Psyc 334 Stimulus Control

Front 1

differential reinforcement

Back 1

responses in S+ are reinforced and those S- are not

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discrimination training

Back 2

establishes control of behaviour by antecedent stimuli

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antecedent stimuli

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those which, when present in teh environment set the occasion for a perticular action or response. e.g. red light set occasion for stopping vehicle

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necessary and sufficient conditions for stimulus control to develop

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train subjects in different training conditions. after each measure which is best.

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measurement of control stimulus

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generalisation test
stimulus control test

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generalisation test procedure

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conducted after training (single stimulus), no reinforcers given. new set of stimuli (new colours). random and brief.
see how much has generalised to other colours. degree of stimulus control can be seen in gradient. steeper= more control.

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absolute

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subjects learn about particular stimuli, those they have experience of. e.g. red = good yellow= bad. hull and spence

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relational

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learn a more abstract/general thing. e.g. colour is related to reinforcement. " the greener the better" lashley and wade. explains peak shift.

Front 9

Hanson 1959 experiment

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single stimulus (control) + 4 others discrimination btwn 2 shades. FOUND:peak shift larger for closer discrimination.
favors relational view

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differences btwn single-stimulus and discrimination training

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peak response rate is higher after discrimination training (behavioural constrast). peak shift- peak response rates occured to short wave lengths. extent of peak shift and gradients steeper after discrimination training.

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intra dimensional discrimination training

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2 stimuli same dimension e.g. yellow vs orange

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extra diamensional discrimination training

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2 stimuli not from same demension e.g. line angle vs yellow

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hull-spence theory

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developed 20 years before hanson. purely hypothetical, didnt know about peak shift etc.

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hull-spence theory key points

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*reinforcement generates excitatory associative strength (promotes responding)
*non-reinforcement generates inhibitory associative strength (reduces responding)
* both of these attach to stimuli S+ and s-. No inhibitory process if s- not present.
*excitation spreads to other stimuli in proportion to their similarity to S+ and s-

Front 15

lashley and wades relational theory

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10 years after hull-spencer but still before the others.
differential reinforcement is essential for discrimination e.g. reinf S+, ext S-. otherwise strength would spread to equally to all other stimuli

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comparison between lashely-wade/ hull-spencer

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l/w =differential reinforcement is sufficient and essential for discrimination. *predicts peak shift but also predicts flat gradient for single stimulus.
H/S = differential reinforcement is sufficient but not necessary for discrimination. *predicts bell gradient for single stimulus

Front 17

predictions form hull-spence theory

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excitatory and inhibitory process form around S+ and S- these add together if same dimension and formnett associative strength.
only occur in discrimination training, predicts a peak shift and close.

Front 18

snag for hull-spence

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cannot predict behavioural contrast the combination of both cannot result in greater responding for discrimination training than for single stimulus training.

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how can an inhibitory process be tested?

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terraces version of discrimination learning. NO s-. without inhibition there shud be no peak shift.
Tested this with 3 groups S+ only, errorless and regular. inhibition / peak shift shown regualr.

Front 20

problem of Terrace's results

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indirect evidence. dont reveal inhibitory process only presence verus absence of a supposed by-product of inhibition (peak shift)

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Honig et al.'s experiment

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direct evidence for inhibitory process

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Honig et al.'s procedure

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exinexcitatory process and pure inhibitory process. blank vs line and switched. varied line angle to change excitatory value (more or less similair to s+) while inhibtion stays the same becoz it does not make it more or less sim to s-

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importance of Honig et al's results

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allow us to see the inhibitory generalisation process that was hypothesised in hull-spence theory

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retard of acquisition test

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begins with strong inhibitory - going to take a long time to become excitatory (get over the negative associations)
hearst et al

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hearst et al's procedure/results

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s+ vi blank and s- ext line.
many line angles were then reinforced including the s-. graph went from pit to mountain over trials.

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results suprrorting relational theory

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Kohler. Baby chicks pecking at cards. replaced darker one wit a lighter one, chicks still preferred the lighter one. must have learn some relational rule.
In the nature of relational learning that contrast effecs will occur (behavioural constrast)

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proven single stimuli flat gradient

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jenkins and harrison.
using auditory stimuli. single and discrim, showed flat gradient. without discrim no context. audio stimuli may have bee the cause, different results with visual stimuli

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big problem for relational theory

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without a pair of stimuli you cant learn a relation. so single stimulus training should produce flat gradient not the peaked one it does.

Front 29

why lashely and wade (relational) theory cannot be dissmissed so easily

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1.subjects came into experiment with pre-experimental experience
2.exposed to differential reinforcement.
wall vs key (reinofrcement, non reinforcement and brightness)

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why lashely and wade (relational) theory cannot be dissmissed so easily
experiment peterson

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ducklings raised under mono chromic light. trained to pick at one light.
then given generalisation test with all colours. results same for all colours ducklings raised under norm light showed peaked gradient

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why lashely and wade (relational) theory cannot be dissmissed so easily
experiment heinemann and rudolph

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3 groups all single stim training. seeing how much subjects relied on brightness to located a key on the wall. degree of stimulus conrtol depends on how useful brightness is in locating the key