Pavlovian Conditioning Flashcards
What is conditioned supression
In this procedure the rat (typically) is trained to press a lever for food pellets. After responding is established, the lever is withdrawn and the pairing of CS (e.g. light, tone) and US (normally shock) of interest takes place. Then testing is performed with the lever back in the chamber. The rate of responding during the CS (=RCS) and just before the CS (=Rpre-CS) is recorded, and a suppression ratio is calculated = “RCS” /”(RCS+Rpre-CS)” .This measure has the property that for good conditioning it will approach 0, and for weak conditioning it will approach 0.5.
what is the supression ratio
“RCS” /”(RCS+Rpre-CS)”
if the CS makes no difference, what is the suppression ratio
0.5
who studied overshadowing?
Mackintosh 1976
Example study of overshadowing
Mackintosh 1976
Stage 1: Train compound of light and noise, or train the light and noise separately. For different groups use different intensities of noise (n=weak noise, N=intense noise).
Stage 2: Test the light and noise.
These labels denote stimulus used in training, so LN means training to compound of light and intense noise.
When testing the light, the light suppression ratio when trained in compound is worse than when light is trained on its own. This shows overshadowing.
When you train two stimuli together, there is a chance that one will overshadow the other and affect conditioning of it.
Who investigated blocking
kamin 1969
study on blocking
Kamin 1969
Stage 1: noise →shock noise→ CR (fear)
Stage 2: noise + light → shock noise + light→ CR
Test: light light→ little suppression (0.45)
When you test light on its own, suppression ratio is .45. However, if you did just stage 2, suppression is .05.
What is rescorla
“truly random control” (involves both partial reinforcement and free-US) leads to no conditioning despite some CS-US pairing: contingency is necessary
what is Kamin ‘blocking’
no acquisition when CS2 is paired with a US to which a strong CR to CS1 has already been established, if CS1 and CS2 are always presented together: is surprise necessary?
what is the Rescorla-Wagner Learning rule
V= aB(^-EV)
explain Rescorla-Wagner learning rule
V= aB(^-EV)
a : learning rate parameter determined by the salience of CS;
B : learning rate parameter determined by the salience of the outcome.
^ : asymptote of associative strength (V). has a positive value on episodes when
the outcome is US with its magnitude being determined by the effectiveness of US.
EV: sum of the associative strengths of all CSs present on the learning episode.
what is (^-EV) referred to as?
the prediction error
what happens when ^ is zero?
no US is presented, non-reinforcement yields a negative (triangle) term and hence a decrement in V, thus producing extinction.
what is electrodermal conditioning
1) The participants expectancy of shock rises for S+ and drops for S-.
2) The change in skin conductance for S+ becomes larger than that for S-.
On this basis Lovibond and others have claimed that this is a form of Pavlovian conditioning in humans
By separating out those participants who are aware of the contingencies (getting shocked to S+ not S-) from those who are not, it is possible to demonstrate that the effect is driven by the participants who have an expectancy of shock. There is little evidence of conditioning in those who do not.
Hence, the claim that Pavlovian conditioning in humans requires a conscious cognitive expectancy of the US, and may not be the same as in other animals (e.g. the rat).
what did Hughdahl & Ohman 1977 find
Further evidence in support of this view comes from the observation that if you now tell participants that no more shocks will occur - then the response quickly disappears (below left), in contrast to those tested in extinction (top left) but not given this information.
This suggests it is under conscious control.
But - there’s more to it than this….
