PSY402 Theories of Learning

1. PSY402Theories of Learning Monday November 17, 2003 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