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Old 16th October 2021, 02:44 AM   #1
carlosy
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Hallucination - how good is the processing power in our brains?

I guess I never had a hallucination. But I always wondered how it actually works with regards to the processing power and visual accuracy?
I'm not sure how graphically correct intense hallucinations can be, but sometimes in movies it is depicted as very accurate.
Like someone on drugs seeing monkeys running around the room etc.

Just from a pure processing point of view:
Imagine some 3D-creator had to make such a scene. Monkeys running/climbing around an existing room filled with furniture.
That's some intensive work that had to be done.

- Creating the monkey model
- Texturing the monkey model
- The shaders
- The lighting and illumination
- The animation
...

Our brain is able to create such a scene, not just a single image, but an animated scene out of thin air? On the fly? So realistic that the person having the hallucination actually thinks what they are seing is real? Just for instance, how does the brain know how to cast visually correct shadows of some non-existing but even animated thing moving around a real environment?

Am I overthinking this?
Are hallucinations actually not that good? More like dreams, very diffuse visually? And the person having hallucination is just not able to notice all the graphical inconsistencies?

Or is it visually so good that you can't notice the difference?
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Old 16th October 2021, 02:48 AM   #2
The Atheist
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Originally Posted by carlosy View Post
Are hallucinations actually not that good? More like dreams, very diffuse visually? And the person having hallucination is just not able to notice all the graphical inconsistencies?

Or is it visually so good that you can't notice the difference?
Speaking personally - and I've had a few hallucinations over many years - they're nothing like dreams, which tend to be story-based. I've never had that during a hallucination, which is more of a warp in reality as I've found them.
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Old 16th October 2021, 03:28 AM   #3
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You're overthinking it. The 'image' that normally reaches your conscious level is already processed and parsed into a scene description, so to say. The first level of processing is as early as your retina, where you already have a sharpening and edge detection filter.

And here's something to think about: saccades. Do you see the image shaking all the time? Because your eyes enhance resolution by quickly moving randomly around. But you never notice that you're seeing through the shakiest cameras ever. (Except in certain illusion patterns designed to exploit a bug in that.) The image that you actually see is re-processed into something steady that has the enhanced resolution. The image you see is BASED on the fact that the camera is moving all the time.

And if we look at how people notice or remember things even immediately, it's clear that even huge parts of the scene are never reaching your conscious processing level. And details get pushed through only when you focus on them. Or can get added later, even if they're actually false. Like you can remember clearly that the guy was wearing a blue shirt with thin white stripes, when it was actually a solid red shirt. The brain clearly has a mechanism to fit the details where it thinks it needs them, and ignore them where not.

And it can even re-create a whole scene based on a story, in false memories.

And I focus on the memory part because the dream is always what you remember that you've dreamed.

There's no reason to think that dreams work any different. The brain just has to generate the scene description and then use the existing mechanisms to push in the details you focus on. And then comes the layer where you remember the dream and think stuff like "wait, what was that guy wearing? what did he sound like?" And we know that the brain is good at retrofitting those details into memories.
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Old 16th October 2021, 05:04 AM   #4
carlosy
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But I think quality wise there is a difference.
Memories and dreams, that's imagination.

But hallucination happens in realtime inside a real environment.
No matter how much my brain has to alter all the information getting through my eyes, the shadow that my guitar standing in the rack is casting on to the wall, is visually correct. If I make a picture of the scene with my camera, my brain and my camera would get the same shadow, because it is actually there, physically/visually correct.

But if the guitar would be a hallucination, I would probably notice the missing or incorrect shadow, if I would be conscious enough to be sceptic during the hallucination. Or would my brain also hallucinate a visually correct shadow? I doubt that.
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Old 16th October 2021, 05:16 AM   #5
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Originally Posted by HansMustermann View Post
There's no reason to think that dreams work any different. The brain just has to generate the scene description and then use the existing mechanisms to push in the details you focus on. And then comes the layer where you remember the dream and think stuff like "wait, what was that guy wearing? what did he sound like?" And we know that the brain is good at retrofitting those details into memories.
I think there is a reason. Dreams are not visual images being processed - they are collections of post-processed memories. I often have recurring dreams that are practically identical, as if the same sequence is being played over again. I don't need to 'retrofit' the details because the dream sequence already has those 'retrofitted' details in it.

