[Mental work: the search for a precise way to measure psychic activity]

Presents three brief case studies to show how cognition and psychic activity were explored as energetic and economic transactions in a variety of experimental settings. First, in the 1870's German psychiatrist Emil Kraepelin began a search for an objective measurement of cognitive performance in which he engaged for several decades. His investigations resulted in a graphic representation of cognitive efficiency, the Arbeitscurve, delineating numbers of additions per time interval in close resemblance to representations of machine efficiency. Second, at the turn of the century American nutrition scientist and agronomist Wilbur Olin Atwater convinced himself in a series of precision measurements that the human motor was a perfectly closed input-output system and that any mental surplus in the form of cognitive energy transformation did not count as contradictions to the principle of the conservation of energy. Third, at the beginning of the 20th century and on the basis of Atwater's results, German psychiatrist Hans Berger stipulated a special form of psychic energy for mediating between the principle of the conservation of energy and mental causality. Berger attempted to quantify psychic energy as one factor of brain metabolism. In the three cases of precision investigations into psychic life presented here, the experimental space of psychophysiology turned mental activity into a form of machine-like behavior.