continuity hypothesis

   In hallucinations research, the term continuity hypothesis is used as a generic term for a group of hypothetical models that conceptualize hallucinations as lying on a continuum with other percepts such as sense perceptions, illusions * dreams, * imagery, and fantasies. In some versions of the continuity hypothesis even cognitive phenomena such as thoughts and memories are taken into the equation. In different models, the alleged continuity between these phenomena is either understood in a phenomenological or a neurophysiological sense. As summarized by the American philosopher C. Wade Savage, "Any of the following formulations are candidates: (1) The experiences listed are composed of the same stuff, so to speak; they differ not in kind, but in degree - degree of vivacity, coherence, volun-tariness, creativeness, concreteness, and veridical-ity. For example, perceptions are often more vivid than dreams; fantasies are usually more voluntary than perceptions. (2) The experiences listed are not sharply distinguishable from one another, as the existence of intermediate cases shows. For example, between a vivid hallucination and a not-so-vivid dream, we can find an experience intermediate in vivacity, and we may be unsure whether to call it a dream or an hallucination. (3) The experiences listed can evolve into, become transformed into, one another. For example, a dream, on waking, may evolve into a fantasy; a perception, on falling asleep, may evolve into a dream. (4) The internal mechanisms of the experiences listed, the processes by means of which they are produced, are similar." Two historical examples of continuity hypotheses are those of the French psychiatrist Jacques-Joseph Moreau de Tours (1804-1884), who stresses the phenomeno-logical similarities between dreams, hallucinations of * delirium, and hallucinations induced by * hashish, and of the French classical scholar and dream researcher Louis-Ferdinand-Alfred Maury (1817-1892), who suggests the existence of a common physiological mechanism called * oneirism underlying both dreams and hallucinations.

   References

   Maury, L.F.A. (1865). Le sommeil et les rêves. Études psychologiques sur ces phénomènes et les divers états qui s'y rattachent. Troisième édition. Paris: Librairie Académique Didier et Cie., Libraires-Éditeurs.

   Moreau, J.-J. (1845). Du hachisch et de l'aliénation mentale. Études psychologiques. Paris: Fortin Masson.

   Savage, C.W. (1975) The continuity hypothesis. In: Hallucinations. Behavior, experience, and theory. Edited by Siegel, R.K., West, L.J. New York, NY: John Wiley & Sons.