Originally Posted by carlosy
I'm not sure how graphically correct intense hallucinations can be, but sometimes in movies it is depicted as very accurate.
Like someone on drugs seeing monkeys running around the room etc.
Movies often aren't very accurate, but they get the point across. Somebody describes hallucinating a 'realistic' monkey. The script calls calls for a 'monkey' and one is provided. But it could be a different species etc. and you wouldn't know - or care. One thing that will be different though is that the movie shows every every detail of the monkey, whereas the hallucinator probably only 'saw' certain details that say 'monkey' to them. So when they watch the movie they might say 'yes, that's a monkey - but not like the one I hallucinated'.

To take a computer analogy - consider a 3d object with polygons, textures, shading etc. The various attributes are attached to the model by numbers or pointers, and the model itself has a name. To render that model the computer simply has to reference it by name, and the details are expressed when it is rendered. So it is with a hallucination - the brain sees something and matches it to what it thinks it is seeing. If the match is wrong then the 'rendered' object is just as detailed as it would be if 'real' - but is not a match to the real object (if any) being viewed.

And as with the computer the details themselves are not unique. So for example you don't 'see' the monkey's actual fur, but a generic memory fragment called 'fur', and from there other memories of fur, including the texture, smell etc., in the same way that a generic 'fur' texture may be mapped onto various 3D objects in a computer.

So imagine the computer is rendering a scene but the data is corrupted, causing it to reference objects that aren't supposed to be there. They will be 'realistic' but wrong.

Quote:
But if the guitar would be a hallucination, I would probably notice the missing or incorrect shadow, if I would be conscious enough to be sceptic during the hallucination. Or would my brain also hallucinate a visually correct shadow? I doubt that.
Yes, it would. Or if it didn't you wouldn't notice. Or perhaps you do notice, but just think "that's weird - a guitar with no shadow. Perhaps it's a vampire!" and start thinking vampire guitars are a thing, because you're looking at one!
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Old 16th October 2021, 05:20 AM   #6
HansMustermann
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Originally Posted by Roger Ramjets View Post
I think there is a reason. Dreams are not visual images being processed - they are collections of post-processed memories. I often have recurring dreams that are practically identical, as if the same sequence is being played over again. I don't need to 'retrofit' the details because the dream sequence already has those 'retrofitted' details in it.
Whether they're retrofitted when you remember it, or fitted into the dream itself as needed, it's still mechanisms that we know the brain has. It doesn't need to create a film, so to speak, is all I'm saying. It just needs to give you a processed scene, with only enough details added when you look at those details.
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Old 16th October 2021, 05:58 AM   #7
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14 days strapped to the bed, heavily sedated, with ICU Psychosis. It was dreams and "memories" that I could not distinguish from reality. Probably not very different from usual dreams, but the part of the brain that tells you "It's only a dream" is broken.

Compare also to pareidolia. Your brain assembles bits of info into the wrong totality. And like dreams, there is some basis in fact but don't interpret too litteraly. Like seeing my nephew that worked his way up from ambulance driver to Battalion Chief pushing an emergency patient through the ICU. Wrong 3-4 ways, but real to me. Or my sister the retired nurse gowned up to help out on the floor. Or the CIA doing drug experimenting on me, that is why I was tied to the bed. Pareidolia on a different level.
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Old 16th October 2021, 06:47 AM   #8
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Originally Posted by carlosy View Post
But I think quality wise there is a difference.
Memories and dreams, that's imagination.

But hallucination happens in realtime inside a real environment.
No matter how much my brain has to alter all the information getting through my eyes, the shadow that my guitar standing in the rack is casting on to the wall, is visually correct. If I make a picture of the scene with my camera, my brain and my camera would get the same shadow, because it is actually there, physically/visually correct.

But if the guitar would be a hallucination, I would probably notice the missing or incorrect shadow, if I would be conscious enough to be sceptic during the hallucination. Or would my brain also hallucinate a visually correct shadow? I doubt that.
Think of it the other way around: Your eyes perceive a scene, let's take the running monkeys. What you get is the full scene; shadows, movement, ambience, perspective. However, that is FAR more data than your conscious brain can handle in a short time, so before it is presented to the consciousness, a lot of processing is performed...

Pattern recognition: The brown shapes are classified as running monkeys.

Shadows: There may be some evaluation of shadows, although I doubt you would notice a few missing in a real scene.

Etc ...

