PSY 402
Theories of Learning
Chapter 4 – Nuts and Bolts of Conditioning
(Mechanisms of Classical Conditioning)
Classical vs. Instrumental

The modern view is that these two types of learning
involve similar learning processes, but differ in the
following ways.
1.
2.
In Classical conditioning, two stimuli are associated with
each other but in Instrumental conditioning, a stimulus
and a response are associated.
In Classical conditioning, the response is a reflex or
involuntary action but in Instrumental conditioning, the
response is a voluntary, freely emitted behavior.
Pavlov’s Conditioned Reflex
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Conditioning -- a stimulus that initially
produces no response can acquire the ability
to produce one.
Learning occurs through pairing in time and
place of one stimulus with another stimulus
that produces an involuntary response.
Political Classical Conditioning
Obama Too
Caught up in the Moment?
Conditioning Processes
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Stimulus generalization – stimuli like the CS
become able to evoke the conditioned
response.
Extinction – if the UCS and CS are not paired,
the CS loses its ability to produce a
conditioned response.
Spontaneous recovery – an extinguished CS
briefly returns but quickly goes away again.
What is Learned?

Pavlov believed the association was between
the two stimuli (tone and meat powder), not
between the tone and salivation.
Either is
possible
Stimulus substitution
Conditioning Situations

Sign-tracking (autoshaping) – animals must
recognize signs of food (UCS) and respond
(UCR).
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Pigeons pecking at key.
This is a UCR, not an operant response, because
pecking behavior is specific to the food stimulus.
Eyeblink conditioning
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UCR is rapid, CR is slow.
Many trials are needed (100 pairings)
3.7 Autoshaping in pigeons (Part 1)
3.7 Results of autoshaping tests in pigeons (Part 2)
3.5 Design of eyeblink conditioning experiment in rabbits (Part 1)
3.5 Results of eyeblink conditioning experiment in rabbits (Part 2)
Conditioned Emotional Responses
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Fear is an anticipatory pain response based on
past experience.
Fear is conditioned (becomes a CR) whenever
a CS is associated with an aversive (painful or
undesirable) event.
Fear motivates two responses:

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Escape (when pain is present)
Avoidance (when pain is about to happen)
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 (bar press).
Second – a CS is paired with an aversive UCS
(light with shock).
Third – the CS is presented in the operant
chamber and the effect on operant responding is
measured.
3.6 Conditioned suppression in rats (Part 1)
Suppression Ratio
During CS
Suppression Ratio =
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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
This will be on the midterm
3.6 Conditioned suppression in rats (Part 2)
Flavor Aversion Learning

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% of the time).
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Even if illness occurs hours later it is linked to the
previous meal.
Not cognitive – you can know the food is not to
blame and still feel an aversion to it.
Acquired Changes in Response
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Habituation – response to a repeated stimulus
decreases with non-threat experience.
Sensitization – response to a variety of stimuli
increases with a single threat experience.
Examples:
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Ingestional neophobia, fear of new food
Rats orient less toward light, startle decreases
Chicks are less frightened by shadows flying
overhead with repeated exposure.
Factors Affecting Conditioning
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Timing – how closely in time are the CS and
UCS, and which occurs first.
Novelty of the CS and UCS.
Intensity (strength) of the CS and UCS.
Consistency of the pairing between the CS
and UCS.

If one or the other appears alone then
conditioning is weakened.
Stimulus Presentation Paradigms
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Delayed conditioning – the CS onset precedes
the UCS onset.
Trace conditioning – the CS starts and ends
before the UCS onset.
Simultaneous conditioning – the CS and UCS
occur together.
Backward conditioning – the UCS starts and
ends before the CS onset.
These paradigms will be on the midterm
3.8 Different ways to present CS and US in time
This works best
The longer the gap (trace interval) the worse this works
This isn’t as good as delayed
This doesn’t work at all
Temporal Conditioning
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The UCS occurs at regular intervals in time.
Nominally, no CS is present, but aspects of
the context in which the UCS occurs become
conditioned to it.
Examples:
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Waking up just before the alarm goes off.
Your dog knows when you will come home.
Getting sleepy right around bedtime.
Massed vs Spaced Trials
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Better learning occurs when trials are spaced
out over time (spaced), rather than bunched
together (massed).
Memory consolidation or rehearsal may be
needed between trials.
The ratio between the exposure to the CS and
the time in-between is the important factor.
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If both are the same duration, learning is weaker.
3.9 Trial spacing in Pavlovian conditioning
This works best
This doesn’t work as well
Importance of Contiguity
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“Wait ‘til your father gets home” is an
ineffective threat because punishment comes
too late.
The further apart the CS and UCS in time, the
less effective the conditioning.
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Intermediate stimuli can form a bridge.
Ideal ISI (inter-stimulus intervals) vary with
the kind of animal and the kind of UCR.
Importance of Predictiveness

Preexposure to the CS (before it is paired with
the UCS) reduces learning.
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The same thing happens with preexposure to
the US (before it is paired with the CS).
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Called latent inhibition because it inhibits
learning of the CS-UCS association.
Called the US preexposure effect
Threat without punishment instills no fear,
even if the child has been punished before.
Effect of Presenting UCS Alone
UCS equally likely to
occur alone or
together with CS
UCS always with CS
Preparedness Affects Learning
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Both instrumental and classical conditioning
are affected by preparedness (the innate
nature of the organism).
Flavor aversion learning is easier with taste
cues than with visual cues, but not shock.
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Counterpreparedness – some CS’s cannot become
associated with a UCS.
Preparedness makes a stimulus more salient.
Humans Show Preparedness
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Humans show preparedness too, appropriate
to our species.
Nausea can be associated with tequila but not
with friends or a shot glass.
Snake and spider phobias may be especially
prevalent due to preparedness.
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People associate shock with spiders or snakes
more readily than with flowers or mushrooms.
Stimulus Intensity (Strength)
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The stronger the US (UCS), the faster the
learning and the stronger the association.
The stronger the CS, the better the learning.
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Salience – how attention-getting the stimulus is in
relation to other stimuli in the environment.
The most salient CS becomes associated with the
UCS.
An overpowering CS may elicit a response of
its own, preventing learning.
Effects of Stimulus Intensity
Pseudo-conditioning
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Responses to the CS may occur due to the
strength of the UCS, not learning.
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Once air has been puffed at the eye, blinking may
occur in response to any stimulus that comes
next, without any learning.
Sensitization resulting from an intense UCS may
cause the response to a CS to be increased, even
when there is not greater learning.
A control group lets you tell the difference.
3.10 Bernstein’s experiment on taste aversion learning
Mapletoff is a novel ice cream prepared
with Maple and Walnut flavored extracts.
Conditioning and Addictions
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Drugs can be associated with environmental
cues present when the drugs are taken.
Instead of the drug response being
conditioned, an opposite adaptive response is
conditioned that lessens the drug’s effect.
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This is called drug tolerance.
Taking a drug under novel circumstances can
produce a drug overdose because the
compensatory effect is not present (no cues).