Abstract
This chapter presents findings indicating that psilocybin-induced visual distortions and impaired executive functioning originate in temporary disruptions of attentional mechanisms. It then revisits a predictive processing account of neural processing and argues that this lacks the resources to provide a unified model of the perceptual mechanisms underpinning psychedelic experiences caused by classic hallucinogens such as psilocybin, lysergic acid diethylamide (LSD), and mescaline. Lastly, an alternative theory of perceptual processing is proposed—the Gist Theory of Perception—that can better explain how the psilocybin-induced disruptions of attentional mechanisms may elicit psychedelic experiences.