What function do hallucinations serve?
December 26, 2022 4:47 PM Subscribe
After reading Frans de Waal's book, Mama's Last Hug, which discusses the function of emotions, I'm wondering how hallucinations can be helpful. I can't find evidence of them being a survival strategy, but I imagine they do perform some function. Can anyone recommend articles/media on this?
Well, hallucinations are generally defined as seeing (or otherwise perceiving) things that aren't real, and I would say that if something is genuinely helpful and provides consistent survival value, it is a real thing. So, by definition hallucinations aren't normally going to be directly helpful for survival
I'm having a hard time finding good writing for the general public about the topic, but this high level scientific article goes over the current scientific theories about hallucinations, many of which are about how the brain predicts things. One simple way to look at it is that the brain is constantly filtering reality to try and differentiate important signals from meaningless noise and make sense of everything. Hallucinations can happen when the brain tries too hard to make sense out of noise, and situations like dreaming or drugs can change how that filter works.
Hallucinations can be helpful when you actively want to see things that aren't (yet) real. There is a lot of similarity in how the brain handles artistic inspiration and literal hallucinations, and in some ways AI art could be considered a simple form of hallucinations.
posted by JZig at 7:42 PM on December 26, 2022 [1 favorite]
I'm having a hard time finding good writing for the general public about the topic, but this high level scientific article goes over the current scientific theories about hallucinations, many of which are about how the brain predicts things. One simple way to look at it is that the brain is constantly filtering reality to try and differentiate important signals from meaningless noise and make sense of everything. Hallucinations can happen when the brain tries too hard to make sense out of noise, and situations like dreaming or drugs can change how that filter works.
Hallucinations can be helpful when you actively want to see things that aren't (yet) real. There is a lot of similarity in how the brain handles artistic inspiration and literal hallucinations, and in some ways AI art could be considered a simple form of hallucinations.
posted by JZig at 7:42 PM on December 26, 2022 [1 favorite]
Response by poster: Well, hallucinations are generally defined as seeing (or otherwise perceiving) things that aren't real, and I would say that if something is genuinely helpful and provides consistent survival value, it is a real thing. So, by definition hallucinations aren't normally going to be directly helpful for survival
In der Waal's book he gets into emotions and why we wouldn't spend so much energy having them if they weren't useful. I can't think of a way that hallucinations would be helpful, but I feel like my perspective could be narrow.
posted by mermaidcafe at 7:49 PM on December 26, 2022
In der Waal's book he gets into emotions and why we wouldn't spend so much energy having them if they weren't useful. I can't think of a way that hallucinations would be helpful, but I feel like my perspective could be narrow.
posted by mermaidcafe at 7:49 PM on December 26, 2022
It does depend on how you define hallucination. In the clinical sense, hallucinations are when you perceive things that are not there. It's hard to think of this as anything but a malfunction, biologically speaking - it would be horribly disadvantageous.
In a broader sense, as the others note, your gestalt perception of the world - the sense of existing, what's happening, where you are and so on - is in many ways a very short term, high-confidence hallucination. Optical illusions are the easiest demonstration of how our brain takes shortcuts in its conversion of raw input data (from the retina, the nerves, the cochlea) and assembles it into a complete and integrated experience.
But, with the caveat that I haven't read the book, I would be wary of looking into the wrong end of the telescope here. The hypothesis that emotions have a definite survival value is not one I would leave unchallenged — not least because emotions are in many ways poorly defined and understood. And how they map to other animals or earlier humans is also almost completely unknown. The idea that everything we have had some kind of evolutionary currency spent purposefully on it is, IMO, misguided - we have lots of design errors and our bodies fail in really obvious ways all the time. The combination nose/throat/windpipe/epiglottis situation is basically proof there was no guiding hand - awful! Hallucinations in their more familiar sense (i.e. as part of psychosis) seem much more likely to represent a failure than any kind of strategic evolutionary gambit.
I think the most profitable way to inquire after this is to read about how hallucinations happen, and then try to understand why a system that produces hallucinations is valuable in spite of that, and valuable to the point where it would be retained generation after generation.
posted by BlackLeotardFront at 8:05 PM on December 26, 2022 [9 favorites]
In a broader sense, as the others note, your gestalt perception of the world - the sense of existing, what's happening, where you are and so on - is in many ways a very short term, high-confidence hallucination. Optical illusions are the easiest demonstration of how our brain takes shortcuts in its conversion of raw input data (from the retina, the nerves, the cochlea) and assembles it into a complete and integrated experience.
