Although he won a Nobel prize for his work in explaining the processes of digestion, Ivan Pavlov is best remembered for his discovery of classical conditioning. A physiologist by training and in practice, Pavlov thought psychology was a fad. His explanations of conditioning were pure physiological but they were interpreted by Watson and others as psychological.
Born in Ryazen (central Russia), Pavlov attended the University of St. Petersburg where he studied under Ivan Schenov (who had been a student of Muller and Helmholtz). After receiving his MD in 1883, he studied physiology for two years in Leipzig, Germany. In 1889, Pavlov’s experiments on the digestive process brought about a curious observation. He noted that the dogs being used as subjects in his experiments salivated not only to the presence of food but to associated stimuli (sound of keeper’s bell jingling, etc.). Exploring the matter as a good physiologist would, Pavlov employed a surgical procedure which allowed him to collect and measure the amount of saliva produced by each dog. Having established a reliable dependent variable, Pavlov varied one independent variable at a time and noted the results.
Pavlov’s classical description notes that the presence of an unconditioned stimulus (food) produces an unconditioned response (saliva of a given amount; varying somewhat between trials and between dogs). After sufficient pairings of the food with another, previously unused stimulus (e.g., light), the conditioned stimulus (light) could bring about a response (conditioned response). The conditioned response was weaker than the unconditioned response (i.e., less saliva) and forgettable (if repeated too often without food being presented).
Pavlov called the conditioned response “psychic secretion,” and explained it as being the result of higher cortical involvement. Interestingly, when the conditioned stimulus was repeatedly given until no psychic secretions occurred, a period of rest was all that was needed for the conditioned response to reappear. Pavlov assumed that this “spontaneous recovery” of the association was due to excitation of neural connections.
Pavlov studied classical conditioning quite thoroughly. He showed that similar stimuli to a conditioned stimulus produced similar results. That is, there was “irradition” (a spread of effect to other parts of the brain). For Pavlov, stimulus generalization was a neurological process. Similarly, neural physiology was assumed to explain discrimination. That is, subjects were able to learn to salivate in response to a particular tone but not salivate when other tones were presented. Naturally, if too fine of a discrimination was required, the dogs could not solve the problem. Pavlov called their resultant barking and unmanageability “experimental neurosis.”
For Pavlov, reinforcement was in terms of reiteration. One reinforced behavior as in reinforcing steel (added more of it). Pavlov believed that mental functioning was completely neurological. He proposed a “dynamic stereotype,” a neurological mapping of the environment.
Here’s a video lecture on Ivan Pavlov.