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Chapter 3. Classical Conditioning. Ivan Petrovich Pavlov (1849-1936). Classical (Pavlovian) conditioning Medical physiologist Digestion Human/animal differences Conditioned reflexes. en.wikipedia.org/wiki/File:Ivan_Pavlov_(Nobel).png en.wikipedia.org/wiki/File:One_of_Pavlov%27s_dogs.jpg.

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Chapter 3 l.jpg

Chapter 3

Classical Conditioning


Ivan petrovich pavlov 1849 1936 l.jpg
Ivan Petrovich Pavlov (1849-1936)

  • Classical (Pavlovian) conditioning

  • Medical physiologist

  • Digestion

  • Human/animal differences

  • Conditioned reflexes

en.wikipedia.org/wiki/File:Ivan_Pavlov_(Nobel).png

en.wikipedia.org/wiki/File:One_of_Pavlov%27s_dogs.jpg


Terminology l.jpg
Terminology

  • Unconditional stimulus (US)

    • Stimulus that elicits the innate reflex (e.g., food)

  • Unconditional response (UR)

    • Reflex action that occurs in response to US (e.g., salivation)

  • Conditional stimulus (CS)

    • Any stimulus that doesn’t originally elicit the UR (e.g., bell)

  • Conditional response (CR)

    • The action elicited by the CS (e.g., salivation)


Conditioning and awareness l.jpg
Conditioning and Awareness

  • Awareness of conditioning not required for learning


Innate l.jpg
Innate

  • US-UR is an innate stimulus-behaviour

  • “Reflex”

  • Hardwired

  • Stereotypic pattern of behaviour


Example bell and food l.jpg

Later Trials

First Few Trials

CS

CS

US

US

UR

CR

UR

Time

Example: Bell and Food

CS = bell

US = food

UR = salivation

CR = salivation


Processes l.jpg
Processes

  • Acquisition

    • Acquiring a CR

    • E.g., pair CS with US

  • Extinction

    • Reduce/eliminate a CR

    • E.g., present CS without US


Measuring conditioning l.jpg
Measuring Conditioning

  • Sometimes difficult to measure CR

    • e.g., if CS & US close together, CR & UR can overlap

  • Test trial (probe trial)

    • Give CS alone

  • Intensity

    • Does CR intensity increase with experience?


Example eyeblink conditioning l.jpg

UR (blink)

US (airpuff)

CR (blink)

Example: Eyeblink Conditioning

CS (tone)

  • Airpuff on eye

  • Blink

  • UR vs. CR eyeblinks

    • UR blink faster than CR blink


Example taste aversion l.jpg
Example: Taste Aversion

  • Very strong

  • Very persistent

  • Usually conditioned after one presentation

  • Experiment

    • Rats fed novel food (CS)

    • Injected with lithium chloride (US)

    • Choice: novel food or regular food

    • Chose regular food


Higher order conditioning l.jpg
Higher-Order Conditioning

  • CSs and USs can be associated (First-order)

  • CSs can be associated with other CSs

  • Second-order conditioning


First order conditioning l.jpg

first-order

tone (CS1) food (US)

First-Order Conditioning

salivation (CR)


Second order conditioning l.jpg

second-order

light (CS2) tone (CS1)

tone (CS1) food (US)

salivation (CR)

Second-Order Conditioning

salivation (CR)

Risk of extinction?


Cs and cs l.jpg
CS+ and CS-

  • CS+ (excitatory CS)

    • CS predicts occurrence of US

    • Activates behaviour related to US

  • CS- (inhibitory CS)

    • CS predicts non-occurrence of US

    • Suppresses behaviour related to US


Slide15 l.jpg

PAVLOV’S PROCEDURE

Trial Type A

Trial Type B

CS+

CS-

US

  • Randomize trial type presentation

NEGATIVE CONTINGENCY PROTOCOL

CS-

US

  • Context cues serve as CS+


Testing for cs l.jpg

CS- produces absence of CR

No CR

You’ve produced CS-

Haven’t learned anything

How to measure nothing…

Summation test

Measure CR with CS+

Compound stimulus of CS+ & CS-; measure CR

Retardation of acquisition

Trained CS- and novel stimulus; pair both with novel US for same number of trials

Measure CR for both

Prior learning of CS- inhibits learning new association

Testing for CS-


Short delay conditioning l.jpg

or

Short Delay Conditioning

  • Strongest and most rapid

  • Simple autonomic responses: 5-30 seconds

  • Quick skeletal responses: 0.5 seconds

CS

US


Long delay conditioning l.jpg

or

Long Delay Conditioning

  • Other distracting stimuli?

