Gustav Fechner
Fechner, along with Wilhelm Wundt and Hermann von Helmholtz, is recognized as one of the founders of modern experimental psychology. His clearest contribution was the demonstration that because the mind was susceptible to measurement and mathematical treatment, psychology had the potential to become a quantified science. Theorists such as Immanuel Kant had long stated that this was impossible, and that therefore, a science of psychology was also impossible.
Wilhelm Wundt
The Americans listed include James McKeen Cattell (the first professor of psychology in the United States), Granville Stanley Hall (the father of the child psychology movement and adolescent developmental theorist, head of Clark University), Charles Hubbard Judd (Director of the School of Education at the University of Chicago), Walter Dill Scott (who contributed to the development of industrial psychology and taught at Harvard University), Edward Bradford Titchener, Lightner Witmer (founder of the first psychological clinic in his country), Frank Angell, Edward Wheeler Scripture. Wundt, thus, is present in the academic "family tree" of the majority of American Psychologists, first and second generation. – Worth mentioning are the Englishman Charles Spearman; the Romanian Constantin Rădulescu-Motru (Personalist philosopher and head of the Philosophy department at the University of Bucharest), Hugo Eckener, the manager of the Luftschiffbau Zeppelin – not to mention those students who became philosophers (like Rudolf Eisler or the Serbian Ljubomir Nedić). – Students (or visitors) who were later to become well known included Vladimir Mikhailovich Bekhterev (Bechterev), Franz Boas, Émile Durkheim, Edmund Husserl, Bronisław Malinowski, George Herbert Mead, Edward Sapir, Ferdinand Tönnies, Benjamin Lee Whorf.