DOUBLE CONSCIOUSNESS. A morbid mental condition, also known as datable person ality, observed in eases of hysteria. hypnosis, and tramp, characterized by the existence of two or more independent, self-consistent groups of conscious which alternate periodically, or are called lip in irregular sequence as favor able eireinnstances arise. Usually these groups are strictly from one another, so that. while one group is in operation. the other is utterly shut out from eonseiousness: a fact which, from the purely psychological point of view, stamps the phenomenon as an instance of general derangement of memory. When the two sets of ideas become complex, and the mutual obliviseen•e is complete, each group develops that 'aura' of sensations and feelings which constitutes selfhood: and the individual whose mind is thus partitioned may be rightly said to possess a 'double' or 'secondary personality.' W hen this division of mentation is radical, there is oftentimes exhibited a curious antithesis be tween the types of the two persfumlities, a con dition popularly set forth, in an exaggerated & pile. in Stevenson's Dr. Jekyll and ii r. Hyde.
The ultimate basis of double consciousness must be sought in certain physiological condi tions of the central nervous system. Partial light is thrown upon the conditions which favor the mental schism by the frequent demarcation of the two 'selves' by specific antithetical moods. This feature makes it probable that the organic sensations, the chief determinants of our gen eral mood or temper, may constitute the nucleus around which are gathered the remaining ele ments of the segregated 'personality.' This function of the somatic elements of conscious ness is well illustrated in Flournoy's study of a remarkable case of divided consciousness, that of the medium 'Mlle. Smith,' who 'incarnates'
several distinct personalities, and whose 'guiding spirit' has his origin, in Flournoy's judgment, in the sexual esemesthesis of the subject herself.
Finally, double consciousness may lie regarded as, in n certain sense, merely an exaggeration of what is termed -motor automatism.' a con dition which is often present, or at least easily developed, in the normal consciousness. Solo mons and Stein have shown experimentally that there exists "a complete analogy between the performances of the second personality and the automatic nets of normal persons." They were able, by practice, to cultivate alitoinatisms of a complicated nature. such as spontaneous auto writing and reading. lf, e.g. A reads aloud to 13, who simultaneously dictates to A, and the rending is sufficiently interesting. B will unconsciously dictate sentences which A unconsciously writes. It remains to be added that hypnosis furnishes excellent examples of the alternation of consciousnesses. Subjects mho. when awakened. are totally ignorant of their hypnotic experience-s. may, in n succeeding hypnosis, return without break to the conscious ness of the former somnambulistic state. Con sult: Flournoy. From /ndia to the Planet Mars New York, 19001: Knelpe, Outlines of Psy chology, trans. by Titchencr (London. 149.i): Wundt, Lei-tures on Human and Animal Psy chology. trans. by Creighton and Titehener al don, 1896) : Dessir, Ilas Doppel-/eh (Leipzig, ; L'alitoinatisme psycholog iq tic (Paris, 1891).