Robin Carhart-Harris: The REBUS Model and the Psychedelic State
About This Video
This Breaking Convention keynote by Robin Carhart-Harris presents the most complete public explanation of the REBUS (Relaxed Beliefs Under Psychedelics) model — the theoretical framework that has become the dominant scientific account of how psychedelics work and why they are therapeutically effective.
Predictive coding — the theoretical framework within which REBUS is embedded — is explained accessibly. The brain is not a passive receiver of sensory input; it is a prediction machine that constantly generates hypotheses about the world and updates them when prediction errors occur. The sense of self is a high-level prediction — a model the brain maintains about who and what you are. Depression, addiction, and PTSD involve high-level priors (beliefs about the self and world) that have become too confident, resistant to updating from new experience.
Psilocybin, through 5-HT2A agonism in high-level cortical regions, 'relaxes' these high-level predictions — reduces their confidence and their capacity to override bottom-up experience. This creates the subjective experience of ego dissolution and also creates the therapeutic opportunity: the session experience can update the prior model more effectively than in ordinary consciousness, where the self's predictions are too confident to allow new information in. REBUS provides the first mechanistically coherent explanation for why psilocybin + therapy outperforms either alone.
Key Takeaways
- REBUS (Relaxed Beliefs Under Psychedelics) proposes that psilocybin reduces the authority of high-level brain predictions, allowing bottom-up experience to update rigid prior models.
- In depression, addiction, and PTSD, self-models and world-models have become too confident — resistant to updating. Psilocybin relaxes their confidence.
- Ego dissolution is what REBUS predicts: the high-level self-model loses its authority when its prior confidence is sufficiently reduced.
- The 2–4 week integration window follows from REBUS: neuroplasticity elevation keeps the brain's predictive hierarchy relaxed, giving therapy maximum leverage.
- REBUS provides the first mechanistically coherent explanation for why psilocybin + therapy outperforms either alone — the medicine creates the window; therapy installs new priors during it.
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