In a double-blind study of 24 adults, psilocybin made people feel like time slowed down, and this matched measurable changes in timing tasks compared to placebo. Participants also became less precise at judging time intervals, especially for periods longer than 2 seconds, showing this was not just a feeling but a real cognitive shift. The findings help explain a common psychedelic experience by showing psilocybin temporarily alters attention and working memory systems that the brain uses to track time.