Scott Alexander examines the 'canalization' theory in computational psychiatry and its refinement through deep learning concepts in the Deep CANAL model. Longer summary

Scott Alexander discusses a new paradigm in computational psychiatry called 'canalization', which models mental processes as an energy landscape with valleys representing attractors or persistent beliefs/behaviors. He then explores a follow-up paper that applies concepts from deep learning to refine this theory, introducing the Deep CANAL model. This model attempts to explain various mental disorders by mapping them onto different types of computational issues in artificial neural networks, such as overfitting/underfitting and the stability/plasticity dilemma. Scott expresses both interest and skepticism about this approach, noting its potential insights but also its limitations and potential contradictions with other theories. Shorter summary

Scott Alexander examines a review of a paper on serotonin receptors, discussing prediction error, suffering, and the effects of different serotonin receptor activations on problem-solving approaches and psychedelic experiences. Longer summary

Scott Alexander reviews George from CerebraLab's analysis of a paper by Nutt and Carhart-Harris on serotonin receptors. The post explores two main points: the relationship between prediction error and suffering in the context of active inference theory, and the different effects of 5-HT1A and 5-HT2A receptor activation. Scott discusses how these concepts relate to depression, psychedelics, and problem-solving approaches. He also considers George's suggestion that using psychedelics for introspection might be more harmful than using them for fun or practical problem-solving. Shorter summary

Scott Alexander explores the concept of 'trapped priors' as a fundamental problem in rationality, explaining how it leads to persistent biases and suggesting potential solutions. Longer summary

Scott Alexander explores the concept of 'trapped priors' as a fundamental problem in rationality. He explains how the brain combines raw experience with context to produce perceptions, and how this process can lead to cognitive biases and phobias. The article discusses how trapped priors can make it difficult for people to update their beliefs, even in the face of contradictory evidence. Scott also examines how this concept applies to political biases and suggests potential ways to overcome trapped priors. Shorter summary

Scott Alexander reviews his intellectual progress in the 2010s across various fields, crediting his blog for accelerating learning. Longer summary

Scott Alexander reflects on the intellectual progress he made in the 2010s, largely tracked through his blog posts. He discusses major updates in his understanding of topics like predictive coding theory, psychedelics, mental health, SSRIs, genetics, willpower, nutrition, x-risk, AI, scientific progress, cost disease, the replication crisis, placebo effect, ethics, politics, cultural evolution, social justice, game theory, and enlightenment. He notes that while some were major shifts in position, many represent 'deconfusion' - gaining a better map of the problem space. Scott credits his blog and reader interactions for accelerating his learning in the latter half of the decade. Shorter summary

The post explores how emotional learning creates hard-to-update mental models, drawing parallels between psychotherapy, psychedelics, and rationality techniques in overcoming these 'mental mountains'. Longer summary

This post discusses the book 'Unlocking The Emotional Brain' (UtEB) and its implications for understanding biases and mental processes. The author explores how emotional learning creates unconscious predictive models that guide behavior, and how these models can be difficult to update even in the face of contradictory evidence. The post draws parallels between UtEB's approach, psychedelic therapy, and rationality techniques, suggesting that they all aim to overcome mental 'mountains' that separate different areas of knowledge or belief. The author proposes that these mental separations might be a necessary feature of how our brains generalize from experiences, but can also lead to problems like cognitive biases and psychiatric symptoms. The post concludes by considering how this framework might help understand and address deeply held but irrational beliefs. Shorter summary

Scott Alexander investigates the prevalence of Hallucinogen Persisting Perceptual Disorder (HPPD) and explores potential connections between perception, cognition, and belief in supernatural phenomena. Longer summary

Scott Alexander explores the prevalence and nature of Hallucinogen Persisting Perceptual Disorder (HPPD), a condition where people experience ongoing visual disturbances after using psychedelics. He discusses results from his own survey, which found that about 12.8% of psychedelic users reported some persisting hallucinations, with 3% still experiencing them. Most cases were mild, involving visual snow, halos, or patterns. Scott then critiques a study claiming HPPD doesn't exist, noting methodological issues. He also considers the possibility that some people naturally experience HPPD-like phenomena without drug use, and speculates on potential links between perception, cognition, and belief in supernatural phenomena. Shorter summary

Scott reviews a paper proposing that psychedelics work by relaxing priors in the brain, potentially treating mental illness but also risking side effects. Longer summary

This post reviews a paper by Friston and Carhart-Harris that uses predictive coding theory to explain the effects of psychedelic drugs. The authors argue that psychedelics 'relax' priors in the brain, allowing for new perspectives and potential therapeutic benefits. They suggest this mechanism could help treat most mental illnesses by allowing patients to break free from maladaptive priors. The post discusses the theory's implications, including potential downsides like HPPD and increased belief in pseudoscience. It also mentions connections to meditation and prior work by other researchers. Shorter summary

