Jiˇr ́ı Wackermann a, ∗, Marc Wittmann b, Felix Hasler c, Franz X. Vollenweider c a Department of Empirical and Analytical Psychophysics, Institute for Frontier Areas of Psychology and Mental Health, Wilhelmstrasse 3a, D-79098 Freiburg i. Br., Germany b Department of Psychiatry, University of California San Diego, La Jolla, USA c University Hospital of Psychiatry and Heffter Research Center, Zu ̈rich, Switzerland Received 16 November 2007; received in revised form 29 January 2008; accepted 4 February 2008
Action of a hallucinogenic substance, psilocybin, on internal time representation was investigated in two double-blind, placebo-controlled studies: Experiment 1 with 12 subjects and graded doses, and Experiment 2 with 9 subjects and a very low dose. The task consisted in repeated reproductions of time intervals in the range from 1.5 to 5 s. The effects were assessed by parameter κ of the ‘dual klepsydra’ model of internal time representation, fitted to individual response data and intra-individually normalized with respect to initial values. The estimates κˆ were in the same order of magnitude as in earlier studies. In both experiments, κ was significantly increased by psilocybin at 90 min from the drug intake, indicating a higher loss rate of the internal duration representation. These findings are tentatively linked to qualitative alterations of subjective time in altered states of consciousness.