In the end, what you "receive" is a fairly compressed stream of information: Grass, running monkeys, direction of running, rough number of monkeys, do they seem hostile ... and such.

Scientific experiments confirm this is the case.

All the hallucination has to supply is that end-product and place it in the right part of your brain, and you will "see" the monkeys.

But let's try to estimate the relative demands for the full scene anyway: I have an MMORPG game on my computer. It can produce a scene of running ... not monkeys, for they are not in the bestiary of this particular game, but other creatures. In full color, shadows, sounds, health labels, etc, and present it to my eyes in real-time. And while my computer is reasonably up to date, I venture the guess (and sincere hope) that it is considerably inferior to a human brain.

Hans
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Old 16th October 2021, 08:11 AM   #9
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Wot the other Hans said.
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Old 16th October 2021, 08:43 AM   #10
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Originally Posted by carlosy View Post
Or would my brain also hallucinate a visually correct shadow? I doubt that.
Why couldn't it? If you thought of it in the first place then why couldn't you hallucinate it? After all, at the end of the process all you have is the conscious idea of the shadow.

You seem to be thinking of this as if the brain is somehow projecting the scene on to the inside of your eyelids. As others have explained, your hallucinations happen at the far other end of the process. It's just a stream of concepts by the time you perceive. It's not even built up in temporal order. Your brain can retroactively insert the memory of that shadow at any time it occurs to your brain that it needs to be there.
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Old 16th October 2021, 08:52 AM   #11
carlosy
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Originally Posted by MRC_Hans View Post
But let's try to estimate the relative demands for the full scene anyway: I have an MMORPG game on my computer. It can produce a scene of running ... not monkeys, for they are not in the bestiary of this particular game, but other creatures. In full color, shadows, sounds, health labels, etc, and present it to my eyes in real-time. And while my computer is reasonably up to date, I venture the guess (and sincere hope) that it is considerably inferior to a human brain.
Hans
Yes, sure. But the computer is highly specialized (graphics card) and very specifically programmed to create dozens of FPS of some scenery.
Our brain would... well basically it would have to do something like imaginary realtime ray tracing of an imaginary moving object, into an existing 3D environment, at least good enough to fool us.
Well, I guess during the hallucination we are not consciuous enough to look for graphical bugs.

BTW, nowadays anyone having a mobile at hand could, if in doubt, take the phone, go in camera mode and point it to the objects in question (or someone else could do it for them). Would our brain also hallucinate the object onto the mobile screen? Or would it just deny the image on the phone?

I guess such tests have been done in some psychiatry.
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Old 16th October 2021, 08:55 AM   #12
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Originally Posted by RecoveringYuppy View Post
Why couldn't it? If you thought of it in the first place then why couldn't you hallucinate it? After all, at the end of the process all you have is the conscious idea of the shadow.

You seem to be thinking of this as if the brain is somehow projecting the scene on to the inside of your eyelids. As others have explained, your hallucinations happen at the far other end of the process. It's just a stream of concepts by the time you perceive. It's not even built up in temporal order. Your brain can retroactively insert the memory of that shadow at any time it occurs to your brain that it needs to be there.
No, not at all. The eyes are just lenses.
But the brain has to add imaginary objects visually correct into an 'existing live scene'.
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Old 16th October 2021, 09:06 AM   #13
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Originally Posted by carlosy View Post
No, not at all.
Yes, at all. Read your post 11.

Originally Posted by carlosy View Post
The eyes are just lenses.
OK. So you don't think it's the eyelids that the scene is being projected on to, you think it's the retina. That's still what post 11 is saying.

Originally Posted by carlosy View Post
Well basically it would have to do something like imaginary realtime ray tracing of an imaginary moving object,
No. No. No. You already have a set of conscious perceptions of what those things look like. It can start with those. Your conscious perceptions of those things are in no way pixel maps or anything like that.
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Old 16th October 2021, 09:21 AM   #14
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Originally Posted by carlosy View Post
No, not at all. The eyes are just lenses.
But the brain has to add imaginary objects visually correct into an 'existing live scene'.
Does it? I'm thinking hallucinations are mostly memory. You're not getting a visually correct image. You're getting a strong impression of experiencing something from memory, without the usual cues the brain provides that this is a remembered experience and not a current one.

