PSY402 Theories of Learning

1. PSY402Theories of Learning Chapter 6, Traditional Theories

2. Two Theoretical Approaches • S-R associative theorists -- inflexible view of behavior. • Mechanistic • Stimulus acquires ability to elicit response through associations formed. • Cognitive theorists – flexible view. • Mentalistic • Learning involves recognition and understanding of environment.

3. Hull’s Drive Theory • Drive motivates behavior and drive reduction is responsible for the S-R associative learning. • Drive – an intense internal force. • Behavior is the combined influence of several factors, which can be expressed mathematically.

4. Hull’s Factors • Excitatory potential (expectation) SER – likelihood that an event will occur. • Drive (D) • Incentive motivation for reward (K) • Habit strength (H) – strength of the S-R association (experience). • Inhibition – also due to experience.

5. Sources of Drives • Unconditioned: • Physiological deprivation, metabolic imbalance. • Intense environmental events with survival consequences. • Pleasurable stimuli (such as saccharin) even without nutritional value. • Acquired – Pavlovian conditioned cues to unconditioned drives.

6. Habit Strength • SUR – an unconditioned or innate habit strength. • SHR – habit strength acquired through prior learning experiences. • If a response reduces a drive state, habit strength increases. • Drive reduction strengthens the S-R bond until behavior becomes habitual.

7. Inhibition • Reactive inhibition -- if a drive persists then all behavior is temporarily inhibited. • Conditioned inhibition – continued failure to reduce drive resulting in a permanent decrease in behavior. • The second strongest response in the habit hierarchy will be performed instead.

8. Incentive Motivation • Hull initially assumed that only drive reduction influences the S-R bond. • Crespi showed that reward magnitude affects responding. • If reward only influenced learning, the change should be more gradual. • Hull proposed that reward also influences motivation by increasing arousal.

9. Importance of Hull’s Theory • THE dominant theory in the 1930s-1960s. • Correct in many respects: • Intense arousal can motivate behavior. • Environmental stimuli can develop the ability to produce arousal, motivating behavior. • Value of the reward influences the intensity of behavior.

10. Problems With Hull’s Theory • You can get increases in behavior without drive reduction: • Olds & Milner, direct brain stimulation • Sensory deprivation motivates behavior to obtain stimulation (Harlow). • Hull’s theory does not explain how secondary rewards can acquire the ability to increase behavior.

11. Drive-Induction Theory • Sheffield -- drive-induction not reduction strengthens behavior. • Rewards produce excitement or arousal which motivates responding. • When secondary rewards are associated with primary rewards they elicit the same arousal. • Also explains Harlow’s findings.

12. Guthrie’s Contiguity Theory • Guthrie rejected the necessity of reward. • Contiguity is enough to establish an S-R association. • A response that occurs when a stimulus is present will automatically become associated with it. • Learning is entirely governed by co-occurrences – contiguity in time.

13. Impact of Reward • According to Guthrie, reward is important, but it does not strengthen the S-R association. • The effect of reward is to change the stimulus context present prior to reward. • New actions are conditioned to this revised stimulus context. • Reward prevents further conditioning of the undesired behavior.

14. Guthrie’s View of Punishment • Punishment is a stimulus that can either be escaped or avoided. • If a response terminates punishment, it will replace the punished behavior next time that context occurs. • Punishment works only if the response elicited by the punishment is incompatible with the punished behavior.

15. Importance of Practice • According to Guthrie, learning occurs in a single trial. • The strength of the S-R bond does not slowly increase with experience. • Performance increases because subjects must learn which stimuli are consistently present. • Over time, many different stimuli become associated with a response.

16. Criticisms of Contiguity Theory • Guthrie conducted few studies to support his theory. • Accurate parts: • Punishment can intensify inappropriate behavior when it elicits a response compatible with the punished response. • Contiguity is essential to prevent conditioning of competing associations. • Not all environmental cues are noticed.

17. Impact of Reward • Guthrie’s view of reward has been disproved. • If what happens after a response is not rewarding, an S-R association is not formed, even if the stimulus changes. • Noble – reward size predicts response better than recency or frequency (contiguity measures).

18. Single-Trial Learning • All-or-nothing (single-trial) learning has been difficult to demonstrate. • Voeks – found single-trial learning of an eye-blink response in humans. • Other studies report gradual learning. • Spence proposed a threshold explanation of single-trial learning using incremental learning theory.

