THEORIES OF CLASSICAL CONDITIONINGChapter 5

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Rescorla-Wagner Explains2

1) Acquisition and extinction of a CS+ 2) Acquisition but not extinction of a CS- 3) Overshadowing and blocking 4) Overexpectation 5) Supernormal conditioning 6) CS-US contingency 7) US preexposure

Contingency and the R-W model P(US/CS), pairing of CS with US P(US/no CS), pairings of context with US

CageExperimental

Context

A day in the life of Sniffy the rat

Rethinking The Contingency Experiment

CS (A)

US

Chance of US per CS = 4/5 = .8

Chance of US outside CS = 2/10 = .2

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P = .6

CONTEXT (X)

(AX+) (X+)(X-) (AX-)

Perfect Positive

Contingency

Perfect Negative

Contingency

Zero

Contingency

P(US/CS) P(US/no CS)

P = .8

P = .6

P = .4

P = 0

P = −.4

P = −.6

P = −.8

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US pre-exposure effect: Exposure to the US before conditioning; it impairs later conditioning when a CS is paired with that US. The R-W model: The presentation of the US

without the CS occurs in a specific environment or context, which results in the development of some associative strength to the context.

Associative strength to the context reduces the level of possible conditioning to the CS on the early trials because VALL is nonzero.

US Pre-exposure Effect

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The US pre-exposure effect is attenuated when the pre-exposure context is different from the conditioning context Other contexts will not have strength,

so conditioning proceeds normally.

Rescorla-Wagner Doesn’t Explain

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1) Failure of a CS- to extinguish (a bad prediction)

2) Second-order conditioning (didn’t include but known; lesson: CS to CS associations)

3) Latent inhibition or CS prexposure effect (didn’t include but known; lesson: should not be fixed)

4) Potentiation rather than overshadowing in taste aversion

5) Performance effects, such as deflation

Potentiation of a Conditioned Response

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Rescorla-Wagner model predicts that when a salient and nonsalient cue are presented together with the US, the salient cue will accrue more associative strength than the nonsalient cue

Overshadowing: In a compound conditioning situation, the prevention of conditioning to one stimulus due to the presence of a more salient or intense stimulus

Potentiation: Tastes often help (rather than hinder) the development of odor aversions

Potentiation and Pregnancy Sickness

Smell&Taste

Smell

StrongCoffee OdorAversion

WeakCoffee OdorAversion

Later

Explanations of Potentiation of a Conditioned Response

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Within-Compound Association (CS− CS association): the association of two stimuli, one of which is paired with a US, which leads both CSs to elicit the CR.

Configural Learning: Compound is treated as a single unitary CS, and individual element for the compound can each trigger the compound.

Sensory-Gate Channeling: Taste opens a gate in the brain allowing odor to serve as a CS for illness when it otherwise would not.

Acquisition versus Performance

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Rescorla-Wagner attributes differences in CR strength to learning. Responding to the CS is determined by the associative strength of the CS on the previous trial.

Comparator hypothesis argues that many differences in CR strength are due to differences performance. CR strength is determined by a comparison of the associative strength of the target CS and the associative other stimuli trained along with the target (CSs or contexts).

Miller’s Comparator Hypothesis

Cue Deflation Effects14

Cue deflation effect: When the extinction of a response to a comparator cue after conditioning leads to an increased reaction to the target CS.

Rescorla-Wagner model cannot explain change in the reaction if a CS if it has not been presented in the interim

Prototypical Cue Deflation Result

Group Stage 1 Stage 2 Test AExper A+ in Context X X- CRControl A+ in Context X Y- cr

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When the extinction of a conditioning context (Context X), but not a control context (Context Y), after conditioning leads to an increased reaction to the target CS (A)

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Mackintosh’s attentional theory proposes that the relevance of and attention to a stimulus determine whether that stimulus will become associated with the US (related to the lesson that should not be fixed)

Baker’s retrospective processing approach suggests that conditioning involves the continuous monitoring of contingencies between a CS and a UCS, with the recognition of a lack of predictiveness diminishing the value of the CS (related to comparator)