2015 Reprint of 1927 Edition. Full facsimile of the original edition. Not reproduced with Optical Recognition Software. Pavlov's description on how animals (and humans) can be trained to respond in a certain way to a particular stimulus drew tremendous interest from the time he first presented his results. His work paved the way for a new, more objective method of studying behavior. The impact on Pavlov's work on all subsequent psychological thought has been overwhelming and the volume remains the best introduction to his contributions. Until this work appeared, Pavlov's findings were known only through individual monographs, most of which had appeared in hard-to-find periodicals published in Eastern Europe. In a series of lectures delivered in 1924, however, Pavlov reviewed his entire course of experiments, summarized his conclusions and outlined his psychological system. This book, which is an expanded version of these lectures, is still an important statement of Pavlov's work.