1 / 47

Chapter 9

Chapter 9. Generalization, Discrimination, and Stimulus Control. Variability. Changing conditions Adaptive learning must adapt Transfer behaviour across situations. Generalization. Tendency for a learned behaviour to occur in the presence of stimuli not present during training

arav
Download Presentation

Chapter 9

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 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 Test with all colours Amount of responding

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

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

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

  13. Reading a Generalization Gradient Response rate Response rate Response rate Stim. continuum Stim. continuum Stim. continuum Broad: Some discrimination Flat: No 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 Don’t Peck 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 MTS Non-match 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 corn PEAS

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

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

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

  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 • 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 • 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 • Lacks support • Spence and Lashley-Wade • 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. Training Test S+ S- absolute transfer Transposition • Transfer relational rule to new stimuli set • Kohler (1939)

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

  45. 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

More Related