 Hi. Good afternoon. Today we're looking at split brain patients and Thomas Nagel on the unity of consciousness. I'm going to do that in just a second. This is the first slide. So we're basically talking about functionalism. But there's some intuitive sense in which your mind is a unity. From the point of view of science and functionalism, the functionalist approach to the mind that science uses, the lesson of the last 100 years or so of brain research has been that the mind is made up of lots of little bits and pieces, separate processing modules. But that really is what functionalism articulates. All these boxes and arrows show you the various bits and pieces that assemble to make a mind. But there's some sense in which the mind is a unity. As you're experiencing things right now, you're getting everything from a single point of view. You have a single perspective on the world. And it's actually very difficult to explain exactly what that comes to from a functionalist point of view. That's what we look at today. On Thursday, we look at artificial intelligence and John Searle's classic article, Can Computers Think. Again, that's a very short article. Of course, that's six pages, but it's had literally thousands of pages devoted to it. And indeed, this Thursday, right after the next lecture in this class, there's one of these on the same page, things in the bannet, I don't know how you pronounce that, the bannetow. Let's call it the bannetow auditorium. Right after this class from 330-5 called Acing the Touring Test, Artificial Intelligence and What Makes Us Human. So the discussion there, that is a panel discussion with four distinguished guys. And it should be absolutely continuous with what we're doing in this class. So if you find at the end of this class on Thursday that your enthusiasm is only beginning, that it hasn't been at all satisfied, then you should check out this Acing the Touring Test, a panel discussion in bannetow, and you should be in shape to explain to them how things really are. So let's start out by just reviewing Descartes' three arguments for saying that the mind is different to the brain. Descartes' three objections to physicalism were your knowledge of your own existence is more certain than your knowledge of any physical thing. That was the thing about, what was that thing about? How did that argument go? Do you remember that argument? How does that go? Key words? Descartes does not count as a key word. What are the key words for this argument? Dualism, that's the conclusion, yeah, fair enough. Anything else? I am, I exist, yep, that's fair enough, yep. Anything else? Dreams, hallucinations, madness. Put up your head if you know why I said those words. Dreams, hallucinations, madness. Okay, three, okay. That's not too good. Four, okay, Austin remember. Descartes' idea there was that so far as your knowledge of the concrete world goes, so far as your knowledge of the physical world goes, you face this question, how do you know it's not all a dream? How do you know it's not all hallucinations you've got? Yes? Do you remember that? And his point was even if you suppose it's all dreams, even if you suppose it's all hallucinations, then still you know that you exist. And that's where the I am, I exist comes in, that your knowledge of your own existence is more certain than your knowledge of any material thing could be. Because your knowledge of the existence of any material thing can be challenged by that question, how do you know it's not all a dream? But your knowledge of your own existence can't be challenged. Put up your hand if you now remember that argument. Put up your hand if you don't quite see how the argument goes. Hello? This isn't one of these moments that make pedagogy so rewarding. Okay, well, you have the chance to raise questions about this argument. Okay, Descartes' second argument was, you can conceive of yourself without a body. Your conception of yourself, your conception of your own mind, and your conception of your own body are quite different, so your body and self must be different. And the last one is the argument we're going to focus on today. The hardest one to get, that matters divisible, but the self is indivisible, is hard to know just what he's talking about there. And Nagel gives a way of trying to articulate that idea. Which one, this one? Yeah, they're closely connected, I agree. My way of carving it up is to put the blockhead argument on the side of two. There's this argument, you can conceive of yourself without a body, so the body and the self must be separate. Your conception of what's going on with you, with a mind, is different to your conception of what's going on with a body. And the stuff we were looking at last time on the inverted spectrum, you can think of that as saying, well, I can know perfectly well what's going on with your body, but are your colour experiences the same as mine? Are they different to mine? Are they completely alien? I have no idea. That was the argument, you'd be functionally, maybe biologically, just exactly the same, whatever your colour experiences were. So my conception of your body is one thing, and my conception of what experiences you're having, that's something quite different. It seems to float free of my understanding of what's going on with your body, or what's going on with you functionally. And Bloch's point was, you can conceive of a body without any mind. That robot driven around by billions of people, that's really a kind of zombie. It doesn't have any sensations, it doesn't have any experiences, but it could be functionally just the same as you or me. So your conception of the body allows for the possibility of something that's functionally just like a body, but has no mind. Can you put your hand