CHAPTER 4 Pavlovian Conditioning: Causal Factors.

CHAPTER 4

Pavlovian Conditioning:

Causal Factors

NECESSARY CONDITIONS FOR PAVLOVIAN CONDITIONING

Contiguity– For Pavlov, conditioning involved simple,

mechanical associations between events that occurred closely together in time.

– Contiguity between CS and US automatically stamped in a connection between them.


Contingency– But, in 1967, Robert Rescorla suggested

that although contiguity between CS and US might be necessary for conditioning to occur, it might not be sufficient.

– What might also be necessary is that there be a differential contingency between CS and US.

– Only then would CS convey information about occurrence of US.


It now appears that information is critical for Pavlovian conditioning.– Does CS provide reliable information as to

whether US is forthcoming?– Just when is US likely to occur?– Such information appears to be taken into

account in production of CRs.

Information and Conditional Probability Imagine two hats: one large, one small. Imagine 10 red balls and 10 green balls

in large hat. Imagine 10 blue balls and 10 yellow

balls in small hat.

Information and Conditional Probability Without knowing hat size, what is P of picking

a red ball from either hat? 10/40 = .25. If hat is large, then what is P of picking a red

ball? 10/20 = .50. If hat is small, then what is P of picking a red

ball? 0/20 = .00. Clearly, P of picking a red ball depends on

hat size. We thus say that P of picking a red ball is

conditional on hat size.

Information and Conditional Probability This analysis suggests that hat size conveys

information about ball color. Information may be critical for conditioning. If CS provides information about occurrence

and timing of US, then organisms should attend to and learn about it.

Such learning might involve:– Positive relations or contingencies– Negative relations or contingencies– Random relations--no contingency whatsoever

Information and Conditional Probability Experimental evidence is consistent

with informational theory. Yet, informational theory is incomplete

without considering role of time in conditioning:– CS-US Interval (ISI)– Intertrial Interval (ITI)– ISI/ITI Ratio

Informativeness, Redundancy, and Blocking Organisms may not only be sensitive to

whether a CS predicts a US, but whether it better predicts the US than other CSs.

In other words, conditioning may involve the selective association of a US with the most predictive CS.

If two or more CSs predict the US, then each is said to be redundant.

Selective Associations

Two prime examples of selective associations:– Overshadowing– Blocking

Overshadowing

If a CS is a compound of two stimuli and one is more salient or noticeable than the other, then nearly all of the conditioning occurs to the more salient stimulus--overshadowing.

The less salient one may be completely overshadowed, even though it alone could have been an effective CS.

Overshadowing

Training Test

Strong

Test

Weak

Group SW SW+ High Resp Low Resp

Group S S+ High Resp --

Group W W+ -- Med Resp

Blocking

An overshadowing effect can occur even if both stimuli are quite salient.

This kind of overshadowing results from organism’s past experience with stimuli.

It further shows selective association based on informativeness of stimuli.

Blocking

Phase 1 Phase 2 Test X

Group B A+ AX+ Low Resp

Group C -- AX+ High Resp

PREDICTIVENESS, FEAR, AND ANXIETY One hallmark of a successful science is that it

yields a technology that can be used to improve human life.

In Pavlovian conditioning, attempts have been made to use Pavlovian principles to explain emotional disorders.

Those attempts have relied on importance of predictiveness to Pavlovian conditioning.

One case is fear versus anxiety.

Fear Versus Anxiety

Fear is said to be objective: focused on particular objects or situations.

Anxiety is said to be subjective: unfocused or diffuse.

Anxiety is thought to be main component of many types of psychopathology.

People with anxiety disorders are emotionally paralyzed and unable to identify source of paralysis.

They become withdrawn, unable to act, and miserable.

Fear Versus Anxiety

There is much evidence for conditioned fear. – Using shocks as USs and tones or lights as CSs

reliably produces fear to light or tone. Evidence for conditioned anxiety comes from

randomly presenting CSs and USs.– This procedure does not produce conditioned fear

to tone. – Rats behave no differently in presence of tone than

in its absence. – Rats suppress lever pressing at all times. – They also huddle, seemingly frozen with terror.

Fear Versus Anxiety

These rats develop stomach ulcers. These ulcers are not produced by shock

itself, but by its unpredictability. Animals exposed to tone-shock pairings

do not develop ulcers. Key here is that predictable shock means

there is a safety signal (no CS). There is no safety signal with

unpredictable shock.

PAVLOVIAN CONDITIONING AND INHIBITION Through pairing of CS and US, CS

comes to excite a CR. But, what happens if--after excitatory

conditioning--subject receives presentations of CS without US?

Answer: Extinction and (perhaps) Pavlovian conditioned inhibition.

PAVLOVIAN CONDITIONING AND INHIBITION What is inhibition? Active suppression of behavior that

would occur under other circumstances. External inhibition is unconditioned. Internal inhibition is conditioned.

PAVLOVIAN CONDITIONING AND INHIBITION Study of conditioned inhibition poses special

methodological problems. A sign of conditioned excitation is presence of a

response that did not occur before conditioning. But, a sign of conditioned inhibition is absence of

a response that might otherwise occur. Mere absence of that response does not

guarantee that conditioned inhibition is present. Response could be absent for many other

reasons--most obviously lack of excitation.

PAVLOVIAN CONDITIONING AND INHIBITION Methods to observe inhibition:

– Disinhibition– Summation– Resistance to reinforcement– Retardation– Approach-withdrawal

Disinhibition

According to Pavlov, presentation of a novel stimulus will inhibit inhibition.

Suppose that salivation to CS has been extinguished and that extinction produces inhibition.

CS is presented and dog does not salivate.

If novel stimulus is given with CS, then dog will resume salivating.

Summation

Phase 1 Phase 2 Testing

Control

Group

Light

Alone

ToneFood

T (High)

T+L (High)

Inhibition

Group

Light and Food Unpaired

ToneFood

T (High)

T+L (Low)

Resistance to Reinforcement

Phase 1 Phase 2

Control

Group

Light

Alone

T+LFood

(Fast learning)

Inhibition

Group


T+LFood

(Slow learning)

Retardation

Phase 1 Phase 2

Control

Group

Light

Alone

LFood

(Fast learning)

Inhibition

Group


LFood

(Slow learning)

Approach-Withdrawal

CS+ Food CS- No Food Animals approach CS+ Animals avoid CS-

CONDITIONS PRODUCING INHIBITION Extinction Conditioned Inhibition Training Negative Contingency Training Inhibition of Delay Discrimination and Generalization

– Excitatory and inhibitory gradients Backward Conditioning

NECESSARY CONDITIONS FOR INHIBITION Inhibitory stimulus must signal absence of

otherwise expected US. It is not sufficient to present a cue in absence

of a US for inhibition to develop. In fact, nonreinforced pre-exposure of CS

retards its ability to become a conditioned excitatory stimulus and it reduces its ability to become a conditioned inhibitor--latent inhibition of excitation and inhibition.

Pavlovian Conditioning: Causal Factors Contiguity and contingency play strong

roles in Pavlovian conditioning. Stimuli seem to compete with one

another for control of Pavlovian CRs. Excitation and inhibition both seem to

regulate Pavlovian CRs. Explanations of Pavlovian conditioning

must take these findings into account.

CHAPTER 4 Pavlovian Conditioning: Causal Factors.

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Transcript of CHAPTER 4 Pavlovian Conditioning: Causal Factors.