decreases the behavior it follows.
(Myers, 2013)
PROBLEMS WITH PUNISHMENT
PUNISHMENT IS NOT FORGOTTEN -- it's suppressed-behavior returns when punishment is no longer eminent
PUNISHMENT CAUSES INCREASED AGGRESSION -shows that aggression is a way to cope with problems -explains why aggressive delinquents and abusive parents
come from abusive homes
ADDITIONAL PROBLEMS WITH
PUNISHMENT
PUNISHMENT CREATES FEAR -- fear of school,
learned helplessness, depression
PUNISHMENT DOES NOT ALWAYS GUIDE TOWARD
DESIRED BEHAVIOR--reinforcement tells you what to
do, punishment tells you what not to do-- combination of
punishment and reward can be more effective than
punishment alone
PUNISHMENT TEACHES HOW TO AVOID IT
Operant vs. Classical Conditioning
Myers, 2013
Observational Learning
Learning by observing and imitating the behaviors of
others
Major Contributor: Albert Bandura
Bobo Doll Study
Watch this:
http://www.youtube.com/watch?v=Z0iWpSNu3NU
Bandura's Bobo doll study
(1961) indicated that
individuals (children)
learn through imitating
others who receive
rewards and punishments.
Courtesy of Albert Bandura, Stanford University
Bandura's Experiments
Observational Learning
Imitating behavior is more likely to occur when:
Model’s behavior is reinforced
Model’s liked and well-respected
Perceived similarities between model and observer
Observer is rewarded for paying attention to model
Model’s behavior is visible
Model’s behavior is within the range of the observer’s
competencies to imitate
(Huffman, 2010)
Applications of Observational Learning
Antisocial models 
antisocial behavior
Prosocial models 
prosocial behavior
(Myers, 2013)
Glassman/ The Image Works
Research shows that
viewing media violence
leads to an increased
expression of aggression.
Bob Daemmrich/ The Image Works
Modeling Violence
Children modeling after pro wrestlers
THERAPIES BASED ON LEARNING
THEORIES
DESENSITIZATION THERAPY
COUNTER CONDITIONING THERAPY
AVERSION THERAPY
BEHAVIOR MODIFICATION