Differential Reinforcement: Stimulus Control

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Differential Reinforcement Stimulus Control
Shaping

• Lesson 11

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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

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Differential Reinforcement

• Response differentiation
• Differentiation of SD and S?
• Contextual cues
• SD B ? successful outcome
• S? 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 Gradient
Hi
SD
Strength of Response
Lo
Shades of Blue
9
Stimulus Discrimination

• Distinguish between 2 similar stimuli
• One never reinforced S?
• 2 classes of Discriminative stimuli
• SD
• S?

10
SD vs S?

• SD signals that B will be reinforced

SD(blue) B (bar press) ? SR(food)
11
Stimulus Similar to SD

• Response occurs

S? (lighter blue) B (bar press) ? no
SR(food)

• S? signals that B will not be reinforced

12
S?

• After training (experience)
• Signals that SR will NOT follow B

S? (lighter blue) no B (no bar press)
13
Before Additional Training Generalization
Hi
SD
Numberof Pecks
Lo
Shades of Blue
14
Generalization ? Discrimination
Pecking not reinforced when S? present
Hi
SD
S?
S?
Numberof Pecks
Lo
Shades of Blue
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Generalization ? Discrimination
Pecking not reinforced when S? present
Hi
SD
Numberof Pecks
S?
S?
Lo
Shades of Blue
16
Generalization ? Discrimination
Pecking not reinforced when S? present
Hi
SD
Numberof Pecks
S?
S?
Lo
Shades of Blue
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Stimulus Discrimination
Pecking during S? diminishes
Hi
SD
Numberof Pecks
S?
S?
Lo
Shades of Blue
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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

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Shaping Successive approximations
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Shaping Successive approximations

• RFT if orients toward

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Shaping Successive approximations

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Shaping Successive approximations

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Shaping Successive approximations
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Shaping Successive approximations