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

8

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