This is the 2007 version. Click here for the 2017 chapter 05 table of contents.

Summary: Classical Conditioning

Ivan Pavlov, a Russian physiologist who was studying digestion in dogs, 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 a reflex response to appropriate situations slightly early. 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 of a classically conditioned response 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, 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 of a classically conditioned response occurs when the predictive relationship between the signal and the reflex is destroyed. The signal is presented but the reflex is prevented or a competing reflex is activated. Soon the signal no longer has predictive power and the animal ceases to respond to it. After a time, or if the context is changed, an extinguished response may reappear. To completely eliminate a conditional response, the response must be extinguished several times.

Generalization is the name for responding the same way to different situations. The more similar the situations, the more generalization will occur. In naturalistic settings, a conditional response may occur or not depending upon how an organism categorizes stimuli.

Discrimination is the name for responding differently to distinct stimuli. It is the opposite of generalization. An animal discriminates between stimuli when it responds differently to them. An example is release from habituation. It occurs even in small babies and can be used to determine whether they distinguish between different categories of stimuli.

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