The severe restrictions which Wundt placed on introspection also manifest themselves in the types of judgment that his experimental subjects were req… - Kurt Danziger

Wundt initiated the first systematic psychological research programme. This achievement occurred at the same time as his elaboration of a philosophy of science which was anti-inductivist and stressed the priority of explanatory motives. Specifically psychological explanations depended on concepts of psychological causality as manifested in apperceptive or volitional processes. The major differences between the Wundtian and other models of psychological experimentation can be understood in the light of this general approach. Thus experimenters and subjects had to be enlightened collaborators and the role of introspection was more significant in an explanatory than in a purely observational context. Wundt's special requirements for the psychological experiment led him to reject other early models as exemplified by the hypnotic experiment in which the experimenter-subject relationship was closer to what was to become the norm in the twentieth century.

The reaction time studies conducted during the first few years of Wundt’s laboratory constitute the first historical example of a coherent research program, explicitly directed toward psychological issues and involving a number of interlocking studies.

Internal perception also fails as a method for scientific psychology. In the nature of the case, it must be casual and therefore unsystematic. It excludes all deliberate investigation, because as soon as it becomes aware of itself it turns into the self-observation that is open to all the well-known and valid criticisms. It is, indeed, the basis of a psychology of consciousness, in the sense that conscious processes must be perceived to be known, but for a science it is not enough.