# Two hemispheres - I do not think it means what you think it means

I am going to address some misconceptions about brain hemispheres -- in popular culture, and in Zizian theory. The latter, because the madness must stop. The former, because it provided a foundation for the latter.

*

Two hemispheres in popular culture
----------------------------------

About 99% of animals are bilaterally symmetric -- the left side and the right side of the body are approximately each other's mirror images. The symmetry is not perfect. For example the human heart is situated slightly on the left side, and its left and right halves have slightly different functions. But in general, it seems like once Evolution Fairy has decided that bilateral symmetry is a good idea, it was easier to keep designing all new organs symmetrically. Butterflies have pairs of wings, humans have a pair of hands.

Sometimes it means that organs come in pairs: we have a pair of eyes, and several pairs of ribs. Sometimes it means that organs have two connected parts, such as the left lung and the right lung. Some organs along the sagittal plane only have one approximately symmetric part, for example the stomach or the vertebrae.

The brain is not an exception to this rule. The parts that come in pairs include the cerebral hemispheres, the cerebellar hemispheres, basal ganglia, thalami, hippocampi, amygdalae, etc. The symmetric parts on the sagittal plane include corpus callosum, medulla, pons, midbrain, pineal gland, hypothalamus, hypophysis, etc.

Popular culture simplifies this as "we have two brains".

Simplifications are inevitable, but I wish humanity had settled on something less confusing and woo-inspiring, such as "the brain has two sides". Instead, *it is known* that:

*   the left brain is logical, the right brain is creative
*   the left brain is mathematical, the right brain is artistic
*   the left brain understands languages, the right brain understands music
*   the left brain prefers Android, the right brain prefers iPhone

...okay, I admit that I made up the last one. The rest is an oversimplification.

To explain, let's consider the language. Broca's area (speech and grammatical structure) and Wernicke’s area (comprehension of written and spoken language) are located in one cerebral hemisphere (almost always both in the same one), usually in the left hemisphere (for over 95% of right-handers and about 70% of left-handers). The left angular gyrus is essential for reading, writing, and connecting written symbols with their meanings. So we can see where the meme comes from. But the right hemisphere, including the right angular gyrus is crucial for understanding the full context of the communication: it processes the tone, rhythm, and intonation; enables understanding of emotional context, sarcasm, jokes; and helps maintain coherence in longer narratives. In tonal languages especially, the right hemisphere processes the melodic components of the speech. So, "which brain contains the language?"

What about mathematics? Understanding the numbers and basic arithmetic operations is a function of the parietal lobe, specifically intraparietal sulcus (understanding numbers and basic arithmetic) and angular gyri (memorizing e.g. multiplication tables), mostly in the left hemisphere (though estimating numbers *without* counting is done by the right hemisphere). Problem solving is done by prefrontal cortex, with the left hemisphere more important for step-by-step solving. Geometry and space visualization are a function of the parietal and occipital lobes, mostly in the right hemisphere. Finally, the visual cortex of both hemispheres is responsible for recognition of numbers and mathematical symbols. Remind me again, "which brain does the math?"

Emotional intensity, fear, and aggression are regulated by amygdalae. Prefrontal cortex regulates emotions. Limbic system memorizes them. Etc. I am simplifying things here.

So, although it is true that the left (usually) hemisphere is generally *more* involved in language, logic, and math... and the right hemisphere is *more* involved in spatial awareness, nonverbal communication, and music... *actually doing* these things requires a cooperation of *both* hemispheres. It's not like one hemisphere does the entire task while the other one is taking a break. Instead, it's more like different parts of the task happen in different places in the brain, some of those parts in one hemisphere and other parts in the other hemisphere, even if one of the hemispheres does a majority of the entire work.

*

### Split-brain syndrome

*"But there was an experiment in which they separated the hemispheres, and clearly one could function without the other. And each of them was a different personality!"*

The brain can survive a surprising amount of damage. There was the famous case of Phineas Gage ([Wikipedia](https://en.wikipedia.org/wiki/Phineas_Gage)), whose large parts of brain were destroyed when an explosion blew an iron rod through his brain; afterwards, the rod landed 25 meters away. With all the help that the 19th century medicine could provide (removing the fragments of skull and brain, disinfecting the wounds using silver nitrate, applying bandages) he survived, miraculously. But the people who knew him reported that he wasn't the same person anymore. Previously, he was a hard-working and responsible man. After the accident, his memory and intelligence appeared unimpaired, but he lost self-control, and became impulsive and uninhibited. But later, his behavior improved. (These facts are disputed.)

