Can the brain explain perception?

[Arra]

I apologize in advance if a thread exists about this already. I'm sure most people know of the problem already. Take colour perception, for example. Let's say that the human brain is studied in depth, and contains no mysteries. It's known exactly what happens when yellow light enters the eye, how the information gets to the brain, exactly which neurons are activated in the brain, and whatever else happens in the brain that results in us knowing that we're perceiving the colour yellow. There is no information missing. The problem is that there is information missing. There is an experience of yellowness that we witness consciously which cannot be discovered no matter how extensive the knowledge of the brain is. There are other examples, like the "What is it like to be a bat?" essay by Thomas Nagel. Someone who has complete knowledge of how echolocation in bats works will still have no idea what it feels like for the bat to echolocate. The same case can be brought up for any conscious experience. This seems to be a problem. Can you explain it? Seriously, this issue is pretty much the only thing that makes me doubt materialism.

[Xei]

You've succinctly expressed what I think it probably the greatest philosophical problem. It also helps to think of it in terms of philosophical zombies; what we essentially have is a deterministic causal system which takes sensory inputs and turns them into responsive outputs. The bizarre thing is that we can conceptualise such a system functioning perfectly adequately without any percepts attached, just as we conceptualise a mousetrap springing or a falling row of dominoes. Many philosophers have tried to explain away this problem, but I don't think I've ever seen it done adequately. I suspect it's impossible to do it adequately, rather like adequately explaining an axiom. In fact I suppose, being a very strict empiricist, as I believe I access all knowledge via perception, it is logically impossible for me to ever explain perception itself (in the sense you mean rather than the physical sense). Sometimes people try to explain it away as an 'illusion', but I find such explanations absurd, as you have invoked the existence of somebody consciously experiencing the subjective phenomenon of the illusion, which was the whole problem in the first place.

[Photolysis]

One thought that provides endless entertainment*, sometimes after imbibing a large quantity of alcohol** is how others perceive colour. Does what I call "blue" actually look the same to you, or does it look say "red". Personally, I think that if you have perfect colour vision, it probably does look the same because of the enormous complexity of the brain and the visual system which must be working the same as mine to function, but I have no way of knowing. An even more interesting question to me is what do colour blind people see? Constructing a picture that gives an impression of what they see in terms I can understand is easy (say by having red to green all appear as yellow, for how someone with red-green colour blindness perceives the world), but there's no way of knowing, at least unless I were to undergo an experiment to cause the same changes in myself. Even then, because I already have experienced those colours even if I can no longer detect them, my mind still holds the concept of them, so the experiment is less valuable. If there were a way of being able to directly share the perceptions that others feel, I suspect we would learn an awful lot about them. *Minor exaggeration included **As someone who doesn't drink, the probability of this is in fact zero Sometimes people try to explain it away as an 'illusion', but I find such explanations absurd, as you have invoked the existence of somebody consciously experiencing the subjective phenomenon of the illusion, which was the whole problem in the first place. But perception is an illusion, to an extent. For instance if I look at and touch my desk, I get the image and sensation of a completely solid object. In actuality that desk (and my hand and everything else) is 99.9...% empty space. If we look at colour or pitch for instance, that is merely the brain describing the frequency at which a photon or pressure waves oscillate and constructing an internal model to present that information. They may correspond to reality in cases but equally, optical illusions can also show how much post-processing is involved. But even if the idea of say 'yellowness' is an illusion, it still doesn't explain where that sensation comes from. I'm tempted to use a Discworld quote here, so I will "take the universe and grind it down to the finest powder and sieve it through the finest sieve and then show me one atom of justice, one molecule of mercy" Whilst we can ultimately describe where concepts like justice and mercy come from, if there were no life in the universe then these concepts would not exist. Similarly if there were no life then concepts like colour would also not exist. The difference is - at least for the moment - we don't have a good way of explaining, nor do we know where say colour stems from.

