Does the Subconscious Even Exist?

Added: 2026-05-17

[00:00:00]I'm increasingly suspicious of the concept of the subconscious. I'm glad to hear you say that that's like a a normal thing that people are discussing because like I don't know. I think typically we think if there's something which what I call my like self, my my sort of reflective linguistic communicative self can't like access, we call it sort of subconscious.

[00:00:27]But then I don't know. I think it depends on the degree to which you believe that consciousness must be centralized and smooth. You know, some people interpret this split-brain related stuff, alien hand syndrome, all of that good stuff as essentially showing that there are kind of two centers of consciousness that are in communication with each other in such a way that I guess you kind of just experience both at one time. And similarly to how like my eyesight really sort of appears to me like it's one thing. Like I'm not sort of aware that I've got two eyes right now.

[00:01:02]It's only by sort of taking one away that I can kind of get a grip on it. It just sort of mixes together, but it's uncontroversial that I've got two eyes.

[00:01:08]There are two things seeing right now, but they just sort of mix together. Some people think that the brains are doing the same thing. What is your view on the like locus of consciousness? Is there one?

[00:01:18]Is there two? Is there many more? Is it sort of a silly question to ask? I don't think it's a silly question to ask. It's a very very hard question to answer.

[00:01:25]Yeah. And there's a lot of debate about the unity of consciousness which I think get gets at the at the heart of this.

[00:01:32]Mhm. And the split-brain cases is one of the key uh pressure points.

[00:01:37]>> Yeah. Um so some people tend to think of the unity of consciousness as being something axiomatic that there can be only one like Highlander. Right. Um because it's very hard to imagine two separate, you know, consciousness being disunified. What what what might that even mean? It's not so much to say there's two A, two conscious agents in in one body. I mean, that that could happen in a split brain. That seems possible. I mean, the evidence is really mixed, by the way, with split brain patients. It gets very interesting when you look at it in in detail. It's like actually there seems to be problems with integrating things across the midline rather than detecting things at all. And there's all these subtleties about cross-cuing, like one half of the brain can see the the other half of the body does and might make inferences Yeah.

[00:02:28]based on on that.

[00:02:29]>> to talk about that. I want to allow you to finish what you were saying, but I would love to talk about that. And but but yeah, to the to the unity point, I I think that if we so I always tend to try and not be I mean, I'm frustratingly noncommittal about these things. Like consciousness seems unified to most of us most of the time. I would not want to build a theory that required that to always be so, because I think it might again be be right back to our discussion of human exceptionalism. Now, there might be cases where conscious experiences becomes interestingly distributed, non-unified in certain ways. Octopuses give me a good provocation here, where maybe their consciousness is decentralized um in a way that that just isn't the case for for animals like us who are highly cephalized.

[00:03:20]So Cephalized? Well, we all our neurons are in the head, and Is that our neural architecture is sort of de- if consciousness evolved, if we think that's a useful perspective for us, it's evolved in such a way that we experience consciousness from a particular perspective, which is somewhere in our heads. So, what's that word? Ce- Cephalized. I think it's a word. I think it means that most of our nervous system is inside is in one place in a in our head.

[00:03:47]>> where does ceph- cephal come from? Is that with like a C? Yeah, c e P H. I mean, some people say cephal rather than sephal, so Yeah, no, I just never heard that word. That's That's a good one.

[00:03:57]>> Cephalopod. Yeah, octopus is cephalopod, which literally means brain foot.

[00:04:01]Um Oh. And they have more neurons in their limbs than in their central [snorts] >> foot.

[00:04:09]>> Brain. Brain Yeah, I mean, it basically is a good description.

[00:04:11]>> cuz I was like, if we're whatever the word is, cephalo cephalo or something.

[00:04:15]Well, we have a lot of cephalization, so our nervous systems are concentrated in the brain.

[00:04:21]>> I was confused cuz I thought cephalopods, but cephalopods don't have it concentrated.

[00:04:25]>> also the pod. Yeah, etymology. I'm having I'm having Adam Aleksic, the the etymology nerd on soon. I'll ask him about it, but it's hardly, you know, either of our fields, but yeah, I I mean, the first time we spoke on on this show years and years ago, uh we talked about the extent to which we experience ourselves as up in the brain as well. And I'm always sort of I sort of wonder, is that because that's where the brain is? Is it because it's where the senses are? You know, we talked about strapping a camera onto like your belt and then like putting on a VR headset and living experiencing the world from from your belt buckle, and and whether you would the sense of where you are would move down to to to your stomach. Um and I I I kind of suspect that that maybe it would. I'm not sure, but it's weird to think about, like where I am.

[00:05:18]I feel unified, but at the same time, I'm if as long as I pay attention, I can separate out the feeling of the chair from the visual experience that I'm having. Um I can sort of I don't know, I can I can pay attention to the fact that maybe, you know, maybe I feel a bit hungry, and maybe I feel a little bit like, you know, I'm a bit uncomfortable, I'm going to shift position. And I I can kind of separate out those experiences. So, I've never quite known exactly what it means to say that consciousness is unified, cuz is true unity of conscious experience would seem to imply like no delineation whatsoever. There's just experience. But I'm I'm I'm already been able to separate out various aspects of my consciousness.

