Ivan Pavlov was a Russian scientist whose work bridged the disciplines of physiology and psychology. Although he was by training a doctor, his most significant contribution lay in the field of behavioral psychology. After working as an experimental researcher, Pavlov became head of the department of physiology at Russia’s Institute of Experimental Medicine. Pavlov received the Nobel Prize in 1904 for his classic experiments in the role of conditioned reflexes in dogs’ neurophysiology.

As sometimes happens in the world of experimental research, Pavlov began his work in an rather ordinary undertaking which took a dramatic turn mid-course. Observations and events quite unrelated to the focus of the experiment took on greater import than the original purpose of the work. In essence, Pavlov’s study is quite easy to understand, yet its implications are profound.

Pavlov began experiments on the digestive activities of dogs. This included, quite simply, studying the saliva and gastric juices which are produced reflexively when food is placed into a dog’s mouth. However, over the course of the experiments, Pavlov noted that the dogs began to salivate when other environmental clues associated with food delivery were presented. Thus, the sound of a ticking metronome which always preceded food delivery could cause the dogs to begin to salivate. Perhaps this does not seem a profound insight on Pavlov’s part. But what he had inadvertently discovered was that inborn reflexes (such as the salivary reflex) could be conditioned to environmental stimuli (such as ticking metronomes). In psychological terms, the unconditioned stimulus (food) which inevitably produces an unconditioned response (salivation and gastric juice secretion) could be paired in such a way that a tone or a sight or a smell could come to elicit the same response (now called a conditioned response). There was no inborn reason why a dog should salivate upon hearing a tone, seeing a lab coat, or smelling a certain odour, but with close time associations, these same reflexes could be programmed to occur. Pavlov discovered that even in the absence of food, these signals from the environment could cause the organism to respond with a conditioned reflex.

Pavlov had discovered one of the key ways in which organisms learn. Reflexes are an important part of inborn survival tools, but learning to hone them through external clues makes the animal or the human much more adaptive and responsive to the nuances of the environment. A neutral event could be paired with a pleasant or an unpleasant unconditioned stimulus and the neutral signal would take on the ability to elicit the reaction. The organism is therefore in a more favourable state to meet the meal or the predator.

Pavlov’s discovery lead to the beginnings of the science of behaviorism – in which an organism’s behavior could be objectively seen and measured. Behaviorism moved psychology from introspection about the mind, to a study of observable events in the environment. It became the second wave of psychological theorizing and methodology.

Classical conditioning is used as a psychotherapy today primarily in desensitization procedures in phobias. It is thought that phobias might be learned by the pairing of rather harmless events with fear-producing ones. However, most adults with phobias seem unable to remember such occurrences. Nevertheless, a counter-conditioning procedure can help them to alter their typical phobic responses. By learning to pair deep relaxation with mental images of their phobic situation, the fear response gradually begins to be marginalized. Relaxation and fear are incompatible responses. As relaxation becomes the conditioned response to the phobia, the fear response is reduced.