You're not getting visually correct objects inserted into a live scene. You're getting a very strong burst of memory of having seen something. "Visually correct" never even enters into the picture. It just feels believable.
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Old 16th October 2021, 09:22 AM   #15
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Originally Posted by RecoveringYuppy View Post
Yes, at all. Read your post 11.
Please point to where
I seem to be thinking of this as if the brain is somehow projecting the scene on to the inside of my eyelids.
is in post 11.
Again, this is not what I am thinking! That's silly.


Originally Posted by RecoveringYuppy View Post
OK. So you don't think it's the eyelids that the scene is being projected on to, you think it's the retina. That's still what post 11 is saying.
Ah, no.

Originally Posted by RecoveringYuppy View Post
No. No. No. You already have a set of conscious perceptions of what those things look like. It can start with those. Your conscious perceptions of those things are in no way pixel maps or anything like that.
The whole point about the hallucination is how good and accurate it's visual conception into an 'existing live scene' is, that is constantly getting processed in my brain. That's the difference from dreams, memories or visions.

If I am hallucinating monkeys running and climbing around my room, while I am awake, looking around the real scene, perceiving all the real environment, that is quite some task for the brain to come up to. Adding those monkeys visually correct into the processed 'real-time scene' in my brain (not my eyes, for sure.).

Last edited by carlosy; 16th October 2021 at 09:23 AM.
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Old 16th October 2021, 09:26 AM   #16
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Originally Posted by theprestige View Post
Does it? I'm thinking hallucinations are mostly memory. You're not getting a visually correct image. You're getting a strong impression of experiencing something from memory, without the usual cues the brain provides that this is a remembered experience and not a current one.

You're not getting visually correct objects inserted into a live scene. You're getting a very strong burst of memory of having seen something. "Visually correct" never even enters into the picture. It just feels believable.
Hmm, I though hallucinations can happen in real time.
Like two people being in a room and one person is seeing a third person, which is actually not there > hallucinating. And the person hallucinating is fully awake and can even talk to the other real person.
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Old 16th October 2021, 09:33 AM   #17
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Originally Posted by carlosy View Post
Hmm, I though hallucinations can happen in real time.
Like two people being in a room and one person is seeing a third person, which is actually not there > hallucinating. And the person hallucinating is fully awake and can even talk to the other real person.
Exactly as happened to my Dad & I when he went into dementia. Then he turned to me and said "You don't see those other people do you?"

aside: So I called my sister the retired ICU & trauma nurse. She knew from experience that end was near. She called hospice. He made it 3 weeks.
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Old 16th October 2021, 09:42 AM   #18
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Originally Posted by casebro View Post
Exactly as happened to my Dad & I when he went into dementia.
But how visually accurate is the imaginative object?
I guess, people with intense hallucination can still walk around a scene, being fully aware and awake and fully perceiving and processing the real environment while adding stuff to their visual conception of the scene that isn't there.

But I guess they are not in a mental state to check for visual inconsistancies, like not fully accurate shadows etc.
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Old 16th October 2021, 10:04 AM   #19
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Originally Posted by carlosy View Post
Adding those monkeys visually correct into the processed 'real-time scene' in my brain (not my eyes, for sure.).
You need to read what other people are writing with a bit of an open mind.
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Old 16th October 2021, 10:13 AM   #20
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Originally Posted by carlosy View Post
Please point to where
I seem to be thinking of this as if the brain is somehow projecting the scene on to the inside of my eyelids.
is in post 11.
It's in several of your posts. You keep talking about this in terms of ray tracing and scenes as if the image on your retina needs to be calculated to determine where a shadow would fall for example.

Your brain would not need to calculate where the shadow needs to be to, say, convince you it is noon. It already knows what perception of a shadow you associate with noon. It would simply put that perception in without doing anything remotely like trying to calculate an actual image. It would only need to calculate the image if this process were starting with and modifying the retinal inputs to the visual cortex.
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Old 16th October 2021, 11:46 PM   #21
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Originally Posted by RecoveringYuppy View Post
It's in several of your posts. You keep talking about this in terms of ray tracing and scenes as if the image on your retina needs to be calculated to determine where a shadow would fall for example.
No. I really don't understand why you're coming up with the retina.
Again, I am telling you it is not what I am thinking, and I'm pretty sure it's not what I am saying.
The raytracing was about the imaginary thing (the hallucinated objects) that my brain adds to the existing scene. And to do that visually correct so that the objects don't appear to me out of place, it would need to calculate the correct shadows, which can be a pretty hefty task in a complex lit scene. Especially if the objects are alive and moving around.