up if you remember that argument? Okay, there's a strong recency effect here. Okay, here's Descartes. The body is by its very nature always divisible, while a mind is utterly indivisible. Now I don't know, the picture is you've got the mind with all its thoughts and sensations and feelings, and that all hangs together somehow. That all coalesces around a single perspective from which the world is being had. And the idea is you can't explain that notion of the single perspective from which the world is being viewed in physicalist terms. So the idea might be you can't explain the unity of the mind in physical terms. I once read a science fiction story that began with an alien sitting in a sofa simultaneously reading two different books. And I've always liked that because it's very low key, right? It's very mundane, he's just reading two different books at once. And the thing is when you think about that for a second, it's absolutely mind bending, right? How could someone, I don't mean switching from one book to another, but truly simultaneously reading two books at once, how could you do that? I mean, it's not really that you couldn't get both books in your field of view at once. You could do that, and if you had eyes that could move independently, you could focus on two different books at once. But there's something about the idea of reading two different stories simultaneously that is mind-boggling. I mean, it's not that your eyes won't do it, it's that your mind won't do it. The only way you could do that is by splitting up your mind. You see what I mean? Okay, thank you. So let's look at Nagle's way of explaining the notion of trying to get at the notion of unity of consciousness. There are some basic points about the cerebral cortex. The cerebral cortex comes in two bits. There's a left bit and the right bit, and the left cortex has, for our point of view, these key characteristics. The left bit controls production of speech, and so the left bit takes in stuff from your right visual field, the right half of your visual field. It controls the production of speech, and it controls what motor output, your limb movements on the right, your right arm and your right leg. On the other hand, your right cerebral cortex takes in input from the left visual field. It does the output on the left hand, the left leg, the left side of the face, but it doesn't do speech. I don't know that they do say the left side is the creative side. I've more often heard it said that the right side is the creative side because it doesn't do speech. But identifying the creative side is really a mug's game. It's not that there isn't such a thing as creativity. It's that there are so many kinds. What's going on? The corpus callosum is a large band of nerve fibers that connects the two hemispheres. If, as I was standing here, a guillotine came down and sliced me in two, and this half conveniently fell away so that you could inspect the brain, then what you would see is something like that. I'm not going to do this right now, and I'm not suggesting you do this yourself, but something like that is what you would see. The brain sliced up and there are the corpus callosum, this broad band of transversely running fibers going right through the brain and connecting the two hemispheres. Now, one question is what's it for? And one suggestion as to what's... Well, Nagle remarks that some people suggested that it was basically structural. It was to stop the two bits of the brain collapsing in one another. It was like a girder or a beam. That is a crazy idea. Another hypothesis is that what this is so handy for is that maybe at an early stage in evolution there were perceptual functions that were duplicated on the two sides of the brain. So that is very common in monkeys and apes that you get this duplication. And you don't actually find it in humans. Everything is very specialized. And Gazanaga suggests that what happens is that in the human brain is that one evolution tries out specializing one half of the brain, what's going on in one of the pathways on one side of the brain for, let's say, language. And so the bit that was originally being used for perception is now being used for language. The bit on the other side that was doing the same perceptual stuff stays being used for perception. But the two sides of the brain can communicate by means of the corpus callosum. So it doesn't matter that this redundant bit of brain is being taken out because you can still get all the data from the perceptual processing on the other side of the brain. While language emerging in the left hemisphere are the cost of pre-existing perceptual systems, so some pre-existing perceptual systems had to go to make language possible, the critical features of the bilaterally present perceptual system were spared in the opposite half brain. So it kept going in the other bit of the brain. So by having the callosum serve as a great communication link between redundant systems, a pre-existing system could be jettisoned as new functions developed in one hemisphere while the other hemisphere could continue to perform the previous function for both half brains, right? Just like an organization with some spare people in it just illuminate their functions, get something else to do their functions, but make sure you keep communication. So that's the corpus callosum. Now in cases of epilepsy, when people are having epileptic fits, my picture is it's kind of like an electrical storm in the brain and one way, just as with a forest fire or something, you contain the forest fire by having a kind of dead area that the fire can't go beyond. So you get massive electrical activity causing the fit in one hemisphere and that electrical activity gets transmitted to the other hemisphere by the