1. PSY402 Theories of Learning
Chapter 5
Theories of Pavlovian Conditioning

2. Contemporary Theories
Nature of the CR – stimulus substitution theory, SOP and AESOP theory
Nature of the conditioning process:
Predictiveness of the CS – the Rescorla-Wagner associative model
Miller’s Comparator theory
Mackintosh’s attentional theory
Retrospective processing approach

3. Comparison of Theories

4. Stimulus-Substitution Theory
What is the nature of the CR – is it just the UCR or is it different?
Pavlov – stimulus-substitution theory:
The CS stimulates the same areas of the brain as the UCS, producing the same response.
Activation of CS together with UCS establishes a neural connection between brain areas.

5. Connections are formed between brain regions

6. Conditioned Opponent Response
The CR and UCR are often different:
CR of fear is different than UCR of pain.
Siegel – best evidence of difference:
Morphine (UCS) produced analgesia, reduced pain (UCR)
Light or tone (CS) produced hyperalgesia, increased pain (CR).
Rats remove paws from heat quickly with CS, slowly with UCS.
Insulin (glycemia) works the same way, producing hypoglycemia as a CR.

7. Conditioning of the Opponent Response (Tolerance)
The M-P-M condition presents the CS without the UCS so the tolerance is extinguished.

8. Drug Tolerance Overdoses
Elimination of a CS results in a stronger response to the UCS, drug.
Extinction of responding to environ-mental cues strengthens drug response
Changing the context in which a drug is administered increases response to the drug.
Novel environment does not elicit an opponent CR.
No difference between small and large doses – both elicit the same withdrawal effect (opponent CR).

9. SOP Theory
Sometimes-Opponent-Process theory (SOP) – explains why CR varies.
UCS elicits primary A1 (fast) and secondary A2 (longer) responses.
A1 & A2 can be same or different.
Conditioning only occurs to A2 – the CR is always an A2 response.
When A1 & A2 differ, UCR & CR differ.

10. SOP Explains Timing Effects
None of the previous models explain why the timing of CS-UCS matters.
SOP model requires that both CS and UCS be in the A1 stage for learning to occur.
With delay more elements of CS decay from A1, becoming A2.
The CR is always the A2 response.

11. Activation of a memory node in SOP theory
bouton-fig jpg

12. bouton-fig jpg

14. Two-Phase Reactions Shock – results in: Morphine – results in:
A1 -- Initial agitated hyperactivity
A2 -- Long-lasting hypoactivity (freezing)
CER (fear) elicited by CS is A2
Morphine – results in:
A1 – sedation, analgesia & hypoactivity
A2 – hyperactivity two hours later & hyperalgesia (greater pain sensitivity)
CR elicited by CS is A2 (hyper)

15. A2 Morphine Hyperactivity
Environment elicits A2 hyperactivity

16. When A1 & A2 Are the Same
Grau showed that unconditioned responding to radiant heat produced:
Instant, short-duration hypoalgesia (decreased sensitivity to pain)
Followed by persistent hypoalgesia, opioid based
The existence of distinct A1 & A2 responses was demonstrated using naloxone, which blocks A2 (opioid) but not A1 (non-opioid).

17. Two Circuits in Rabbit Eyeblinks
Fast-acting direct circuit (A1) to sensory trigeminal nucleus to motor nuclei
Slow-acting A2 circuit through inferior olive

18. Affective Extension of SOP Theory
Why do different A2 responses have different optimal CS-UCS intervals?
Two distinct UCR sequences activate distinct A1 & A2 sequences:
A1 -- Sensory
A2 -- Emotive
These distinct sequences can have different strengths, time scales (latencies), or eliciting CS’s.

19. Faster
bouton-fig jpg
Slower

20. The Nature of Conditioning
Theories about the nature of conditioning have difficulty explaining three observed phenomena:
Preexposure effects
Overshadowing
Blocking

21. Rescorla-Wagner Theory
There is a maximum associative strength between CS and UCS.
UCS determines the limit
Strength gained on each training trial depends on prior training – diminishing returns.
More learning early, less later on
Rate of conditioning varies.
Conditioning of a CS depends on prior conditioning to other stimuli with that UCS.

22. Rates of Conditioning Vary

23. Rescorla Wagner Model

24. UCS Preexposure Effect
If the UCS is encountered without the CS prior to pairing of the two, less learning occurs.
UCS becomes associated with other environmental stimuli (without CS).
Since there is a limit to association strength, some is drained off by such prior associations.
CS-UCS association is weakened.
Rescorla-Wagner explains this fine

25. Problems with Rescorla-Wagner
Overshadowing – salient cues have more associative strength.
Sometimes a salient cue potentiates another cue instead of overshadowing.
Garcia says cues are indexed as food-related.
R-W says the two cues are seen as a unitary stimulus (one joint CS).
Unclear which explanation is correct.

26. UCS Preexposure Effect
+C1/C1 Preexposure and conditioning in same environment
+C1/C2 Preexposure in one environment and conditioning in another
-C1/C1 & -C1/C2 are control groups with no preexposure

27. More Problems
CS preexposure effect – appearance of CS without UCS prior to learning weakens learning.
Shouldn’t have any effect according to Rescorla-Wagner theory, but it does.
Cue-deflation effect – extinction of a more salient cue enhances learning for the less salient cue.
Should be no change according to R-W.

28. Comparator Theory
If two CS’s are associated, extinction of one should reduce responding to the other.
Sometimes true, other times not. Why?
CS-UCS associations exist for many stimuli but are exhibited only for the strongest.
Comparator theory says the CS’s are judged in relation to each other.

29. Organisms might learn about elemental or configural CS nodes
Wagner & Brandon
bouton-fig jpg
Pearce

30. Attentional View
Mackintosh – learned irrelevance occurs during preexposure of CS.
Animals exposed to a novel stimulus exhibit an orienting response.
No orienting with preexposure.
Habituation results in failure of conditioning – no attention is paid to a habituated stimulus.
Pairing of CS/UCS in novel context results in learning.

31. Learned Irrelevance

32. Retrospective Processing
Most theories assume the level of responding will be constant after learning.
Baker & Mercier suggest association can change after learning.
Retrospective processing – CS-UCS contingency reevaluated after learning.
Backward blocking – support for theory
Suggests animals have mental representations, memory for events.

33. Comparison of Theories