But, with the caveat that I haven't read the book, I would be wary of looking into the wrong end of the telescope here. The hypothesis that emotions have a definite survival value is not one I would leave unchallenged — not least because emotions are in many ways poorly defined and understood. And how they map to other animals or earlier humans is also almost completely unknown. The idea that everything we have had some kind of evolutionary currency spent purposefully on it is, IMO, misguided - we have lots of design errors and our bodies fail in really obvious ways all the time. The combination nose/throat/windpipe/epiglottis situation is basically proof there was no guiding hand - awful! Hallucinations in their more familiar sense (i.e. as part of psychosis) seem much more likely to represent a failure than any kind of strategic evolutionary gambit.
I think the most profitable way to inquire after this is to read about how hallucinations happen, and then try to understand why a system that produces hallucinations is valuable in spite of that, and valuable to the point where it would be retained generation after generation.
posted by BlackLeotardFront at 8:05 PM on December 26, 2022 [9 favorites]
Here is a recap of Netflix's "The Mind, Explained", episode 5, which talks about hallucinations and the functions they might serve.
posted by mezzanayne at 8:34 PM on December 26, 2022 [1 favorite]
posted by mezzanayne at 8:34 PM on December 26, 2022 [1 favorite]
You ignore your blind spots, because if you didn't, you'd have an obvious hole in your center of vision all the time; you hallucinate the visual information in that spot. It's impossible in normal life to notice your blind spot directly, though I imagine the right drugs might alter your perception. You can see it in action!
You probably hallucinate color around the edge of your vision, too. Your color perception is a lot less accurate around the periphery of your retina, but you usually don't notice.
So, those are two functional "hallucinations" though they're very low-key!
As to proper "seeing and hearing things that aren't there", Oliver Sacks wrote a collection of essays about hallucinations. This is his interview with Fresh Air: "On The Hallucination That Saved His Life":
You probably hallucinate color around the edge of your vision, too. Your color perception is a lot less accurate around the periphery of your retina, but you usually don't notice.
So, those are two functional "hallucinations" though they're very low-key!
As to proper "seeing and hearing things that aren't there", Oliver Sacks wrote a collection of essays about hallucinations. This is his interview with Fresh Air: "On The Hallucination That Saved His Life":
GROSS: You write in your book "Hallucinations" about an auditory hallucination you had that really might have saved your life. You were mountain climbing, and you had injured your foot or your leg. And part of you just wanted to just, like, slow down, sleep. But then you heard a voice, which said what?posted by BungaDunga at 8:34 PM on December 26, 2022 [7 favorites]
SACKS: Well, the impulse to sleep - I'd torn off most of the thigh muscles and the knee was dislocating backwards. And at one point I got quite shocked and thought it'd be nice to have a little sleep. And the voice said, no, that would be death. Go on. You've got to keep going. Find a pace you can keep up and keep it up. And this was a very clear, commanding voice. It was a sort of life voice and it was not to be disobeyed.
GROSS: And so you kept going in spite of the horrible shape that your leg and knee was in.
SACKS: Yeah. I was sort of lowering myself down with my arms. I had splinted the leg as best I could with an umbrella stick and my anorak, which I tore in two. Incidentally, I thought that was going to be the last day of my life. And it had every prospect of being, but I was found at twilight by two hunters. This was in north Norway. But that voice was crucial for me.
And I've heard many other stories like this. One of them was from a young woman who was brokenhearted after a love affair and determined to commit suicide. And she had a bottle of sleeping tablets and a tumbler of whisky to wash them down. And she had raised the tablets to her mouth when she heard a voice saying, don't do that. I wouldn't do that if I were you, you won't always be feeling the way you're feeling now. It was a man's voice. She didn't recognize it. She was fairly startled. She said, who was that? Who was that? And she said a figure materialized in a chair opposite her for a few seconds, a figure in 18th century dress that vanished. But she feels that hallucination saved her life. And I think her story is not that uncommon. Nor mine, for that matter.
Here's one explanation:
My voices, visions and beliefs are not symptoms of a mental illness, they are meaningful reactions to the trauma I survived as a child. They are no longer a burden that I bear, they are opportunities to understand and integrate different aspects of my life story and my self. The voices carry feelings and memories that I was once unable to bear, using metaphors when the content is too painful to speak directly. My overwhelming beliefs were meaningful, too. Built with the feelings born of trauma and vulnerability, they allowed me to express painful truths without needing to confront a reality I was not yet safe to explore. They hid the trauma in plain sight and, once I had the support to explore it, gave me a starting place to work from.posted by spiderbeforesunset at 8:59 PM on December 26, 2022 [5 favorites]
From another, probably bunk angle, there's The Origin of Consciousness in the Breakdown of the Bicameral Mind which proposed that ancient humans weren't conscious and, during that time, routinely experienced hallucinations commanding them to do things in lieu of a single coherent consciousness.
