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Brain researcher Robert Carhart-Harris and physicist Karl Friston suggest that psychedelics will save humanity. They are, of course, far from the first people to do so. But they’re the first to explain how psychedelics will save humanity using the theory of predictive processing, which was developed in large part by Friston himself. And so with my interest sufficiently piqued, allow me to condense a decade of research on the Entropic Brain Hypothesis into a few paragraphs.

Our brains evolved to model the environment and minimize surprise and uncertainty. Since our environment is complex and dynamic, so are more evolved brains. fMRI allows us to measure brain entropy, how unpredictable is one’s brain state in the future based on its current state. It’s a proxy for a brain’s flexibility and complexity. 

Human brains are more entropic than those of our animal relatives, which in turn have more entropic brains than phylogenetically distant species. But humans have also developed a brain structure that suppresses entropy: the default mode network (DMN). According to Friston, optimal prediction is achieved when the brain is finely poised between order and disorder, rigidity and entropy. The DMN is less developed in children, and is suppressed in REM sleep, the onset of psychosis, and by psychedelics — all the above states are characterized by wandering thoughts, creativity, and magical thinking (hello, Ribbonfarm!) that isn’t strongly constrained by reason and prior experiences.

The DMN is also overactive in people with depression. This manifests in two features of depression: “depressive realism” (a capacity to judge reality more accurately) and rigidity of thought (the mind is stuck in a negative bias that doesn’t respond to changes in the environment). In fact, many other mental disorders can be thought of as disorders of mental rigidity. For example: addiction (the brain is stuck in loops of craving and indulgence), autism, PTSD, and schizophrenia. Psychedelics increase brain entropy and “shake it out” of its rigid habits, allowing it to settle into more salubrious patterns (especially if guided by a good therapist).

There’s another effect that psychedelics cause by inhibiting the DMN — the dissolution of ego and the sense of self. Should we think of self-identity too as a disorder of mental rigidity? Stay tuned.

Before talking more about self-identifying, it’s worthwhile to consider why we even think that there is anything to identify  — a “self” that we can attach labels to. This is not a given; many people “…report no individualized sense of self, no self-related thoughts” This is from a paper on Persistent Non-Symbolic Experiences, a sciencey-sounding term for what is normally called “enlightenment”.

Who’s “enlightened”? If you ask them, any and all of:

• An old monk wireheading in a cave, oblivious to suffering and desire.
• A rationalist breaking through his default ontology to play with frameworks at will.
• Me, after eating way too many mushrooms.

Whatever do these all have in common? Here’s my Predictable Identities conjecture: the sense of self comes from habitual and repeated thoughts; novel thoughts make the self dissolve.

“Habitual thoughts” means everything from high-level cogitation to low-level processing of stimuli. Kaj Sotala points out that something as simple as the perception of hearing a stick hitting a woodblock is the result of complicated processing that combines several auditory frequencies, your previous experience with wood objects, and mental imagery. This processing usually happens automatically: [hear sound] -> [imagine block]. 

But, with enough concentration, one can break this habit, leaving just the raw sounds to do with as one wishes. The same is true of “habits” like [feel pain] -> [experience suffering] or [see object of desire] -> [experience craving] that are the common focus of the monk’s meditation, or the frameworks of social interaction Valentine writes about. 

When the part of your brain that monitors itself notices repeated patterns of thought it creates a high-level model called “self” that it can use for prediction. “I” am interpreting the sound as a stick hitting a woodblock. “I” suffer when in pain. “I” think of everything in terms of predictive processing. And “I” will likely continue to do so in the future.

But when a thought or interpretation arises that can’t be predicted from the habits of my mind, there is no reason to assign it to a consistent thinking “self”. The thoughts I’m used to thinking are mine, but the novel ones could be anyone’s or no one’s.