corpus callosum. So if that's happening, then one way of containing the storm is to cut the corpus callosum. Just cut that whole band of transversely running fibres. No, far from it. In fact, there are... I don't think it's really legal for me to show... I was just looking at this up this morning. I can't really show YouTube videos in this class. I mean, for copyright reasons, I'm not supposed to be able to download them. I mean, is that right? But there are wonderful... If you Google up Split Brain Video, then there are wonderful videos of Split Brain patients talking and explaining what's going on with them and these people are perfectly okay. If you talk to one of them, it might be you or me, it might be anyone in the class, you really couldn't tell. Their cognitive functioning is just fine. They can drive a truck, they can play tennis. They say, I don't feel any different after the cut of the corpus callosum than I did before. I feel exactly the same. So the picture is you've got on the left field your information coming to the right hemisphere and then that's controlling the movement on the left side. From the right visual field, you've got information coming to the left hemisphere and that's controlling movement on the right. And then information has been transmitted between the hemispheres very fast via the corpus callosum. So if you cut this, you don't get this rapid transfer of information between the two hemispheres. That's Nagel's diagram. This is to explain what's going on in Nagel's diagram. I think this is a little bit more perspicuous. So the blue here is the right half of the visual field going up to the left hemisphere that does the speech. The red here is the left half of the visual field going up to the right hemisphere. So if you're seeing an apple and a pencil, then you're getting the apple. If the apple is in the left side you're getting the apple in the right hemisphere. If the apple's on the right side you're getting the apple in the left hemisphere. If the pencil is on the left side you're getting the pencil in the right hemisphere. Yeah? If you just think of, if you shut one eye, there is still the left side of the visual field and the right side of the visual field. You see what I mean? Each of the visual fields is shared between the eyes. Okay, so the thing is, when you cut the corpus callosum so these two hemispheres can't dialogue anymore, it doesn't really matter very much because if you just think as you sit here right now, your eyes are scanning the whole time, your eyes are moving around, yeah? So what's in the left side of your visual field at one moment is on the right side of your visual field a moment later? Yeah, you can try this right now, right? You're in the left side of my visual field? Well, now you're in the right side of my visual field, you see what I mean? You can try this yourself, right? So long as you can do rapid head or eye movements, it doesn't really matter because if the apple was here one moment, it'll be here the next moment. So it'll be perfectly obvious to you that you've got an apple and a pencil there, yeah? Well, as Nagel says, no significant behavioural or mental effects in these patients could be observed. The patients could play tennis just fine if you're good at tennis before, you're going to be good at tennis afterwards, yeah? After the cut, after your brain is bisected because all you're losing is this very rapid transfer of information between hemispheres and you can get by without that because you can turn your head, you can move your eyes very rapidly. Each hemisphere can get, you can get the effect of each hemisphere having the information that the other one has, yep? No, it can't talk directly, that's the whole point, that's the way the two hemispheres talk to one another. You have cut the telephone system between the two hemispheres and they don't have a direct way of dialoguing. What you can make sure is that one gets the information that the other one has by turning your head, that's right, that's right. If you've got a stimulus on the left side, yeah, you've got to move to get a stimulus now on the right side. Oh, yes, yes, yes, yes, yes, you've not lost feeling, it's just the communication between centres of feeling. So if you're looking at someone playing tennis, say, or you're looking at someone driving a van and you say, well, functionally, if I look at a box and arrow diagram of this person, are they fully integrated? Then the only answer you can give is, well, of course, they're fully integrated. I mean, lack of functional integration would be something like your arm starts to move autonomously. You know, people have, say, an archic hand syndrome where your hand takes on a life of its own and it really may start, in some cases, start trying to attack the patient or it may just remove the patient's clothing while the patient is, when the patient's not aware, yeah. There you really have a functional dissociation. You have the hand moving in a way that's not integrated with the rest of what the patient wants or is trying to do. But there's nothing like that going on with split-brain patients. They are functionally perfectly ordinary. This difference is between split-brain patients and everybody else really only showed up when psychologists developed stochistoscopic presentations. That is presentations of stimuli on computer screens that were very, very brief and you had the patients trying to do these tasks in just a few hundred milliseconds. So the idea was that you were going to show the patients stimuli in such a way that it was too fast for them to scan or turn their heads. You couldn't get information from both sides of the visual field because the thing was being shown for such a short time. I mean, nowadays you get