This idea is speculative and isn't precisely science, but it's an idea that's been pretty influential.
posted by BungaDunga at 9:17 PM on December 26, 2022 [1 favorite]
This idea is speculative and isn't precisely science, but it's an idea that's been pretty influential.
posted by BungaDunga at 9:17 PM on December 26, 2022 [1 favorite]
In der Waal's book he gets into emotions and why we wouldn't spend so much energy having them if they weren't useful. I can't think of a way that hallucinations would be helpful, but I feel like my perspective could be narrow.
I'd make a couple points here: just because something happens doesn't mean it's adaptive. For example, it's not uncommon for people to break a bone. I wouldn't really call it adaptive to break a bone--just something that can't always be avoided. Furthermore, I don't know that we can assume we spend a lot of energy on having hallucinations. If we did spend energy on it, then that would support the idea that it was adaptive, but I'm not ready to assume that we're spending energy on it.
Maybe you can find certain types of hallucination that are exceptions--perhaps dreaming while we sleep. It's still heavily debated what dreaming really is, but it seems to be for something.
I agree with the point above that just constructing our reality is akin to a hallucination. We do spend a lot of energy on constructing this reality. However, if things are going well, our picture of reality is as accurate as it can be. If the picture of reality goes off the track, then that's a hallucination. So a hallucination is what our apparatus of constructing reality does when the system isn't working right. A better analogy than breaking a bone might be developing a cancer. Cancer cells mutate to do things like replicate, avoid orders to self destruct, and build blood vessels for the tumor. These are things that are adaptive in another context, but the cancer cells are doing them in the wrong way or at the wrong time. Cancer isn't adaptive, but it can't always be avoided because it takes processes that are adaptive and does them at the wrong time. A hallucination is a result of the very adaptive processes that construct reality for us, but the processes are fitting together wrong.
posted by polecat at 10:21 PM on December 26, 2022 [15 favorites]
I'd make a couple points here: just because something happens doesn't mean it's adaptive. For example, it's not uncommon for people to break a bone. I wouldn't really call it adaptive to break a bone--just something that can't always be avoided. Furthermore, I don't know that we can assume we spend a lot of energy on having hallucinations. If we did spend energy on it, then that would support the idea that it was adaptive, but I'm not ready to assume that we're spending energy on it.
Maybe you can find certain types of hallucination that are exceptions--perhaps dreaming while we sleep. It's still heavily debated what dreaming really is, but it seems to be for something.
I agree with the point above that just constructing our reality is akin to a hallucination. We do spend a lot of energy on constructing this reality. However, if things are going well, our picture of reality is as accurate as it can be. If the picture of reality goes off the track, then that's a hallucination. So a hallucination is what our apparatus of constructing reality does when the system isn't working right. A better analogy than breaking a bone might be developing a cancer. Cancer cells mutate to do things like replicate, avoid orders to self destruct, and build blood vessels for the tumor. These are things that are adaptive in another context, but the cancer cells are doing them in the wrong way or at the wrong time. Cancer isn't adaptive, but it can't always be avoided because it takes processes that are adaptive and does them at the wrong time. A hallucination is a result of the very adaptive processes that construct reality for us, but the processes are fitting together wrong.
posted by polecat at 10:21 PM on December 26, 2022 [15 favorites]
Here to also strongly recommend Oliver Sacks' book Hallucinations. It's one of those books that I find myself citing in all kinds of contexts. He covers the many varieties -- caused by something internal, such as a migraine, or external, such as drugs -- and gets as close to any evolutionary purpose as anyone can, I think. The whole book is amazing and an excellent example of what happens when he puts his mind to examining and explaining something.
posted by gingerbeer at 11:46 PM on December 26, 2022 [4 favorites]
posted by gingerbeer at 11:46 PM on December 26, 2022 [4 favorites]
Agree with polecat to question the assumption that everything is adaptive. A more on topic example might be Charles Bonnet Syndrome: crazy hallucinations which affect up to 20% of people with with visual impairment. We all thought that my 90-something macular-degenerated mother was adding dementia to her deficits until a bit of light googling turned up CBS as an explanation - phew!. tl;dr in CBS the visual cortex makes stuff up to fill in for the information that is no longer incommming from the retina.
