Transcript 281 Lecture 5

Classical Conditioning
Underlying Processes and Practical
Application
S-S versus S-R Learning
Why does CC occur?
S-S versus S-R Theories
NS/CS
Pavlov
CR
UCS
UCR
Pavlov’s stimulus substitution theory:
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Theory: The CS becomes a substitute for the UCS.
3 problems:
1. Size of the CR and UCR may differ
2. Not all components of the UCR become the CR ( if the
stimulus is food, the CR only elicits salivation. The UCR also
entails chewing and swallowing etc.)
3. CR is sometimes in opposite direction of UCR (conditioned
compensatory response)
What would you predict?
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Addiction brought to America
1000s of American soldiers addicted?
Spread to rest of population?
This did not happen.
Soldier return to normal life.
What happened?
Drug Tolerance as…
a Conditioned Response:
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1st heroin use (1 unit) - euphoria
Anytime with repeated use….
2 units  “10”
3 units  “10” so, you need more of the
drug to achieve the same effect.
Compensatory Responses
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Decrease in the effectiveness of a drug
with repeated use is called tolerance.
Why does tolerance occur?
1. Physiological changes: metabolism is altered.
2. Due to classical conditioning
Compensatory Responses
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Seigel (1975) : drug tolerances due to
contextual stimuli that regularly precede
a drug administration.
The room in which the drug is
administered (CR) has the effect of an
increased sensitivity to pain.
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The result effect is that the CR + UCR
cancel each other out
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More drug is required
Compensatory Responses
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When the room changes, the former CSs are
removed, thus the compensatory reaction is
also removed
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Heroin (5 units, with room change…)
 physiological overload
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OD, coma, and perhaps results in death
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Compensatory Responses
Friends, Place, Smells, behaviors prior to use
CR
UCS
UCR
Compensatory responses
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Treatment…
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Exposure to cues, initially causes craving
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Without UCS, cravings decrease
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By Santoro, Deletis, Bergman
Rescorla-Wagner Model
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Mathematical model of classical
conditioning, on a trial by trial basis
The key is the relationship between
1) expectation
2) strength of UCS
6 Rules of RWM
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1. If 2> 1 it is excitatory conditioning
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2. If 2< 1 it is inhibitory conditioning
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3. If 1=2 no conditioning occurs
6 Rules of RWM
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4. Greater discrepancies result in greater
conditioning
5. Salient conditioned stimuli condition faster
than subtle conditioned stimuli
6. If two or more conditioned stimuli are
presented together, the expectation is that
CS1 + CS2
RWM
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Consider: A light becomes a CS for food (UCS). On
the first trial, the subject has no expectation of food,
therefore the strength of the UCS is greater than the
expectation, which results in excitatory conditioning
(consists of rules 1 and 4.)
Blocking: same expectations as above, but the tone
is added after a number of conditioning trials.
no conditioning occurs because there is no surprise
the strength of the subject’s expectations matches
the strength of the UCS. (rule 3)
RWM
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Extinction and Conditioned Inhibition:
same expectations as above, and a tone
is added after a number of trials, but no
food is delivered. (extinction trial).
this time, expectation exceeds the UCS
strength (1>2), which is consistent with
rule 2.
RWM
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Overshadowing:
If a strong CS is paired with a weak CS,
when presented in a compound form,
the strong CS will overshadow
(condition faster) than the weak CS.
Consistent with rule 5 (more salient
stimuli will condition faster)
Rescorla Wagner Model: (formula)
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this model predicts the outcome of classical
conditioning on a trial by trial basis.
Total/change in learning = TCL
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TCL= salience of CS x (UCS strength - expectation)
is constant
A product of past learning
RWM
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Let’s suppose….
Trial 1
TCL = ? (we have to calculate)
Salience = .5
Strength of UCS = 100
1. Vn = 0.5 x (100-0) = 50
2. Vn = 0.5 x (100-50) = 25  50 +25 = 75
3. Vn = 0.5 x (100-75) = 12.5
4. Vn = 0.5 x (100-87.5) = 6.25