1. Classical Conditioning
Chapter 3
Classical Conditioning

2. 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

3. Terminology Unconditional stimulus (US) Unconditional response (UR)
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)

4. Conditioning and Awareness
Awareness of conditioning not required for learning

5. Innate US-UR is an innate stimulus-behaviour “Reflex” Hardwired
Stereotypic pattern of behaviour

6. Example: Bell and Food CS US UR CR Later Trials CS US UR
First Few Trials
Time
CS = bell
US = food
UR = salivation
CR = salivation

7. Processes Acquisition Extinction Acquiring a CR E.g., pair CS with US
Reduce/eliminate a CR
E.g., present CS without US

8. 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?

9. Example: Eyeblink Conditioning
CS (tone)
US (airpuff)
Airpuff on eye
Blink
UR vs. CR eyeblinks
UR blink faster than CR blink
CR (blink)
UR (blink)

10. 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

11. Higher-Order Conditioning
CSs and USs can be associated (First-order)
CSs can be associated with other CSs
Second-order conditioning

12. First-Order Conditioning
tone (CS1) food (US)
salivation (CR)

13. Second-Order Conditioning
light (CS2) tone (CS1)
salivation (CR)
Risk of extinction?
salivation (CR)
tone (CS1) food (US)

14. CS+ and CS- CS+ (excitatory CS) CS- (inhibitory 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

15. 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+

16. Testing for CS- 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

17. Short Delay Conditioning
Strongest and most rapid
Simple autonomic responses: 5-30 seconds
Quick skeletal responses: 0.5 seconds CS US or

18. Long Delay Conditioning
Other distracting stimuli?
Timing estimation required CS US or

19. Trace Conditioning From “memory trace” Must remember CS
Other stimuli interfere
trace interval CS US

20. Simultaneous Conditioning
Weaker than short delay
CS can’t signal onset of US
Not predictive CS US

21. Backward Conditioning
Ignores order; US comes first
CS has no predictiveness
Might become CS- CS US

22. Influences in Classical Conditioning

23. 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

24. CS-US Contingency If-then situation X iff Y
Consistency of pairing CS and US
Greater contingency, greater learning

25. Stimulus Features Nature of stimulus affects its conditioning ability
Intensity
Novelty

26. Compound Stimuli Two+ simple CSs presented at the same time
Paired with US

27. Overshadowing Salience
Exclusive regulation of CR by most salient CS in compound stimuli

28. Latent Inhibition Repeatedly present neutral stimulus (N)
Pair N with US
Harder to condition N as CS
CS- or habituation

29. Blocking CS1 -- US CS1 and novel stimulus (CS2) with US CS1 --> CR
CS2 --> no or very weak CR

30. 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.”

31. Sensory Preconditioing
Pair two neutral stimuli repeatedly
Pair one with US repeatedly until CR produced
Test other stimulus
CR produced

32. Number of CS-US Pairings
Acquisition curve
Non-linear
Asymptote
asymptote
CR Strength
Conditioning Trials

33. Intertrial Interval ITI
Time between each CS-US pairing (i.e., between trials)
Generally, around 30 seconds effective

34. Extinction of CR

35. Extinction CS without US --> Extinction
Weakening and stopping of CR
Not forgetting
A type of conditioning
CS paired with absence of US

36. Spontaneous Recovery After extinction, let time pass
Present CS again (no US)
Temporary, small return of CR
Shows extinction is not forgetting

37. Relearning/Reacquisition Effect
Extinguish CR
Recondition with CS-US pairing
Fewer trials required

38. Putting it Together Strength of CR Trials/Time Spontaneous Recovery
Acquisition
Extinction
Reacquisition
Strength of CR
CS&US
CS alone
CS alone
CS&US
Trials/Time

39. Theories of Classical Conditioning
Associationism, Stimulus Substitution, Preparedness, Rescorla-Wagner

40. Associationism Linking together of: Contiguity, similarity, contrast
Events
Memories
Actions and consequences
Contiguity, similarity, contrast
Central to study of learning and behaviour

41. Ebbinghaus’ Memory Experiments
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%

42. Major Findings List length Effects of repetition Effects of time
Overlearning
Effects of time
Role of contiguity
Backwards associations
Forgetting Curve
Time between study and relearning
20min
1hr
8.8hr
1day
2days
6days
31days
100 75 50 25
Percent Savings

43. Classical Conditioning
Innate US-UR reflex pathway
CS is associated with the US
Through the associative process, CR is produced

44. 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

45. 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

46. Biological Predispositions
Burns & Domjan (2000)
Timberlake & Grant (1975)

47. 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

48. Preparatory Response Theory
Learn responses that prepare organism for US occurrence
Sometimes CR same as UR, sometimes different

49. Example: Drug Tolerance
Neurophysiological dependencies
Siegel (1975)
Contextual stimuli act as CSs
Compensatory CR
Morphine

50. 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

51. 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

52. Interpretation US: Morphine UR: Pain reduction CS: Injection room
CR: Pain sensitivity
CS prepares rats for morphine injection
Body homeostasis

53. Rescorla-Wagner Theory
Contiguity account
Associative strength
CS acquires limited amount of associative strength on any one trial

54. Three Factors in Theory
Maximum associative strength
Difference between current and maximum strength
Number of additional CSs

55. 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 ( )
: maximum associative strength (magnitude of UR)
Vn-1: associative strength already accrued by CS

56. 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

57. Total associative strength Vn (or “VTotal”) after two trials:
First CS-US pairing:
DVn = c( - Vn-1)
DV1 = 0.25( )
= 2.5
Second CS-US pairing:
DV2 = 0.25( )
= 1.88
Total associative strength Vn (or “VTotal”) after two trials:
V1 + V2 = = 4.38
Third CS-US pairing:
DV3 = 0.25( )
= 1.41

58. Acquisition Phase  Trial DVn Vn (VTotal) 0 0.00 0.00 1 2.50 2.50
Trials
Associative Strength (Vn)
DV3
DV2
DV1

59. Extinction Example: After first extinction trial:
Set c = 0.25,  = 0.0
After first extinction trial:
DVn = c ( - Vn-1)
= 0.25( )
= -2.5

60. Extinction
Trials
Associative Strength (Vi)
 = 0.0
DV1
DV2
DV3

61. 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( )
Only 1 unit of associative strength left to split between the tone and the light
Ultimately, Vtone=9.5 and Vlight=0.5