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

Pavlovian Conditioning: "It's not what you think it is"

Robert A. Rescorla of the University of Pennsylvania was probably the most influential classical conditioning researcher in the late 20th Century. In a 1988 American Psychologist article addressed to his fellow academic psychologists titled "Pavlovian Conditioning: It's not what you think it is," Rescorla complained that psychologists had ignored developments in research on classical conditioning during the preceding 20 years. Rescorla cited the out-of-date description of classical conditioning in a 1966 introductory psychology textbook he had as a student.

[Quoting the 1966 textbook] "The essential operation in conditioning is pairing of two stimuli. One, initially neutral in that it elicits no response, is called the conditioned stimulus ( CS) ; the other, which is one that consistently elicits a response, is called the unconditioned stimulus (US). The response elicited by the unconditioned stimulus is the unconditioned response (UR). As a result of the pairing of the conditioned stimulus (CS) and the unconditioned stimulus (US), the previously neutral conditioned stimulus comes to elicit the response. Then it is called the conditioned response (CR)."

Rescorla noted, "This description is typical of those found in both introductory and advanced textbooks 20 years ago." The problem was that the same sort of description was continuing to appear in 1988, when Rescorla wrote his article, despite "dramatic conceptual changes that had taken place." In fact, it is still typical of how classical conditioning is described in many textbooks, an additional 20 years later, as we approach 2008. What was wrong with the old-fashioned description of conditioning? Rescorla cited these problems:

What were problems with many textbook descriptions of classical conditioning, in Rescorla's view?

1. The textbook description emphasized contiguity [closeness in time] of the conditional stimulus and unconditional stimulus, while modern studies emphasize the informative or predictive nature of the conditional stimulus.

2. The textbook description gave the impression any two stimuli could be associated as conditional stimulus and unconditional stimulus. Modern research shows that some stimuli are much easier to associate with a particular biological response than others.

3. The old textbook description gave the impression conditioning was slow and gradual, requiring many repetitions or trials. Rescorla wrote, "Although conditioning can sometimes be slow, in fact most modern conditioning preparations routinely show rapid learning" requiring from 1 to 8 trials.

Rescorla also wanted to change the image of classical conditioning. He said, his professors back in the 60s conveyed the impression classical conditioning was "all spit and twitches," because famous experiments relied on reflexes like salivation, eyeblinks, and finger withdrawal. Rescorla pointed out that classical conditioning in the modern era is relevant to much more than spit and twitches. Classical conditioning "is intimately involved in the control of central psychological processes, such as emotions and motivation." The following section of the chapter contains many examples that support Rescorla's arguments. Classical conditioning is now known to be involved with the immune system, sexual anticipation, tolerance to addictive drugs, and much more.

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