How is this even possible? My explanation has two parts. First, although the two sides of the brain are somewhat specialized, they are also somewhat *redundant*, just like most other symmetrical organs in the body. We don't have two kidneys so that one can filter the blood, and the other one can e.g. meditate. We have two kidneys so that if one fails, we can still survive. After all, Evolution Fairy loves bilateral symmetry. Both sides being redundant is business as usual; it's the lateral specialization that requires a special explanation.

Second, there is this thing called "neuroplasticity". The brain changes all the time. When we learn things or acquire habits, the connections between the neurons change. Doing a lot of the same thing can measurably change the brain structure and function. Playing the piano using both hands thickens your corpus callosum (coordination of the hemispheres). Driving a cab for years makes your hippocampus larger (spatial memory). Athletics and dancing better connects your motor and sensory areas. Mathematics can increase the gray matter in your intraparietal sulcus (numerical reasoning). Meditation can thicken your prefrontal cortex (attention) and reduce your amygdala size (anxiety). Blind people have their visual cortex rewired to sound localization and Braille reading. If a part of a brain gets damaged, the nearby regions or the opposite hemisphere can compensate (but this is only true for some parts of the brain, and depends on age).

How is this related to separating the hemispheres by cutting the corpus callosum?

In case of Phineas Gage, I believe that the interpretation "after parts of his brain were damaged, his personality *changed*" makes much more sense than speculating that maybe the new (impulsive and uninhibited) personality has *always been there*, hiding inside his brain, invisible, waiting for the once-in-a-million-lifetimes opportunity to get liberated. No. Previously, *all* parts of his brain were parts of the old (reliable and hard-working) personality. The accident destroyed some parts of his brain, and the result was the new personality. All *parts* of the new personality have always been there, but they have previously been parts of the old personality; the new personality *as a whole* was *created* by the accident.

I don't see why we shouldn't apply the same logic to corpus callosotomy. Destroying the major connection (though not the only one: there is also the anterior commissure, posterior commissure, and hippocampal commissure) between the cerebral hemispheres *damages* the brain; obviously. The parts that have previously cooperated fluently now have a problem to cooperate. The split-brain syndrome is a result of the damage. However, despite that, the split-brain patients typically maintain a unified sense of self and personality, it's just that some of their information processing systems are disconnected. Which makes it even less likely that in people with intact corpus callosum the two brain hemispheres secretly act as two different personalities.

Similarly, the article *"*[*The Apologist and the Revolutionary*](https://www.lesswrong.com/posts/ZiQqsgGX6a42Sfpii/the-apologist-and-the-revolutionary)*"* should not be interpreted as there being two different personalities inhabiting one body. It is the same personality, only (if the experiment replicates) some *parts* of it can be temporarily turned off.

*

### Dissociative identity disorder

*"But we have examples where multiple personalities live in the same body (without any surgery). Ever heard about Dr Jekyll and Mr Hyde?"*

Yes, but I believe that these are completely different things.

It is tempting to imagine that if someone has *two* alters (personality states) and *two* cerebral hemispheres, then these numbers have to be related somehow.

But there is no law of nature saying that if there is *n* of something, and *n* of something else, then there must be a 1:1 correspondence between these two sets. For some reason, we have a strong feeling that there *should* be such correspondence. There is an ancient tradition of creating tables assigning e.g. the 4 temperaments to 4 alchemical elements to 4 seasons to 4 entrepreneurship styles to 4 tastes etc. But reality does not work like that.

Also, there are not necessarily *two* alters. Among the people diagnosed with dissociative identity disorder (less than 1% of the population), most of them have 2 or 3 alters, but it is relatively common to have up to 10 alters, and cases with more than 10 alters are rare, but known and well-documented. On the other hand, everyone has *two* brain hemispheres. So how could there be a 1:1 correspondence? And if there isn't one in the general case, why should we assume that it must be there even for exactly 2 alters?

Although different alters can show unique brain activity patterns (for example in hippocampus and amygdala), generally all alters use *both* sides of the brain. Which is kind of obvious, if you realize that otherwise each alter could only control one hand and one leg.

