Stimulus Control

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Stimulus Control
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Stimulus Control of Behavior

• Having stimulus control means that the
  probability of the behavior varies depending upon
  the stimuli present
• Most of our behavior is under stimulus control
• A person that contributes to charity generously
  while in church may watch every penny spent while
  at work

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Discrimination and Stimulus Control

• Discrimination is demonstrated when the subject
  responds differently to different stimuli.

Reynolds (1961)
Train
Test
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Generalization

• Generalization is when responses to one stimulus
  occur to other, usually similar, stimuli
• Generally, as the training and test stimuli
  become more different responding will decline,
  producing what is called a generalization gradient

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Generalization GradientGuttman Kalish (1956)

• pigeons reinforced for pecking a 580 nm lit key
  (orange-yellow) (S) on a VI schedule
• A test session was then given where many
  different colored key lights were presented in
  extinction

S
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Interpreting Generalization Gradients
Pigeons trained to peck a moderately bright light
(S) to get food. (S- dim light) After
asymptote is reached, present occasional
non-reinforced probe trials at various
wavelengths or levels of brightness.
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Excitatory andinhibitory gradients
Pigeons trained to peck at a 800 hz tone (S),
with a 500 nm light S-.
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1000 Hz Tone S / 950 Hz Tone S-
1000 Hz Tone always on
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Peak Shift Effect Hanson (1959)
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Spences Theory to Account for Peak Shift
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Interdimensional discrimination
Discrimination S 555nm Light S- Tone
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How do we learn discriminations with complex
stimuli?
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Perceptual learning Examples
Pre-exposure Devalue Test -- Saline-Lemon?LiC
L Sucrose-Lemon? Lemon Saline-Lemon?LiCL Sucro
se-Lemon?
Another example
Pre-exposure Devalue Test -- Saline-Lemon?LiC
L Sucrose-Lemon? Sal-L/Suc-L Saline-Lemon?LiCL
Sucrose-Lemon?
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How do we learn discriminations with complex
stimuli?
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Peceptual learning Mechanism
Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 Trial 6 Total Presentations
Sucrose Sucrose Sucrose 3
Saline Saline Saline 3
Lemon Lemon Lemon Lemon Lemon Lemon 6
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Perceptual Learning The Method of Pre-Exposure
Matters
Pre-Exposure AX?BX?AX?BX CX?CX?CX?CX Devalue
AX?LiCL Test BX? CX? Question How much does
aversion generalize to BX and CX?
A lemon B salt C sucrose X quinine
Mondragon Hall (2002)
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Whats going on?

• Juxtaposition of stimuli clearly matters
• But why?
• AX?AX?AX produces habituation to AX

Remember expected things are less salient or
associable
AX?BX?AX?BX.
A
B
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Treating Different Stimuli Alike Categorization

• Categorization can be viewed as the ability to
  treat similar, but not identical, things as
  somehow equivalent, by sorting them into their
  proper categories and by reacting to them in the
  same manner (Huber, 2001)
• Classical view categories united by a defining
  feature or features (e.g., triangles v.
  non-triangles)
• But Consider Oak leaves v. Non-oak leaves
• Chairs v. non chairs

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What is Chairness
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Categorization Experiments
Train Test Scenes with Trees New Set tree
scenes Scenes w/o trees - New Set of no-tree
scenes
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Other categories pigeons can form

• Aerial v. non-aerial photos
• Chairs
• Humans
• Cars
• Defective pharmaceutical capsules!
• Oak leaves versus other leaves

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Human v. Non-Human
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How do they do it?

• Exemplar theory remember category members and
  then generalize.
• Vaughn Greene 1984 pigeons can remember no
  less than 320 individual slides! Outdoor scenes
  randomly assigned to or

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Testing exemplar theory
Category symmetric v. asymmetric
Huber et al., (1999)
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Exemplar theory more evidence

• Cook (1990)
• Birds versus Mammals used in slides
• Real Category Group Birds v. Mammals
• Pseudocategory Group Random Bird Mammals
  versus Random Birds Mammals

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Feature Theory

• Individual features acquire associative value.
• Response rate to stimulus depends on total
  expectancy (V) evoked.

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Feature Theory Evidence
Cerella (1980) Train Charlie Brown , other
characters Test Keep all features intact,
but alter whole
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Prototype theory

• Abstract the ideal (or average) category
  exemplar.
• To test train with only extreme exemplars, test
  with average of extremes.

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Prototype Theory
Posner Keele 1968
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Conclusions

• Not clear whether birds can extract abstract
  concepts in categorization experiments
• Birds may use features and exemplars
• Another animals may be capable of more complex
  feats.