Writing brains: tracing the psyche with the graphical method.

At the end of the 19th century, the graphic method kindled attempts to use it for investigating psychic processes. In Germany, Hans Berger took up this line of research, later to become the pioneer of electroencephalography (EEG). This trajectory of Berger's work is analyzed as an "enabling constraint" guiding him toward the EEG at a time when nobody else was pursuing this line of research and also causing serious methodological problems. In the epistemological perspective of this analysis, many of his problems extend beyond the local context of his work and point toward ambiguities surrounding the project to trace the psyche with the graphic method. From the mid-1930s, the EEG inspired ongoing attempts to decipher the specific meanings of these recordings, and large ensembles of machinery were mobilized, molding concepts of the psyche according to the results and the specifications of the graphic method.