The discovery of the principles of reinforcement, extinction, generalization, and differentiation of conditional reflexes in Pavlov's laboratories.

The discovery of reinforcement, extinction, generalization, and differentiation with the conditional reflex method in Pavlov's laboratories is described. Modern American introductory texts show that contemporary understanding of the experimental work on conditioning in Pavlov's laboratories is derived from a 1927 English translation of Pavlov's lectures on the conditional reflexes. The lectures present the discoveries topically, not chronologically. In contrast, this article presents a chronological account of the contributions of S.G. Vul'fson, I.F. Tolochinov, and B.P. Babkin, which led to the conceptualization of reinforcement and extinction, and the work of V.N. Boldyrev and N.A. Kashereninova, which led to the formulation of the concepts of generalization and differentiation. This historical approach avoids giving the impression that the development of the Pavlovian paradigm was a highly systematic pursuit.