Transcript LTNov19

PSY402
Theories of Learning
Wednesday, November 19, 2003
Chapter 6 -Traditional Theories (Cont.)
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.
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).