To study the basic mental processes involved in immediate experience, Wundt used a variety of methods, including introspection. Wundt’s use of introspection bore little resemblance, however, to how the empiricists and sensationalists used it to study ideas and association. Wundt distinguished between pure introspection, the relatively unstructured self-observation used by earlier philosophers, and experimental introspection, which he believed to be scientifically respectable:
Experimental introspection made use of laboratory instruments to vary the con- ditions and hence make the results of internal perception more precise, as in the psychophysical experiments initiated by Fechner or in the sense-perception exper- iments of Helmholtz. In most instances saying “yes” or “no” to an event was all that was needed, without any description of inner events. Sometimes the subject responded by pressing a telegraph key. The ideal was to make introspection, in the form of internal perception, as precise as external perception. (Hilgard, 1987)