Chapter 3: Pavlovian Conditioning: Foundations
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Transcript of Chapter 3: Pavlovian Conditioning: Foundations
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 • 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• 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
• Let’s go through an example in more detail– consider Empiricists rules of association (chapter 1)
• Saliency– CS
• Tone• 10 seconds• 500Hz• 70 db
– US • 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)
• Frequency– trials: = 60 (frequency of associations or number of trials can affect strength of
conditioning– Test every 10th trial
• How do we test?
• Let’s look at how the findings might have come out
• Graph– Y axis?– X axis?
• Baseline
0 10 20 30 40 50 600
2
4
6
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10
12
Idealized (made up) Data
Trials
CR (S
aliv
atio
n in
mls
.)
• 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 non-contingent 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
– USCS – 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
• 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)
• 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+ • • Salivation to CS1?• Salivation to CS2?• Salivation to CS1- and CS2+?• Note – increasing the baseline (by conditioning salivation) allows us to see this
– 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
retardation gp control• phase 1 US(food)CS(bell)• phase 2 (10 tr) CS(bell)(food) CS(bell)(food)• test CS alone CS alone