To boil down my initial question:
What would we see, if we could get a live stream of someone's perceived imagery who is having a hallucination?

a) Is the hallucinated object completely drawn visually correct with all the shading, shadows, geometry as the rest of the already existing scene. So that the person won't notice any visual flaws and therefore is so convinced that the objects are real?

b) Or is the hallucinated object diffuse but the person is not in a mental state to notice that?

And if a) is true, that would be some very extreme task by our brains.
MRC_Hans answered that to some extent.
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Old 17th October 2021, 12:31 AM   #22
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I’m generally healthy and don’t take drugs. A few years ago on a commercial flight I saw a large drone flying beside the jet. I can still bring up the memory. I remember the colours, contours and speed. It was as real as anything I’ve ever seen. And impossible. Drones don’t fly that fast for one, and alarms would have been going crazy in the cockpit.

Whatever caused this, I’m very curious to know. I haven’t really investigated this before.
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Old 17th October 2021, 02:58 AM   #23
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Originally Posted by carlosy View Post
No. I really don't understand why you're coming up with the retina.
Again, I am telling you it is not what I am thinking, and I'm pretty sure it's not what I am saying.
The raytracing was about the imaginary thing (the hallucinated objects) that my brain adds to the existing scene. And to do that visually correct so that the objects don't appear to me out of place, it would need to calculate the correct shadows, which can be a pretty hefty task in a complex lit scene. Especially if the objects are alive and moving around.

To boil down my initial question:
What would we see, if we could get a live stream of someone's perceived imagery who is having a hallucination?

a) Is the hallucinated object completely drawn visually correct with all the shading, shadows, geometry as the rest of the already existing scene. So that the person won't notice any visual flaws and therefore is so convinced that the objects are real?

b) Or is the hallucinated object diffuse but the person is not in a mental state to notice that?

And if a) is true, that would be some very extreme task by our brains.
MRC_Hans answered that to some extent.

But as explained that is not how the brain and our visual system works. What we usually think we see we now know is in fact not the case. For example, we only have a small "high resolution" area in our retina, it covers a patch that is a circular 2 degrees (see visual angle). That does not mean that I feel that I see the rest of my visual space in a lower resolution.

I think you are getting hung up thinking that we process our vision the way a computer has to generate a realistic scene; our visual system does not work in that way. In a very real sense, our vision is already a "hallucination".

Perhaps if you move away from thinking about visual hallucinations you can let go of the computer analogy? Hallucinations can be auditory, be a smell or a touch, think about how they are generated - the brain doesn't create molecules of a particular scent when we think we have smelled lemon, it doesn't combine sine and square waves to create a noise.
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Old 17th October 2021, 06:06 AM   #24
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Originally Posted by lionking View Post
Iím generally healthy and donít take drugs. A few years ago on a commercial flight I saw a large drone flying beside the jet. I can still bring up the memory. I remember the colours, contours and speed. It was as real as anything Iíve ever seen. And impossible. Drones donít fly that fast for one, and alarms would have been going crazy in the cockpit.

Whatever caused this, Iím very curious to know. I havenít really investigated this before.
Boredom? Are you familiar with Gremlins on long air flights? See Wiliam Shatner in Twilight Zone.
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Old 17th October 2021, 06:09 AM   #25
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Probably related to schizophrenia. Which is when you don't like the current situation but can't do anything about it. It's hopeless. So you create a new "reality".
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Old 17th October 2021, 06:16 AM   #26
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A fully rendered scene is not how the brain works, nor does the emotion of believability require physical possibility.

I had a dream once where our car was in the family room in the corner, where it couldn't possibly fit. But my brain had no problems with it.

As for processing power, your brain is ridiculously powered with parallel processing. Keep in mind the circuits don't even run at 2/3 the speed of light, but rather 200mph. That's how much parallelism you have.

And, for the record, that is exactly what your mind specializes in: a virtual world that maps to the outside world, so you can exist inside it. Assuming you aren't a brain in a vat. Hallucinations, dreams, drug trips, these are all the famed "altered states of consciousness", but they all use the same core hardware to generate the subjective perceptual experience called consciousness.

