form-constant

   The term form-constant was coined in or shortly before 1928 by the German-American biological psychologist and philosopher Heinrich Klüver (1897-1979) to denote a recurring geometric element or form that can be observed during the initial stages of * visual hallucinatory experience due to mescaline intoxication. Although Klüver himself stresses the near impossibility of classifying the variety of visual phenomena occurring during the mescal state, he proposes a classification of form-constants comprising (1) *chessboard design (also referred to as grating, lattice, fretwork, filigree, and honeycomb), (2) cobweb figure, (3) tunnel (also referred to as funnel, alley, cone, and vessel), and (4) spiral. As Klüver maintains, "No matter how strong the inter- and intra-individual differences may be, the records are remarkably uniform as to the appearance of... forms and configurations. We may call them form-constants, implying that a certain number of them appear in almost all mescal visions and that many 'atypical' visions are upon close examination nothing but variations of these form-constants." Klüver's form-constants are not exclusively associated with mescaline intoxication. They have been reported in association with the use of other *hallucinogens as well, and also in association with non-drug-related phenomena such as * migraine aura, * aura due to epileptic activity, and * hypoglycaemia. Nor would it seem that Klüver was the first to notice the recurrence of certain forms and patterns in hallucinatory images. As early as 1899, the French physician Pierre Dheur had already reported on various stereotyped patterns of movement and disappearance in * visual hallucinations. An alternative classification of form-constants, referred to as * dimensions of visual imagery, was devised during the early 1970s by the American psychophar-macologists Ronald K. Siegel and Murray E. Jarvik.

   References

   Dheur, P. (1899). Les hallucinations volontaires (l'état hallucinatoire). Suivi d'un chapitre sur les hallucinations. Notes manuscrites et inédites du Dr. J. Moreau (de Tours). Paris: Société d'Éditions Scientifiques.

   ffytche, D H (2007) Visual hallucinatory syndromes: Past, present, and future. Dialogues in Clinical Neuroscience, 9, 173-189.

   Klüver, H. (1966). Mescal and Mechanisms of hallucinations. Chicago, IL: University of Chicago Press.

   Siegel, R.K., Jarvik, M.E. (1975). Drug-induced hallucinations in animals and man.In: Hallucinations. Behavior, experience, and theory. Edited by Siegel, R.K., West, L.J. New York, NY: John Wiley & Sons.