The artist had once taken into his service the investigator to assist him, now the servant was stronger and suppressed his master. When we find in the portrait of a person one single impulse very forcibly developed, as curiosity in the case of Leonardo, we look for the explanation in a special constitution, concerning its probable organic determination hardly anything is known. Our psychoanalytic studies of nervous people lead us to look for two other expectations which we would like to find verified in every case. We consider it probable that this very forcible impulse was already active in the earliest childhood of the person, and that its supreme sway was fixed by infantile impressions; and we further assume that originally it drew upon sexual motive powers for its reënforcement so that it later can take the place of a part of the sexual life. Such person would then, e.g., investigate with that passionate devotion which another would give to his love, and he could investigate instead of loving. We would venture the conclusion of a sexual reënforcement not only in the impulse to investigate, but also in most other cases of special intensity of an impulse. Observation of daily life shows us that most persons have the capacity to direct a very tangible part of their sexual motive powers to their professional or business activities. The sexual impulse is particularly suited to yield such contributions because it is endowed with the capacity of sublimation, i.e., it has the power to exchange its nearest aim for others of higher value which are not sexual. We consider this process as proved, if the history of childhood or the psychic developmental history of a person shows that in childhood this powerful impulse was in the service of the sexual interest. We consider it a further corroboration if this is substantiated by a striking stunting in the sexual life of mature years, as if a part of the sexual activity had now been replaced by the activity of the predominant impulse.