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Psychology (3,805)
PSYC 2330 (214)
Lecture 4

# Week 4.pdf

24 Pages
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School
University of Guelph
Department
Psychology
Course
PSYC 2330
Professor
Francesco Leri
Semester
Winter

Description
Week lecture 4 Rescorla-Wagner Model; Neurobiology of Prediction Error “Surprisingness” of the US Robert Rescorla & Allan Wagner The model is a mathematical expression of surprise: Learning will occur only when the subject is surprised - that is, when what happens is different from what the subject expected to happen Blocking (Leon Kamin) Group Phase 1 Phase 2 Test Result Blocking L-US L & T-US T no CR Control L & T-US T CR This experiment is important because it shows that: 1. Conditioning is not an automatic result of CS-US pairings 2. For conditioning to occur, the CS must be informative and the US surprising Reality Measure of size of CR during CS-US conditioning trials Theory V = associative strength between CS and US V max= maximum associative strength ▯V = change in associative strength on each conditioning trial Quantification of ▯surprisingness▯ of the US More Less surprise surprise ▯V = V max - Vn Vn= strength of the association at the beginning of trial n ▯Vn= change is the strength of the association produced by trial n Learning curves can differ in terms of: 1. V max 2. Rate of acquisition Vmaxis determined by the magnitude of the US ▯ and ▯ relate to the salience of the CS and the US, respectively. Their values are between 0 and 1. ▯V = n▯ (V max -▯V ) n ▯V =n▯▯ (V max - V n Rescorla-Wagner model: valuable predictions ▯V = ▯▯ (V -▯V ) n max n This model precludes quantitative predictions but allows interesting qualitative predictions (increases, decreases, and more). ACQUISITION Assume ▯▯ = 0.3 and Vmax = 1 Trial Vn ▯Vn = ▯▯ (Vmax - ▯Vn) 1 0.00 ▯V =10.3 (1 - 0.00) = 0.30 2 0.00 + 0.30 ▯V =20.3 (1 - 0.30) = 0.21 3 0.00 + 0.30 + 0.21 ▯V =30.3 (1 - 0.51) = 0.15 4 0.00 + 0.30 + 0.21 + 0.15 ▯V =40.3 (1 - 0.66) = 0.10 Vmax = 0 EXTINCTION The weakening of a conditioned response when a CS is presented by itself Trial Vn ▯Vn = ▯▯ (Vmax - ▯Vn) 1 0.00 ▯V =10.3 (1 - 0.00) = 0.30 2 0.00 + 0.30 ▯V =20.3 (1 - 0.30) = 0.21 3 0.00 + 0.30 + 0.21 ▯V =30.3 (1 - 0.51) = 0.15 4 0.00 + 0.30 + 0.21 + 0.15 ▯V =40.3 (1 - 0.66) = 0.10 1 Ext 0.00 + 0.30 + 0.21 + 0.15 + 0.10 ▯V =50.3 (0 - 0.76) = - 0.22 CONDITIONED INHIBITORS have negative associative strength BLOCKING When two CSs are used (a & b), the association or expectation at the beginning of a trial would be the sum of the strengths of each of the stimuli present ▯V = V + V ab a b Therefore, the amount of conditioning on a compound trial in which a and b occur together would be ▯V a ▯V = b▯ (V max- ▯V ab In the blocking group, if the Vmax for the light (L) = 1.0, then: VL= 1.0 at the end of Phase 1 (because of extensive L conditioning) when the light and the tone (T) are presented in combination on trial 1 of Phase 2 ▯V LT = VL+ V T 1.0 + 0 = 1.0 Therefore, the amount of conditioning to the T in the blocking group after 1 trial of conditioning with the LT compound is: ▯V T ▯▯ (V max- ▯V LT= 0.3 (1.0 - 1.0) = 0 Tone ------>shock Light ------>shock OVEREXPECTATION EFFECT Tone + Light-------> shock Tone ? Assume that only few trials w
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