Scott Alexander explores Hallucinogen Persisting Perception Disorder (HPPD) and other conditions where drugs cause permanent effects, discussing potential mechanisms and their implications. Longer summary

Scott Alexander discusses Hallucinogen Persisting Perception Disorder (HPPD), a condition where some people experience permanent hallucinatory effects after using psychedelic drugs, particularly LSD. He explores the prevalence, potential mechanisms, and implications of this disorder. The post compares HPPD to other conditions with persistent effects like tardive dyskinesia, and examines various theories about how drugs could cause permanent changes in the brain. Scott considers two main hypotheses: the killing-off of specific neurons, and the idea of the brain as a chaotic system settling into new attractor states. He expresses a preference for the neuron death theory as it seems more understandable and less scary, but acknowledges the complexity and uncertainty surrounding these issues. Shorter summary

Scott reviews a theory about serotonin receptors that explains how they help cope with stress, and discusses its implications and limitations. Longer summary

This post reviews a theory about serotonin receptors proposed by Robin Carhart-Harris and David Nutt. The theory focuses on two key receptors: 5-HT1A and 5-HT2A. It suggests that 5-HT1A promotes 'passive coping' (stoicism, bearing stress), while 5-HT2A promotes 'active coping' (increasing brain plasticity to find new solutions). The author finds the theory plausible and explains how it accounts for various effects of antidepressants and psychedelics. However, he also points out some remaining questions and potential biases in the theory. The post combines a detailed explanation of the theory with critical analysis and broader reflections on brain function and drug effects. Shorter summary

The post explores how Bayesian processes in the brain might explain perception and various mental disorders, linking neurotransmitters to different aspects of Bayesian reasoning. Longer summary

This post explores the application of Bayes' Theorem to neuroscience and psychiatry. It discusses how the brain might use Bayesian processes for perception and cognition, and how disruptions in these processes could explain various mental disorders. The author first explains Bayes' Theorem and its relevance to perception, then delves into a neuroscientific model that links neurotransmitters to different aspects of Bayesian processing. The post then applies this model to explain phenomena in schizophrenia, psychedelic experiences, and autism. The author concludes by pointing out some limitations and inconsistencies in the model, while still appreciating its potential as a high-level framework for understanding brain function and mental disorders. Shorter summary

Scott Alexander reviews PiHKAL by Alexander and Ann Shulgin, exploring the book's blend of autobiography, chemistry, and psychedelic experiences. Longer summary

Scott Alexander reviews the book PiHKAL by Alexander and Ann Shulgin, which combines autobiography, chemistry, and psychedelic experiences. The review covers the book's structure, the Shulgins' work on psychedelics, their social circle, and the psychology portrayed in the book, while also reflecting on the potential impact and limitations of psychedelic research. Shorter summary

Scott Alexander examines why early psychedelic researchers often became eccentric, proposing that psychedelics might permanently increase openness to unusual ideas. Longer summary

Scott Alexander explores the phenomenon of early psychedelic researchers becoming notably eccentric or 'weird' after their experiments. He presents brief biographies of several prominent researchers, including Timothy Leary, Richard Alpert, John Lilly, and Kary Mullis, highlighting their transition from respected scientists to advocates of unconventional ideas. The post then discusses potential explanations for this trend, including self-selection bias, the impact of psychedelic experiences, and the possibility that psychedelics might directly alter personality traits like Openness to Experience. Scott concludes by suggesting that the early psychedelicists might serve as a natural experiment, providing unique data on the long-term effects of psychedelic use that are difficult to study in controlled settings. Shorter summary

Scott Alexander hypothesizes that mystical experiences, hallucinations, and paranoia might be linked to an overactive pattern-matching faculty in the brain. Longer summary

Scott Alexander explores the relationship between mysticism, pattern-matching, and mental health. He suggests that hallucinations, paranoia, and mystical experiences might all be related to an overactive pattern-matching faculty in the brain. The post begins by discussing how the brain's failure modes differ from computers, then explains top-down processing and pattern matching using visual examples. It then connects these concepts to hallucinations, paranoia, and mystical experiences. Scott proposes that certain practices like meditation, drug use, and religious rituals may strengthen the pattern-matching faculty, leading to experiences of universal connectedness or enlightenment. He acknowledges that this hypothesis doesn't explain all aspects of mystical experiences and their benefits. Shorter summary

A fictional DMT trip where the narrator tries to prove the reality of entities by asking them to factor a number, but receives cryptic responses about love and joy instead. Longer summary

This post is a fictional story about a person's DMT trip, where they encounter a cactus person and a big green bat in a surreal landscape. The narrator tries to prove the reality of the DMT entities by asking them to factor a large number, based on a methodology suggested in a paper. However, the entities respond with cryptic messages about universal love and transcendent joy, frustrating the narrator. The story explores themes of spirituality, enlightenment, and the limitations of rational thinking in understanding psychedelic experiences. It ends with a humorous twist where the entities actually know the answer but don't reveal it until after the narrator has left. Shorter summary