19. Skinner • Emphasized the importance of environment (reinforcers & contingencies). • Validation of hypothetical constructs interferes with analysis of the variables controlling behavior. • Anti-theory

20. Spence’s Acquired Motives • Spence was a colleague of Hull. • Spence elaborated the idea that reward size matters (K in Hull’s theory). • It isn’t enough to say that reward size matters – how specifically does it affect behavior? • Spence proposed a mechanism.

21. Goal Responses • Reward elicits an unconditioned goal response RG. • This response produces an internal stimulus state SG that motivates consummatory behavior. • Reward value determines the size of the goal response RG.

22. Anticipatory Goal Responses • Cues become associated with reward through classical conditioning. • These produce an anticipatory goal response rG. • Cues lead to internal stimulus changes sG that motivate behavior. • Thus Pavlovian conditioning motivates approach behaviors.

23. Amsel’s Frustration Theory • Amsel applied Spence’s theory to avoidance of aversive events: • Frustration motivates avoidance. • Frustration suppresses approach. • Nonreward produces unconditioned frustration response RF. • The stimulus associated with it SF motivates escape behavior.

24. Anticipatory Frustration Response • As with goal states, classical conditioning results in anticipatory frustration response rF. • The conditioned stimuli associated with them sF motivate avoidance of a frustrating situation. • Example: car that won’t start. • SF motivates leaving the car, sF motivates selling it.

25. Mowrer’s Two-Factor Theory • Mowrer proposed a drive-based two-factor theory to avoid explaining avoidance using cognitive (mentalistic) concepts. • Avoidance involves two stages: • Fear is classically conditioned to the environmental conditions preceding an aversive event. • Cues evoke fear -- an instrumental response occurs to terminate the fear.

26. Mowrer’s View (Cont.) • We are not actually avoiding an event but escaping from a feared object (environmental cue). • Miller’s white/black chamber – rats escaped the feared white chamber, not avoided an anticipated shock. • Fear reduction rewards the escape behavior.

27. Criticisms of Two-Factory Theory • Avoidance behavior is extremely resistant to extinction. • Should extinguish with exposure to CS without UCS, but does not. • Levis & Boyd found that animals do not get sufficient exposure duration because their behavior prevents it. • Avoidance persists if long latency cues exist closer to the aversive event.

28. Is Fear Really Present? • When avoidance behavior is well-learned the animals don’t seem to be afraid. • An avoidance CS does not suppress operant responding (no fear). • However, this could mean that the animal’s hunger is stronger than the fear. • Strong fear (drive strength) is not needed if habit strength is large.

29. Avoidance without a CS • Sidman avoidance task – an avoidance response delays an aversive event for a period of time. • There is no external cue to when the aversive event will occur – just duration. Temporal conditioning. • How do animals learn to avoid shock without any external cues for the classical conditioning of fear?

30. Kamin’s Findings • Avoidance of the UCS, not just termination of the CS (and the fear) matters in avoidance learning. • Four conditions: • Response ends CS and prevents UCS. • Reponse ends CS but doesn’t stop UCS. • Response prevents UCS but CS stays. • CS and UCS, response does nothing (control condition).

31. D’Amato’s Acquired Motive View • D’Amato proposed that both pain and relief motivate avoidance. • Anticipatory pain & relief responses. • Shock elicits unconditioned pain response RP and stimulus SP motivates escape. • Classically conditioned cues sP elicit anticipatory pain response rP that motivates escape from the CS.

32. Anticipatory Relief Response • Termination of the UCS produces an unconditioned relief response RR with stimulus consequences SR. • Conditioned cues elicit an anticipatory relief response rR with stimulus consequences sR. • Example: dog bite elicits pain response, sight of dog elicits anticipatory pain, house elicits relief

33. A Discriminative Cue is Needed • During trace conditioning no cue is present when UCS occurs and no avoidance learning occurs. • A second cue presented during avoidance behavior slowly acquires rR-sR conditioning. • Similarly, in a Sidman task, cues predict relief -- associated with avoidance behavior, not the UCS.

34. How is rG Measured? • Anticipatory goal responses were initially measured as peripheral nervous system (ANS) response. • No consistent relationship between such measures and behavior could be found. • Now, Rescorla & Solomon propose that these anticipatory states are due to CNS activity (brain states).