Transcript LT2Ch2

PSY402
Theories of Learning
Chapters 2 & 3
Acquisition, Extinction, and
Spontaneous Recovery
Little Albert
Watson & Raynor
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Human fears can be acquired
through Pavlovian conditioning.
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Rat paired with loud noise
Stimulus generalized to other white
objects (white rabbit, white fur coat)
Mary Cover Jones developed
counterconditioning -- a technique
for eliminating conditioned fears.
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Acquisition of fear-inhibiting response
Ethics of Learning Research
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Animals and humans are now
protected by oversight and ethical
guidelines.
Pain or injury to animals must be
weighed against and justified by the
knowledge to be gained.
Electric shock typically is
uncomfortable and upsetting but
not physically harmful.
Instinctive Systems
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Lorenz & Tinbergen – evolution
occurs when a species incorporates
environmental knowledge into its
genetic structure.
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Greylag goose and egg-rolling.
Learning can sometimes modify
instinctive behavior – even though
the fixed action patterns are innate.
Energy Model
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Action-specific energy builds up but
is blocked (inhibited).
The energy motivates appetitive
(approach) behavior.
Presence of a sign stimulus releases
the energy by stimulating an innate
releasing mechanism.
The behavior occurs as a fixed
action pattern (or chain of actions).
Releasing Signs
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Releasing signs can be complex:
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Grayling butterfly signs include
darkness of female, distance from
male, and pattern of movement.
Intensity of the sign influences the
behavior but so does the amount of
accumulated energy (time since the
last response).
Hierarchical System
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Specific behaviors are controlled by
a central instinctive system.
Energy can accumulate at each
level in the system.
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Hormones generate energy.
Release of energy at higher levels
flows to lower levels.
The sign stimulus determines which
behavior will occur.
Conflicting Motives
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If two incompatible signs appear at
the same time, energy flows to a
third instinct system.
This third behavior is called
displacement.
Conditioning Affects Behavior
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Conditioning experiences can
change sensitivity to releasing
signs.
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Only the consummatory response
(eating, mating) at the end of a chain
cannot be changed.
Conditioning fine tunes the
response to the environment and
enhances survival.
Criticisms of the Energy Model
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Best viewed as a metaphor.
The brain does not literally
accumulate energy in any centers
and nothing flows.
Willows & Hoyle – alternating
contractions in sea slug allow it to
escape from a starfish.
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Brain areas producing this response do
not correspond to energy model.
Acquired Changes in Response
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Habituation – response to a
repeated stimulus decreases with
experience.
Sensitization – response to a
repeated stimulus increases with
experience.
Examples:
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Ingestional neophobia, fear of new food
Startle response
Experimental Evidence
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Rats drink little saccharin water at
first but increase over time.
Loud tones (110 db) produce
different responses depending on
the background noise (60 vs 80 db).
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Habituation occurred at 60 db
Sensitization occurred at 80 db
A loud background is arousing, leading
to greater reactivity, not less.
Conditions Producing Change
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More intense (stronger) stimuli
produce stronger sensitization, less
likely to produce habituation.
Greater sensitization and
habituation occur when the stimulus
is repeated frequently.
Changes in the stimulus prevent
habituation.
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Turkeys respond to shape changes.
Conditions (Cont.)
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Sensitization can occur to many
kinds of stimuli but habituation
occurs only with innate responses.
Habituation and sensitization are
transient (go away after seconds or
minutes between stimuli).
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Except long-term habituation.
Dishabituation – response returns
when a sensitizing stimulus occurs.
Opponent-Process Theory
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An explanation for addictions.
All experiences produce an affective
reaction (pleasant or unpleasant) –
called the A state.
This reaction gives rise to its
opposite – called the B state.
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B state is less intense and lasts longer.
Over time, the A state diminishes
and the B state increases.
The Addiction Process
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Tolerance – diminished A state.
Withdrawal – increased B state.
Addictive behavior is a coping
response to the change in B state.
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People try to enhance A state to offset
the unpleasantness of the B state.
Without withdrawal symptoms there is
no addictive behavior.
Time prevents B state strengthening.
What Sustains Addiction?
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The B state is a non-specific
aversive feeling.
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Anything similarly aversive will
motivate the addictive behavior, even if
it has no relation to the substance.
Daily life stress produces a B state that
results in behavior to create an A state.
Parachute jumpers – create a B
state in order to feel the A state.
Acquisition of a Conditioned
Response
Chapter 3, pages 37-46
Acquisition, Extinction, and
Spontaneous Recovery
Conditioned Emotional Responses
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Fear is an anticipatory pain
response based on past experience.
Fear is conditioned whenever a CS
is associated with an aversive
(painful or negative) event.
Fear motivates two responses:
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Escape (when pain is present)
Avoidance (when pain is imminent)
Examples of Conditioning
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Popcorn at the movies.
Fear of flying -- stronger with more
turbulence (a stronger UCS).
An antelope shying away from low
tree branches.
Nausea at the smell of alcohol after
a hangover.
Conditioning Situations
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Sign-tracking (autoshaping) –
animals must recognize signs of
food (UCS) and respond (UCR).
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Pigeons pecking at key.
UCR, not an operant response, because
behavior is specific to the stimulus.
Eyeblink conditioning
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UCR is rapid, CR is slow.
Many trials are needed (100 pairings)
Fear conditioning
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Avoidance is not a good measure of
fear.
Suppression of an operant behavior
occurs with a feared stimulus.
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First – an operant behavior is learned.
Second – a CS is paired with an
aversive UCS.
Third – the CS is presented in the
operant chamber.
Suppression Ratio
During CS
SuppressionRatio =
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During CS + Without CS
The amount of time during and without the
CS is equal.
The more fear, the lower the suppression
ratio.
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Ratios typically fall between 0 and .5
Flavor Aversion Learning
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Garcia – rats will not drink water
with saccharin if they get ill after
drinking.
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Significant avoidance occurs after just
one trial.
Human food aversions are related
to illness (89%).
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Even if illness occurs hours later it is
linked to the previous meal.
Not cognitive – know food not to blame