Indeed the fact drugs alters this is evidence consciousness is based on the physical, biological brain, and is not part of a true dualist existence, where the consciousness exists in some other, usually spiritual, plane of reality.
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Old 17th October 2021, 07:28 AM   #27
RecoveringYuppy
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Originally Posted by carlosy View Post
No. I really don't understand why you're coming up with the retina.
Again, I am telling you it is not what I am thinking, and I'm pretty sure it's not what I am saying.
And then you turn around and say it again the very next sentence.
Originally Posted by carlosy View Post
The raytracing was about the imaginary thing (the hallucinated objects) that my brain adds to the existing scene.
This implies the signal from the retina.

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Old 17th October 2021, 07:32 AM   #28
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Originally Posted by carlosy View Post
And if a) is true, that would be some very extreme task by our brains.
MRC_Hans answered that to some extent.
"a)" is almost certainly not true. And are you sure you understood what MRC_Hans said? I just went back and don't see that what your are saying shows an understanding of what he said.
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Old 17th October 2021, 09:30 AM   #29
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Originally Posted by carlosy View Post
No. I really don't understand why you're coming up with the retina.
Again, I am telling you it is not what I am thinking, and I'm pretty sure it's not what I am saying.
The raytracing was about the imaginary thing (the hallucinated objects) that my brain adds to the existing scene. And to do that visually correct so that the objects don't appear to me out of place, it would need to calculate the correct shadows, which can be a pretty hefty task in a complex lit scene. Especially if the objects are alive and moving around.

To boil down my initial question:
What would we see, if we could get a live stream of someone's perceived imagery who is having a hallucination?

a) Is the hallucinated object completely drawn visually correct with all the shading, shadows, geometry as the rest of the already existing scene. So that the person won't notice any visual flaws and therefore is so convinced that the objects are real?

b) Or is the hallucinated object diffuse but the person is not in a mental state to notice that?

And if a) is true, that would be some very extreme task by our brains.
MRC_Hans answered that to some extent.
it is C), as I described:

Something (disease, drugs, exhaustion), presents your brain with the usual "digested" information of a perception. The difference is that the undigested (full rendering) image never existed.

Then I noted that far lesser computers than our brain can actually create a picture that appears valid to our eyes.

You are obsessed with your original idea. Get over it.

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Old 17th October 2021, 10:41 AM   #30
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Originally Posted by carlosy View Post
Hmm, I though hallucinations can happen in real time.
Like two people being in a room and one person is seeing a third person, which is actually not there > hallucinating. And the person hallucinating is fully awake and can even talk to the other real person.
Yes. Usually when you're seeing someone and talking to them, it's an actual person impinging on your senses and triggering sensations in your brain.

Other times, you're just remembering such an incident.

Rarely, your brain assembles such an incident from remembered bits and pieces, and feeds it back to you as a current experience. Real time, but not a real experience. Just a very strong sensation in your brain of a real experience.

It's a bottom-up thing: The feeling of having the experience results in mental impressions reconstructed from memories of such experiences. You're thinking top-down: Your visual cortex or whatever spontaneously renders a convincing scene, which your brain then experiences.
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Old 18th October 2021, 05:20 AM   #31
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Originally Posted by RecoveringYuppy View Post
"a)" is almost certainly not true. And are you sure you understood what MRC_Hans said? I just went back and don't see that what your are saying shows an understanding of what he said.
I think I understand what MRC_Hans said.
I don't think I understand why you think I would think that the image on my retina needs to be calculated to determine where a shadow would fall for example, that is certainly not what I think!

Sorry.

The thing about ray tracing was an analogy. I said virtual/imaginary ray tracing of an imaginary object. Because shadows falling on complex structures can be very tricky. If you paint a 2D picture of a 3D scene, it can be very tricky to imagine all the correct shadows - just by imagination, not recreating something you already do see. Let alone having to do that with objects being constantly in motion. And in real-time (hallucination).
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Old 18th October 2021, 05:22 AM   #32
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Originally Posted by Darat View Post
But as explained that is not how the brain and our visual system works. What we usually think we see we now know is in fact not the case. For example, we only have a small "high resolution" area in our retina, it covers a patch that is a circular 2 degrees (see visual angle). That does not mean that I feel that I see the rest of my visual space in a lower resolution.
Yes, but our brain doesn't have to create a shadow for an existing object. The information is already there and provided (even though more complex) through the eyes.
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Old 18th October 2021, 05:35 AM   #33
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Originally Posted by carlosy View Post
Yes, but our brain doesn't have to create a shadow for an existing object. The information is already there and provided (even though more complex) through the eyes.
But it does, that's what you don't seem to be understanding, an example is this classic optical illusion:

https://www.illusionsindex.org/ir/checkershadow

The photons are entering your eye, they are activating the rods and cones correctly i.e. any objective measure would have the two squares being the same, but that is not what we "see".