[Xei]

But perception is an illusion, to an extent. For instance if I look at and touch my desk, I get the image and sensation of a completely solid object. In actuality that desk (and my hand and everything else) is 99.9...% empty space. That's not what I mean. I'm more aware than anyone that humans have pretty much zero intuitive grasp on 'actual reality'. There's no such thing as solid objects, space is not rectilinear, and even causality is just an approximation. All humans have knowledge of is functionally useful models of reality. When I say people explain percepts away as 'illusions', I don't mean to say that percepts are genuine representations of the world. What I mean to refer to is people saying that the percepts don't actually exist; that in some sense we really are just philosophical zombies, 'tricked' into thinking we're not.

[Photolysis]

What I mean to refer to is people saying that the percepts don't actually exist; that in some sense we really are just philosophical zombies, 'tricked' into thinking we're not. Ah, I get you. That isn't a position I can agree with. (Though I also see the idea of a philosophical zombie as it is normally presented as being self-contradicting)

[Original Poster]

You've succinctly expressed what I think it probably the greatest philosophical problem. It also helps to think of it in terms of philosophical zombies; what we essentially have is a deterministic causal system which takes sensory inputs and turns them into responsive outputs. The bizarre thing is that we can conceptualise such a system functioning perfectly adequately without any percepts attached, just as we conceptualise a mousetrap springing or a falling row of dominoes. Many philosophers have tried to explain away this problem, but I don't think I've ever seen it done adequately. I suspect it's impossible to do it adequately, rather like adequately explaining an axiom. In fact I suppose, being a very strict empiricist, as I believe I access all knowledge via perception, it is logically impossible for me to ever explain perception itself (in the sense you mean rather than the physical sense). Sometimes people try to explain it away as an 'illusion', but I find such explanations absurd, as you have invoked the existence of somebody consciously experiencing the subjective phenomenon of the illusion, which was the whole problem in the first place. This is precisely why I had no reason not to buy into the philosophy that if a tree falls in the forest and there's no one around to hear it then there is no sound. But not literally of course, in fact it sort of requires the postulation of God, but not one of intelligence or judgment so much as just a layer of pure perception underlying all manifestation. Other than the very clear minded and relieving feeling I obtain from recognizing my perception as what I am perceiving rather than something separate with properties of its own, I have no empirical evidence to support this idea. That is impossible by the definition of the idea for if God is pure perception then anything perceptible is not God but a Creation of God.

[Wayfaerer]

I think the core of what your talking about is sort of an essential duality of life. There is the ineffable truth of the universe of which our experience is a part of, and there is the symbolic reflection of it. There is this, and there is a realm of symbolic entities, numbers, words, and symbols that emerge upon reflection of it so that we can create patterns to survive, communicate, and maybe find out a little more about what all this really is. Of course symbolic reflection will never equate to the actual experience or thing being labeled, I'm not sure where you think the problem is. The color example is especially interesting though. Some neurological process breaks up a continuous light spectrum into very distinct experiences, it would be difficult to really explain the quality of these distinctions through anything but actually experiencing them.

[Arra]

The problem is sometimes explained by comparing consciousness to other 'emergent properties', like the water-H2O example. You could examine every molecule of water but never determine the quality of 'wetness' in any single molecule. Similarly, you could examine every brain cell and determine how it works, but never explain the feeling of subjectivity. But there are problems with this explanation. Firstly, I think that you can explain the quality of wetness from examining all of the water molecules. Analyzed together, all of the molecules should produce wetness, and should affect other objects to make them float, etc. Water has no mysterious quality that arises which can't be explained with a thorough investigation. But this can't be done with consciousness. A proper analogy to water might be to say that, as molecules of water cause things to float, groups of neurons working together cause behaviors which can't be explained by examining any individual neural connection. Consciousness can't be explained, though, by considering all of the neurons and other components working together. Consciousness isn't just a property that emerges at a higher level of the brain system which we can infer exists while considering it all together. It isn't necessary at all. It's just there for no particular reason. One might argue that the subjective experience of wetness in water can't be inferred even from analyzing all of the molecules together. But this is just the original perception problem restated, since that perception of wetness depends on consciousness, which is what we're trying to explain.

