Transcript LTFeb26
PSY402 Theories of Learning Wednesday February 26, 2003 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. 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. 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. 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. 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. 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. 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. 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. Is Fear Really Present? When avoidance behavior is welllearned 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. 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? 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). 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. 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 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. 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).