Pavlovian conditioning. It's not what you think it is.

Current thinking about Pavlovian conditioning differs substantially from that of 20 years ago. Yet the changes that have taken place remain poorly appreciated by psychologists generally. Traditional descriptions of conditioning as the acquired ability of one stimulus to evoke the original response to another because of their pairing are shown to be inadequate. They fail to characterize adequately the circumstances producing learning, the content of that learning, or the manner in which that learning influences performance. Instead, conditioning is now described as the learning of relations among events so as to allow the organism to represent its environment. Within this framework, the study of Pavlovian conditioning continues to be an intellectually active area, full of new discoveries and information relevant to other areas of psychology. Pavlovian conditioning is one of the oldest and most systematically studied phenomena in psychology. Outside of psychology, it is one of our best-known findings. But at the same time, within psychology it is badly misunderstood and misrepresented. In the last 20 years, knowledge of the associative processes underlying Pavlovian conditioning has expanded dramatically. The result is that modern thinking about conditioning is completely different from the views psychologists held 20 years ago. Unfortunately, these changes are very poorly appreciated by psychologists at large. The last time many psychologists read anything about Pavlovian conditioning was before these changes took place. Even those more recently educated often received that education from textbooks and instructors that had largely ignored the dramatic conceptual changes that had taken place. The result is that many think of Pavlovian conditioning as an obsolete technical field that is intellectually stagnant. My intention in this article is to show that this view is incorrect. First, I will review some of the changes that have occurred in Pavlovian conditioning in order to give the flavor of its contemporary form. I will argue that it is an intellectually challenging field, in which substantial and exciting progress has been made. Second, I will argue that conditioning continues to have a central place in psychology generally. I will describe how it touches on and informs several related fields that are currently more in vogue. To begin the discussion, consider how conditioning was described 20 years ago, when those in my generation were students. One popular introductory text put it thus: The essential operation in conditioning is a 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).  This description is typical of those found in both introductory and advanced textbooks 20 years ago. Unfortunately, it is also typical of what one finds in textbooks today. One popular introductory American Psychologist, 43(3), 151-160