If you enjoyed that book, you might like Mel Konner's The Tangled Wing, biological constraints on the human spirit [scathing review by Peter Singer]. Konner is the same age as de Waal and will have the same bias towards "naive pan-selectionism": everything must have a reason. Me too.
posted by BobTheScientist at 12:50 AM on December 27, 2022 [4 favorites]
If you enjoyed that book, you might like Mel Konner's The Tangled Wing, biological constraints on the human spirit [scathing review by Peter Singer]. Konner is the same age as de Waal and will have the same bias towards "naive pan-selectionism": everything must have a reason. Me too.
posted by BobTheScientist at 12:50 AM on December 27, 2022 [4 favorites]
One very interesting aspect of hallucinations is that they are common in Parkinson's disease and Lewy body dementia, and it turns out that antipsychotics will suppress them in that population apparently as effectively as they do in schizophrenics.
And (even unmediated, as I recall) schizophrenics are generally resistant to many of the optical illusions that most other people experience, such as the face illusion, in which a concave face carved into a surface is seen as convex, which seems to draw a surprisingly sharp line of demarcation between hallucinations and illusions.
posted by jamjam at 2:32 AM on December 27, 2022
And (even unmediated, as I recall) schizophrenics are generally resistant to many of the optical illusions that most other people experience, such as the face illusion, in which a concave face carved into a surface is seen as convex, which seems to draw a surprisingly sharp line of demarcation between hallucinations and illusions.
posted by jamjam at 2:32 AM on December 27, 2022
Came in to recommend highly Oliver Sacks book on Hallucinations. It is written quite accessible, and very captivating to read. Sacks' book contains quite a bit in the cultural role and function of hallucinations.
Also interesting, but not as easy to read, is his book on Migraine, which also includes sections on auras and hallucinations.
posted by 15L06 at 3:20 AM on December 27, 2022
Also interesting, but not as easy to read, is his book on Migraine, which also includes sections on auras and hallucinations.
posted by 15L06 at 3:20 AM on December 27, 2022
IRT to emotions and ...
> we wouldn't spend so much energy having them if they weren't useful
I don't think that's entirely accurate. They were useful 50k years ago on the African savanna or whatever but that doesn't mean that they're still useful in the modern world. Maybe, but I tend to regard emotions as non-verbal parts of my brain that are trying to communicate with me in the only way they have available. Trouble is that those non-verbal bits are OLD and they don't understand the modern world and a huge amount of the time they're getting it wrong and if I pay too much attention to them I get pushed into unskillful action.
IRT to hallucination... I don't think they have to serve a purpose. Maybe they're just what happens when you take a brain outside of it's normal working parameters and it gets wonky. You don't give it enough oxygen or food or whatever, you bath it in stress hormones and it keeps trying to do what it always does but it does have what it needs to operate so the result isn't coherent. I guess I would regard dreams in a similar way. It's sort of like we shut down a large chunk of the operating system, but not all of it, and the bit that's left running tries to work but it doesn't have the same guard rails on it so it produces some really weird stuff.
posted by Awfki at 5:39 AM on December 27, 2022 [1 favorite]
> we wouldn't spend so much energy having them if they weren't useful
I don't think that's entirely accurate. They were useful 50k years ago on the African savanna or whatever but that doesn't mean that they're still useful in the modern world. Maybe, but I tend to regard emotions as non-verbal parts of my brain that are trying to communicate with me in the only way they have available. Trouble is that those non-verbal bits are OLD and they don't understand the modern world and a huge amount of the time they're getting it wrong and if I pay too much attention to them I get pushed into unskillful action.
IRT to hallucination... I don't think they have to serve a purpose. Maybe they're just what happens when you take a brain outside of it's normal working parameters and it gets wonky. You don't give it enough oxygen or food or whatever, you bath it in stress hormones and it keeps trying to do what it always does but it does have what it needs to operate so the result isn't coherent. I guess I would regard dreams in a similar way. It's sort of like we shut down a large chunk of the operating system, but not all of it, and the bit that's left running tries to work but it doesn't have the same guard rails on it so it produces some really weird stuff.
posted by Awfki at 5:39 AM on December 27, 2022 [1 favorite]
Most of evolution is not adaptive. De Waal is an excellent biologist, so I know he knows this, but I haven't read his book on emotions, so I don't know how well he explains it there. As far as I know, hallucinations are just misfires of the brain, things that happen when the usual biochemical functions (which are mostly adaptive) get scrambled for some reason (fever) or other (intentional ingestion of a poison that at low doses causes misfires without being fatal).
posted by hydropsyche at 8:49 AM on December 27, 2022 [5 favorites]
posted by hydropsyche at 8:49 AM on December 27, 2022 [5 favorites]
A phenomenon doesn't have to be adaptive itself, if it's a necessary side effect of something that IS adaptive. Cancer above is a good example, or autoimmune disorders - you need an immune system; you need cells that grow; you even use the immune system to keep those cells in check. Sometimes under some conditions those things do undesired behaviors, but there isn't like a gene somewhere for autoimmune disorders that is separate from the genes for overall immune strength.
