Transcript LTFeb10
PSY402 Theories of Learning Monday February 10, 2003 Partial Reinforcement Effect (PRE) Extinction is slowest when behavior was intermittently reinforced during learning. With humans, the lower the slot machine payoff, the longer people play (resistance to extinction). But, if the percent of reinforced trials is too low, rapid extinction occurs (U-shaped relationship). Explanations for PRE Two explanations: Amsel – frustration-based Capaldi – sequential theory Both provide good explanations for observed data. Amsel’s Frustration Theory Frustration leads to rapid extinction during continuous reinforcement. During intermittent reinforcement, frustration becomes associated with responding. Frustration then elicits not suppresses responding. Capaldi’s Sequential Theory If reward follows a nonrewarded trial, memory of the nonrewarded trial is associated with responding. During continuous reinforcement, animals do not associate lack of reward with responding. When they encounter the first nonrewarded trial, the state it produces is not associated with responding. Contingency Management Assessment phase – determine the frequency of behavior and the situations in which it occurs. Contracting phase – specifies the relationship between responding and reinforcement. Management phase – implement the contract and evaluate results. Aversive Conditioning Chapter 5 Aversive Events Unpleasant, undesirable, bad for survival. Typically evoke strong negative emotion: Pain, fear, embarrassment or shame, anxiety, frustration. Strong emotions motivate escape and avoidance behaviors. Escape Conditioning Escape response – behavior motivated by an aversive event. Rewarded by termination of the aversive event. Miller’s shuttlebox – rats escape shock by turning a wheel that opens a door so they can escape. Factors Affecting Escape Intensity of the aversive event – the stronger the aversive event the greater the escape response. Amount of negative reward – escape depends on receiving relief from the aversive event. Reward must be prompt – delayed reward interferes with escape learning. Eliminating an Escape Response Removal of negative reward – escape response stops if the aversive event continues despite it. Removal of aversive event -- escape response stops if the aversive event no longer occurs. Continues for a while due to conditioned anticipatory pain responses. This must be extinguished. Vicious-Circle Behavior Why did rats run into a pathway with shock when staying still would mean no shock? Two explanations: Fear motivates running and is conditioned to the start box. The animals do not realize that no shock will occur if they don’t run. Avoidance Active avoidance response – an action is necessary to avoid aversive event. Passive avoidance response – not responding prevents aversive event. Mowrer’s hurdle jumping paradigm. CS causes animal to jump to other side to avoid onset of shock. Effects of Event Intensity Except in two-way avoidance learning, a stronger aversive event leads to faster avoidance learning. The greater the aversive event intensity, the faster the passive avoidance learning. Greater delay between CS and UCS interferes with avoidance learning. One-Way vs Two-Way Avoidance One-way – animal can avoid shock by jumping to other side. Two-way – animal can jump to other side, but after a rest, it must jump back again to avoid shock. Animal avoids shock only by returning to the place where it was first shocked. The animal must ignore situational cues. Induces a conflict. Flooding Avoidance behaviors perpetuate phobias. Techniques for eliminating avoidance are important to treating phobias. Flooding forces a person to experience the conditioned feared stimulus without an aversive consequence.