An important aspect of predictive processing is that each hypothesis generated by a level in the hierarchy is associated with a notion of confidence in the hypothesis, which in turn is based on prior expectations. Could psychedelics be altering our perception of reality by messing with this process? Friston and Robin Carhart-Harris think so. If psychedelics mess with prior beliefs, that might also explain why they cause one to hallucinate a reality that’s untethered from real-world expectations.

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