Similarly, hallucinations probably aren't possible to extricate from our overall visual system. It seems pretty clear though that our pattern-matching ability and the "guessing" our brains do (to see a predator even when it's covered partly by branches, to pick up on subtle movement or identify faces even from far away, or even just generally to turn a 2d input into an understanding of the 3d world) is also associated with errors, like thinking you see motion when there is none, optical illusions, seeing faces in a piece of toast, etc.
posted by Lady Li at 9:36 AM on December 27, 2022 [2 favorites]
Similarly, hallucinations probably aren't possible to extricate from our overall visual system. It seems pretty clear though that our pattern-matching ability and the "guessing" our brains do (to see a predator even when it's covered partly by branches, to pick up on subtle movement or identify faces even from far away, or even just generally to turn a 2d input into an understanding of the 3d world) is also associated with errors, like thinking you see motion when there is none, optical illusions, seeing faces in a piece of toast, etc.
posted by Lady Li at 9:36 AM on December 27, 2022 [2 favorites]
Anil Seth's Being You: A New Science of Consciousness (here's my review) has the provocative thesis that consciousness itself is a hallucination... to be precise a "controlled hallucination", meaning that it's modified (but not controlled) by sensory input. His model is that the brain is actively imagining what's out in the world, rather than passively accepting an already accurate view of the world.
From his viewpoint, then, the advantage of hallucinations is that they are you, they are a smart animal's way of modeling the world. (Seth downplays how direct our senses are: our consciousness is locked in a lightless skull with only nerves coming in; everything we experience, we are creating.)
A dream is what he'd call an uncontrolled hallucination. Same lightless skull, same process, but here sensory inputs aren't being used to update the model.
posted by zompist at 1:14 PM on December 27, 2022
From his viewpoint, then, the advantage of hallucinations is that they are you, they are a smart animal's way of modeling the world. (Seth downplays how direct our senses are: our consciousness is locked in a lightless skull with only nerves coming in; everything we experience, we are creating.)
A dream is what he'd call an uncontrolled hallucination. Same lightless skull, same process, but here sensory inputs aren't being used to update the model.
posted by zompist at 1:14 PM on December 27, 2022
I think one of the common hallucinations that healthy people experience is the experience of seeing or hearing ghosts. When someone significant to you dies, you are likely to occasionally sense them as being in your surroundings. You hear your husband who died last week, downstairs clearing his throat, or you get the strong sensation that your mother is behind you in the kitchen. People frequently do things like turn on lights and look for them.
Another way people encounter ghosts is when they have a spiritual experience, for example seeing a deer move in the darkness past their house, and being visited with the conviction that the deer is their brother, still with them, watching over them protectively, or sending them one last message. These kind of experiences are really common.
Grieving hallucinations are functional. They are your brain throwing up a message "Nathan should be here. Go and find Nathan!" If you get a hallucination of this sort when Nathan has merely gone to the corner store you shrug it off and maybe have an anecdote to share when he comes home. "I thought you came home early, because I heard something downstairs, but it was just one of the cats knocking things over, as usual." Hallucinations of absent people are only distressing when they remind us that the person in question is gone and trigger a terrible sense of loss. They aren't distressing at all when they remind us that Nathan will be coming back with milk and bananas any time now, and we should probably put the heat on in the sitting room so he can warm up when he comes in from the snow, or maybe just give us the realization that we should stop eating handfuls of dry cereal and wait for the milk and bananas.
But they are so common and so distressing when someone dies, or dumps us, that we have rituals around death and break ups. We gather for funerals and hold viewings to confirm the person is dead. Bodies are dangerous because of infection and rot and the fact that they could attract scavenging animals, yet we leave them lying around on display. One important purpose of the funeral rite is to lay the hallucinatory ghosts. Such ghosts are far worse when the person dies unexpectedly and we don't get to have a funeral or see the body. If you see the body, you prevent hallucinations of ghosts because it is brought firmly home to us that the person is gone for good. They are also far worse if we were dependent on the person or they were dependent on us. We are left needing to go to them and hearing them and seeing them more often and more distinctly, according to how important it was during their life that we reconnect with them.
The worst most poignant ghosts occur when we feel that we should have prevented the death. Parents who don't move on after a crib death are responding to the biological imperative to save the baby and will be drawn again and again to go to the nursery. Their instincts are functional in that any future babies will experience obsessive vigilance. Checking the empty crib is the same vigilance occurring before the missing baby is replaced.
