Differential Reinforcement: Stimulus Control & Shaping Lecture 12

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 ~

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

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

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? ~

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

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 ~

Stimulus Generalization Gradient Hi SD Strength of Response Lo Shades of Blue

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

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

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

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

Before Additional Training: Generalization Hi SD Number of Pecks Lo Shades of Blue

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

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

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

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

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 ~

Shaping: Successive approximations

Shaping: Successive approximations RFT if orients toward ~

Shaping: Successive approximations

Shaping: Successive approximations

Shaping: Successive approximations

Shaping: Successive approximations