[Original Poster]

I think the core of what your talking about is a sort of unavoidable duality of life. There is the ineffable truth of the universe of which our experience is a part of, and there is the symbolic reflection of it. There is this, and there is a realm of symbolic entities, numbers, words, and symbols that emerge upon reflection of it so that we can create patterns to survive, communicate, and maybe find out a little more about what all this really is. Of course symbolic reflection will never equate to the actual experience or thing being labeled, I'm not sure where you think the problem is. The color example is especially interesting though. Some neurological process breaks up a continuous light spectrum into very distinct experiences, it would be difficult to really explain the quality of these distinctions through anything but actually experiencing them. Well sort of because our ability to think abstractly and individually causes the presumption that we are our brains and our thoughts and I was explaining that my only evidence anything I'm saying is true is the incredible feeling of clarity I received by recognizing life in a non-dualistic fashion. I am freed of the requirement to think constantly in order to feel like I'm still a person and can use my thoughts for more important tasks. I am free from the need to be a person and to see a world of essential significance. The non-dualistic worldview that I learned from Buddhism is that perception is manifestation. The object is inseparate from the watcher. But the watcher is no particular part of the object. The watcher is the entirety of the experience, it is not one individual part of the experience.

[Wayfaerer]

Consciousness can't be explained, though, by considering all of the neurons and other components working together. Consciousness isn't just a property that emerges at a higher level of the brain system which we can infer exists while considering it all together. Why do you say this? Why couldn't everything "consciousness" experiences be explained by considering both the external stimuli (like water) and neurology together? I see what your saying though, it's strange to think that the experience of something like wetness is only just a combination of electrical impulses in the brain or something, it seems like such a distinct truth from physical processes because we experience it so directly.

[Toch]

The problem is that there is information missing. There is an experience of yellowness that we witness consciously which cannot be discovered no matter how extensive the knowledge of the brain is. What is the nature of the "information" that is missing? Does it have any propositional content? I would argue that it is a confusion of concepts to say that the "experience of yellowness" is a "fact" that can be "known." Suppose you are the archetypical expert neuroscientist who has never seen color, and suppose that you see yellow for the first time but are not told what it is. What fact have you learned from this experience? The bizarre thing is that we can conceptualise such a system functioning perfectly adequately without any percepts attached, just as we conceptualise a mousetrap springing or a falling row of dominoes. If we truly understood how the system works, and if we truly understood what we meant by "perception" (awareness, qualia, subjectivity, what-have-you), then we would find it impossible to coherently conceptualize one without the other. It is only our limited knowledge that makes it seem that a "philosophical zombie" is a conceivable thing, in much the same way as you might initially think that a "2-dimensional planar map that cannot be colored with fewer than 5 colors" is a conceivable thing (which, we now know, it isn't). Now, we do not yet understand consciousness to the point where the contradiction becomes obvious, but there is no reason to suppose that we won't in the future.

[stormcrow]

Superb thread. The problem described in the OP is analogous to the Mary's room thought experiment. Mary lives in a black and white room and watches the outside world from a black and white tv. She spends her time studying the science of color, measuring wavelengths, the nervous system, etc. Theoretically she knows all the physical, psychological and physiological aspects of colors. So the question is, if she is released from the room and experiences, say the color red, for the first time, would she learn anything new? This thought experiment draws attention to the idea that materialism does not adequately describe the raw subjective experiences (qualia) we have. This problem has some very heavy epistemological (I guess that is obvious) aspects to it, namely the problem arises as to what meets the criteria for acquiring the knowledge of the color red? Does measuring the wavelengths or examining the cone and rod cells in the retina give us knowledge of the color red? Or does the immediate experience or sensation of the color red meet the criteria for knowledge? This distinction was made by the phenomenologist’s like Husserl and Merleau-Ponty, arguing that consciousness must be examined from within experience not external to it. Personally I believe that it is fallacious to state that it has to be one or the other, not both. We can have knowledge of the color red that is derived from sensation that is not necessarily entailed in the wavelength measurements. Likewise we can also have knowledge of the color red from neuroscience and biology that is not entailed in the mere subjective sensation of red. With the scientific method we can examine the structure of the experience of red. Both methods are indispensible to our knowledge of “red”.

