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Pavlovian (Classical) Conditioning

Pavlovian (Classical) conditioning is learning an association between two stimuli. It is named for I. P. Pavlov, the Russian physiologist who first systematically investigated this form of associative learning. In Pavlovian conditioning, the subject learns to associate a previously unrelated neutral stimulus with another stimulus that reliably elicits some kind of reaction. Pavlov used food or mild acid in the mouth to elicit salivation reliably. As you may recognize, the stimulus that reliably elicits a specific response is a reflex.

Pavlovian conditioning involves two kinds of stimuli and the responses that go with them:

  • The unconditioned stimulus (US) and the unconditioned response (or reflex) it elicits
  • The conditioned stimulus and the conditioned response (or reflex) it can elicit after Pavlovian conditioning has taken place.

To help you remember what "conditioned" and "unconditioned" mean, click HERE for an explanation of how they originated.

The unconditioned stimulus (US) is a stimulus that elicits a response unconditionally whenever it is presented, without past training or practice.

The response that a US elicits is the unconditioned response (UR).

Some examples of unconditioned responses:

  • A tickle in the nose elicits a sneeze
  • an air puff to the eye elicits a blink
  • moderate electric shock elicits a flinch and increased perspiration
  • a taste of food elicits (triggers) salivation in a hungry individual.

The conditioned stimulus (CS) is an initially neutral stimulus that becomes able to elicit a new response when it reliably predicts a US. The first time it is presented, it elicits an orienting reaction (see above under habituation). By pairing a neutral stimulus with a US, it becomes a CS and becomes able to elicit a new response (or reflex).

The conditioned response (CR) is the response that the CS triggers. The capacity of the CS to elicit the CR is conditional upon (depends upon) its association with a US.

Some examples of conditioned responses:

  • Seeing a dish of double fudge ice cream triggers salivation. This visual signal reliably predicts (precedes) taste of the ice cream, which reliably elicits salivation. (The first time you saw a dish of ice cream, it was neutral, because it was unrelated to the taste of the ice cream.)
  • A flash of lightning makes many people jump. This visual signal predicts loud thunder, which reliably makes them jump.

The relations between CS and initial orienting reaction and between US and UR are often represented diagrammatically, as shown in Figure 1:

For more information see exercise asgn3a, b, and c.