Abstract
Serotonergic psychedelics are remarkable for their capacity to induce variable yet reproducible modifications to human consciousness. The acute effects of these compounds include perceptual alterations, predominantly in the visual domain, yet these alterations have been mostly documented only by subjective reports. We used eye-tracking to quantify the effects of low vs. high doses of psilocybin mushrooms on eye movements during the exploration of complex visual stimuli under semi-naturalistic conditions, focusing on the case of aesthetic perception. The experimental condition (high vs. low dose) was a priori unknown to participants and experimenters. High doses resulted in a more local visual exploration of paintings, and a less entropic distribution of fixations. While psilocybin altered gaze behavior and increased subjective emotional intensity and feelings of flow, it did not affect the aesthetic ratings of the stimuli, suggesting a dissociation between perceptual and evaluative aspects of aesthetic experience. These findings suggest that psilocybin may influence gaze fixation by altering the perception of low-level visual features, including textures, shapes, and colors. Our work highlights the possibility of investigating psychedelics by addressing their effect on behavior under complex naturalistic conditions, contributing to maintaining subject engagement while also increasing the ecological validity of the findings.