[Patrick]

I think I remember being given this problem in a Philosophy class a few years ago. I think I came to the conclusion that objective knowledge of everything is possible, but subjective experience can never be fully known in the same way. You can never know what it is like to be a crow, for example, because you would not be 'you' anymore. Basically I'm just happy to accept that you can't ever know every possible experience. As for the nature of perception, I personally believe that consciousness and perception are just phenomena of the physical brain. Not immaterial in any way, just a subjective result of the material brain. That seems like the simplest explanation to me anyway.

[Arra]

Yay, stormy's back. Why do you say this? Why couldn't everything "consciousness" experiences be explained by considering both the external stimuli (like water) and neurology together? Because the external stimuli and neurology together still don't imply that there should be a sensation of yellowness. What is the nature of the "information" that is missing? Does it have any propositional content? I would argue that it is a confusion of concepts to say that the "experience of yellowness" is a "fact" that can be "known." Suppose you are the archetypical expert neuroscientist who has never seen color, and suppose that you see yellow for the first time but are not told what it is. What fact have you learned from this experience? You've learned what yellowness looks like for the first time, knowledge that was missing before experiencing it, even though every bit of the brain was understood. If we truly understood how the system works, and if we truly understood what we meant by "perception" (awareness, qualia, subjectivity, what-have-you), then we would find it impossible to coherently conceptualize one without the other. It is only our limited knowledge that makes it seem that a "philosophical zombie" is a conceivable thing ... I disagree. Do you think that a human brain could ever be simulated on a computer? I do computer programming. The programs I've made so far have been relatively small, and I cannot imagine them being conscious. Any program which simulated a human mind would not be conscious either, or I don't see why it should be. It would be the same cold, mindless program, running on for-loops, if-statements, etc. "If this is true, store some memory", "While that is true, produce some output". It isn't going to get much more complicated at a fundamental level. The only difference between that and a program simulating a mind would be that the latter program would be really fucking huge. No matter how many red bricks you stack, the result is never going to be a green building.

[tommo]

That's not what I mean. I'm more aware than anyone that humans have pretty much zero intuitive grasp on 'actual reality'. Well that explains why you think you're more aware than anyone of this fact. I disagree. Do you think that a human brain could ever be simulated on a computer? I do computer programming. The programs I've made so far have been relatively small, and I cannot imagine them being conscious. Any program which simulated a human mind would not be conscious either, or I don't see why it should be. It would be the same cold, mindless program, running on for-loops, if-statements, etc. "If this is true, store some memory", "While that is true, produce some output". It isn't going to get much more complicated at a fundamental level. The only difference between that and a program simulating a mind would be that the latter program would be really fucking huge. No matter how many red bricks you stack, the result is never going to be a green building. I disagree. Why would it not be "conscious", if it's an exact replica? Someone being born, eventually develops consciousness. Their brain is just a mish-mash of their mother's and father's brain. While whatever part of the prefrontal cortex produces consciousness, is almost an exact replica.

[Arra]

I disagree. Why would it not be "conscious", if it's an exact replica? Someone being born, eventually develops consciousness. Their brain is just a mish-mash of their mother's and father's brain. While whatever part of the prefrontal cortex produces consciousness, is almost an exact replica. Maybe it would be conscious. What I'm saying is that I see no reason that it should be, just as I see no reason our brains should be conscious. Consciousness is just some strange phenomena which exists, but as far as I can tell it shouldn't. I used the computer example to further explain why it shouldn't (in addition to the explanations above). Also it wouldn't be an 'exact' replica, since computers don't use neurons among other reasons. But the difference would be irrelevant, I think. To be honest I think that I'm wrong, somehow, that I'm making some logical error, since the brain logically giving rise to consciousness is what would make the most sense. It's like, if I were to do some calculations and conclude that 2+2=5, I'd think that I'm probably making some mistake, even though I might not know what it is yet.

