A response may be produced with very high probability after a specific stimulus. This type of stimulus-response relation -- or reflex -- does not require prior learning.

The reflex is the building block of Pavlovian conditioning. The unconditioned stimulus and unconditioned response together comprise the reflex.

The eye blink to a puff of air to the cornea is an example of a reflex.

Pavlovian Conditioning

Pavlovian conditioning is an important form of learning that involves the pairing of stimuli independent of an organism's behavior. The key stimulus and response elements of Pavlovian conditioning are:

Unconditioned stimulus

This type of stimulus unconditionally elicits a response, also referred to as a respondent. For example, a puff of air to the cornea of the eye is an unconditioned stimulus that produces a blinking response.

Unconditioned response

This type of response occurs to an unconditioned stimulus without prior conditioning. The blinking response after a puff of air to the cornea of the eye is an example of an unconditioned response.

Conditioned stimulus

A conditioned stimulus in Pavlovian conditioning is an initially neutral stimulus that is paired with the unconditioned stimulus. For example, a tone sounded just prior to the puff of air being delivered to the cornea of the eye. Without prior training, the tone does not elicit an eye blink: however, after a number of tone-puff pairings, the tone alone comes to elicit the blinking response.

Conditioned response

A conditioned response in Pavlovian conditioning is the response that the conditioned stimulus elicits after it has been repeatedly paired with an unconditioned stimulus. The conditioned response may be similar in form to the unconditioned response. For example, the eye blink to the tone conditioned stimulus may involve the same bodily musculature as the eye blink to the puff of air to the cornea.


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