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Summary: Classical Conditioning

Ivan Pavlov, a Russian physiologist, was studying digestion in dogs. He discovered classical conditioning accidentally.

Pavlov noticed that a dog salivated at the sight of a food bowl. Pavlov recognized this as an important phenomenon.

It represented the triggering of a biological reflex (salivation) by learning (in this case, by the sight of the bowl). Pavlov studied this phenomenon in the laboratory and called it signalization.

Classical conditioning always starts with a reflex: an unlearned stimulus-response circuit in the nervous system. In many situations, an organism benefits by making an anticipatory response, if it knows the reflex will be activated.

Therefore animals are sensitive to cues that predict the activation of a reflex. Such signals allow the animal to make an anticipatory biological response. This is classical conditioning.

Learning or acquisition occurs when a signal or cue is put before the activation of a reflex. Learning is fastest if the signal comes about a half second before the reflex, particularly if the reflex involves skeletal muscle movement, such as a knee jerk or withdrawal of a fingertip. Learning typically occurs after only a few pairings of signal with reflex.

Extinction or unlearning occurs when the predictive relationship between a signal and reflex is destroyed. The signal is presented but the reflex is prevented or a competing reflex is activated.

If the signal no longer has predictive power, and the animal ceases to respond to it. That is extinction. Typically a creature respond to the signal again, after some time has passed, to see if the predictive relationship has returned. This is called spontaneous recovery.

To completely eliminate a conditional response, the recovered response must be extinguished again after spontaneous recovery. This procedure must be repeated until a response does not come back, for extinction to be complete.

Generalization is the label for giving the same response to different stimuli. The more similar the stimuli, the more generalization will occur.

In naturalistic settings, a conditional response may or may not occur, depending on how an organism categorizes stimuli. If a young child puts all four-legged creatures into the same category, being scratched by a cat will make the child scared of dogs as well.

Discrimination is the name for giving different responses to distinct stimuli. It is the opposite of generalization. An animal discriminates between stimuli when it responds differently to them.

Habituation is cessation of response to a repeated stimulus. It occurs even in small babies. Dishabituation (release from habituation) can be used to determine whether babies discriminate between different categories of stimuli.

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