Effects of varied doses of psilocybin on time interval reproduction in human subjects

Introduction

Awareness of temporal order and the ability to discriminate durations are features of normal wakeful consciousness, while altered states of consciousness (ASC) commonly produce changes in subjective time experience. Earlier research has reported that psilocybin, a serotonergic hallucinogen acting primarily at 5-HT2A/1A receptors, produces subjective and objective alterations in time perception: shortened reproductions of intervals longer than about 2.5 s, impaired synchronization to slower inter-beat intervals, slowed preferred tapping rates, working-memory deficits, and reported disturbances in subjective time sense. These findings align with evidence that serotonergic modulation of prefrontal cortex—an area implicated in timing behaviour—can alter timing performance. This study applies a parametric modelling approach to duration-reproduction data, using the dual klepsydra model (DKM) of internal time representation. Rather than analysing reproduction errors separately for each stimulus duration, the investigators fit the DKM to whole-response functions and focused on its single key parameter κ, the loss-rate coefficient of the model's leaky accumulators. The paper reports two double-blind, placebo-controlled experiments aimed at testing whether psilocybin alters κ during the peak drug effect and thereby affects the internal representation of supra-second time intervals.