This is just a speculation, but I think that dissociative identity disorder is one extreme of a spectrum; a hypertrophied version of something that exists in everyday life. The spectrum could go somewhat like this:

*   mental models of other people
*   role playing and social masks - acting differently in different situations
*   daydreaming, "losing yourself" in a book or a movie
*   depersonalization - feeling as if you are watching yourself from outside
*   dissociative amnesia - forgetting your old identity and assuming a new one
*   dissociative identity disorder - with distinct personality alters

I also think that the *milder* parts of the spectrum are *adaptive*. A person at the opposite extreme of the spectrum with zero identity shifts would be acting the same in all social contexts, unable to enjoy fiction, unable to change their thought patterns and adopt different perspectives.

It just seems that when your personality becomes *too* flexible, you may lose control over the changes, and also start forgetting things that happened to your other identities. This typically happens as a result of childhood trauma, or cult abuse. Some people try to self-experiment and create a similar effect [on purpose](https://www.lesswrong.com/w/tulpa); not sure whether that is a good idea.

*

Two hemispheres in Zizian theory
--------------------------------

Ok, now we are ready to review the Zizian theory of brain.

First, let's bring some evidence that Zizians actually take the two brains seriously. Because someone will probably try to sanewash their theory by suggesting that obviously they only meant it metaphorically, or that it was just an idea they have briefly played with and then abandoned it.

> Sufficient unfolding of this infohazard grants individual self-awareness to both hemispheres of your brain, each of which has a full set of almost all the evolved adaptations constituting human mind, can have separate values, genders, are often the primary obstacle to each other thinking. Often desire to kill each other.
> 
> *   Ziz, [Good Group and Pasek’s Doom](https://sinceriously.blog-mirror.com/good-group-and-paseks-doom/)

> Left Good - Someone having a good left hemisphere, including a double good. Good left hemispheres tend to be more into consequentialism than praxis.
> 
> Right Good - Someone having a good right hemisphere, including a double good. Tend to be more into praxis than consequentialism. Very common among animal rights people.
> 
> Left-Only Good - Someone with a good left hemisphere and a nongood right hemisphere.
> 
> Right-Only Good - Someone with a nongood left hemisphere and a good right hemisphere.
> 
> Left-Female - Of a human, having a female left hemisphere.
> 
> Right-Female - Of a human, having a female right hemisphere.
> 
> Left-Male - Of a human, having a male left hemisphere.
> 
> Right-Male - Of a human, having a male right hemisphere.
> 
> lmrf - Left-male, right-female.
> 
> lfrm-  Left-female, right-male.
> 
> Double-Female - Both hemispheres female. Cis women or binary trans women.
> 
> Double-Male - Both hemispheres male. Cis men or binary trans men.
> 
> *   Ziz, [Infohazardous Glossary](https://sinceriously.blog-mirror.com/infohazardous-glossary/)
> 
> This is one instance of a trend at MIRI to exclude jailbroken altruistic right hemispheres.
> 
> CFAR covers only a narrow portion of mental tech, mostly about left hemisphere optimization listening more to right hemisphere optimization.
> 
> \[T\]he president and cofounder of CFAR, has created and supported a culture that is cissexist, anti right hemisphere reorientation \[...\]
> 
> The leaders of MIRICFAR have been systematically excluding, discrediting, and/or neutralizing humans with alive enough right hemispheres \[...\]
> 
> This is what a mind looks like when the right hemisphere has already written its bottom line.
> 
> Whatever else \[he\] says, I know what his right hemisphere’s bottom line is.
> 
> This is yet another of the many right hemispheres trying to warp to discredit our statements \[...\]
> 
> *   Gwen, [Case study: CFAR](https://web.archive.org/web/20230130204522/https://everythingtosaveit.how/case-study-cfar/)

Writings of Zizians are often full of jargon, hysterical exaggerations, and death threats against virtually everyone. Surprisingly, these definitions written by Ziz are quite comprehensible. (In other places, Ziz often talks about "cores". That seems to be more or less a synonym for a hemisphere. "Two of them per organism.")

I have also included selected sentences from a longer text written by Gwen (inventor of the "unihemispheric sleep"), to illustrate how the "left brain, right brain" model is taken for granted.

