Pavlovian Conditioning

Basic Principles

Thomas G. Bowers, Ph.D.

Penn State Harrisburg

Development of a Conditioned Reflex

CSUCS

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

0

50

100

150

200

250

Licks per minute

Pret

est

Post

test

Period

Learning to Poison

Taste

Light+Noise

Taste Aversion Learning

050

100150200250300350

Licks per minute

Pret

est

Post

test

Period

Learning to Noise

Taste

Light+Noise

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

% of CR

Trials

CS-

CS+

Discrimination Gradient

% of CR

600 700 900 1KHz

CS+

Inhibitory Gradient

% of CR

600400 450 550 nm

Light wavelength CS-

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”