Classic Conditioning
Classic (also
called respondent conditioning results from the repeated pairing of a
neutral conditioned) stimulus with one that evokes a response (unconditioned
stimulus), such that the neutral stimulus eventually conies to evoke the
response. The lime relation between the presentation of the conditioned and
unconditioned stimuli is important and varies tor optimal learning from a
fraction of a second to several seconds.
The Russian physiologist and Nobel Prize winner Ivan
Petrovich Pavlov observed in his work on gastric secretion that a dog salivated
not only when food was placed in its mouth hut also at the sound of the
footsteps of the person coming to feed it. even though the dog could not see or
smell the food. Pavlov analyzed these events and called (he saliva flow that
occurred with the sound of footsteps a conditioned response (CR)—a
response elicited under certain conditions by a particular stimulus.
In a typical pavlovian experiment, a stimulus (S)
that had no capacity to evoke a particular response before training did so
after consistent association with another stimulus. For example, under normal
circumstances, a dog does not salivate at the sound of a bell, but when the
bell sound is always followed by the presentation of food, the dog ultimately
pairs the bell and the food. Eventually, the bell sound alone elicits salivation
(CR).
Because the food naturally produces
salivation, it is referred to as an unconditioned stimulus (UCS).
Salivation, a response that is reliably elicited by food (UCS) is referred to
as an unconditioned response (UCR). The bell, which was originally unable
to evoke salivation but came to do so when paired with food, is referred to as
a conditioned stimulus (CS). Classic conditioning is most often applied
to responses mediated by the autonomic nervous system.
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