1. Differential Reinforcement: Stimulus Control & Shaping
Lecture 12

2. Modifying Behavior Response variability
Engage in many different behaviors
Differential reinforcement
Some Bs reinforced, some not
Response selection
Stimulus control
Generalization & Discrimination
Shaping
Changes in response probability ~

3. Differential Reinforcement
Response differentiation
Differentiation of SD and SΔ
Contextual cues
SD: B  successful outcome
SΔ: B  unsuccessful outcome
Example:
switching lights for class ~

4. Differential Reinforcement
B1: Flip left switch
SDs
B2: Flip middle switch
B3: Flip right switch
Example: Puzzle box
Contextual cues?
Possible responses? ~

5. Differential Reinforcement: Continuous Variations in Behavior
On a single behavior
Variations in strength of extent
e.g., baking time for cookies
Not enough  doughy
Too much  burnt
SDs for good cookies?
SDs for bad cookies?
Other examples? ~

6. Stimulus Control Generalization similar stimuli  similar response
Discrimination
after more experience
differential reinforcement
similar stimuli  different response
Stimulus generalization gradient
lower similarity  lower response ~

7. Stimulus Generalization
Present new stimulus
Similar to SD or CS
associative
Response occurs
even though not reinforced
or paired with US
Novel stimulus
presented only a few times ~

8. Stimulus Generalization GradientHi SD
Strength
of Response Lo
Shades of Blue

9. Stimulus Discrimination
Distinguish between 2 similar stimuli
One never reinforced: SΔ
2 classes of Discriminative stimuli SD
SΔ ~

10. SD vs SΔ SD signals that B will be reinforced ~
SD(blue) : B (bar press)  SR(food)

11. Stimulus Similar to SD Response occurs
SΔ (lighter blue) : B (bar press)  no SR(food)
SΔ signals that B will not be reinforced ~

12. SΔ After training (experience) Signals that SR will NOT follow B
SΔ (lighter blue) : no B (no bar press)

13. Before Additional Training: GeneralizationHi SD
Number of Pecks Lo
Shades of Blue

14. Pecking not reinforced when SΔ present
Generalization  Discrimination
Pecking not reinforced when SΔ present Hi SD SΔ SΔ
Number of Pecks Lo
Shades of Blue

15. Pecking not reinforced when SΔ present
Generalization  Discrimination
Pecking not reinforced when SΔ present Hi SD
Number of Pecks SΔ SΔ Lo
Shades of Blue

16. Pecking not reinforced when SΔ present
Generalization  Discrimination
Pecking not reinforced when SΔ present Hi SD
Number of Pecks SΔ SΔ Lo
Shades of Blue

17. Pecking during SΔ diminishes
Stimulus Discrimination
Pecking during SΔ diminishes Hi SD
Number of Pecks SΔ SΔ Lo
Shades of Blue

18. Systematic Shaping Bar pressing: natural behavior for rats?
Differential reinforcement of successive approximations
Reinforce Bs similar to part of desired B
Progressively shift to closer approximations
B – SR contingency ~

19. Shaping: Successive approximations

20. Shaping: Successive approximations
RFT if orients toward ~

21. Shaping: Successive approximations

22. Shaping: Successive approximations

23. Shaping: Successive approximations

24. Shaping: Successive approximations