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Negative Reinforcement Escape Negative reinforcement - Avoidance Avoidance: Experimental Paradigm Light = CS Light Shock Shuttling stops shock The shuttle box Two-Process Theory of Avoidance Light Shock ( = Pavlovian Conditioning) -Light elicits fear Shuttling Reduction of Fear (= negative reinforcement) Now, what happens with continued training? Learned Helplessness Paradigm “Triadic” Design Phase 1 Group A: Escapable Shock Group B: Yoked Inescapable Shock Phase 2 Escape/Avoidance training Group C: Exposure to apparatus only (For Group A shock can be terminated by rotating a wheel.) Phase 2 Results Inescapable shock Inescapable shock Possible Explanations • Learned Helplessness: Organisms learn that their behavior is ineffectual • Poverty of activity: inescapable shock reduces the variability in behavior that is so crucial for operant conditioning • Inattention: animals stop attending to their own behavior LH in the Spinal Cord • Recall: many reflexes are mediated within the spinal cord. • Operant conditioning can occur within SC (escape/avoidance of leg shock after SC transection) • Grau: Experience with inescapable legshock will prevent subsequent avoidance learning. LH in Humans LH produced by… insoluble logic problems living in a crowded dorm LH in the Spinal Cord • Recall: many reflexes are mediated within the spinal cord. • Operant conditioning can occur within SC (escape/avoidance of leg shock after SC transection) • Grau: Experience with inescapable legshock will prevent subsequent avoidance learning. Extinction Session 1 Extinction Session 2 Session 3 Spontaneous recovery occurs as a function of time 8-day break no break no CS Theories of Extinction • Forgetting? • Associative loss? (= “reverse acquisition”) Extinction Associative Loss “Renewal” Train Tone Shock Extinguish Test Tone - Tone: CR Tone - Tone: CR Context A Context B Bouton & King (1983) In contrast, acquisition is not context-specific Train Tone Shock Test Tone: CR Tone: CR Context A Context B Extinction Associative Loss “Reinstatement” Train Extinguish Reinstatement Shock alone ToneShock Test Tone: CR Tone -- Tone: CR Extinction Associative Loss Post-extinction sensitivity to outcome devaluation Rescorla 1996 So, what is learned in extinction? An inhibitory SR association? Context S R Inhibitory SR Associations Theory • In extinction, the context effectively becomes a conditioned inhibitor. • Why? Just like in normal CI, there is the violation of expectations of reinforcement • But is this true? Inhibitory SR Associations Does extinction produce them? • Summation test Train Ext Test A+/B+ A- Test: AB Does A inhibit responding to B? • Retardation test Train A+ Ext A- Train AB+ Does A inhibit acquisition to B? So, what is learned in extinction? An inhibitory SR association? Context S R Paradoxical Effects of Reward • Overtraining extinction effect: more training leads to faster extinction • Reinforcement magnitude effect: Big rewards lead to faster extinction • And, of course, the partial reinforcement extinction effect (PREE) Paradoxical effects of reward: Why? • Frustration hypothesis (Amsel): animals learn to make response as a reaction to nonreward. • Discrimination hypothesis: Nonreinforcement is easier to detect after CRF than PRF. • Sequential theory (Capaldi): The memory of nonreinforcement becomes a cue that elicits responding.