Chapter 3: Pavlovian Conditioning: Foundations
• Pavlovian Conditioning or Classical Conditioning
• Ivan Pavlov
– Early 1900s
– A Russian physiologist
• digestive system
– Nobel prize
• Interested in the Salivary reflex.
• The reflex seemed to depend on the nature of the
stimulus.
– marble = little saliva
– sand = quite a lot.
• Sometimes dogs would salivate prior to
receiving food
• Puzzling to Pavlov
– Reflex in the absence of stimulus presentation
– Psychic secretions
• How was it possible that experience could
alter the salivary reflex?
• Pavlov carefully examined the
development of psychic secretions
• Eliciting factors?
– sight and smell of food
– food bowl
– lab coats
– footsteps
• Dog had associated these visual and
auditory stimuli with taste?
• Elements of Pavlovian Conditioning.
• First let’s distinguish between excitatory and inhibitory conditioning.
• Excitatory Conditioning
– Learning that a stimulus predicts the presence of another stimulus
– Pavlov’s initial studies
• Inhibitory Conditioning
– Learning that the stimulus predicts the absence of another stimulus
– We will discuss this more later
• Back to Excitatory Conditioning
• First Pavlov described the basic reflex
– e.g., Food elicits salivation
– Pavlov named the stimuli
• Unconditioned Stimulus (US) elicits Unconditioned Response (UR)
• Pavlov began to put together a theory
• Two distinct kinds of reflexes.
– 1) Unconditional Reflex
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inborn and unlearned (innate)
usually permanent reflex
Found in virtually all members of a species
varies little from individual to individual.
– salivary reflex
– patellar reflex
– 2) Conditional Reflex
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must be acquired through experience (not innate)
not permanent.
varies considerably from species to species
Varies from individual to individual.
– salivating to footsteps.
• Conditioned Stimulus (CS)
– a previously neutral stimulus
• Pavlov’s bell
• Normally doesn’t elicit salivation
• What response would it elicit?
– Known as orienting response
• Pair the Conditioned Stimulus with an Unconditioned
Stimulus
– tone  food = salivation.
– CS  US = UR
• After several CS  US pairings
– Test to see if learning occurred
• How?
• Test with CS alone
• Look for Conditioned Responding (CR)
– CS now elicits CR
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Let’s go through an example in more detail
– consider Empiricists rules of association (chapter 1)
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Saliency
– CS
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Tone
10 seconds
500Hz
70 db
– US
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5.0 gm meat powder
Contiguity
– CS-US interval = 20 seconds (from offset of the CS to the onset of the US)
– Intertrial Interval = 10 minutes (also can have effects on contiguity)
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Frequency
– trials: = 60 (frequency of associations or number of trials can affect strength of
conditioning
– Test every 10th trial
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How do we test?
• Let’s look at how the findings might have
come out
• Graph
– Y axis?
– X axis?
• Baseline
Idealized (made up) Data
12
CR (Salivation in mls.)
10
8
6
4
2
0
0
10
20
30
Trials
40
50
60
• Control Groups? –
• Typically a learning experiment uses control groups.
• In the hypothetical Pavlovian experiment we have been discussing
thus far, we already have a control condition.
– Baseline measurement
• Is that enough?
• What other controls would be important?
– A group that receives the tone alone.
• CS alone control -
– A group that receives the meat powder in the absence of the tone.
• US alone control
– Any increase in salivation in these control groups can be viewed as noncontingent learning.
• Sensitization?
– The US (meat powder) alone group may be particularly important to rule
out any unintended cues that indicate reinforcement is about to occur.
• Confounds
• What other controls might be appropriate?
– Maybe just experiencing bells and food sensitizes
the animal and gets them drooling.
• Either one alone is not enough, but both creates
sensitization
– Remember 12 checks vs. 4 checks in infant study (chapter
2)
• How can we control for this?
• Three ways
• 1) Backward Conditioning control
– USCS
– may cause conditioning (learning).
• What kind?
– Known as inhibitory (we will discuss this more later)
• 2) Random control
– The CS and US occur randomly
• Sometimes the CS will precede the US
• equally often the US will precede the CS.
• Also the temporal relationship between the CS and US varies
– Seems it should prevent association of tone and food
– Nevertheless sometimes the animals still associate
• 3) Explicitly unpaired control
– Present CS and US on separate trials
• Length of ITI necessary - varies depending on task
– Must be long (i.e., 24 hours for CTA)
• There is some debate about whether random or explicitly unpaired
controls are best
– Some form of learning seems to occur in all situations
• conditioning a patellar reflex?
