Gustav Fechner began conducting psychophysics research in Leipzig in the 1830s, articulating the principle that human perception of a stimulus varies logarithmically according to its intensity. Fechner's 1860 Elements of Psychophysics challenged Kant's stricture against quantitative study of the mind. In Heidelberg, Hermann von Helmholtz conducted parallel research on sensory perception, and trained physiologist Wilhelm Wundt. Wundt, in turn, came to Leipzig University, establishing the psychological laboratory which brought experimental psychology to the world. Wundt focused on breaking down mental processes into the most basic components, motivated in part by an analogy to recent advances in chemistry, and its successful investigation of the elements and structure of material. Paul Flechsig and Emil Kraepelin soon created another influential psychology laboratory at Leipzig, this one focused on more on experimental psychiatry.
Psychologists in Germany, Denmark, Austria, England, and the United States soon followed Wundt in setting up laboratories. G. Stanley Hall who studied with Wundt, formed a psychology lab at Johns Hopkins University in Maryland, which became internationally influential. Hall, in turn, trained Yujiro Motora, who brought experimental psychology, emphasizing psychophysics, to the Imperial University of Tokyo. Wundt assistant Hugo Münsterberg taught psychology at Harvard to students such as Narendra Nath Sen Gupta—who, in 1905, founded a psychology department and laboratory at the University of Calcutta. Wundt students Walter Dill Scott, Lightner Witmer, and James McKeen Cattell worked on developing tests for mental ability. Catell, who also studied with eugenicist Francis Galton, went on to found the Psychological Corporation. Wittmer focused on mental testing of children; Scott, on selection of employees.