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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.
NECESSARY CONDITIONS FOR PAVLOVIAN CONDITIONING
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.
NECESSARY CONDITIONS FOR PAVLOVIAN CONDITIONING
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 Positive Relation
– P(US|CS) > P(US|No CS): Excitation Negative Relation
– P(US|CS) < P(US|No CS): Inhibition Random Relation
– P(US|CS) = P(US|No CS): Learned irrelevance or learned helplessness
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
Light and Food Unpaired
T+LFood
(Slow learning)
Retardation
Phase 1 Phase 2
Control
Group
Light
Alone
LFood
(Fast learning)
Inhibition
Group
Light and Food Unpaired
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.