*

### Unihemispheric sleep

What is the "unihemispheric sleep"? I didn't find a description by any Zizian. According to [zizians.info](https://zizians.info/), they prefer to keep it secret among themselves. It is described as:

> 1.  You need to be tired.
> 2.  You need to be laying down or sitting up. (It is important that you stay in a comfortable position that won't require you to move very much.)
> 3.  In either case you want to close one eye and keep the other open.
> 4.  Distract the open eye with some kind of engagement. (This works best if you have a partner who can help you.)
> 5.  Eventually you should feel yourself begin to fall asleep on one side. That side will also become numb. (The degree of numbness is a good way to track how deep into sleep the side is.)
> 6.  Once into UHS, it is supposed to be possible to infer which aspects of your personality are associated with which side of the brain. (This is a little farfetched, and the more likely explanation is that it disrupts peoples visceral sense of what is and isn't socially okay.)

Apparently, you don't even need to cut your corpus callosum to separate the two personalities living in your brain. It is sufficient to wait until one of them falls asleep!

By the way, notice the implied popular misconception. It is *generally* the rule that each brain hemisphere controls the opposite side of the body. But there is an exception...

...can you guess it?

(I am giving you a chance to figure it out on your own, and prove to yourself that you understand the secrets of the human hemispheres better than Zizians.)

Ready?

Okay then: it's the eyes. Despite a popular misconception that each brain hemisphere controls the eye on the opposite side (which *is* actually the case with fish, amphibians, and reptiles), in humans and other primates, each hemisphere controls about 50% of each eye. Instead, the left hemisphere processes the right *visual field* (of both eyes), and the right hemisphere processes the left visual field (of both eyes). This is related to the fact that our eyes are facing forward.

Which means that keeping one eye closed and the other eye engaged will definitely *not* make one of your hemispheres fall asleep and keep the other one awake. Both of them are equally stimulated by this clownery. So whatever actually happens during the "unihemispheric sleep", it must be something other than what is advertised.

*

### A sidenote about sleep deprivation

By the way, sleep deprivation is a standard mind-control technique in cults.

Sleep deprivation has a strong impact on prefrontal cortex, amygdala, and hippocampus. (Yes, the prefrontal cortex of *both* hemispheres. It makes no difference which side are you laying on, or which eye is open.) The prefrontal cortex is responsible for logical thinking and decision making. Sleep deprivation impairs your judgment. Amygdala processes emotions. Sleep deprivation makes you anxious and irritated; you respond more strongly to threats. Hippocampus controls memory formation and spatial navigation. Sleep deprivation makes it more difficult to remember new things.

How would a cult benefit from this? Skeptical thinking is an active process; it does not happen automatically. When we hear people say something, [by default we believe them](https://www.readthesequences.com/Do-We-Believe-Everything-Were-Told). It takes an active effort to notice problems and disbelieve. Making people tired makes them more likely to believe.

Most cults impose sleep deprivation using some pretext. It's not that sleep is bad, *per se*, but there is so much work to do, and so little time! Or, it's better for your health to wake up early (but somehow we forget that it is also better for your health to go to bed early).

It is clever to figure out a way how to keep people sleep deprived, without having to organize all the work for them, or do the early morning prayers/meditation.

*

### What actually happens

*"But we have empirical evidence that the Zizian sleep tech actually did something important to the people who tried it. Some of them have successfully communicated using their individual hemispheres. How can you explain that?"*

I am not denying that *something* happened as a consequence of experimenting with sleep deprivation. All I am saying is that it had nothing to do with the brain hemispheres.

But then, what was it?

Well, I wasn't there, and I didn't have an opportunity to talk to those people. But given the information I have, my best guess is that it was...

...some kind of dissociation...

...which has nothing to do with the brain hemispheres, as I have already explained.

Just imagine being there. Tired. So tired. Almost falling asleep. But you can't. You keep one eye open to keep yourself awake. There is Ziz. Talking to you. Ziz is a scary person. ("I was physically afraid in a way I’ve never been with anyone else" - [Anna Salamon](https://openvallejo.org/2025/01/31/zizian-namesake-who-faked-death-in-2022-is-wanted-in-two-states/)) Ziz keeps you awake. Ziz is talking about good and evil. You must fight, she says. But you want to sleep. The world depends on you. If we fail, millions will die. Evil has to be eliminated, at any cost. Only Ziz is double-good. You are single-good, which means there is a good person and an evil person in you. You want to sleep. You must not. It is the evil person inside you who wants to destroy the universe. The evil person doesn't care. You don't care. You just want to sleep. You must not, Ziz insists. The good person in you must stay awake and defeat the evil person. It is a timeless decision. The eternity depends on your choice. If you die, you can still live in another universe, but if you give up, if your algorithm gives up, you are lost in all of them. Make the good person awake. Say something...

