Classical Conditioning

Classical conditioning is a learning process in which an organism learns to associate two stimuli (e.g. food and a pleasant event), such that one stimulus (the food) comes to produce a response (feeling happy) that originally was produced only by the other stimulus (the pleasurable event). Unlike habituation, it involves learning an association between stimuli.

Classical conditioning is also known as Pavlovian conditioning, to reflect the contributions of Ivan Pavlov, who discovered that classical conditioning alerts organisms to stimuli that signal the impending arrival of an important event. Through experiments with dogs, he learned that after a neutral stimulus such as a tone is repeatedly associated with food (unconditioned stimulus), the tone becomes capable of eliciting a salivation response.

Basic Principles of Classical Conditioning

Classical conditioning involves pairing a neutral stimulus (e.g. a tone) with an unconditioned stimulus (UCS) (e.g. food) that elicits an unconditioned response (UCR) (e.g. salivation). Through repeated pairing, the neutral stimulus becomes a conditioned stimulus (CS) that evokes a conditioned response (CR) similar to the original UCR. In other words, the tone becomes a conditioned stimulus, and salivation becomes the conditioned response.

The UCR is a natural, unlearned (unconditioned) reflex, while the CR represents a learned (conditioned) response.

You can find a good illustration of classical conditioning as it relates to Pavlov’s experiment here.

Classical conditioning is usually strongest when

1. there are repeated CS-UCS pairings

2. the UCS is more intense

3. the sequence involves forward pairing (the CS appears immediately before the UCS), and

4. the time interval between the CS and US is short.

Acquisition refers to the period during which a response is being learned. The acquisition phase involves pairing the CS with the UCS. Each pairing is called a learning trial.

Extinction is the disappearance of the CR, and occurs when the CS is presented repeatedly in the absence of the UCS. Sometimes, spontaneous recovery occurs after a rest period, and the CS will temporarily evoke a response even after extinction has taken place.

Stimulus generalization occurs when a CR is evoked by a stimulus similar to the original CS.

Discrimination occurs when a CR occurs to one stimulus but not another.

Once a stimulus becomes a CS, it can now be used in place of the original UCS to condition other neutral stimuli. This is called higher-order conditioning.

A wide range of bodily and psychological responses can be classically conditioned, including fears, sexual attraction, and positive and negative attitudes. Techniques based on classical conditioning are very successful in treating fears and phobias.

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