Other functional hallucinations include the belief that we have been in an unfamiliar location before. "Wait! I know this corner!!" It's a false positive that is part of our homing instinct, that if this is somewhere that might be a path back to old home territory we should not ignore it. Many a hunter gatherer has had this type of hallucination and it has caused their steps to turn and take them back to the old place. The leaves begin to fall and they remember the green valleys of the warm south. Nostalgia and homesickness can both be hallucinatory experiences. Of course most of us are so sensible that we discount the hallucinations as merely thoughts and memories of the past. But those thoughts and memories of the place we came from can be so strong that they make us buy plane tickets and return to the place we were glad to leave, just to see how it changed, how it's still not the place where we want to live. For some people those thoughts and memories are so vivid that they can cry out, "I turned the corner and just for a moment I thought I was on Wellington Street. I was certain the old cobbler's shop was just a block down from me!"
Other hallucinations can impel us to strive for things we want but that seem out of reach. An example of this would be someone going into an empty performance venue and having an intense feeling of hearing a crowd cheering for them, or having a recurring image/sensation of coming into the room where their mother is, and having her turn around smiling, because they have just told her that they got their diploma. Hallucinations like these ones are private spiritual experiences that give us the incentive to practice our music or apply for a degree program. We can be convinced they mean something and chase them, even if in fact we are an execrable musician.
Other unhappy hallucinations occur when we get obsessed with the feeling and the image that their are worms writhing on the floor or that there is someone in the empty apartment beside us. These type of hallucinations can trigger self protective behaviour. And of course if they are at the functional level - "I felt so dirty, I mopped the hell out of the floor and then I took a long shower!" they don't cause harm. It's when the signal cannot be stopped that they move from functional to harmful. The person who washes their hands until they are raw and sores become infected, has a hallucination that is way too strong. That's a hallucinatory experience gone wrong.
We often immerse ourselves in our imagination and court hallucinations. If you are deeply into some kind of media you can hear and see it in your mind's eye. Some people experience it so vividly they can immerse themselves in the memory of the fandom just by choosing to. Others can't summon the vivid sensory experiences without a trigger, such as reading the book or watching the film or listening to the music. When you court these kinds of experiences you get some of the same brain chemicals and pleasures as if these things were happening to you. People who feel all happy and warm after watching a rom-com are very sensibly seeking imaginary experiences that make them feel good. Some of us create our own fantasy or our own music. Inspiration is a hallucinatory experience in a mild way, but we take pride in it, and enjoy it instead of thinking we must be sick if we have a lilting tune with playing through our head while we are riding the subway home after work. We know it is memory or creativity and we don't fear it, or fight it. Yet that too can go wrong to a point where it drives us demented, such as when we have an ear worm playing on an endless loop.
Hallucinations may be a form of sleep disorder. Sleep is complicated. Among other things certain brain chemicals ebb during sleep and others are produced much more. One of these brain chemicals is an amnesiac. It prevents us from remembering our dreams and is produced as the end of deep sleep. If you sleep shallowly you don't produce enough of it and you remember your dreams. Anesthetic employs a similar drug which does the same thing biochemically. It wipes the memory of what happened during the surgery, and protects us from trauma. Unconsciousness without an amnesiac leaves us with shadowy memories of what we dreamed.
The natural work our brain does during sleep of consolidating memories, and converting short term memories into long term ones, produces messy and confusing images. A purple scarf floats though the air and strangles a sign post, the floor melts away under us and we are walking in the hall of a civic building. We see a stranger, miniature but adult, in a fetal curl on the floor. Soon they are walking with us, lecturing us about beavers. Then we turn into a beaver ourself... If there is spillage of this type of work that the brain does while we are awake, we usually blink and shake our head hard. "I started to drift off there..." If this kind of spillage occurs regularly while we are awake we may be in trouble, especially if it occurs so vividly that we can't tell what is real and what is not. But the experience is still, at the root, a functional one. We need to consolidate memories and forge stronger synaptic connections.
Something is going wrong when the moods and images and sounds thrown up by our brain during nightly maintenance intrude into our waking time. For most of us going off caffeine and getting a good night's sleep makes it a brief experience. Others of us live in a daze, images and voices coming at us in all directions, like the invisible voices and images being broadcast from a TV station. We can pick up the sounds and images that other people with a different tuned system never experience. We may be creatives lost in a happy daze of creation, or paranoid schizophrenics suffering a terrifying bombardment of misery and fear, but we go through life semi immersed, swimming to the surface to interact with others and then letting ourselves be taken by the flow. For every person who sees a burning bush and leads his people out of Egypt there are millions of others who see a burning bush and remember to check the smoke detector battery, or make an inept painting, or who blink and keep going, or who add bushes on the hilltop at sunset to the list of things to avoid looking at.
