While Müller ended his life as the experimentalist, he did not start out as one. His second doctoral subject was experimental physics (taught by Wilhelm Weber), but his dissertation of 1873 and his habilitation of 1876 (Müller, 1878a) would today be book-length versions of a Psychological Review articles, since there is no original data in either one. In the Habilitation, he defined much of the standard psychophysics that has been passed down to students (Haupt, 1995); recommended using both ascending and descending methods of limits to limit bias and the method of constant stimuli, which he extensively developed with the Müller weights, would seem to be another method designed to improve the usefulness of a threshold, but he did not provide any new experimental data. In the early papers on memory by Müller and Schumann, he seems to have originated a number of important procedural controls for the study of association. Kroh (1935, p. 155) puts Müller in the same group (first generation of psychologists) with Stumpf and Külpe, for which the transition to being an experimentalist was a significant step; a step that was not required for anyone trained as a physicist (Fechner) or physiologist (Wundt).