[00:05:57]>> Yeah, I don't think it I don't think unity implies lack of differentiation of what's happening within consciousness. I think most uses of the term unity in in this context suggest that all of these things are happening within a unified conscious field. Yeah. You can pay attention to different parts of it and they can have different characteristics.

[00:06:20]But there's no sort of um there's [snorts] no way in which the consciousness of your of of redness in the environment is is happening completely separately from consciousness of your other parts of your your visual field. It's all bound into into one. But yes, it has structure, too. I think that's that's fine. So, talk to me about this uh mixed evidence about split-brain patients and consciousness because like the the pop science and pop philosophy version of this is like, "Whoa, how cool it is that if you take a split-brain patient who's had the connection severed between their two hemispheres, their brain seem to act independently.

[00:07:02]You can show them a word to only one side and they'll tell you they didn't see it, but they'll be able to draw it um and some other really weird stuff like you can I think like if you show somebody the words like I'm trying to think of an example here, but like um uh I mean it's not a great example, but like the word market and super, you know, and and they're on one side, they'll sort of separate out the concepts. They'll they'll draw a market and then they'll draw some representation of super. Whereas healthy brains would put them together into supermarket. Stuff like that's going on.

[00:07:36]Stuff like that. I mean, a classic example would would be, you know, you you um you show the it's by the way it's not each eye so a Yeah. You have to visual hemi fields rather than eyes but anyway >> Yes, the left visual field goes to the right side.

[00:07:52]>> Exactly. Exactly. But you can still talk if you set it up right you can still talk in terms of left brain right brain.

[00:07:58]And so one thing you might do is recognizing that in most cases language is lateralized to the the left brain the left hemisphere you can show let's say an image to the left hemisphere um and then something else to the to the right hemisphere and then see what happens. And I think a classic example of right back to Mike Gazzaniga and so on is that um you show something relatively prosaic to the to the left verbal hemisphere and then you show something kind of funny to the right hemisphere and the person starts laughing and then you ask them why they're laughing and what they'll do is they'll kind of confabulate a reason why what was shown to the left hemisphere might be funny. Yeah.

[00:08:45]>> But it's got nothing to do with that because there was something funny shown to the the other part of the brain. So that they have these amazing examples of dissociations. Of course the most amazing thing about split brain patients is that under almost any circumstances it's impossible to tell that anything's happened at all. I find this really quite quite astounding.

[00:09:05]>> Yeah. You need these very specific experimental setups.

[00:09:08]But it does get a bit um complex. Now firstly a lot of these things tend to resolve over time. Very few split brain operations completely segregate right hemispheres. These days they're not done that much because medication thankfully for epilepsy has has improved. Uh a former post doc of mine now a professor at in Amsterdam did a series of experiments on vision Mhm.

[00:09:32]>> um showing that in a split brain patient actually that they were each hemisphere was able to detect visual stimuli anywhere in the visual field. But what they couldn't do was integrate across it. So this is a bit like your supermarket argument. It was the integration across the midline that was that was not um possible. Yeah.

[00:09:55]So I I still find it fascinating. One possibility Tim Bayne, one of my colleagues, um talked about sometimes is that it may not be a stable thing. May maybe under some circumstances there's one agent and under other circumstances there are two.

[00:10:11]Again, putting pressure on the assumption we might make which is that the number of conscious agents hosted by a yeah, by a skull has to be the same.

[00:10:21]Well, octopus is a great for that, too, because like the the limbs will kind of like do their own thing. It almost seems like sometimes an octopus's arm will go over here and then it will be like, "Oh, you know what's that?" As if the the arm is informing the the brain. But if there's a predator that comes by, suddenly the legs will just like shoot into space in into place and and they sort of swim away real fast as if when needed they can sort of act as one mind, but when not, they can sort of separate out a little bit. Maybe something similar goes on in the brain. You you said that some of these cases resolve over time.

[00:10:57]Well, this is now I'm I'm kind of reaching very very into the the recesses of my memory at the moment, but I'm I think you see the the strongest examples like the one of of the person laughing when you show something funny.

[00:11:11]I think these are most prominent quite soon after after surgery. A lot of these things that they're most fascinating about cases of of brain surgery or brain injury tend to sort of normalize a little bit.

[00:11:26]So another famous one is neglect where people seem to be unaware of what's happening on one half of their visual field after brain damage. That too tends to kind of ameliorate a little bit over time.

[00:11:39]>> It doesn't mean it's not real. It just means that it is one of the reasons these things are quite hard to study.

[00:11:43]Yeah. Yeah, the brain is quite impressive.

[00:11:47]>> other Do you know about the craniopagus twins? I don't think so.

[00:11:50]>> This is the other is the kind of the opposite of split brain, which I think it is is almost more fascinating.

[00:11:56]>> Sure. Um so this is a case you know you can get conjoined twins.