Hallucinations are just sensory experiences thrown up by our brains so vivid that they cross the threshold of idle thoughts. They can be so many different things. How functional they are depends on our individual ability to make use of our capacity to hallucinate and how distressing they are to us. Too much imagination, or too many hallucinations can be exhausting. Bad hallucinations can so closely mirror real bad experiences that they make our life hellish. Most hallucinations are benign, and so we don't worry about them and even don't consider them hallucinations. Sometimes we worry when we don't realise how universal they are. Often people think they must be going crazy when they first notice they have hallucinated. But most of us are just unaware of them. Brains and thoughts are messy. Hallucinations are just one of the messy things about having a brain.
posted by Jane the Brown at 6:25 AM on December 28, 2022
Another way people encounter ghosts is when they have a spiritual experience, for example seeing a deer move in the darkness past their house, and being visited with the conviction that the deer is their brother, still with them, watching over them protectively, or sending them one last message. These kind of experiences are really common.
Grieving hallucinations are functional. They are your brain throwing up a message "Nathan should be here. Go and find Nathan!" If you get a hallucination of this sort when Nathan has merely gone to the corner store you shrug it off and maybe have an anecdote to share when he comes home. "I thought you came home early, because I heard something downstairs, but it was just one of the cats knocking things over, as usual." Hallucinations of absent people are only distressing when they remind us that the person in question is gone and trigger a terrible sense of loss. They aren't distressing at all when they remind us that Nathan will be coming back with milk and bananas any time now, and we should probably put the heat on in the sitting room so he can warm up when he comes in from the snow, or maybe just give us the realization that we should stop eating handfuls of dry cereal and wait for the milk and bananas.
But they are so common and so distressing when someone dies, or dumps us, that we have rituals around death and break ups. We gather for funerals and hold viewings to confirm the person is dead. Bodies are dangerous because of infection and rot and the fact that they could attract scavenging animals, yet we leave them lying around on display. One important purpose of the funeral rite is to lay the hallucinatory ghosts. Such ghosts are far worse when the person dies unexpectedly and we don't get to have a funeral or see the body. If you see the body, you prevent hallucinations of ghosts because it is brought firmly home to us that the person is gone for good. They are also far worse if we were dependent on the person or they were dependent on us. We are left needing to go to them and hearing them and seeing them more often and more distinctly, according to how important it was during their life that we reconnect with them.
The worst most poignant ghosts occur when we feel that we should have prevented the death. Parents who don't move on after a crib death are responding to the biological imperative to save the baby and will be drawn again and again to go to the nursery. Their instincts are functional in that any future babies will experience obsessive vigilance. Checking the empty crib is the same vigilance occurring before the missing baby is replaced.
Other functional hallucinations include the belief that we have been in an unfamiliar location before. "Wait! I know this corner!!" It's a false positive that is part of our homing instinct, that if this is somewhere that might be a path back to old home territory we should not ignore it. Many a hunter gatherer has had this type of hallucination and it has caused their steps to turn and take them back to the old place. The leaves begin to fall and they remember the green valleys of the warm south. Nostalgia and homesickness can both be hallucinatory experiences. Of course most of us are so sensible that we discount the hallucinations as merely thoughts and memories of the past. But those thoughts and memories of the place we came from can be so strong that they make us buy plane tickets and return to the place we were glad to leave, just to see how it changed, how it's still not the place where we want to live. For some people those thoughts and memories are so vivid that they can cry out, "I turned the corner and just for a moment I thought I was on Wellington Street. I was certain the old cobbler's shop was just a block down from me!"
Other hallucinations can impel us to strive for things we want but that seem out of reach. An example of this would be someone going into an empty performance venue and having an intense feeling of hearing a crowd cheering for them, or having a recurring image/sensation of coming into the room where their mother is, and having her turn around smiling, because they have just told her that they got their diploma. Hallucinations like these ones are private spiritual experiences that give us the incentive to practice our music or apply for a degree program. We can be convinced they mean something and chase them, even if in fact we are an execrable musician.
Other unhappy hallucinations occur when we get obsessed with the feeling and the image that their are worms writhing on the floor or that there is someone in the empty apartment beside us. These type of hallucinations can trigger self protective behaviour. And of course if they are at the functional level - "I felt so dirty, I mopped the hell out of the floor and then I took a long shower!" they don't cause harm. It's when the signal cannot be stopped that they move from functional to harmful. The person who washes their hands until they are raw and sores become infected, has a hallucination that is way too strong. That's a hallucinatory experience gone wrong.
