Once I had an idea for a sci-fi setting, about a society where it is possible to create a second personality in your brain. Just like tulpa, except that it is done using technology. Your second personality does not know about you, it thinks it is the only inhabitant of your brain. While your second personality acts, you can observe, or you can turn yourself off (like in sleep) and specify events that would wake you up (that automatically includes anything unusual). So for example, you use your second personality to do your work for you, while you sleep. That feels like being paid for sleeping 8 extra hours per workday, which is why it becomes popular.

When the work is over, you can take the control of the body. As the root personality, you can make choices about how the second personality perceives this; essentially you can give them false memories. You can just have fun, and decide your second personality will falsely remember it as them having fun. Of you can do something that your second personality will not know about (either will remember nothing, or some false memory: for example of spending the whole afternoon procrastinating online). This can be used if you want your second personality to be different than you so much that it would not agree with how you spend your free time. You can create a completely fictional life story for your second personality, to motivate it to work extra hard.

When this becomes popular, obviously your second personality (who doesn't know it is the second personality) would possibly want their own second personality. But that would be a waste of resources! The typical hack is to edit the second personality's beliefs to oppose this technology; for example you can make them believe to be a member of a religion that opposes it.

And the sci-fi story itself would obviously be about someone who finds out they are a second personality... presumably of an owner who does not mind them knowing. Or an owner who committed a mental suicide by replacing themselves by the second personality 100% of the time. But there is a chance that the owner is merely sleeping and waiting until some long-term goal is accomplished. The hero needs to discover their real past and figure out the original personality's intentions...

But MechanicalTulpa is good for far more than economizing on cost. The key lies in T-Wave's proprietary recursive tulpa technology, whereby our tulpas themselves create tulpas, and so forth, potentially ad infinitum.

One day you talk with a bright young mathematician about a mathematical problem that's been bothering you, and she suggests that it's an easy consequence of a theorem in cohistonomical tomolopy. You haven't heard of this theorem before, and find it rather surprising, so you ask for the proof.

"Well," she says, "I've heard it from my tulpa."

"Oh," you say, "fair enough. Um--"

"Yes?"

"You're sure that your tulpa checked it carefully, right?"

"Ah! Yeah, I made quite sure of that. In fact, I established very carefully that my tulpa uses exactly the same system of mathematical reasoning that I use myself, and only states theorems after she has checked the proof beyond any doubt, so as a rational agent I am compelled to accept anything as true that she's convinced herself of."

"Oh, I see! Well, fair enough. I'd still like to understand why this theorem is true, though. You wouldn't happen to know your tulpa's proof, would you?"

"Ah, as a matter of fact, I do! She's heard it from her tulpa."

"..."

"Something the matter?"

"Er, have you considered..."

"Oh! I'm glad you asked! In fact, I've been curious myself, and yes, it does happen to be the case that there's an infinitely descending chain of tulpas all of which have established the truth of this theorem solely by having heard it from the previous tulpa in the chain." (This parable takes place in a world without a big bang -- tulpa history stretches infinitely far into the past.) "But never to worry -- they've all checked very carefully that the previous tulpa in the chain used the same formal system as themselves. Of course, that was obvious by induction -- my tulpa wouldn't have accepted it from her tulpa without checking his reasoning first, and he would have accepted it from his tulpa without checking, etc."

"Uh, doesn't it bother you that nobody has ever, like, actually proven the theorem?"

"Whatever in the world are you talking about? I've proven it myself! In fact, I just told you that infinitely many tulpas have each proved it in slightly different ways -- for example my own proof made use of the fact that my tulpa had proven the theorem, whereas her proof used her tulpa instead..."

Hypnosis, when the subject carries out the hypnotist's suggestions without a subjective feeling of acting, as in the floating arm test.

There are probably more relevant effects in hypnosis. Parts negotiation comes to mind.

A felt presence of God.

That depends a lot what you mean with "felt". I think people who talks to god and perceive to get answer are a better example as people who feel transcendence.

From descriptions of lucid dreamers discussing issues with independent identities during dreams, I would add lucid dreaming to this list.

What experimental test could you perform to determine that you have successfully learned "parallel tulpa processing"?

I tried that last week. I lost. We were actively trying to not share our strategies with each other, although in our case abstract knowledge and skills are shared.

The general impression I got from reading a lot of the stuff that gets posted in the various tulpa communities leads me to believe it is, at its core, yet another group of people who gain status within that group by trying to impress each other with how different or special their situation is.

Used to be, when I read stories about "astral projection" I thought people were just imagining stuff really hard and then making up exaggerated stories to impress each other. Then I found out it's basically the same thing as wake initated lucid dreaming, which is a very specific kind of weird and powerful experience that's definitely not just "imagining things really hard". I still think people make up stories about astral projection to impress each other, but the basic experience is nevertheless something real and unique. The same thing is probably happening with tulpas.

Read almost any post where somebody is trying to describe their tulpa, and you'll see very obvious attempts to show how unique their tulpa is or how it falls into some unprecedented category or how they created it in some special way.

Given that tulpa are probably strongly influenced by the hosts beliefs I wouldn't expect all tulpas to be exactly the same. I would expect most tulpa's to be unique in some sense.

I also would expect that given the effort that involved in creating a tulpa that people do vary the protocol.

None of the sources posted offer any sort of good evidence that people who claim to have tulpas have any sort of advantages.

"Good evidence" depends on your priors. For me the evidence that exists is good enough to find the phenomena interesting and worthy of further attention.

For a community which likes to talk about things like the exact nature of consciousness, ethics of simulations, etc. this seemed like an interesting practical case

I don't agree with the tone of this comment, but I admit there's something about this that feels deeply weird to me.

What do these have to do with rationality?

Rationality includes instrumental rationality, and imaginary friends can be useful for e.g. people who are lonely.

deluding yourself into believing it has autonomy

Not sure of what exactly you mean by "autonomy" here, but there are plenty of processes going on in people's brains which are in some sense autonomous from one's conscious mind. Like the person-emulating circuitry that tulpas are likely born from: if I get a sudden feeling that my friend would disapprove of something I was doing, the process responsible for generating that feeling took autonomous action without me consciously prompting it. And I haven't noticed people suggesting that tulpas would necessarily need to be much more autonomous than that.

that if revealed to other people would make them concerned about your mental well-being

Someone might make his social circle concerned over his mental well-being if he revealed himself to be an atheist. Simply the fact that other people may be prejudiced against something is no strong reason for not doing said something, especially something that is trivial to hide. Also, the fact that tulpas are already a somewhat common mental quirk among a high-status subgroup (writers) can make it easier to calm people's concerns.

It depends whether the company that you seek values people who signal that they are contrarian or whether people are expected to be "normal".

In general the idea isn't that you will tell everyone that you meet about the fact that you have a tulpa if you interact with the kind of people who would see it as a sign of mental illnesses.

Given that tulpas are in your mind you don't have to tell anyone about them.

While obviously you have great motivation to just lie on this, I'd be curious what your utility function/values are, and how they differ from your host or humanity in general.

I believe I experienced it a few times when we were experimenting with switching

How does being conscious feel in respect to not being conscious?

I believe I experienced it a few times when we were experimenting with switching, and it wasn't particularly pleasant.

This is scary. I might stay away from switching for now if it carries a serious risk of accidentally creating and then destroying consciousness!

Probably only one thing: turning duplicates of the same person into new unique persons rapidly. Aka, a cheaper replacement for the kind of application where you'd otherwise have to simulate an entire childhood.