generalization, discrimination, and stimulus control 1

Generalization, Discrimination, and Stimulus Control 1

Variability Changing conditions Adaptive learning must adapt Transfer behaviour across situations 2

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

Discrimination Tendency for a learned behaviour to occur in the presence of certain stimuli, but not in their absence Inversely related to generalization 4

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

Discrimination Training Any procedure that establishes the ability to discriminate between stimuli Process by which stimulus control is established 6

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

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

trials Probe Trials Insert occasional unreinforced test stimulus Wont extinguish since there are still many reinforced trials training stimulus (reinforced) probe stimulus (unreinforced) 10

Extinction Blocks Train stimulus to asymptote Blocks of extinction trials Each stimulus presented once/block Extinction constant across stimuli 11

Extinction Blocks Block 1 Block 2 Block 3 and so on... Training 42015123 7311511 051013 4+3+1 = 8 20+15+10 = 45 15+11+5 = 30 12+7+3 = 22 3+1+0 = 4 # of responses 50 30 10 40 20 Responses Light wavelengths Generalization Gradient 12

Reading a Generalization Gradient Stim. continuum Response rate Flat: No discrimination Broad: Some discrimination Narrow: Lot of discrimination 13

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

Generalization Post Extinction Classical or Operant training, then extinction Produces reduction in generalization to other stimuli 15

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

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

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

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

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

Pavlovs Theory Physiological interpretation Species influenced Discrimination training produces establishes areas of activation in brain CS+ --> excitatory regions CS- --> inhibitory regions 23

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

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

Spences Theory Opponent process theory Excitatory (CS+ or S+) and inhibitory (CS- or S-) gradients Net sum effect of gradients Resultant behaviour 26

Peak Shift Change in generalization gradient Peak level of responding Shift in peak level of responding away from S+ in direction opposite S- 27

Peak Shift S+ Responses Exp. 1 (S+ & S-) Control (S+ only) shift direction S- 28

Peak Shift: Shift Away from S- S+ +10 +5 -5 -15 -10 +15 +5 +10 +15 S- Excitatory gradient Inhibitory gradient Net gradient 29

Support for Spences Theory? Honig et al. (1963) Excitatory and inhibitory gradients Responses Group 1 S+S- Group 2 S+S- 30

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

Predictions Previous experience with stimuli will make discrimination training of those stimuli easier Lack of previous experience will make subsequent training harder 32

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

Results Ambiguous Possibility that special rearing environment produces neurological damage 34

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

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

Theories Pavlovs Lacks support Spence and Lashley-Wade Both have situations that support and contradict predictions 37

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

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

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

Example 42

Transposition Transfer relational rule to new stimuli set Kohler (1939) TestTraining S+S- transfer absolute 43

Stimulus Control Absolute stimulus control Successive discrimination tasks Relational stimulus control Simultaneous discrimination tasks Animals do whatever is easiest 44

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

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

Experimental Neuroses When not possible to distinguish between stimuli in discrimination conditions Consumer situations Frustration No-choice as option 47

generalization, discrimination, and stimulus control 1

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