Transcript LT2Ch6

PSY402
Theories of Learning
Chapter 6, Traditional Theories
Two Theoretical Approaches
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S-R associative theorists -inflexible view of behavior.
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Mechanistic
Stimulus acquires ability to elicit
response through associations formed.
Cognitive theorists – flexible view.
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Mentalistic
Learning involves recognition and
understanding of environment.
Hull’s Drive Theory
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Drive motivates behavior and drive
reduction is responsible for the S-R
associative learning.
Drive – an intense internal force.
Behavior is the combined influence
of several factors, which can be
expressed mathematically.
Hull’s Factors
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Excitatory potential (expectation)
SER – likelihood that an event will
occur.
Drive (D)
Incentive motivation for reward (K)
Habit strength (H) – strength of the
S-R association (experience).
Inhibition – also due to experience.
Sources of Drives
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Unconditioned:
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Physiological deprivation, metabolic
imbalance.
Intense environmental events with
survival consequences.
Pleasurable stimuli (such as saccharin)
even without nutritional value.
Acquired – Pavlovian conditioned
cues to unconditioned drives.
Habit Strength
 SUR
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– an unconditioned or innate
habit strength.
SHR – habit strength acquired
through prior learning experiences.
If a response reduces a drive state,
habit strength increases.
Drive reduction strengthens the S-R
bond until behavior becomes
habitual.
Inhibition
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Reactive inhibition -- if a drive
persists then all behavior is
temporarily inhibited.
Conditioned inhibition – continued
failure to reduce drive resulting in a
permanent decrease in behavior.
The second strongest response in
the habit hierarchy will be
performed instead.
Incentive Motivation
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Hull initially assumed that only drive
reduction influences the S-R bond.
Crespi showed that reward
magnitude affects responding.
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If reward only influenced learning, the
change should be more gradual.
Hull proposed that reward also
influences motivation by increasing
arousal.
Importance of Hull’s Theory
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THE dominant theory in the 1930s1960s.
Correct in many respects:
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Intense arousal can motivate behavior.
Environmental stimuli can develop the
ability to produce arousal, motivating
behavior.
Value of the reward influences the
intensity of behavior.
Problems With Hull’s Theory
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You can get increases in behavior
without drive reduction:
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Olds & Milner, direct brain stimulation
Sensory deprivation motivates behavior
to obtain stimulation (Harlow).
Hull’s theory does not explain how
secondary rewards can acquire the
ability to increase behavior.
Drive-Induction Theory
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Sheffield -- drive-induction not
reduction strengthens behavior.
Rewards produce excitement or
arousal which motivates
responding.
When secondary rewards are
associated with primary rewards
they elicit the same arousal.
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Also explains Harlow’s findings.
Guthrie’s Contiguity Theory
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Guthrie rejected the necessity of
reward.
Contiguity is enough to establish an
S-R association.
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A response that occurs when a stimulus
is present will automatically become
associated with it.
Learning is entirely governed by cooccurrences – contiguity in time.
Impact of Reward
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According to Guthrie, reward is
important, but it does not
strengthen the S-R association.
The effect of reward is to change
the stimulus context present prior
to reward.
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New actions are conditioned to this
revised stimulus context.
Reward prevents further conditioning of
the undesired behavior.
Guthrie’s View of Punishment
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Punishment is a stimulus that can
either be escaped or avoided.
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If a response terminates punishment, it
will replace the punished behavior next
time that context occurs.
Punishment works only if the
response elicited by the punishment
is incompatible with the punished
behavior.
Importance of Practice
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According to Guthrie, learning
occurs in a single trial.
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The strength of the S-R bond does not
slowly increase with experience.
Performance increases because
subjects must learn which stimuli
are consistently present.
Over time, many different stimuli
become associated with a response.
Criticisms of Contiguity Theory
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Guthrie conducted few studies to
support his theory.
Accurate parts:
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Punishment can intensify inappropriate
behavior when it elicits a response
compatible with the punished response.
Contiguity is essential to prevent
conditioning of competing associations.
Not all environmental cues are noticed.
Impact of Reward
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Guthrie’s view of reward has been
disproved.
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If what happens after a response is not
rewarding, an S-R association is not
formed, even if the stimulus changes.
Noble – reward size predicts
response better than recency or
frequency (contiguity measures).
Single-Trial Learning
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All-or-nothing (single-trial) learning
has been difficult to demonstrate.
Voeks – found single-trial learning
of an eye-blink response in humans.
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Other studies report gradual learning.
