Classical Conditioning

Classical conditioning (also named Pavlovian conditioning, for Ivan Pavlov, the researcher who pioneered the topic) is considered, along with habituation, to be a fundamental form of learning. The term conditioning is used because classical, along with instrumental and operant, is considered a simpler and more basic form of learning. As a form of learning, classical conditioning involves a relatively permanent change in behavior potentiality that arises as a result of particular experiences. Hence, at one time a certain behavior does not take place. But as a result of independent variables (or imposed stimulus contingencies), a particular target behavior then does take place with greater probability.

Unlike habituation, which involves only a single stimulus, classical conditioning involves two stimuli that are paired. The purpose of one stimulus is to reliably elicit behavior. This is the unconditional stimulus (or US, because it will provoke a response unconditionally), also called unconditioned stimulus (because the response to it did not have to be trained). It elicits the unconditional, or unconditioned, response (UR), which is already in the organism's repertoire. The other stimulus—the conditional stimulus (CS), because the response to it is conditional, or conditioned stimulus, because the response to it must be learned—is neutral with respect to the US. The CS, in order to be a stimulus, must evoke some response; but that response, or pattern of responses, is unrelated to the US, and hence, those responses have little or no similarity to the UR. If training is effective, then the CS has acquired some capacity to elicit a response that resembles the UR. But because it is elicited by the CS alone, it is considered a learned response—a conditioned (learned), or conditional, response (CR).

Training consists of pairing CS and US, ideally with CS onset preceding US onset on each trial. So, initially, before conditioning, the CS provokes little or no conditioned response, which serves as a baseline for evaluating the amount of learning reflected in the amount (percentage, magnitude, probability) of CR following training.

All of the basic phenomena that take place in learning paradigms (to include instrumental, operant, and habituation) are found in classical conditioning. As in other paradigms, acquisition occurs as a negatively accelerated function, meaning that the greatest behavior change takes place during early trials. A practical implication is that those initial trials are rather crucial because this is the time when errors are readily mastered, and considerable training will be needed to extinguish those flawed behaviors. Another implication arises later in learning when performance is nearing asymptote. As a curve of decreasing returns, less and less additional change in performance (reflecting less and less further learning) is observed with additional training trials. (Good examples of these considerations are found in learning physical or sport skills. During initial training, mistakes can be learned quite readily—pointing out the importance of guidance and error-free training for novices. Later, highly skilled performers have difficulty maintaining motivation to keep working when their efforts seem to show very little payoff.) The other basic phenomena include such matters as extinction, spontaneous recovery, stimulus generalization (positive transfer), stimulus discrimination, external inhibition, disinhibition, and so on.

...