You need to drop the idea that the only way to represent the world is how a computer generates a 3D scene, that has nothing in common with how our visual system works.
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Old 18th October 2021, 05:36 AM   #34
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Originally Posted by carlosy View Post
I think I understand what MRC_Hans said.
You're not demonstrating it. And sure sounds to me like he said just you aren't understanding.
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Old 18th October 2021, 05:39 AM   #35
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Originally Posted by MRC_Hans View Post
it is C), as I described:

Something (disease, drugs, exhaustion), presents your brain with the usual "digested" information of a perception. The difference is that the undigested (full rendering) image never existed.
That's something I actually don't understand (context-wise). But might be a language barrier on my side.

Originally Posted by MRC_Hans View Post
Then I noted that far lesser computers than our brain can actually create a picture that appears valid to our eyes.
Yes, but I guess those computers are still fed with information of the 3D-scene. Like the position of light sources etc.

Originally Posted by MRC_Hans View Post
You are obsessed with your original idea. Get over it.
I'm not obsessed and I actually was just wondering about how and why hallucinations work. And how exact and visually correct it appears to the person having it.
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Old 18th October 2021, 05:41 AM   #36
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Originally Posted by carlosy View Post
...snip...

I'm not obsessed and I actually was just wondering about how and why hallucinations work. And how exact and visually correct it appears to the person having it.
The example I link to above allows us all to consistently "see" an hallucination.
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Old 18th October 2021, 05:59 AM   #37
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Originally Posted by Darat View Post
But it does, that's what you don't seem to be understanding, an example is this classic optical illusion:
https://www.illusionsindex.org/ir/checkershadow
I know that illusion. But it's not about what I am trying to say.
Because yes, A and B have the same value. But the depicted shadow of the cylinder is actually there (drawn) because those squares where the shadows edges are have actual different grey values. My brain doesn't have to make up the shadow of the cylinder. It is already depicted in the image.

I know what you're saying. I don't disagree. I just think we've got our wires crossed.

Anyway the topic has already been answered and established.


Edit:
Maybe to clarify, I never meant to talk about the correct shadow intensity on any given square inch of any given sureface, but I was always talking about the correctly drawn shadow shape. Especially with regards to complex lit scenes.

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Old 18th October 2021, 06:32 AM   #38
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The correctly drawn shadow isn't necessary for verisimilitude. You're not looking at a scene. You're experiencing a memory.
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Old 18th October 2021, 06:47 AM   #39
carlosy
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Originally Posted by theprestige View Post
The correctly drawn shadow isn't necessary for verisimilitude. You're not looking at a scene. You're experiencing a memory.
Well, to some extent it can be, I think.
Comparing it with playing games on PC. I often notice inconsistent or faulty shadows or other visual glitches, which can break the immersion.

If I would have a hallucination of seeing something/someone in my room, while another person is telling me 'such thing is not there, you are having a hallucination', I might me able check for clues of visual inconsistencies like incorrect shadows drawn on surfaces, by comparing shadows to of other objects in the room.

But surely that is something a person having a hallucination is not up to in that moment.

Last edited by carlosy; 18th October 2021 at 06:51 AM.
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Old 18th October 2021, 06:57 AM   #40
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Originally Posted by carlosy View Post
I know that illusion. But it's not about what I am trying to say.
Because yes, A and B have the same value. But the depicted shadow of the cylinder is actually there (drawn) because those squares where the shadows edges are have actual different grey values. My brain doesn't have to make up the shadow of the cylinder. It is already depicted in the image.

I know what you're saying. I don't disagree. I just think we've got our wires crossed.

Anyway the topic has already been answered and established.


Edit:
Maybe to clarify, I never meant to talk about the correct shadow intensity on any given square inch of any given sureface, but I was always talking about the correctly drawn shadow shape. Especially with regards to complex lit scenes.
The shadow is not there - that is why this is a hallucination, if the shadow was there the squares' luminosity wouldn't be the same. What you are experiencing as the "shadow" is an hallucination, it is created by your brain, it does not exist in the "real world". This is because it taps into some of the many ways our nervous system and brain takes shortcuts to provide us with a "real" 3D world.
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