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Classical Conditioning II
What are the necessary conditions for classical
conditioning?
CS USDelay
CS USTrace
CS USExplicitly Unpaired CS
minutes
Wea
ker
cond
itio
ned
resp
ondi
ng
Is contiguity necessary?
Conditioned taste aversion methodology
Distinctive flavor
LiCl injection
Choice Test
vs
?
Is contiguity sufficient?
CS-US belongingness
From Garcia & Koelling, 1966
Conclusion thus far:
• Forward pairings (contiguity) neither necessary nor sufficient.
• Something more is required– Belongingness– Kamin: Surprise
Leon Kamin: Blocking
Group Phase 1 Phase 2 TestBlock AUS AXUS X?Control BUS AXUS X?
US has to be “surprising” to the animal for learning of the CS-US association to occur.
Because A already predicts the US in the Blocking group, the US is not surprising during Phase 2 trials.
Conclusion thus far:
• Forward pairings (contiguity) neither necessary nor sufficient.
• Something more is required– Belongingness– Kamin: Surprise– Relative salience
Salience effects
Overshadowing – in compound conditioning, the more salient CS wins
Group Treatment Test xOvershadow Ax+ crControl x+ CR
Conclusion thus far:
• Forward pairings (contiguity) neither necessary nor sufficient.
• Something more is required– Belongingness– Kamin: Surprise– Contingency– Relative salience– Contingency
Rescorla’s contingency experiment
Correlated
Group
CS
US
Uncorrelated
Group
CS
US
Rate of US Occurrence: 0.1US/sec during CS; 0US/sec outside of CS
Rate of US Occurrence: 0.1US/sec during CS; 0.1US/sec outside of CS
Rescorla’s contingency experiment
Correlated
Group
CS
US
Uncorrelated
Group
CS
US
Rate of US Occurrence: 0.1US/sec during CS; 0US/sec outside of CS
Rate of US Occurrence: 0.1US/sec during CS; 0.1US/sec outside of CS
Rescorla’s contingency experiment
Correlated
Group
CS
US
Uncorrelated
Group
P (US|CS) = 0.5 P(US|noCS) = 0.5
CS
US
P(US | CS) P(US | ~CS))
CR
P(US | CS) = .4 for all groups
P(US | noCS)
.40 .1 .2
Results of Rescorla’s (1968) Contingency Experiment
It’s a little like…
Animals are scientists, trying to make causal predictions.
…trying to determine whether the US is contingent on the CS
Other Contingency Phenomena
US preexposure effect: Presenting the US repeatedly prior to CS-US trials retards acquisition.
CS preexposure effect: Presenting the CS repeatedly prior to CS-US trials retards acquisition. (a.k.a. Latent Inhibition)
US and CS preexposure designs
US preexposure Group Phase 1 Phase 2 Test CS Experimental US CSUS cr Control ---- CSUS CR
CS preexposure Group Phase 1 Phase 2 Test CS Experimental CS- CSUS cr Control ---- CSUS CR
Factors That Affect ConditioningContiguity: The closer two stimuli are in space and time, the stronger can be the association between them.
“Belongingness”: The “fit” between CS and US
Contingency: “Information value.” The higher the correlation between two stimuli, the stronger the conditioned response.
Salience: More intense or noticeable stimuli condition more rapidly.
Other conditioning phenomena discovered by Pavlov
Conditioned inhibition: A stimulus predicts the absence of the US.
Second-order conditioning: Pairing a neutral stimulus with a CS confers associative strength upon the neutral stimulus
Conditioned Inhibition
A US A US
A USA US
A US A USA
A
X
A
X
X
Second-Order Conditioning
• A+/AX- training. Look familiar?
• However, number of AX- trials is critical- Few AX- trials leads to SOC- Many AX- trials leads to conditioned inhibition
• also, SOC typically produced in two phases.- A+ training followed by AX+ training.
Design of Conditioned InhibitionPhase 1 Test XA+/AX- CI
(Many AX- trials -- tens to hundreds)
Design of Second-Order ConditioningPhase 1 Phase 2 Test XA+ AX- CR
(Few AX- trials -- typically not more than 8-10)
∆VCS = change in associative strength of CS
VCS = associative strength of CS
λ = Asymptote of learning
Learning rate parameters
α = CS salience (0-1; 0 = no CS)
β = US salience (0-1; 0 = no US)
∆VCS = αβ(λ-VSUM)
The Rescorla-Wagner Model (1972)
R-W and Blocking
∆VCS = αβ(λ-VSUM)
Blocking group∆VX = αβ(λ -VA+X)∆VX = 1(1 –[1+0]) = 0
Acq group∆VX = αβ(λ -VA+X)∆VX = 1(1 – [0+0]) = 0
Group Ph. 1 Ph. 2 λ VA Block A+ AX+ 1 1Acq B+ AX+ 1 0
Phase 2
Rescorla-Wagner Spreadsheet
R-W model accounts for:
Blocking (Kamin)
Overshadowing (Pavlov)Ax+, A-US association develops faster than X-US CSs have unequal learning rate parameters.
Conditioned inhibition (Pavlov)A+/AX-, (λ-VA+X) = (0-[1+0]) = -1X develops negative associative strength!
Overexpectation Effect
Group Ph. 1 Ph. 2 Test XExperimental A+/X+ AX+ cr Control A+/X+ --- CR
What is learned in CC?
CS
US
UR
Clark Hull (S-R theory) Pavlov (S-S theory)
CS
US
UR
Test – Devaluation ExperimentHolland & Straub (1979)
Train Devaluation Test
TonePellet PelletRotation ToneCR
Pellet | Rotation Tone CR