  • Timing estimation required

CS

US


Trace conditioning l.jpg

trace interval

Trace Conditioning

  • From “memory trace”

  • Must remember CS

  • Other stimuli interfere

CS

US


Simultaneous conditioning l.jpg
Simultaneous Conditioning

  • Weaker than short delay

  • CS can’t signal onset of US

    • Not predictive

CS

US


Backward conditioning l.jpg
Backward Conditioning

  • Ignores order; US comes first

  • CS has no predictiveness

  • Might become CS-

CS

US



Cs us contiguity l.jpg
CS-US Contiguity

  • Closeness together in time and/or space

  • Usually, more learning if greater contiguity between CS & US

  • Type of conditioning may influence this

  • e.g., eyeblink vs. taste aversion


Cs us contingency l.jpg
CS-US Contingency

  • If-then situation

  • X iff Y

  • Consistency of pairing CS and US

  • Greater contingency, greater learning


Stimulus features l.jpg
Stimulus Features

  • Nature of stimulus affects its conditioning ability

  • Intensity

  • Novelty


Compound stimuli l.jpg
Compound Stimuli

  • Two+ simple CSs presented at the same time

  • Paired with US


Overshadowing l.jpg
Overshadowing

  • Salience

  • Exclusive regulation of CR by most salient CS in compound stimuli


Latent inhibition l.jpg
Latent Inhibition

  • Repeatedly present neutral stimulus (N)

  • Pair N with US

  • Harder to condition N as CS

  • CS- or habituation


Blocking l.jpg
Blocking

  • CS1 -- US

  • CS1 and novel stimulus (CS2) with US

  • CS1 --> CR

  • CS2 --> no or very weak CR


Textbook error p 77 l.jpg
Textbook Error: p. 77

  • “But suppose we eat two foods, one spicy and the other bland. If we then become sick, thanks to blocking we are likely to develop an aversion to the spicy food -- even though it may have been the bland food that caused our illness.”


Sensory preconditioing l.jpg
Sensory Preconditioing

  • Pair two neutral stimuli repeatedly

  • Pair one with US repeatedly until CR produced

  • Test other stimulus

  • CR produced


Number of cs us pairings l.jpg
Number of CS-US Pairings

  • Acquisition curve

  • Non-linear

  • Asymptote

asymptote

CR Strength

Conditioning Trials


Intertrial interval l.jpg
Intertrial Interval

  • ITI

  • Time between each CS-US pairing (i.e., between trials)

  • Generally, around 30 seconds effective



Extinction l.jpg
Extinction

  • CS without US --> Extinction

  • Weakening and stopping of CR

  • Not forgetting

  • A type of conditioning

  • CS paired with absence of US


Spontaneous recovery l.jpg
Spontaneous Recovery

  • After extinction, let time pass

  • Present CS again (no US)

  • Temporary, small return of CR

  • Shows extinction is not forgetting


Relearning reacquisition effect l.jpg
Relearning/Reacquisition Effect

  • Extinguish CR

  • Recondition with CS-US pairing

  • Fewer trials required


Putting it together l.jpg

Spontaneous

Recovery

Reacquisition

Acquisition

Extinction

Putting it Together

Strength of CR

CS&US

CS alone

CS alone

CS&US

Trials/Time


Theories of classical conditioning l.jpg

Theories of Classical Conditioning

Associationism, Stimulus Substitution, Preparedness, Rescorla-Wagner


Associationism l.jpg
Associationism

  • Linking together of:

    • Events

    • Memories

    • Actions and consequences

  • Contiguity, similarity, contrast

  • Central to study of learning and behaviour


Ebbinghaus memory experiments l.jpg
Ebbinghaus’ Memory Experiments

  • 1880s

  • Nonsense syllables

    • E.g., ZOG, PAF, TOB

  • One subject

  • Recite from memory

  • Savings

    • E.g., if 10 trials initially, then after a delay 3 more trials, savings = (10-3)/10 = 7/10 = 70%


