After joining the staff of the Burgholzli Mental Hospital in 1900, Jung developed and applied the word-association tests for studying normal and abnormal psychology. The studies have remained a significant phase in the development of Jung's conceptions and an important contribution to diagnostic psychology and psychiatry. Between 1904 and 1907 he published nine studies on the tests. These studies, together with two lectures on the association method given in 1909 at Clark University and three articles on psychophysical researches from American and English journals in 1907-1908, compose this volume.

Jung's association studies showed the definite influence of Bleuler and also of Freud, with whom he worked closely for several years.

With this volume, the Collected Works are complete except for the Miscellany, Bibliography and Index volumes.