[tommo]

It is advantageous to be aware of what you're doing, to a certain extent. Why it would arise in the first place.... I don't know, random mutation. There doesn't have to be a reason for it. As for why it would emerge in the brain, from neurons, I see no reason why it couldn't. It's not like every neuron is the same. And consciousness isn't a special attribute. It's just as mechanical as moving away from something that is burning you.

[Arra]

But it is a special attribute. Someone with complete knowledge of how brains and bodies work could deduce that people will move away from things that burn them. The subjective feeling of pain could not be deduced. If it's something that just arises as a logical consequence of the brain chemistry, shouldn't it be deducible? You'd say yes if we were dealing with anything else besides consciousness, so why should it be an exception?

[tommo]

Whether it's deducible is a moot question. You would need a conscious organism to figure out how it works anyway. So they would already know. But, I don't get what the point is.... You can only assume the someone's pain feels the same as your pain. There's no reason to think it's much different, since most brains are more or less the same. And an explanation does not = an experience. I don't see why you think you should be able to know what the experience feels like just by knowing how something works. It doesn't work for any experience, including being conscious. Any explanation of anything is just an explanation, not the actual thing.

[♥Mark]

My brain can't.

[Arra]

Whether or not a conscious organism is needed is irrelevant. Besides, a computer designed for the purpose of analyzing systems (or something) could analyze it too and there would be the same problem. Yes, I assume that other minds experience consciousness like mine does. That's also irrelevant though. Being conscious isn't just an experience, it encompasses all experience. The word 'consciousness' anywhere in this thread could be replaced with 'subjectivity' or 'experience'. Yeah, you can't know what the experience feels like just by knowing how the brain works. But why not? That's the point, the problem. If you know everything about any system, you should be able to determine every effect it's going to produce. With anything else, any other system in nature, if you know everything about it, you can determine everything that will happen. But with consciousness, you can't. Everything about it is known, but there's an effect that can't be determined. Can you see the logical problem with that?

[Xei]

If we truly understood how the system works, and if we truly understood what we meant by "perception" (awareness, qualia, subjectivity, what-have-you), then we would find it impossible to coherently conceptualize one without the other. It is only our limited knowledge that makes it seem that a "philosophical zombie" is a conceivable thing, in much the same way as you might initially think that a "2-dimensional planar map that cannot be colored with fewer than 5 colors" is a conceivable thing (which, we now know, it isn't). Now, we do not yet understand consciousness to the point where the contradiction becomes obvious, but there is no reason to suppose that we won't in the future. Very eloquently put, though I am not sure it's correct. After all, there are many things which we can recognise as inconceivable; for instance, we know you will never be able to fill up a square by drawing circles of various sizes. We know this because at each stage, whatever shape we have drawn, it'll have edges of a rounded character, not straight. Is it not legitimate, in the same way, to say that given any causal system, we will be able to envisage it functioning without percepts attached, because it'll have the character of falling dominoes? I just read Dianeva's response after writing this and they're extremely similar by the way; we even used analogous analogies. You've learned what yellowness looks like for the first time, knowledge that was missing before experiencing it, even though every bit of the brain was understood. This thought experiment draws attention to the idea that materialism does not adequately describe the raw subjective experiences (qualia) we have. This problem has some very heavy epistemological (I guess that is obvious) aspects to it, namely the problem arises as to what meets the criteria for acquiring the knowledge of the color red? Does measuring the wavelengths or examining the cone and rod cells in the retina give us knowledge of the color red? Or does the immediate experience or sensation of the color red meet the criteria for knowledge? This distinction was made by the phenomenologist’s like Husserl and Merleau-Ponty, arguing that consciousness must be examined from within experience not external to it. Personally I believe that it is fallacious to state that it has to be one or the other, not both. We can have knowledge of the color red that is derived from sensation that is not necessarily entailed in the wavelength measurements. Likewise we can also have knowledge of the color red from neuroscience and biology that is not entailed in the mere subjective sensation of red. With the scientific method we can examine the structure of the experience of red. Both methods are indispensible to our knowledge of “red”. Here's the rub though: I think it's fair to characterise the new knowledge as 'being able to recognise the quale attached to red the next time you see it'. In other words, it's a kind of memory (what knowledge isn't?). So, it's physically embodied somehow in the physical synapses of your brain (to deny this would be to be very much a dualist; if I were to ask you if you have new knowledge, you'd say 'yes', yet this action is clearly a physical one that can be traced back to your neurons). Now ask the question: how did it come to be there? Surely it's just the causal result of the experience, tracing it back, and not a distinct thing, as you say. As for the nature of perception, I personally believe that consciousness and perception are just phenomena of the physical brain. Not immaterial in any way, just a subjective result of the material brain. That seems like the simplest explanation to me anyway. Consider this: wetness is not objectively real, in the following sense: you can explain it in terms of the constituent molecules adhering and the like. It isn't a 'fundamental thing'. Where does the concept of wetness exist? Well, it's a subjective result of the material brain, to use your phrase; it can be said to exist in the sense that it's the objective pattern of motions of some molecules in your brain, representing the concept. This seems to be a satisfying and complete answer. But I think there's a problem: describing the subjective experience in terms of an objective pattern of motions is basically the same issue as describing wetness as an objective pattern of motions. So what have we really achieved? And crucially: if we justify the objective existence of emergent phenomena in terms of an objective mind (patterns in matter), what do we use to justify the objective existence of the mind, which is itself an emergent phenomenon? If we pull the same trick don't we have a cyclical fallacy? A tangential (?) point: why do we consider molecules to be objective but wetness to be subjective; that is to say, why do we give special treatment to molecules? Well that explains why you think you're more aware than anyone of this fact. Que?

