Also referred to as funnel, alley, cone, and vessel. All five terms were introduced in or shortly before 1928 as more or less synonymous terms by the German-American biological psychologist and philosopher Heinrich Klüver (1897-1979) to denote one of the four "form-constants of " geometric visual hallucinations which may occur during the initial stages ofmescaline intoxication. Klüver uses the term form-constant to denote certain visual forms and elements that "appear in almost all mescal visions". According to him, "many 'atypical' visions are upon close inspection nothing but variations of these form-constants." The examples of the tunnel or funnel shape given by Klüver, based on the observations of different test persons, are rendered by him as follows. " 'Sometimes I seemed to be gazing into a vast hollow revolving vessel, on whose polished concave mother-of-pearl surface the hues were swiftly changing'; 'the field of vision is similar to the interior of a cone the vertex of which is lying in the center of the field directly before the eyes (or vice versa)'; 'vision of a tunnel in copper-brown color... lines seem to converge in the infinite'; 'a large black corridor seen in extremely deep perspective'; 'upon pressure on the closed eyes I saw first an alley in very deep perspective'; 'deep beautiful perspectives... growing into the infinite...'; 'in deep perspective a suite of oriental rooms'; 'extending away from me a long narrow corridor... often looking into cupolas which widen more and more... the cupola became increasingly deeper, more funnel-shaped, narrower'; 'I was standing in a very long and wide tunnel'; 'long narrow funnels... the ends of which appear in the distance as brilliant points... their walls and the perspective effects are in most cases formed by small parallel lines...'; 'a large cylindrical hall'; 'the designs occupied the wall of a colossal cone'; 'the pyramid changes into a luminous cone'." Klüver names the three remaining form-constants "chessboard design, "cobweb figure, and "spiral. In parapsychology, seeing a tunnel shape is sometimes interpreted as a sign of the individual's passage to another plane of existence. According to the American parapsy-chologist Raymond A. Moody, Jr. (b. 1944), for example, seeing a tunnel is a common feature of " near-death experiences (NDEs).
References
Klüver, H. (1966). Mescal and Mechanisms ofhallucinations. Chicago, IL: University of Chicago Press.
Moody, R.A. (1975). Life after life. New York, NY: Bantam Books.
Dictionary of Hallucinations. J.D. Blom. 2010.