Or maybe it wasn't anything like this. As I said, I wasn't there. I am just looking for the most likely explanation, in a situation where the proposed explanation clearly contradicts the facts we know about the human brain.

My explanation is that you basically start playing a role, under social pressure multiplied by the sleep deprivation. You are given an explanation, which we now know is bullshit, but you believe it, because it seems supported by the things you have heard. You desire to fit in. You want to save the world, and in the process also save yourself. Talking about timeless algorithms and counterfactual worlds makes you feel surreal. You want to sleep.

And so you *create* a new personality, modeled after what Ziz wants it to be. *Two* personalities, actually. You give them names, and assign your individual traits to them, according to the provided scheme: one of them gets the things that Ziz considers good, the other one gets the things that Ziz considers evil. An angel, and a devil.

(And then the angel prevails, and you become a loyal follower of Ziz. Or the devil prevails, and then you kill yourself to prevent the devil from destroying the universe.)

*

### Don't do this

If you are the kind of person who is at high risk, please listen to me and don't do this.

But I don't really expect you to listen. Why would you? I am not that convincing.

My hope is that by explaining all of this, I may have ruined the conversion process for you. Active cooperation was needed on the side of the person doing the experiment, and because Ziz was recruiting among aspiring rationalists, having a [scientifically-sounding](https://www.readthesequences.com/Science-As-Attire) explanation for the experiment played an important role. As a proper rationalist, you would not want to deny the existence of the two brain hemispheres, would you?

Even if the explanation was wrong, the process of creating the new dissociated personalities was probably helped a lot by the belief that the personalities are *already there*, and therefore you are only exposing what [already exists](https://www.lesswrong.com/w/litany-of-gendlin) (a noble goal for an aspiring rationalist!), as opposed to... giving yourself a milder version of dissociative identity disorder, just because someone told you that they had a secret tech.

Now that you know that the two brains theory is bullshit, and that the "unihemispheric sleep" actually has nothing to do with the brain hemispheres... maybe the magic of Ziz will fail to convert you (or drive you to suicide).

You are *one* person. Your brain has multiple *parts*, but together they make one person. (Or not, because your brain is fragile and can be shattered. Don't do that on purpose.)

Also the good and evil do not work the way Ziz describes them. Moral dilemmas cannot be reduced to "one hemisphere wants to destroy the universe, the other wants to save it". You don't have an *angel* sitting in one of your brain hemispheres, and a *devil* sitting in the other. (Renaming them to "good" and "nongood" doesn't make it any more plausible.) That's not how any of this stuff works. And you should be smart enough to realize that Ziz calling herself pure good and calling you half-good/half-evil is blatantly self-serving, because it implies that whenever the two of you disagree, she is right and you are wrong.

But that's a conclusion you should reach on your own (or not). I am just trying to put one popular misconception about human brains out of your way.

*

Key points
----------

Human brain is bilaterally symmetric, just like the rest of our (most animals) bodies.

There is some lateral specialization, but not in the sense "language is here, math is there", but rather like "language/math/art/etc. are composed of many different functions that are implemented in many different parts of the brain... and even if a majority of these parts are on one side, the cooperation of all parts (both sides) is what makes it work".

There is a thing called "split-brain syndrome". There is a thing called "dissociative identity disorder". Those are two *completely different concepts*. The people whose cerebral hemispheres were partially separated still maintain a coherent sense of self (one personality). The people who have multiple personalities use the entire brain for each personality.

Therefore, the Zizian beliefs about "hemispheres" are completely wrong, and the "unihemispheric sleep" couldn't work even in principle (because the inputs from each eye are processed by both cerebral hemispheres).

So it seems that what Zizians actually do is *dissociation*, which is the opposite of what our cultural wisdom would suggest, with the predictable results (suicide, murder).