PSY402 Theories of Learning

1. PSY402Theories of Learning Monday December 1, 2003 Chapter 9 – Contemporary Theories

2. Contemporary Theories • Shift from global theories (e.g., Hull’s drive theory) to theories about specific aspects of learning. • Global theories were about operant responding not classical conditioning. • An animal’s biology influences whether, what, and how fast it can learn. • Cognitive view requires emphasis on specific cognitive processes.

3. Contemporary Theories (Cont.) • Classical Conditioning: • Nature of the CR – stimulus substitution theory and SOP theory • Predictiveness of the CS – Rescorla-Wagner associative model, comparator theory, attentional theory, retrospective processing approach. • Operant Conditioning: • Nature of reinforcement • Behavioral economics

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 with UCS establishes neural connection between brain areas.

5. 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

6. 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.

7. 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.

8. Two-Phase Reactions • Shock – results in: • A1 -- Initial agitated hyperactivity • A2 -- Long-lasting hypoactivity (freezing) • CER elicited by CS is A2 • Morphine – results in: • A1 – sedation or hypoactivity • A2 – hyperactivity two hours later • CR elicited by CS is hyperactivity

9. More Support for SOP Theory • Rabbit eyeblink mechanisms support the idea of two-phases. • Backward conditioning – learning occurs if the CS is presented just before the peak of the A2 response. • Larew – conditioning occurred with a 31 sec lapse but not 60 sec or 1 sec.

10. 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: • Sensory • Emotive • These distinct sequences can have different strengths, time scales (latencies), or eliciting CS’s.

11. 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. • More learning early, less later on • Rate of conditioning varies. • Conditioning of a CS depends on prior conditioning to other stimuli.

12. 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.

13. 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. • R-W says cues are seen as unitary stimulus. • Unclear which explanation is correct.

14. 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.

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

16. 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. • Pairing of CS/UCS in novel context results in learning.

17. 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.

18. 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.

19. Operant Conditioning • Nature of reinforcement: • Premack’s probability differential theory • Response deprivation theory • Behavioral economics: • Behavioral allocation – blisspoint • Choice behavior – Herrnstein’s matching law. • Momentary maximization theory • Delay-reduction theory

20. Probability-Differential Theory • Premack – a reinforcer can be any activity that is more likely to occur than the reinforced behavior. • Manipulators vs eaters • High probability behaviors can be used as reinforcers of low probability behaviors. • Frequency of the reinforcer decreases when it is made contingent on another response.

21. Response Deprivation Theory • Timberlake & Allison – deprivation occurs when an activity is used as a reinforcer and is not freely emitted. • The activity is reinforcing because it satisfies the deprivation created. • The animal tries to return to its pre-deprivation level of responding. • Activities can be reinforcing even if their baselines were not higher.

22. Behavioral Allocation • Blisspoint (paired basepoint) – the free operant level of two responses. • Unrestricted responding with two choices of behaviors. • Blisspoint is used to figure out how much behavior an animal will engage in to obtain a reward. • Animals try to get as close to the blisspoint as possible.

23. Problems with Contingencies • Blisspoint is established by looking at behavior before a contingency is established. • The established contingency must take blisspoint into account or it may not increase desired behavior.

24. Choice Behavior • Herrnstein’s matching law – describes how animals act when they have two or more choices. • Different responses have different schedules of reinforcement. • Responding to each choice is proportionate to the reinforcement for each choice – after learning. • This can be expressed mathematically.

25. Delayed Gratification • Why does anyone choose a smaller reward part of the time? • Animals and people typically choose a small immediate reward over a larger delayed reward. • Large rewards are selected when: • The choice is made in advance of reward. • Reinforcers are not visible or reward is already present (pleasurable activity).

26. Complexities of the Matching Law • Maximizing law – sometimes the aim is to obtain as many rewards as possible. • Explains FR-10 vs FR-40 schedules. • Doesn’t work for VI vs VR schedules. • Momentary maximization theory – choose best alternative at the time. • Delay reduction theory – choose what will get the reward the fastest.