[00:12:01]>> Yeah. Um so twins born they cannot be separated. Usually joined somewhere in the abdomen or the hips or they may share a parts of a digestive system or something like that or even or even a heart. Um >> [snorts] >> there's at least one case of conjoined twins who share a brain. Mhm.

[00:12:19]And they cannot be surgically separated and then then now they've been around for I don't know how old they are, but I think they're in the teens now.

[00:12:27]Um Wow. And what is going on there?

[00:12:31]Well, what is it like? Are they are they are they individuals? Do they They seem to be.

[00:12:36]Yeah. Yeah. So I I've I've never met them. I've only used to read about them second hand. Yeah. But they they seem to have somewhat different personalities.

[00:12:46]>> Uh-huh. Uh but they also seem to share things. So one will be able to taste what the other one eats for instance.

[00:12:54]>> Yeah, that's weird. Are they are they like aware of each other's thoughts? Is there even a meaningful distinction between their their thoughts?

[00:13:00]>> They seem to be as you might imagine extraordinarily synchronized Yeah.

[00:13:05]>> in their in their behaviors. So it's I don't know what their thoughts are, >> Wow. but they in in and I've just seen these video I mean I feel bad cuz I'm this is just me watching videos of these things, but but they seem to complete each other's sentences. Yeah.

[00:13:20]>> So that seems to indicate that maybe they do sort of share at least the you know the contours of a single thought.

[00:13:29]>> But then again, basically they're getting pretty much the same sensory input all the time and they have a the same sensory experiences going back Yeah.

[00:13:36]>> throughout their whole lives. That's it's incredible, isn't it? I mean, I like never know how to make heads or tails of of these people. And in fact, there's an interesting analogous question to be asked about AI, which I'll ask in a minute. But first, just because it came to mind when you were talking about um showing one thing to one eye and and not the other.

[00:13:54]Um you know, I I really like Iain McGilchrist. And one of Iain McGilchrist's most important concepts is the concept of focus.

[00:14:02]And he says that focus isn't really it doesn't seem to be like a brain activity as such.

[00:14:07]I don't quite know how he characterizes it, but he talks about how like if if I played two sequences of of like random numbers or words into each of your ears, so different sequence in each ear, and I just told you, "Just pay attention to the right ear."

[00:14:22]Then afterwards, you could recite, you know, the the series of numbers, but you wouldn't be able to tell me what what the left one was. Whereas if I asked you to focus on the left-hand side, you could do it vice versa.

[00:14:35]And that just it's it's extremely simple. Like, yeah, obviously, yeah, I'm focusing on one and not the other. But that just baffles me because I'm like, well, what's the difference? What is the thing that's changing when I just decided to I'm not moving, there's no new information really, there's no I'm just making this decision to to sort of I'm just I'm just pushing my attention over here and pushing my attention over here.

[00:14:58]>> That's the difference. But like >> Attention. that just seems so such a strange like what do you think attention is? Like do you think attention is just a another kind of brain activity? Do you think it's a a sort of pre-brain activity like a qualifier as to how the brain activity occurs? Like do you know what I mean? Like it seems weird for me to say that that attention or focus is just a brain activity because it seems to be the means through which I determine what brain activity happens. You know what I mean? Yeah. I think both I think that's it. It would be strange if it didn't. I don't think it would have the functional role that that it has. I think attention is one of those words it's only slightly less mysterious than than consciousness. I think it is less mysterious. I think it's less sort of metaphysically loaded.

[00:15:44]But it's one of those things that seems fairly natural. Like I pay attention to something, but but when you ask what that really means very difficult very very quickly.

[00:15:54]Um But there are lots of of ways to study it. I mean it's one of the classic paradigms. Indeed, as you said, you can pay attention to different streams of sensory information.

[00:16:04]And that will make a difference to what you can remember, to what you do, and and and so on. Many things.

[00:16:10]Uh It is, I think something that affects conscious experience. We're more likely to be conscious of things we pay attention to.

[00:16:23]I don't think it's a a complete gate.

[00:16:25]You know, some people might take an extreme view and say we're only conscious of that which we're paying attention to.

[00:16:30]I think this is probably overstating it.

[00:16:33]But I think conscious contents have become dominated by by attention. And in the brain you can think of many ways that might play out. You know, the more extreme views might take it as a sort of really strict gating mechanism that that only things you're paying attention to get through the gate and can influence other parts of the brain.

[00:16:53]I prefer to think of it using the the overall framing of this brain as a prediction machine idea.

[00:17:01]That attention is Firstly, it's not just one thing, it's many things. It's kind of many ways of adjusting the sort of the gain, the signal-to-noise ratio.

[00:17:09]How much does the brain update its inferences about what's going on based on some sensory data. Paying attention to something is equivalent to saying, "This sensory prediction error, this piece of sensory information, is is worth uh well, I was going to say worth paying attention to you, but that's a bit circular.

[00:17:30]Is going to have more of an impact on the perceptual inference on this sort of continuing unfolding process of prediction error and prediction error minimization."