Visual hallucinations (VHs) occur in psychedelic states and various psychiatric and neurological conditions, but their phenomenology is hard to characterize due to a lack of large-scale datasets. Stroboscopic light stimulation (SLS) with closed eyes reliably induces VHs in healthy people, producing vivid colors and dynamic geometric patterns similar to simple VHs in other contexts. Researchers developed an unsupervised computer-vision pipeline to analyze 10,598 drawings made after hallucination-inducing SLS at a public installation. Most drawings contained geometric forms, consistent with prior observations, but novel patterns like concentric squares, crosses, and hyperbolic shapes also appeared. The pipeline organized the drawings into interpretable classes, mapping the diversity of simple geometric VHs and placing new constraints on theoretical accounts.
Exposure to rapid and bright stroboscopic light can induce vivid visual hallucinations of color and geometric forms, a phenomenon first documented by Purkinje over 200 years ago. Despite centuries of scientific, therapeutic, and cultural interest, fundamental questions remain about its phenomenology, physiological origins, and potential clinical applications. This narrative review summarizes the historical research on stroboscopic light stimulation, its use in recreational and lay-therapeutic settings, and discusses the phenomenology of these experiences. It also examines current perspectives on the neural mechanisms that may underlie stroboscopically induced experiences and outlines directions for future research.