PSY402 Theories of Learning

1. PSY402Theories 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

14. Two-Phase Reactions • Shock – 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 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 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