PSY 402Rescorla-Wagner Model4.1 Growth of associative strength (V) to a CS as a function of CS-US pairingsParts of the Model4.2 The effect of US magnitude on learning (Part 1)4.2 The effect of CS salience on learning (Part 2)Multiple Conditioned Stimuli (CS’s)BlockingUnblockingExtinction4.3 Conditioning and extinction in the Rescorla-Wagner modelInhibition4.4 The conditioning of inhibition in the Rescorla-Wagner modelProtection from ExtinctionOverexpectation Effect4.5 “Overexpectation” of the US: Kremer's two experiment designs (Part 1)4.5 “Overexpectation” of the US: Predictions (Part 2)4.5 “Overexpectation” of the US: Predictions (Part 3)Contextual Cues4.6 (A) Negative contingency between CS and US; (B) Zero contingency between CS and USComparator TheoriesProblems with Rescorla-Wagner4.7 (A) Mackintosh-Turner experiment; (B) Results of exposure to LN-shock trialsThe Mackintosh ModelCriticisms of the Mackintosh Model4.8 (A) A Hall and Pearce experiment design; (B) Results of conditioning during Phase 2Pearce Hall Model4.9 A rat orienting toward a light CS (Part 1)4.9 Orienting to the light CS with a US pairing (Part 2)PSY 402Theories of LearningChapter 4 – Theories of ConditioningRescorla-Wagner ModelClassical conditioning occurs only if the US (UCS) is surprising to the organism.If the UCS is already predicted by a CS, then it is not surprising – it is expected.When the CS predicts the UCS perfectly, no further learning occurs.The asymptote (lambda, ) is the point where the learning levels off (no increase in learning occurs).4.1 Growth of associative strength (V) to a CS as a function of CS-US pairingsasymptoteParts of the ModelV = ( – V)V is the Associative Strength (amount of learning).V is the change in learning (increase in Associative Strength. and are the salience of the CS and UCS – V is the surprisingness of the US (the distance away from the asymptote).4.2 The effect of US magnitude on learning (Part 1)Larger UCSSmaller UCS4.2 The effect of CS salience on learning (Part 2)Smaller CSLarger CSMultiple Conditioned Stimuli (CS’s)The basic model explains changes in learning with one UCS and one CS.This doesn’t explain what happens during blocking and unblocking, with multiple CS’s.V = ( – ΣV)When multiple CS’s are present, V is the sum of the associative strengths of all of the CS’s (such as VN + VL).BlockingFirst a noise is conditioned so that VN = 1.0Next a light is added. The formula predicts its associative strength:VL = ( – ΣV)ΣV = VN + VLIf we assume that and VN is 0 because no learning has occurred yet, then:VL = .2[1.0 – (1.0 + 0)] = 0UnblockingAs before, a noise is conditioned so that VN = 1.0A stronger US is presented with the new CS (VL).As before, the formula predicts its associative strength:VL = ( – ΣV)ΣV = VN + VLAgain, we assume that and VN is 0 but now the stronger US is 2.0 instead of 1.0:VL = .2[2.0 – (1.0 + 0)] = .2[1.0] = .2ExtinctionDuring extinction, the CS is presented without the UCS.This is the same as presenting a UCS with intensity = 0.The formula predicts the associative strength during extinction:VN = ( – V) but is now 0 (due to extinction)VN = .2[0 – 1] = -.2The associative strength is decreasing.Use the decreased value for VN (1-.2) for the next trial.4.3 Conditioning and extinction in the Rescorla-Wagner modelInhibitionDuring inhibition, a second CSL is presented that has never been associated with the UCS (V = 0).The formula predicts the associative strength for both CS’s: VN = ( – V) and VL = ( – V) VN = .2[0 – (1.0 + 0)] = -.2VL = .2[0 – (1.0 + 0)] = -.2V = VN + VL.4.4 The conditioning of inhibition in the Rescorla-Wagner modelProtection from ExtinctionWhen extinction of an excitor takes place together with extinction of an inhibitor, the excitor is never fully extinguished.This is called protection from extinction.To fully extinguish an excitor, and to extinguish it faster, pair it with another excitor (another CS associated with the US).The model predicts both of the these results.Overexpectation EffectThe value of a model is that it predicts new findings.If you pair two previously conditioned CS’s (excitors) on the same trial, V for each will decrease until V equals .This is because V “overexpects” the UCS.Similarly, if a new CS (X) is added to the pair, it will become an inhibitor.4.5 “Overexpectation” of the US: Kremer's two experiment designs (Part 1)4.5 “Overexpectation” of the US: Predictions (Part 2)4.5 “Overexpectation” of the US: Predictions (Part 3)Contextual CuesContextual cues consist of everything in the environment in addition the CS and UCS.They cannot be ignored simply because the experimenter is not manipulating them.Whenever a CS or a UCS appears “alone,” it is still being paired with the context.When the context is considered another CS, then ideas about blocking explain learning.Zero contingency occurs because context is blocked.4.6 (A) Negative contingency between CS and US; (B) Zero contingency between CS and USCS becomes an inhibitorNo learning occursComparator TheoriesAn alternative theory to Rescorla-Wagner proposes that the CS and UCS are associated and the UCS and context are associated.The two sets of associations are compared to determine the amount of responding to the CS.The comparison determines the responding, not the learning.Strengthening or weakening the context, after learning, affects the amount of responding, supporting the theory.Problems with Rescorla-WagnerIt predicts that presenting an inhibitory CS without the UCS should lead to extinction, but it doesn’t.The model cannot account for latent inhibition (preexposure to the CS).Mackintosh demonstrated that animals learn to ignore redundant stimuli – the model doesn’t predict this learning.4.7 (A) Mackintosh-Turner experiment; (B) Results of exposure to LN-shock trialsMore learningLess learningThe Mackintosh ModelMackintosh proposed that the amount of learning depends on how much attention the animal pays to the CS.The attention to the CS is the term in the Rescorla-Wagner
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