PSY236 Lecture Notes - Lecture 3: Latent Inhibition, Operant Conditioning, United States Naval Observatory

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Week 3 PSY236 Lectures:
Classical Conditioning 5 - Contingency
Contiguity or contingency?
Contiguity = the connectedness in time and space of the CS and US
As the delay increases between the CS-US so the rate of learning decreases
But the CS also becomes less useful as a predictor of the US
Contingency = the predictability of the occurrence of one stimulus from the presence of another
o Contingency = probabilistic relationship with US given that a CS has occurred refers to the
extent to which the pairing of the CS with the US is necessary and sufficient for learning to
occur
So contiguity is necessary
But NOT sufficient for classical conditioning to occur
There must also be a consistent relationship or correlation between the CS and the US
To experience a reliable correlation between the CS and the US the subjects must be exposed to
numerous instances of the CS and US, thus many trials are typically necessary for conditioning
Most learning curves support this, especially in appetitive learning situations
Aversive conditioning they do not wait to learn the relationship once was enough
So contiguity and contingency is necessary
Kamin’s seminal study on blocking showed that contiguity alone was not sufficient
Blocking
o Phase 1: train light CS
o Phase 2: train light CS in compound with neutral (but equally salient) metronome CS
o Phase 3: test elements of compound individually: pre-trained light blocks conditioning to
metronome
Kamin’s procedure and results
o Pre-training Noise blocked light from CR
o NO pre-training of noise no blocking, so L CR
Why didn’t light a CR?
It had been paired (in compound with Noise) contiguously with the US?
Because Noise already predicted that the US would follow
Learning during a conditioning trial is a function of predictive error: the discrepancy between the
actual outcome of a conditioning trial and the expected outcome of that trial
Unblocking occurs because there is a discrepancy between expectation and reality
Contingency will depend on:
Reliability of CS-US pairing:
o How often is the CS followed by US?
o What is the probability that the US will occur given that the CS has just occurred
Uniqueness of CS-US pairing:
o How often does US happen without CS?
o What is the probability of the US occurring given that No CS has occurred?
Contingency
Refers to the predictive relationship between stimuli (CSs and USs)
The CS has to convey information about US occurrence. ‘Unpacking’ the terminology of Rescorla to
describe these relationships:
o The probability (p) of a US occurring given that (/) a CS is present, is greater than the
probability (p) of a US given that NO CS is present
Rescorla’s equation describing a positive correlation between the CS and US
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p(US/CS) > p(US/No CS)
o The left side of the equation notes the percentage of CSs that are temporally contiguous
(paired) with a US
If p = 1.0 then 100% of CSs are paired with USs
If p = 0.5 then 50% CSs are paired with UCSs and 50% of CSs are presented alone
If p = 0 then all CSs are presented alone, there are no CS-US pairings
o The right side of the equation notes the percentage of time intervals without a CS in which a
US occurs
If p = 1.0 then USs are presented on 100% of time intervals with No CS present
If p = 0.5 then USs are presented on 50% of time intervals with NO CS present
If p = 0 then USs are never presented when NO CS is present
No contingency between CS and US
If the CS is an unreliable predictor of the US, then the CS and US are not correlated
Negative contingency between CS and US
If the CS reliably predicts the absence of the US, then the CS AND US are negatively correlated
The effect of contingency on classical conditioning:
Group A vs. Group B
Bell rings, shock occurs and no shock can occur group B = conditioned fear of the bell
For both groups, there’s only 40% chance that bells will be followed by shock. However, for group B,
shock is less likely when no bell is sounded and for this group, the bell becomes a fearful stimulus
Positive contingency
P(US/CS) > p(US/NO CS)
40% > 20%
Bell Fear CR
Negative contingency
P(US/CS) < p(US/NO CS)
40% < 80%
bell inhibitory stimulus
shock less likely to occur after CS
So how do we calculate the relative probability of learning occurring?
First take notice that timeline is divided into 12 equal intervals of time
Next we calculate the left side of the equation
There are 4 time intervals with a cs
A US occurs in all 4 CS intervals
Therefore the probability of a US given the presence of a CS is 1.0
Next we wil calculate the right side of equation
o There are 8 time intervals with NO CS
o A US occurs in 0 of these no-CS intervals (i.e. 0/8)
o There probability of a US given the absence of a CS is 0
This is called EXCITATORY CONDITIONING
Inhibitory conditioning
When the relationship is negative (<) instead of positive (>)
Summary:
When subjects experience CSs and UCSs that are positively correlated they acquire a conditioned
response to the CS; this is called excitatory conditioning
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Document Summary

Contingency: refers to the predictive relationship between stimuli (css and uss, the cs has to convey information about us occurrence. If p = 1. 0 then 100% of css are paired with uss. If p = 0. 5 then 50% css are paired with ucss and 50% of css are presented alone. If p = 0 then all css are presented alone, there are no cs-us pairings: the right side of the equation notes the percentage of time intervals without a cs in which a. If p = 1. 0 then uss are presented on 100% of time intervals with no cs present. If p = 0. 5 then uss are presented on 50% of time intervals with no cs present. If p = 0 then uss are never presented when no cs is present. If the cs is an unreliable predictor of the us, then the cs and us are not correlated.

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