Transcript LTNov17

PSY402
Theories of Learning
Monday
November 17, 2003
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