Pavlovian Conditioning
Basic Principles
Thomas G. Bowers, Ph.D.
Penn State Harrisburg
Development of a Conditioned
Reflex
CS
UCS
UCR
CS
UCS
UCR
Development of a Conditioned
Reflex
• Onset of CR advances to the onset of the CS
• CR does not exactly mimic the UCR, but
generally closely resembles the UCR
Conditioned Fear Responses
• If the UCS is a brief noxious stimuli (such
as an electric shock) conditioned fear can
result
• Includes increase in heart rate, respiration,
tension, urination and so on
• Also called conditioned emotional response
(CER) or conditioned suppression
Conditioned Fear Responses
• CER can suppress a well developed operant
• Suppression ratio
Rate Csa
_______________________
Rate CSa + Rate CSb
Autoshaping
• Automatic shaping of key pecking or
similar behavior
• Key pecking is elicited after successive
trials of lighting key just before food
delivery
Autoshaping
• Similar to Breland & Breland’s difficulty
with shaping Racoon behavior
• Also described as sign tracking
Taste Aversion Learning
• Research by Gracia and Koelling (1966)
• Posed a paradox in our understanding of
behavior
• Animals appearing to optimally learn some
relationships, but to not managed to learn to
other stimulus relationships
Taste Aversion Learning
Learning to Poison
250
200
Licks per 150
minute 100
Taste
Light+Noise
Posttest
0
Pretest
50
Period
Taste Aversion Learning
Learning to Noise
Taste
Posttest
Light+Noise
Pretest
350
300
250
Licks per 200
minute 150
100
50
0
Period
Why Is Learning Selective?
• There can be learning to non-optimal
temporal contiguity
• Yet no effective learning to more optimal
temporal relationships
• Sometimes described as an associative bias
Inhibition and Excitation
• Most conditioning we discuss is excitatory
in nature
• Extinction was thought to develop an
inhibition of the conditioned response rather
than a simple erasure of the CS-UCS
connection
Methods to Detect Inhibition
• Presentation of a novel stimulus during
extinction of of CS-UCS relationship should
result in a CR
• This process is described as disinhibition,
and the response returns in a full blown
fashion
• Summation Test
Methods to Detect Inhibition
• Compound stimuli where a stimulus
predicted safety should be able to reduce
conditioned fear
• Resistance to reinforcement test - Previous
training to a neutral stimulus should
develop inhibition, and hence take longer to
acquire a CR
Conditions Producing Inhibition
• Extinction
• Inhibition and delay
– In delay conditioning, the CR tends to occur
only in the later part of the CS
– Presenting a novel stimulus early in the CS
will result in increased CR
Conditions Producing Inhibition
• Discrimination and Generalization
• Process of distinguishing between CS+ and
CS-, where CS+ signals the UCS is coming
while CS- predicts the UCS will not be
available
Conditions Producing Inhibition
CS+
% of CR
CSTrials
Discrimination Gradient
CS+
% of CR
600
700
900
1K
Inhibitory Gradient
Light
wavelength
CS-
% of CR
400 450
550
600
nm
Conditioned Inhibition
• Backward conditioning
– Recall that if UCS precedes the CS, then
conditioning does not occur
– However, the CS becomes a conditioned
inhibitor
What Is Learned in Conditioned
Inhibition?
• S-S associations?
• S-R associations?
• CS appear to be “occasion setters”