5-MeO-DMT sometimes cancels the Ebbinghaus illusion

A researcher recounts that during an eight-week Qualia Research Institute retreat, a vaporised 5-MeO-DMT session produced a near-complete cancellation of the Ebbinghaus illusion. Using roughly 3.4 mg dose increments, the author reports that shifting attention to the center between two groups of circles eliminated the usual size-distortion, and that this cancellation was under voluntary control - moving attention back to a group restored the standard illusion. Other retreat participants who noticed changes reported a weakening of the illusion, sometimes with different subjective control dynamics. A subsequent higher-dose session did not reproduce the effect for the author, showing intra-subject variability.

The account contrasts 5-MeO-DMT’s effect with a 2025 study finding that psilocybin increased the Ebbinghaus effect, links the difference to 5-MeO-DMT’s primary 5-HT1a pharmacology, and describes the cancelled illusion as feeling like field-like pushes and pulls among objects. This subjective report is used to motivate empirical research into dose-response, reproducibility, mathematical models of the putative field-like interactions, and broader implications for theories of consciousness such as electromagnetic-field ideas. A modest controlled study is proposed.