Major findings l.jpg

100

75

Percent Savings

50

25

20min

1hr

8.8hr

1day

2days

6days

31days

Time between study and relearning

Major Findings

Forgetting Curve

  • List length

  • Effects of repetition

    • Overlearning

  • Effects of time

  • Role of contiguity

  • Backwards associations


Classical conditioning l.jpg
Classical Conditioning

  • Innate US-UR reflex pathway

  • CS is associated with the US

  • Through the associative process, CR is produced


Stimulus substitution theory l.jpg
Stimulus Substitution Theory

  • Pavlov

  • CR and UR produced by same neural region

  • CS takes on properties of US

  • Substitution

  • CR should be the same as UR


Example sign tracking l.jpg
Example: Sign Tracking

  • Response not required

  • US often food

  • Stimulus (CS) indicates US availability

  • Subject “tracks” the sign more and more

  • CS takes on properties of US

  • Pigeon autoshaping

  • Longbox autoshaping

F

= CS

F

= US


Biological predispositions l.jpg
Biological Predispositions

Burns & Domjan (2000)

Timberlake & Grant (1975)


Problems with sst l.jpg
Problems with SST

  • CS not a complete substitute for US

    • e.g., eyeblink differences

    • Magnitudes

  • CSs produce different responses

    • Omissions and additions

  • Compensatory conditional responses


Preparatory response theory l.jpg
Preparatory Response Theory

  • Learn responses that prepare organism for US occurrence

  • Sometimes CR same as UR, sometimes different


Example drug tolerance l.jpg
Example: Drug Tolerance

  • Neurophysiological dependencies

  • Siegel (1975)

  • Contextual stimuli act as CSs

  • Compensatory CR

  • Morphine


Contextual stimuli theory l.jpg
Contextual Stimuli Theory

  • Rats on hotplate

  • Between-groups study

  • Independent variables:

    • Morphine or placebo

    • Location of injection (Home or Injection room)

  • Dependent variable: time to lift feet


Results l.jpg
Results

  • Control (placebo): 13 sec.

  • Exp. Gr. 1 (morphine): 24 sec. (day 1) to 13 sec. (day 4)

    • Injection room gives contextual cues

    • Compensatory CR

  • Exp. Gr. 2 (morphine):

    • Day 1-3 injection room: 24 --> 13 sec. latency

    • Day 4 home room: 28 sec. latency


Interpretation l.jpg
Interpretation

  • US: Morphine

  • UR: Pain reduction

  • CS: Injection room

  • CR: Pain sensitivity

  • CS prepares rats for morphine injection

  • Body homeostasis


Rescorla wagner theory l.jpg
Rescorla-Wagner Theory

  • Contiguity account

  • Associative strength

  • CS acquires limited amount of associative strength on any one trial


Three factors in theory l.jpg
Three Factors in Theory

  • Maximum associative strength

  • Difference between current and maximum strength

  • Number of additional CSs


Rescorla wagner equation l.jpg
Rescorla-Wagner Equation

DVn = c( - Vn-1)

DVn: change in associative strength for CS on one trial

c: represents salience of CS and US; a constant (0.0-1.0)

: maximum associative strength (magnitude of UR)

Vn-1: associative strength already accrued by CS


Acquisition phase l.jpg
Acquisition Phase

  • Example: set c = 0.25,  = 10.0

  • Vn-1 starts at 0.0

    • For the first trial Vn-1 = V1-1 = V0

    • For the second trial Vn-1 = V2-1 = V1


Slide57 l.jpg

  • Second CS-US pairing:

    DV2 = 0.25(10.0 - 2.5)

    = 1.88

  • Total associative strength Vn (or “VTotal”) after two trials:

    V1 + V2 = 2.5 + 1.88 = 4.38

  • Third CS-US pairing:

    DV3 = 0.25(10.0 - 4.38)

    = 1.41


Acquisition phase58 l.jpg

DV3

Associative Strength (Vn)

DV2

DV1

Trials



Acquisition Phase

Trial DVn Vn (VTotal)

0 0.00 0.00

1 2.50 2.50

2 1.88 4.38

3 1.41 5.79

4 1.05 6.84

5 0.79 7.63

6 0.59 8.22

7 0.45 8.67

8 0.33 9.00

9 0.25 9.25

10 0.19 9.44


Extinction59 l.jpg
Extinction

  • Example:

    • Set c = 0.25,  = 0.0

  • After first extinction trial:

    DVn = c ( - Vn-1)

    = 0.25(0.0 - 10.0)

    = -2.5


Extinction60 l.jpg

DV3

Associative Strength (Vi)

DV2

DV1

Trials

 = 0.0

Extinction


Blocking61 l.jpg
Blocking

  • Learned CS blocks subsequent CSs

  • Example

    • CS = tone, novel CS = light

    • c = 0.25,  = 10.0

    • Completed 8 trials with just tone, V8 = 9.0

    • DVn = 0.25(10.0 - 9.0)

  • Only 1 unit of associative strength left to split between the tone and the light

  • Ultimately, Vtone=9.5 and Vlight=0.5


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