THE variations of personality found in diseased subjects take on a great number of forms, of which, the phenomenon resembling the presence of two or more personalities in the same individual — or "multiple personality" — is the subject of our present special study. It is common in hysteria, and the hysterical cases are those which have been most adequately investigated. These cases are often described as cases of somnambulism. In popular usage somnambulism is the state of those who rise in the night and perform automatic and even intelligent acts without waking. They dress themselves, perhaps, resume their day's work, solve a problem to which they had vainly sought the solution before, then return to bed and to sleep again; the next morning they have no memory of having been up in the night. Indeed, they are often much surprised to see a piece of work now finished which had been unfinished the evening before. Or they walk on the roof or perform some other equally startling feat. Authors are not as yet entirely agreed upon the nature of this sleep-walking, but the general tendency of the day is to admit that it covers a mass of irregular phenomena which resemble one another in appearance only, being really quite distinct in nature. In these phenomena we may see an example of double personality. These noctambulists are two persons. The person who rises in the night is entirely distinct from the one who is awake during the day, since the latter has no knowledge or memory of anything that has happened during the night. But it is not possible to make an adequate analysis of this state; the elements are too obscure.
Another form of natural somnambulism is "daytime" somnambulism, or vigilambulism, and concerns hysterical patients who possess, besides their normal and regular life, another psychological existence or second state, so to speak, of which they retain no memory in their normal condition. The peculiar characteristic of this second state is that it constitutes a complete psychological existence; the subject lives the everyday life, his mind is alive to all ideas and perceptions, and he is not delirious. Uninformed persons would never know that the subject is in a state of somnambulism.
The best examples that can be cited of the somnambulism that
- From Alterations of Personality. By Alfred Binet. Translated by Helen Green Baldwin, with Notes and a Preface by J. Mark Baldwin. (International Scientific Series.) In press of D, Appleton & Co.