1. Generalization, Discrimination, and Stimulus Control
Chapter 9
Generalization, Discrimination, and Stimulus Control

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

3. 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

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

5. 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

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

7. Generalization

8. 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)

9. Generalization Gradients
Measure of generalization/discrimination
Respond to stimuli more like trained stimuli
Train on one stimulus, test on others
Techniques/methodologies
Train with yellow stimulus
Amount of responding
Test with all colours

10. Probe Trials Insert occasional unreinforced test stimulus
Won’t extinguish since there are still many reinforced trials
trials
training stimulus
(reinforced)
probe stimulus
(unreinforced)

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

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

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

14. Semantic Generalization
Doesn’t 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

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

16. 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
Number of Responses

17. Discrimination & Training Techniques

18. 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
Peck
Don’t Peck
Don’t Peck (No Go)
Peck (GO)

19. 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
Delayed MTS
Non-match
MTS
Don’t Peck
Peck

20. 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

21. Differential Outcomes Effect
Different reinforcers available for different responses
Can produce faster and stronger discrimination training than basic forms
Faster learning and accuracy
DOE
Normally…
Response
Response
CORN
corn
nothing
Sample
Sample
nothing
PEAS
corn

22. Theories of Generalization and Discrimination

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

24. 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

25. 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

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

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

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

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

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

31. 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

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

33. 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

34. Results
Ambiguous
Possibility that special rearing environment produces neurological damage

35. Jenkins & Harrison (1960) Group 1 pigeons Group 2 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

36. Results Group 1 birds Group 2 birds Supports Lashley-Wade theory
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

37. Theories Pavlov’s Spence and Lashley-Wade Lacks support
Both have situations that support and contradict predictions

38. Applications

39. 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

40. Herrnstein’s 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

41. 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

42. Example

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

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

45. R R R 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

46. 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

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