[MindGames]

This is one of the things I've wrestled with myself, too. A "conscious" organism is just a physical system, take a simple organism for example. We could (relatively) easily trace all the "dominoes" from the sensory input to the output, and there would be nothing surprising. We could effectively understand each and every action and thought that occurs to the organism and understand that it's just a function with as sure an outcome as a meteor flying through space. The same could also be said for humans, and also yourself. With the proper tools you could just as effectively analyze another human and see that its thought processes are just a figurative row of dominoes. Even knowing this applies to me, this doesn't make me any less seemingly conscious. Anyway I burnt my brain out trying to think about this, but I'd like to contribute that we don't know everything there is to know about the brain, and at some point we may be able to understand the phenomenon of subjective reality. After all, our brains are nothing special, and if we were to convert our flesh and neurotransmitters into functionally identical silicon and electricity, we would still have the same subjective experiences.

[Arra]

But I think there's a problem: describing the subjective experience in terms of an objective pattern of motions is basically the same issue as describing wetness as an objective pattern of motions. So what have we really achieved? And crucially: if we justify the objective existence of emergent phenomena in terms of an objective mind (patterns in matter), what do we use to justify the objective existence of the mind, which is itself an emergent phenomenon? If we pull the same trick don't we have a cyclical fallacy? I strongly agree with this.

[Wayfaerer]

This is such an awesome topic. It's made me think a lot, but I still come to the same conclusion. There is existence, what Nature is, including our experience. It is what it is, it is how it is, independent of how we model it. Then there is our attempt to break it up into entities and patterns and obtain 'knowledge' of it. Neither of these seem complete when considered alone, but seem to overlap each other in certain ways. Our quest for knowledge of Nature is impossible without... well, Nature, without our pure subjective experience. So far our patterns have only gotten closer and closer to a supposed 'true' pattern of Nature, could there not be a final attainable pattern and be forever asymptotic? On the other hand, life could not survive without pattern making, finding better ways to emulate 'true' Nature, it seems an intrinsic part of subjective existence. The vision of obtaining complete knowledge and ridding Nature of mystery is doubtful at best, but it would still only be a superficial communicative tool for it's independent essence.