Current%20Theoretical%20Approaches%20and%20Issues%20in%20Classical%20Conditioning

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Current Theoretical Approaches and Issues in
Classical Conditioning

• Psychology 3306

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Everything you know is wrong

• So, the number of pairings is an important, maybe
  all important, variable in determining the amount
  of conditioning, right?
• Fine, then explain Kamin Blocking to me

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Kamin (1968)
Group Phase 1 Phase 2 Test Result
Control Nothing LT T CR
Blocking L LT T No CR
L Light T Tone CS (shock)
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Blocking is rocking

• Same number of tone shock pairings in both groups
• It is NOT just number of pairings
• The tone predicts nothing in the blocking group
  (nothing extra anyway)
• These results, and some others, lead to the
  Rescorla Wagner Model

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You said thered be no math!

• Yes, it is a math model
• Trial by trial
• Assumes you can get excitatory conditioning,
  inhibitory conditioning or nothing
• All based on what the CS predicts
• Lets look at the rules

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The Rules

• If the strength of the US is greater than
  expected then excitatory conditioning to the CS
  is the result
• If the strength of the US is LESS than expected,
  then you will get inhibitory conditioning
• The larger the discrepancy between what is
  observed and what is expected, the greater the
  conditioning

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More rules

• The more salient the CS, the more conditioning
  you will get
• Two or more CSs together, their strength is
  additive
• This is, in essence, a model of surprise! The
  more surprised the animal, the more it learns

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The model makes some groovy predictions

• Slope of the acquisition curve
• Blocking
• Conditioned inhibition
• Overshadowing
• Overexpectation

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Overexpectation
Group Phase I Phase II Test Result
Exp L T LT L, T Weak CR
Control L T nothing L, T Strong CR
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The Model

• ?Vi Si(Aj-Vsum)
• i CS
• j US
• S Salience
• A Value of the US
• V amount of conditioning
• These quantities are, of course, hypothetical

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An example

• OK, say a food pellet 100
• Say salience of a light CS .2
• Vsum 0 (at the start of the experiment, there
  is no conditioning yet

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OK, now for the numbers

• Trial 1
• ?Vi Si(Aj-Vsum)
• .2(100 0)
• 20
• Trial 2
• ?Vi .2(100-20)
• 16

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Continued.

• Trial 3
• ?Vi Si(Aj-Vsum)
• ?Vi .2(100-36)
• -12.8
• And so on.
• Less and less conditioning as time goes by
• Coo eh

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Overshadowing

• CS1 -gt Light, S .2
• CS2 -gt Noise, S .5
• 2 CSs, so two calculations per trial
• Trial 1
• ?VLight .2(100-0) 20
• ?VNoise .5(100-0) 50

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Overshadowing

• Trial
• ?VLight .2(100-70) 6
• ?VNoise .5(100-70) 15
• OK, how does blocking work?
• Well there is no strength left
• Conditioned inhibition?
• Negative for old CS
• Additive model

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Stuff it cannot deal with

• CS preexposure
• Change S?
• Mackintoshs attentional theory does this, S
  becomes an attention parameter
• Pearce Hall model
• Gallistels model

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Types of associations

• First order conditioning is S-S
• Second order is S-S and S-R
• CS - context associations too
• US context associations
• Context Blocking
• CS CS associations in compound stimulus
  experiments
• Occasion setting (Holland)

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Constraints on Pavlovian Conditioning

• Taste aversions
• Not just sickness
• Not the aftertaste
• Only to certain elements of the food, which
  depends on the species
• Special?
• Could just be a quantitative difference (Andrews
  and Braverman, 1975)

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Form of the CR

• CR is often like the UR but not always
• Weaker
• Opposite direction
• Drug tolerance
• Compensatory CRs with opiates
• Context as CS
• Shooting gallery effect
• Could depend on drug action being in PNS or CNS
  (Stewart et al)

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Physiological Basis

• New synapses formed in Aplysia
• Increase in transmitter release in neurons
  sensitive to CS (very cool)
• Just like habituation!
• What about more complex creatures

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Five points about Physiology and conditioning

• 1) CR and UR pathways are often different
• 2) CR production is distributed
• 3) Conditioning is distributed
• 4) Different CRs, different brain regions
• 5) Sometimes it is individual neurons
• My conclusion then is that we have a very basic
  mechanism at work here