– E. B. Twitmeyer (1902)
• PhD thesis at University of Pennsylvania
• Zeitgeist
• CS?
– Tone
• US?
– Tap knee
• UR?
– Kick
• When?
• CR?
– Kick
• When?
• An introduction to contemporary
conditioning methods
– There are many ways to examine Classical
Conditioning
– It’s not all slobbering dogs
• Fear Conditioning
– Little Albert
– Watson and Raynor
– Conditioned Emotional Response
• Aversive Conditioning vs. Appetitive Conditioning
• Fear Conditioning in animals?
– How do we measure fear?
– Freezing behavior?
• How do you quantify it?
• Would be nice to have initial activity to serve as a baseline
• Conditioned Suppression procedures
– lick suppression procedure
• Water deprived
• Measure licks on water bottle
• Present fear stimulus
– slows licking
– Conditioned Emotional Response procedure
• Phase 1
– Train rat to press lever to receive food.
• Phase 2
– Pair tone with shock
• Test
– Introduce tone while rat is lever pressing for food
• Often use Suppression Ratio as Dependent
Variable
CS responding / (CS responding + pre-CS responding)
• Suppression ratios vary from 0 (complete
fear) to .50 (no fear at all)
– Lower suppression ratio = more fear
• 0/(0+10) = 0  complete fear
• 1/(1 + 10) = .09  almost complete fear
• 10/(10+10) = .50  no fear at all
• Conditioned eye-blink procedure.
– Often rabbits
• but has also been shown in rats and humans.
– also aversive conditioning.
• CS, US, UR, CR?
• Taste Aversion Conditioning
– novel flavor (CS; often saccharin or chocolate
milk)
– CS?
• Taste
– US?
• LiCl
– UR?
• Illness
– CR?
• Illness
• How do you measure this?
• Conditioned Taste Aversion
– one-trial learning
– long-delay learning
• Eye-blink takes many many trials to learn
– Why the large difference?
• Preparedness to learn?
• Sign Tracking (AKA – autoshaping)
– Brown and Jenkins (1968)
• Key light reliably predicts food – Operant Chamber
• 8 second Key light then Food
– How do you think the pigeons behaved?
• Pigeons pecked the key
– remember pecking was not required
• The Long Box Study = Hearst and Jenkins (1974)
– Three feet long
• Key at one end
• Food at the other
– Video
• Temporal factors in conditioning
– Short Delayed Conditioning
• CS onset shortly precedes (less than a minute) US
onset.
– Trace conditioning
• a lag between CS offset and US onset.
• closer = stronger the conditioning will be
• too long = no conditioning
– Long delayed Conditioning
• CS onset occurs 5-10 minutes before US onset
– Simultaneous conditioning
• CS and US occur simultaneously
• ultimate in contiguity.
• weaker conditioning than above
– Backward Conditioning
• US offset occurs simultaneously with CS onset.
• Another example of contiguity of stimuli,
• Excitatory Conditioning?
– often results in inhibitory conditioning.
• What if CS = tone and US =shock?
– How would you recognize inhibitory conditioning?
– Safety behaviors
» Increased activity during CS
• Inhibitory Conditioning
• Backward US-CS pairings tend to cause
inhibitory conditioning.
– No salivation if food precedes the bell
– activity “safety” if the shock precedes the bell
• Conditioned inhibition can be difficult to
measure\
– such a small amount of initial behavior that it
cannot be decreased.
• saliva
– special procedures are needed
• Summation test
• Retardation test
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In the summation test an animal is trained in two ways.
1) they are trained that one (CS-) is a conditioned inhibitor using backward
conditioning.
US(food) CS1- (bell)
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2) they are trained that a second (CS+) is a conditioned exciter
CS2+( light)US(food).
Need at least two groups
summation group
Control
• train
US (food)CS1- (bell)
CS2+(light)US(food)
CS2+(light)US(food)
• test
CS1- and CS2+
CS1- and CS2+
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• Salivation to CS1?
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Salivation to CS2?
• Salivation to CS1- and CS2+?
• Note – increasing the baseline (by conditioning salivation) allows us to see this
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It is also interesting in its own right
independent learning about CS+s and CS-s can summate
• Retardation test
– this is a simple idea
– it should be more difficult to train an excitatory
response to a stimulus that has become a
conditioned inhibitor than it would be to one
that has not become a conditioned inhibitor
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phase 1
phase 2 (10 tr)
test
retardation gp
control
US(food)CS(bell)
CS(bell)(food)
CS alone
CS(bell)(food)
CS alone