Link: https://slatestarcodex.com/2020/01/08/what-intellectual-progress-did-i-make-in-the-2010s/

One of the best parts of writing a blog is being able to answer questions like this. Whenever I felt like I understood new and important, I wrote a post about it. This makes it easy to track what I learned.

I think 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 two 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.