CHAPTER 11

1. CHAPTER 11 Stimulus Control of Operant Behavior

2. PERVASIVENESS OF STIMULUS CONTROL • It is difficult to think of an example of operant behavior that is consistently reinforced in all situations. • Law of Effect may tell us how organisms learn what to do. • But, just as important as knowing what to do is knowing when to do it. • Any complete theory of behavior must also account for stimulus control.

3. DISCRIMINATION AND GENERALIZATION • Study of stimulus control of operant behavior may have two faces: • Discrimination: responding differently to different stimuli. • Generalization: responding similarly to different stimuli. • Understanding stimulus control involves comprehending processes of discrimination and generalization.

4. METHODS TO STUDY STIMULUS CONTROL • Simultaneous discrimination • Successive discrimination • Generalization gradient testing

5. PROCESS OF DISCRIMINATION • When different stimuli equivalently predict reinforcement, which controls responding may be beyond experimental control. • Salience of stimuli and past history of subject will determine effective stimulus. • But, experimenter is not altogether helpless.

6. PROCESS OF DISCRIMINATION • To ensure control of responding by a stimulus requires that it is best predictor of reinforcer availability. • Way to do so is discrimination training.

7. PROCESS OF DISCRIMINATION • First example: • GV+: poor control by line tilt • GV+/G-: good control by line tilt • GV+/R-: poor control by line tilt

8. PROCESS OF DISCRIMINATION • Second example: • 1000-Hz tone+: poor control by auditory frequency • 1000-Hz tone+/no tone-: moderate control by auditory frequency • 1000-Hz tone+/950-Hz tone-: strong control by auditory frequency

9. PROCESS OF DISCRIMINATION • If there is no best predictor of reinforcement, then almost any aspect of situation might control responding. • When tone is best predictor, one or more aspects of tone will control responding. • When frequency of tone is best predictor, that specific aspect of tone will control responding.

10. Attention in Discrimination Learning • We might say discrimination training teaches organisms to payattention. • It teaches which aspects of environment to notice and which to ignore. • When tone is S+ and no tone is S-, animal learns to pay attention to tone.

11. Attention in Discrimination Learning • Are there other implications of an attentional interpretation of discrimination learning? • One answer is theory that discrimination learning may be a two-step process. • One learns to which stimuli to attend. • One also learns to do specific things in presence of specific stimuli.

12. Attention in Discrimination Learning • Two-step theory makes predictions about transfer of training effects. • Animals trained on one kind of task are later given a second kind of task. • Behavioral measure of interest is extent to which training on first task affects, or transfers to, learning second task.

13. Attention in Discrimination Learning • One transfer comparison is critical to attentional theory: • intradimensional discrimination shift (different values on same dimension) • vs. extradimensional discrimination shift (different relevant dimensions)

14. Testing Objects Training Objects - + Group 1: Color Relevant G Intradimensional Shift (ID) - - + + R - + - + Group 2: Shape Relevant - + Extradimensional Shift (ED) Intradimensional Shift vs. Extradimensional Shift

15. Attention in Discrimination Learning • Intradimensional shift is learned faster than extradimensional shift. • Provides strong behavioral support that discrimination learning involves learning to pay attention to relevant (predictive) stimulus dimensions.

16. Attention in Discrimination Learning • In fact, discrimination learning may involve both learning to pay attention to relevant dimensions and to ignore irrelevant dimensions. • Key phenomenon here is learned irrelevance.

17. GENERALIZATION: EXCITATION AND INHIBITION • Perhaps most famous theory of discrimination learning focuses on association of excitation and inhibition with S+ and S-, respectively. • Kenneth W. Spence was author. • Our own building is part of Spence’s legacy.

18. Spence Laboratories of Psychology

19. Spence Laboratories of Psychology

20. Spence Laboratories of Psychology

21. GENERALIZATION: EXCITATION AND INHIBITION • Spence’s theory states that, when stimulus is paired with reinforcement, gradient of excitation develops around it. • Peak excitation produced by training stimulus, with orderly decreases in excitation seen as stimuli are increasingly removed from it. • In a parallel fashion, when stimulus is paired with nonreinforcement, gradient of inhibition, develops about it.

22. GENERALIZATION: EXCITATION AND INHIBITION

23. GENERALIZATION: EXCITATION AND INHIBITION • Spence’s theory makes a surprising prediction: • Peak of intradimensional generalization gradient will not be at S+. • Peak will be at a stimulus farther removed from S- • Phenomenon is called peak shift. • Spence’s theory may also apply to transposition.

24. GENERALIZATION: EXCITATION AND INHIBITION

25. GENERALIZATION: EXCITATION AND INHIBITION

26. GENERALIZATION: EXCITATION AND INHIBITION • Transposition was initially studied over 60 years ago by Gestalt psychologist Wolfgang Kohler. • Train: 3+/4- • Test: 1/2 and 5/6 • Choice of 1 and 5 implies relational rather than absolute stimulus control. • Experimental evidence does not unequivocally support either possibility.

27. Compound Stimulus Control • Control of behavior by combinations of two or more separate (or so-called “elemental”) stimuli. • Compound stimulus control is common. • Little research in compound stimulus control has been conducted in operant conditioning. • Most relevant research has been conducted in Pavlovian conditioning.

28. Compound Stimulus Control • Configural conditioning: is whole stimulus compound treated differently from its individual parts? • Overtraining with AX+ might increase control by AX at expense of A and X. • Evidence says “no.”

29. Compound Stimulus Control • Positive patterning: discrimination learning technique gives reinforcement on compound trials, but not on element trials: AX+, A-, X-. • Pavlov (1927) first investigated effects of such discrimination training. • He found greater responding to compound stimulus (AX) than to its elements (A alone and X alone).

30. Compound Stimulus Control • Positive patterning might be due to summation of excitation. • A + X should exceed A alone and X alone. • This account cannot explain negative patterning.

31. Compound Stimulus Control • Negative patterning: discrimination learning technique gives reinforcement on element trials, but not on compound trials: AX-, A+, X+. • Pavlov (1927) first investigated effects of such discrimination training. • He found greater responding to elements (A alone and X alone) than to compound stimulus (AX).

32. Compound Stimulus Control • How can negative patterning be explained? • Here, unique configural cues have been hypothesized. • Procedurally: AX-, A+, X+. • Theoretically: AX-, A+, X+. •  is a unique configural cue: enhances distinctiveness of compound stimulus.

33. Compound Stimulus Control • Unique configural stimuli also helps to explain biconditional discriminations:AC+, BD+, AD-, BC-. • Challenge here is that each element--A, B, C, D--is equally often reinforced and nonreinforced. • Way out is to hypothesize unique configural cues: AC, BD, AD, BC.

34. Stimulus Control: Summary • Individual and compound stimuli come to control operant behavior. • Organisms appear to pay attention to stimuli that are associated with different schedules of reinforcement. • Attention participates in discrimination learning and stimulus generalization. • So may excitation and inhibition.