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Configural learning Learning about holistic stimulus representations. no food. food. Structural discriminations George Ward-Robinson & Pearce, 2001. food. no food. Structural discriminations George Ward-Robinson & Pearce, 2001. Can this be solved in terms of simple associations?
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Configural learning Learning about holistic stimulus representations
no food food
Structural discriminations George Ward-Robinson & Pearce, 2001 food no food
Structural discriminations George Ward-Robinson & Pearce, 2001
Can this be solved in terms of simple associations? Can it be solved with conditional learning? food no food
If green: red-left + red-right - If blue: red-left - red-right + If green: blue-right + blue-left - food no food
If green: red-left + red-right - If blue: red-left - red-right + If green: blue-right + blue-left - relies on use of compound cues - red-left etc food no food
so why not use fact these stimuli are all unique? red-left&green-right+ red-right&green-left - food no food
Some types of learning associative theory cannot explain. Last week we saw how conditional learning can explain some of these Today we consider an alternative approach - configural learning Can associative theory adapt by changing the way in which the stimulus is represented?
So far have assumed that a compound stimulus is equivalent to the sum of its parts: A --> food B--> food A --> cr B --> cr AB --> CR Predict SUMMATION
Feature negative discrimination A --> food AB --> no food CR cr
VA= ( - V ) Learning stops when (=V ) A --> food AB --> no food VA = 1 VA + VB = 0
VA= ( - V ) Learning stops when ( = V ) A --> food AB --> no food VA = 1 VA + VB = 0 A becomes excitatory: V = +1 B becomes inhibitory: V = -1 thus A alone predicts food, whereas A+B is neutral
Feature positive discrimination A --> no food AB --> food cr CR
VA= ( - V ) Learning stops when ( = V ) A --> no food AB --> food VA = 0 VA + VB = 1
VA= ( - V ) Learning stops when ( = V ) A --> no food AB --> food VA = 0 VA + VB = 1 B becomes excitatory: V = +1 A eventually becomes neutral: V = 0 Thus A alone predicts nothing, but when B is present food is expected
Performance on feature negative and feature positive discriminations can be explained by the Rescorla-Wagner equation If you condition to asymptote, it predicts perfect performance But how about.......
Positive patterning discrimination: A --> no food B --> no food AB --> food cr cr CR
VA= ( - V ) Learning stops when (=V ) A --> no food B --> no food AB --> food VA = 0 VB = 0 VA + VB = 1
A --> no food B --> no food AB --> food VA = 0 VB = 0 VA + VB = 1 This one is insoluble - you can never reach asymptote: what is gained on AB trials is lost on A and B trials
A --> no food B --> no food AB --> food But associative theory can explain accurate performance Both A and B acquire associative strength on compound trials, and lose some on element trials Animals respond more on AB trials (when two signals for food are present) than on A or B trials (when there is only one) But it doesn't predict perfect performance
Negative patterning discrimination A --> food B --> food AB --> no food CRCR cr
VA = ( - V ) Learning stops when (= V ) A --> food B --> food AB --> no food VA = 1 VB = 1 VA + VB = 0
Simple associative theory can never predict accurate performance here A --> food B --> food AB --> no food If A and B have enough associative strength to elicit responding, then the compound of A and B must elicit more responding, not less -- violates summation principle So can animals learn nonlinear discriminations of this type?
Wagner (1971) and Rescorla (1972) suggested the unique stimulus account: A stimulus compound should be treated as the combination of its elements... + A B
A stimulus compound should be treated as the combination of its elements... PLUS a further stimulus that is generated only when those elements are presented together: + A B ab
A stimulus compound should be treated as the combination of its elements... PLUS a further stimulus that is generated only when those elements are presented together: + A B configural stimulus not very salient; so only learned about when absolutely "forced" ab
Now the negative patterning discrimination looks like this: A --> food B --> food AB --> no food
Now the negative patterning discrimination looks like this: A --> food B --> food AB ab --> no food
Now the negative patterning discrimination looks like this: A --> food B --> food AB ab --> no food VA = 1 VB = 1 VA + VB+ Vab = 0
A --> food B --> food AB ab --> no food VA = 1 VB = 1 VA + VB+ Vab = 0 B becomes excitatory: V = +1 A becomes excitatory: V = +1 ab becomes inhibitory: V = -2 ...and the discrimination is solved...
Rescorla tested this interpretation with the following experiment: A + B + AB - AB + A ? B ? A + B + C - AB + A ? B ? Which group will respond more in the test?
Stage 1 Stage 2 Test A + B + AB ab - AB ab + A ? B ?
Stage 1 Stage 2 Test A + B + AB ab - AB ab + A ? B ? In Stage 1 A and B become excitatory and ab inhibitory; the combination of A, B and ab should therefore be neutral
Stage 1 Stage 2 Test A + B + AB ab - AB ab +A ? B ? In Stage 1 A and B become excitatory and ab inhibitory; the combination of A, B and ab should therefore be neutral In Stage 2 the neutral AB ab is paired with food; the food is surprising, and A, B and ab all gain associative strength
Stage 1 Stage 2 Test A + B + AB ab - AB ab + A ? B ? In Stage 1 A and B become excitatory and ab inhibitory; the combination of A, B and ab should therefore be neutral In Stage 2 the neutral AB ab is paired with food; the food is surprising, and A, B and ab all gain associative strength In the Test A and B now have more associative strength than they started with
Stage 1 Stage 2 Test A + B + C - AB + A ? B ?
Stage 1 Stage 2 Test A + B + C - AB + A ? B ? In Stage 1 A and B become excitatory
Stage 1 Stage 2 Test A + B + C -AB + A ? B ? In Stage 1 A and B become excitatory In Stage 2 the excitatory A and B both predict food -- thus two foods are predicted, but only one happens; this produces inhibitory learning, and the strength of A and B drops...
Stage 1 Stage 2 Test A + B + C - AB + A ? B ? In Stage 1 A and B become excitatory. In Stage 2 the excitatory A and B both predict food -- thus two foods are predicted, but only one happens; this produces inhibitory learning, and the strength of A and B drops... In the Test A and B now have less associative strength than they started with
So.. can Rescorla & Wagner explain everything? Not quite: consider the following discriminations: Discrimination 1: A+ AB- Discrimination 2: AC+ ABC- In the second case a common element C has been added on both reinforced and nonreinforced trials; this should make the discrimination harder...
So.. can Rescorla & Wagner explain everything? Not quite: consider the following discriminations: Discrimination 1: A+ AB- Discrimination 2: AC+ABC- In the second case a common element C has been added on both reinforced and nonreinforced trials; this should make the discrimination harder...
BUT Rescorla & Wagner's theory predicts that the AC+ ABC- discrimination will be learned most easily Because AC has more elements than A, it will acquire associative strength faster Discrimination 1: A+ AB- Discrimination 2: AC+ABC-
BUT Rescorla & Wagner's theory predicts that the AC+ ABC- discrimination will be learned most easily Because AC has more elements than A, it will acquire associative strength faster Discrimination 1: A+ AB- Discrimination 2: AC+ABC-
on first trial VA= ( - V ) =( - 0 ) Vc= ( - V ) = (- 0 ) So AC will have twice as much strength as A after trial 1 Faster EXCITATORY learning Discrimination 1: A+ AB- Discrimination 2: AC+ABC-
And the more AC predicts food, the greater the surprise on ABC- trials, and so the faster B will become inhibitory Faster INHIBITORY learning Discrimination 1: A+ AB- Discrimination 2: AC+ABC-
The faster the excitatory and inhibitory learning is acquired, the faster the discrimination is acquired oops!