Rescorla’s Experiment

Contingencies in Classical Conditioning

Three Phases

Phase 1: Avoidance Conditioning: Establish a behavioral measure (operational definition) of “fear” (intervening variable).

Phase 2: Classical Conditioning: Arrange positive, negative, and zero contingencies between tone and shock.

Phase 3: Avoidance Conditioning: Present CS from Phase 2 at random times during avoidance procedure; see if fear increases, decreases, or stays the same.

Rescorla’s ExperimentPhase 1: Avoidance Conditioning: Establish a behavioral measure (operational definition) of “fear” (intervening variable).Avoidance behavior is behavior that prevents the occurrence of an aversive stimulus, like shock.

Some theories say it is motivated by fear:

Avoidance responseFea

r

The avoidance behavior can serve as an operational definition of fear: stronger behavior = more fear.

Rescorla’s ExperimentPhase 1: Avoidance Conditioning: Establish a behavioral measure (operational definition) of “fear” (intervening variable).

Apparatus: “Shuttle box”

Dog jumps over barrier from one compartment to the other to avoid shock.

If he stays in one compartment, he gets shocked every 10 seconds (shock-shock, S-S) interval.If he jumps before 10 seconds are up, he’s safe for 30 seconds (response-shock, R-S) interval.

Rescorla’s ExperimentPhase 1: Avoidance Conditioning: Establish a behavioral measure (operational definition) of “fear” (intervening variable).

Apparatus: “Shuttlebox”

If he jumps before the 30 seconds are up, he gets another 30 seconds.

But if he messes up and gets shocked, then the S-S interval takes over, and he gets shocked again in 10 seconds.

Result: The dogs keep jumping at a steady, moderate pace, and avoid most of the shocks.

Rescorla’s ExperimentPhase 1: Avoidance Conditioning: Establish a behavioral measure (operational definition) of “fear” (intervening variable).

Apparatus: “Shuttlebox”

The rate at which he jumps is the operational definition of fear.

The faster he jumps, the more afraid he is.

Jumping responseFea

r

Rescorla’s ExperimentPhase 2: Classical Conditioning: Arrange positive, negative, and zero contingencies between tone and shock.

US= shock

UR=pain

CS=tone

CR=fearTones come on at random intervals,

averaging 30 seconds. Each lasts 5 seconds.

There are three groups that get shocks in different patterns so there is a zero, positive or negative contingency between the shocks and the tones.

Rescorla’s ExperimentPhase 2: Classical Conditioning: Arrange positive, negative, and zero contingencies between tone and shock.

Group R (random pattern of shocks) There is a zero contingency. The probability of shock right after a tone is the same as it is before tones and between tones.

A B C D

Note that shocks B and D are paired with tones, but overall the tone has no predictive value.

Rescorla’s ExperimentPhase 2: Classical Conditioning: Arrange positive, negative, and zero contingencies between tone and shock.

Group P (positive contingency)

A B C D

Note that Groups P and R get the same number of pairings, important to Pavlov but not Rescorla.

Same as Group R except that only shocks that come right after tones get through; there are no shocks before or between tones.

Rescorla’s ExperimentPhase 2: Classical Conditioning: Arrange positive, negative, and zero contingencies between tone and shock.

Group N (negative contingency)

A B C D

There are no CS-US pairings in Group N.

Same as Group R except that NO shocks due to come right after tones get through, only the shocks before and between tones.

Analyzing Contingencies in Phase 2

This chart summarizes conditions for Groups R, P and N in terms of conditional probabilities.

P (US|CS) P (US|no CS)GroupRescorla predicts...

P Above 0 0 Fear CR

N 0 Above 0 Relaxation CR

R Equal values No CR

Analyzing Contingencies in Phase 2

This chart summarizes conditions for Groups R, P and N in terms of conditional probabilities.

P (US|CS) P (US|no CS)GroupPAVLOV predicts...

P Above 0 0 ?N 0 Above 0 ?R Equal values ?

Fear CR

Fear CR

No CR

Rescorla’s ExperimentPhase 3: Avoidance Conditioning: Present CS from Phase 2 at random times during avoidance procedure; see if fear increases, decreases, or stays the same.

The contingencies from Phase 2 are discontinued. When the tone comes on, it stays on for 5 seconds, then goes off.

The dog gets shocked only if he waits too long to jump, as required by the avoidance procedure.

It has nothing to do with the avoidance procedure; it’s just something added on top of it.

Rescorla’s ExperimentPhase 3: Avoidance Conditioning: Present CS from Phase 2 at random times during avoidance procedure; see if fear increases, decreases, or stays the same.

The question is: When the tone comes on, does the dog jump faster, slower, or at the same rate as before the tone?

Therefore, we can make the following inferences:

Rate of jumping is the operational definition of fear.

Rescorla’s ExperimentPhase 3: Avoidance Conditioning: Present CS from Phase 2 at random times during avoidance procedure; see if fear increases, decreases, or stays the same.

Jump rate means the tone produced an increase in overall fear.

Jump rate means the tone produced a decrease in overall fear.

If the rate of jumping doesn’t change, it means there was no CR to the tone.

Rescorla’s ExperimentPhase 3: Avoidance Conditioning: Present CS from Phase 2 at random times during avoidance procedure; see if fear increases, decreases, or stays the same.

If the tone has nothing to do with the shocks, how can it increase the animal’s level of fear?

?

Total Fear

Jump

Avoidance procedure

Fear

CS CR (fear)

CR (fear) adds to the fear from the avoidance procedure.

It’s total fear that controls jumping.

Rescorla’s ExperimentPhase 3: Avoidance Conditioning: Present CS from Phase 2 at random times during avoidance procedure; see if fear increases, decreases, or stays the same.

How can the tone decrease the animal’s fear?

Avoidance fear

Suppose the tone produces a conditioned response of inhibition instead of fear.This inhibition suppresses some of the fear produced by the avoidance procedure.

Another term for this inhibition is “relaxation”.

- Relaxation response

= Less total fear

Less total fear means less jumping.

Scorecard: Pavlov Versus Rescorla

Here are the results. Who made the right predictions?

Rate of jumping... PavlovGroup Rescorla

P INCREASED

N DECREASED X

R NO CHANGE X