Generalization, Discrimination, and Stimulus Control 1
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Variability Changing conditions Adaptive learning must adapt
Transfer behaviour across situations 2
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Generalization Tendency for a learned behaviour to occur in the
presence of stimuli not present during training e.g. Little Albert
conditioned fear to white rat, also afraid of terrier, santa mask,
fur coat 3
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Discrimination Tendency for a learned behaviour to occur in the
presence of certain stimuli, but not in their absence Inversely
related to generalization 4
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Stimulus Control Stimuli come to exert influence over behaviour
Application of generalization and discrimination CS+ and CS- S+ and
S- S+ indicates more reinforcing outcome, S- less reinforcing (or
even aversive) outcome 5
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Discrimination Training Any procedure that establishes the
ability to discriminate between stimuli Process by which stimulus
control is established 6
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Generalization Not a given Can increase generalization by
training in a variety of settings Generalization not always
appropriate or useful (e.g., generalizing violence from video game
to real world) 8
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Generalization Gradients Measure of
generalization/discrimination Respond to stimuli more like trained
stimuli Train on one stimulus, test on others
Techniques/methodologies 9 Amount of responding Train with yellow
stimulus Test with all colours
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trials Probe Trials Insert occasional unreinforced test
stimulus Wont extinguish since there are still many reinforced
trials training stimulus (reinforced) probe stimulus (unreinforced)
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Extinction Blocks Train stimulus to asymptote Blocks of
extinction trials Each stimulus presented once/block Extinction
constant across stimuli 11
Reading a Generalization Gradient Stim. continuum Response rate
Flat: No discrimination Broad: Some discrimination Narrow: Lot of
discrimination 13
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Semantic Generalization Doesnt have to be a perceptual stimuli
Generalization of abstract feature Adults ate candy (US) to
salivate (UR) while shown words (style, urn, freeze, surf) Shown
homophones (stile, earn, frieze, serf) Shown synonyms (fashion,
vase, chill, wave) CRs for homophones, but very strong CRs for
synonyms 14
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Generalization Post Extinction Classical or Operant training,
then extinction Produces reduction in generalization to other
stimuli 15
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Generalization of Punishment Suppression of behaviour via
punishment also generalizes Honig & Slivka (1964) Pigeons peck
coloured disk, get reinforced (7 colours) Next, peck green disk,
get shocked Gradient forms Greatest reduction of pecking to greener
colours 16 Number of Responses
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Presence/Absence Training Successive Discrimination Training
Go-No Go procedure (operant) Sometimes, reinforced for no go S+
& S- alternate randomly (S+ --> reinf., S- --> extintion)
Simultaneous Discrimination Training S+ & S- presented at same
time 18 Peck (GO) Dont Peck (No Go) Peck Dont Peck
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Matching to Sample (MTS) Select from 2+ alternatives
(comparison stimuli) the stimulus that is the same as the sample
Mismatching (non- matching to sample) Like MTS, but pick comparison
stimulus not like sample Delayed Matching to Sample (DMTS) Like
MTS, but delay between presentation of sample and choice 19 Peck
Dont Peck Delayed MTSMTSNon-match
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Errorless Discrimination Training Previous techniques slow Many
mistakes where S- selected Present S+ as normal, but start S- at
low salience (short time and faint) Gradually increase salience of
S- to equal S+ Quick, relatively little frustration for S- choice,
greater discrimination learned 20
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Differential Outcomes Effect Different reinforcers available
for different responses Can produce faster and stronger
discrimination training than basic forms Faster learning and
accuracy 21 Sample Response Normally Sample Response corn nothing
corn nothing DOE CORN PEAS
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Pavlovs Theory Physiological interpretation Species influenced
Discrimination training produces establishes areas of activation in
brain CS+ --> excitatory regions CS- --> inhibitory regions
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Activation Stimuli similar to CS+ will excite parts of brain
close to CS+ area Dissimilar stimuli will not activate CS+ area
Result is CR or no CR, respectively 24
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Inferential Interpretation Theory based on inference from
observed behaviour No independent validation of brain area
generation through conditioning Physical proximity of brain areas
not needed for response generation 25
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Spences Theory Opponent process theory Excitatory (CS+ or S+)
and inhibitory (CS- or S-) gradients Net sum effect of gradients
Resultant behaviour 26
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Peak Shift Change in generalization gradient Peak level of
responding Shift in peak level of responding away from S+ in
direction opposite S- 27
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Peak Shift S+ Responses Exp. 1 (S+ & S-) Control (S+ only)
shift direction S- 28
Support for Spences Theory? Honig et al. (1963) Excitatory and
inhibitory gradients Responses Group 1 S+S- Group 2 S+S- 30
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Lashley-Wade Theory Generalization gradients depend on prior
experience with stimuli similar to those used in testing
Discrimination training --> discrimination because it teaches
subjects to tell the difference between S+ and other stimuli
Everyday experiences produce discrimination learning 31
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Predictions Previous experience with stimuli will make
discrimination training of those stimuli easier Lack of previous
experience will make subsequent training harder 32
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Standard Design Rear animals under specific environmental
condition e.g., darkness so no experience with colours Give S+/S-
training Test for generalization gradient If gradient of
perceptually deprived subjects flatter than normally reared
subjects, then support for Lashley-Wade theory 33
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Results Ambiguous Possibility that special rearing environment
produces neurological damage 34
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Jenkins & Harrison (1960) Group 1 pigeons S+ (tone) -->
reinf., S- (quiet) --> no reinf. Group 2 pigeons S+ (tone)
--> reinf., no S- (i.e., tone always on) Test both groups for
generalization to other tones and to periods of silence 35
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Results Group 1 birds Less likely to respond during silent
periods Show standard generalization gradient to tones Group 2
birds Responded same amount during tone or silence Flat
generalization gradient (i.e., no discrimination of tones) Supports
Lashley-Wade theory 36
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Theories Pavlovs Lacks support Spence and Lashley-Wade Both
have situations that support and contradict predictions 37
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Concept Formation Concept: any class of things sharing one or
more defining features Defining features allow discrimination
between stimuli within class and outside class Concepts can be
learned through discrimination training 39
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Herrnsteins Studies Stimuli from natural environment Train/test
many stimuli Positive and negative instances Pigeons, 80 pictures
Tree/no tree = positive/negative instances Learn discrimination
easily Generalization test Supports concept formation, not
memorization 40
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Concepts of Absolute or Relative Concept of absolute Learn
individual stimuli Specify features of members of class Concept of
relative: Learn relationship between stimuli Degrees of similarity
of features of class members 41
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Example 42
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Transposition Transfer relational rule to new stimuli set
Kohler (1939) TestTraining S+S- transfer absolute 43
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Stimulus Control Absolute stimulus control Successive
discrimination tasks Relational stimulus control Simultaneous
discrimination tasks Animals do whatever is easiest 44
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Mental Rotation Rotate letter various amounts and/or inverted
i.e., backwards Determining inversion takes longer the greater the
degree of rotation Mental rotation of internal representation
Gradient of response times looks like generalization gradients R R
R 45
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Smoking Relapse Smoking gives frequent reinforcement But, not
only physiological effects of nicotine Social reinforcement
Environmental factors become conditioned as S+ for smoking Smoke in
many situations, strong generalization 46
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Experimental Neuroses When not possible to distinguish between
stimuli in discrimination conditions Consumer situations
Frustration No-choice as option 47