We often immerse ourselves in our imagination and court hallucinations. If you are deeply into some kind of media you can hear and see it in your mind's eye. Some people experience it so vividly they can immerse themselves in the memory of the fandom just by choosing to. Others can't summon the vivid sensory experiences without a trigger, such as reading the book or watching the film or listening to the music. When you court these kinds of experiences you get some of the same brain chemicals and pleasures as if these things were happening to you. People who feel all happy and warm after watching a rom-com are very sensibly seeking imaginary experiences that make them feel good. Some of us create our own fantasy or our own music. Inspiration is a hallucinatory experience in a mild way, but we take pride in it, and enjoy it instead of thinking we must be sick if we have a lilting tune with playing through our head while we are riding the subway home after work. We know it is memory or creativity and we don't fear it, or fight it. Yet that too can go wrong to a point where it drives us demented, such as when we have an ear worm playing on an endless loop.
Hallucinations may be a form of sleep disorder. Sleep is complicated. Among other things certain brain chemicals ebb during sleep and others are produced much more. One of these brain chemicals is an amnesiac. It prevents us from remembering our dreams and is produced as the end of deep sleep. If you sleep shallowly you don't produce enough of it and you remember your dreams. Anesthetic employs a similar drug which does the same thing biochemically. It wipes the memory of what happened during the surgery, and protects us from trauma. Unconsciousness without an amnesiac leaves us with shadowy memories of what we dreamed.
The natural work our brain does during sleep of consolidating memories, and converting short term memories into long term ones, produces messy and confusing images. A purple scarf floats though the air and strangles a sign post, the floor melts away under us and we are walking in the hall of a civic building. We see a stranger, miniature but adult, in a fetal curl on the floor. Soon they are walking with us, lecturing us about beavers. Then we turn into a beaver ourself... If there is spillage of this type of work that the brain does while we are awake, we usually blink and shake our head hard. "I started to drift off there..." If this kind of spillage occurs regularly while we are awake we may be in trouble, especially if it occurs so vividly that we can't tell what is real and what is not. But the experience is still, at the root, a functional one. We need to consolidate memories and forge stronger synaptic connections.
Something is going wrong when the moods and images and sounds thrown up by our brain during nightly maintenance intrude into our waking time. For most of us going off caffeine and getting a good night's sleep makes it a brief experience. Others of us live in a daze, images and voices coming at us in all directions, like the invisible voices and images being broadcast from a TV station. We can pick up the sounds and images that other people with a different tuned system never experience. We may be creatives lost in a happy daze of creation, or paranoid schizophrenics suffering a terrifying bombardment of misery and fear, but we go through life semi immersed, swimming to the surface to interact with others and then letting ourselves be taken by the flow. For every person who sees a burning bush and leads his people out of Egypt there are millions of others who see a burning bush and remember to check the smoke detector battery, or make an inept painting, or who blink and keep going, or who add bushes on the hilltop at sunset to the list of things to avoid looking at.
Hallucinations are just sensory experiences thrown up by our brains so vivid that they cross the threshold of idle thoughts. They can be so many different things. How functional they are depends on our individual ability to make use of our capacity to hallucinate and how distressing they are to us. Too much imagination, or too many hallucinations can be exhausting. Bad hallucinations can so closely mirror real bad experiences that they make our life hellish. Most hallucinations are benign, and so we don't worry about them and even don't consider them hallucinations. Sometimes we worry when we don't realise how universal they are. Often people think they must be going crazy when they first notice they have hallucinated. But most of us are just unaware of them. Brains and thoughts are messy. Hallucinations are just one of the messy things about having a brain.
posted by Jane the Brown at 6:25 AM on December 28, 2022
Here's an old thread that touches on this subject, including some comments from folks with personal experience that I especially appreciated.
posted by spiderbeforesunset at 8:21 PM on January 12, 2023
posted by spiderbeforesunset at 8:21 PM on January 12, 2023
This thread is closed to new comments.
You know how you think you can think you hear your name in a noisy room? this is because your brain is very used to hearing your name and so a lot of stimuli that sound kinda-sorta like your name will be interpreted as your name. But rarely will you think, "did that person say wakalixes?" since your brain gives a very low weight to the belief that that is what you heard.
People who experience psychosis, according to this theory, have brains that are ready to believe anything, to the point that the predictions get decoupled from sensory input. This could be due to phantom input that doesn't come from the outside world, or to being too unwilling to discard unlikely predictions, or some combination.
So one reason why taking hallucinogens might be therapeutic for instance is that, by breaking you out of bad priors, they help you consider possibilities that you were previously not open to.
posted by goingonit at 6:11 PM on December 26, 2022 [12 favorites]