PSY402 Theories of Learning Monday November 17, 2003 Chapter 6, Traditional Theories

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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