Spence proposed a threshold
explanation of single-trial learning
using incremental learning theory.
Skinner
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Emphasized the importance of
environment (reinforcers &
contingencies).
Validation of hypothetical constructs
interferes with analysis of the
variables controlling behavior.
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Anti-theory
Spence’s Acquired Motives
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Spence was a colleague of Hull.
Spence elaborated the idea that
reward size matters (K in Hull’s
theory).
It isn’t enough to say that reward
size matters – how specifically does
it affect behavior?
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Spence proposed a mechanism.
Goal Responses
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Reward elicits an unconditioned goal
response RG.
This response produces an internal
stimulus state SG that motivates
consummatory behavior.
Reward value determines the size of
the goal response RG.
Anticipatory Goal Responses
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Cues become associated with
reward through classical
conditioning.
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These produce an anticipatory goal
response rG.
Cues lead to internal stimulus
changes sG that motivate behavior.
Thus Pavlovian conditioning
motivates approach behaviors.
Amsel’s Frustration Theory
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Amsel applied Spence’s theory to
avoidance of aversive events:
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Frustration motivates avoidance.
Frustration suppresses approach.
Nonreward produces unconditioned
frustration response RF.
The stimulus associated with it SF
motivates escape behavior.
Anticipatory Frustration Response
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As with goal states, classical
conditioning results in anticipatory
frustration response rF.
The conditioned stimuli associated
with them sF motivate avoidance of
a frustrating situation.
Example: car that won’t start.
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SF motivates leaving the car, sF
motivates selling it.
Mowrer’s Two-Factor Theory
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Mowrer proposed a drive-based
two-factor theory to avoid
explaining avoidance using cognitive
(mentalistic) concepts.
Avoidance involves two stages:
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Fear is classically conditioned to the
environmental conditions preceding an
aversive event.
Cues evoke fear -- an instrumental
response occurs to terminate the fear.
Mowrer’s View (Cont.)
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We are not actually avoiding an
event but escaping from a feared
object (environmental cue).
Miller’s white/black chamber – rats
escaped the feared white chamber,
not avoided an anticipated shock.
Fear reduction rewards the escape
behavior.
Criticisms of Two-Factory Theory
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Avoidance behavior is extremely
resistant to extinction.
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Should extinguish with exposure to CS
without UCS, but does not.
Levis & Boyd found that animals do
not get sufficient exposure duration
because their behavior prevents it.
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Avoidance persists if long latency cues
exist closer to the aversive event.
Is Fear Really Present?
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When avoidance behavior is welllearned the animals don’t seem to
be afraid.
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An avoidance CS does not suppress
operant responding (no fear).
However, this could mean that the
animal’s hunger is stronger than the
fear.
Strong fear (drive strength) is not
needed if habit strength is large.
Avoidance without a CS
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Sidman avoidance task – an
avoidance response delays an
aversive event for a period of time.
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There is no external cue to when the
aversive event will occur – just
duration. Temporal conditioning.
How do animals learn to avoid
shock without any external cues for
the classical conditioning of fear?
Kamin’s Findings
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Avoidance of the UCS, not just
termination of the CS (and the fear)
matters in avoidance learning.
Four conditions:
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Response ends CS and prevents UCS.
Reponse ends CS but doesn’t stop UCS.
Response prevents UCS but CS stays.
CS and UCS, response does nothing
(control condition).
D’Amato’s Acquired Motive View
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D’Amato proposed that both pain
and relief motivate avoidance.
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Anticipatory pain & relief responses.
Shock elicits unconditioned pain
response RP and stimulus SP
motivates escape.
Classically conditioned cues sP elicit
anticipatory pain response rP that
motivates escape from the CS.
Anticipatory Relief Response
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Termination of the UCS produces an
unconditioned relief response RR
with stimulus consequences SR.
Conditioned cues elicit an
anticipatory relief response rR with
stimulus consequences sR.
Example: dog bite elicits pain
response, sight of dog elicits
anticipatory pain, house elicits relief
A Discriminative Cue is Needed
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During trace conditioning no cue is
present when UCS occurs and no
avoidance learning occurs.
A second cue presented during
avoidance behavior slowly acquires
rR-sR conditioning.
Similarly, in a Sidman task, cues
predict relief -- associated with
avoidance behavior, not the UCS.
How is rG Measured?
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Anticipatory goal responses were
initially measured as peripheral
nervous system (ANS) response.
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No consistent relationship between
such measures and behavior could be
found.
Now, Rescorla & Solomon propose
that these anticipatory states are
due to CNS activity (brain states).