the single most important thing I discovered this decade (due to a random comment in the SSC subreddit!) was the predictive coding theory of the brain. I started groping towards it (without knowing what I was looking for) in Mysticism And Pattern-Matching, reported the exact moment when I found it in It’s Bayes All The Way Up, and finally got a decent understanding of it after reading Surfing Uncertainty. At the same time, thanks to some other helpful tips from other rationalists, I discovered Behavior: The Control Of Perception, and with some help from Vaniver and a few other people was able to realize how these 2 overarching theories were basically the same. Discovering this area of research may be the best thing that happened to me the second half of this decade (sorry, everyone I dated, you were pretty good too).

Psychedelics are clearly interesting, and everyone else had already covered all the interesting pro-psychedelic arguments, so I wrote about some of my misgivings in my 2016 Why Were Early Psychedelicists So Weird?. The next step was trying to fit in an understanding of HPPD, which started with near-total bafflement. Predictive processing proved helpful here too, and my biggest update of the decade on psychedelics came with Friston and Carhart-Harris’ Relaxed Beliefs Under Psychedelics And The Anarchic Brain, which I tried to process further here. This didn’t directly improve my understanding of HPPD specifically, but just by talking about it a lot I got a subtler picture where lots of people have odd visual artifacts and psychedelics can cause slightly more (very rarely, significantly more) visual artifacts. I started the decade thinking that “psychedelic insight” was probably fake, and ended it believing that it is probably real, but I still don’t feel like I have a good sense of the potential risks.

In mental health, the field I am supposed to be an expert on, I spent a long time throwing out all kinds of random ideas and seeing what stuck – Boorsboom et al’s idea of Mental Disorders As Networks, The Synapse Hypothesis of depression, etc. Although I still think we can learn something from models like those, right now my best model is the one in Symptom, Condition, Cause, which kind of sidesteps some of those problems. Again, learning about predictive processing helped here, and by the end of the decade I was able to say actually useful things that explained some features of psychiatric conditions, like in Treat The Prodrome. Friston On Computational Mood might also be in this category, I’m still waiting for more evidence one way or the other.

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