this effect by, I mean, when Nagle was writing this was brand new, nowadays you get, they get this effect by eye tracking and image stabilization. So you have a gadget keeping track of where the eyes are, where the eyeballs are pointing and you have a gadget moving the image about so that it's always on the left side or always on the right side. And once you got that, you got, yes, it's not how fast you can process it is the communication between the processing and the two sides of the screen. And it's not only vision, it applies to touch too, yeah. Okay, so suppose you have a computer display being shown up very briefly and you've got a tray of items in front of the patient. So there's various household objects on it. And on the left field it flashes up pencil. On the right field it flashes up toothbrush and you do that very fast. Then what's going to happen with if pencil is being flashed up on the left, then which hemisphere gets that? The right. And so which hand is going to hunt for the pencil? Left, right. And if it's toothbrush being flashed up on the right, which hemisphere gets that? The left, right. And so which hand hunts for the thing? The right, okay. That is a little bit tricky and I'm not saying I will not get lost in it sometimes, but it's basically very straightforward, yeah. So here you have someone who's pointing, I mean as usual in these experiments, the top of the head is cut off so that you can see what's going on. So you can see here the two hemispheres and the cut. So he's being shown an array of objects. He's got key being presented in the left. Ring being presented in the right. So which finger is hunting for the key? Right, because the key thing has gone up here. Yeah. And the ring word has gone up here. Has he at any point seen the word key ring? Yeah, he does not have a third hand that is searching for the key ring. Do you see what I mean? The two different things. He's just got key and he's got ring but he doesn't have key ring, yeah? So if you ask him what are you searching for, what's he going to say? That's right. He's going to say the ring. Is he going to say the key? Is he going to say the key? Right, and if you ask him, how come you've got a key in your hand? What's he going to do? So he calls the key a ring. Yeah, he might say that's a ring. He might stick to his guns, yeah, right. He might do that. It's hard to know exactly what he'll do because it's the left hemisphere that is doing the language and it doesn't know anything about the ring, yeah? So there are two kinds of disunity here. Tim Ben pointed this out that there's a disunity in how he behaves. The two hands are hunting for different things. And there's a disunity in what he's representing because he's got a visual representation of key and a visual representation of ring. But he hasn't got a visual representation of key ring. The vision, the representation of the world in vision seems to have come apart. It seems to have got broken up somehow, yeah? Here's a classic case. The patient, again with the top of his head off, is shown this scene, the snow scene in the left and the chicken food on the right. And he's given this a rare things and he's asked point to the thing that goes with the scene you're looking at, yeah? So on the left, he's got the snow scene. So he's got the snow scene represented in the right hemisphere. And then with his left hand, he's pointing to the shovel because there's our car buried in the snow there. He's going to dig out, yeah? You're going to dig out the shovel out the snow. Over on the right, we've got the chicken food, the chicken claw being represented here. And he's pointing to the chicken on the display. So suppose now you point out to him, you're pointing to the shovel. Why are you doing that? What's he going to say? How come I'm pointing to the shovel, right? He has no idea why he's pointing to the shovel, yeah? And is that fairly clear? Yeah, this is your, if I'm explaining this correctly, this should be abundantly clear. OK, there should be no sense of mystery here at this point. But if he's pointing to the shovel, then he's going to have to answer it by using the left hemisphere, which is doing the speech production. In fact, people in this kind of situation very rarely say just, I don't know why I did that. What they do is they make up some story. When asked why the chicken, he said, it goes with the chicken claw. When asked why the shovel, he responded to clean up the chicken coop. Yeah, I mean, people make up a story. Why did I do that, yeah? The language center is doing its best to rationalize what you're doing, yeah? That's right, that's right. I mean, with these very brief presentations, yeah? So you didn't get a chance to do the head movement and take it all in. There, the bit they got, the claw is controlling your movement, and is going to be controlling your speech too. That's right, that's right. The thing that goes to the left side, you're going to be able to say, well, understand, it's harder to say, but you're going to be able to say why you pointed to the thing that's on the left, because it's the left hemisphere that's in charge of the speech. Well, that's a hard question. He's going to say, he's certainly never going to say, I pointed to it because of the snow scene, yeah? So is that consistent with him understanding it? One, two, yeah? Yeah, you might say he's got two minds in his head. There are two different minds here, yeah? I mean, it's difficult, because the difference between this case and the ordinary case, and the case of you and me right now, is just that these two senses are able to talk to one another, yeah? So if that's the right description of this case, presumably it's the right description of you or my case, that we have two different minds, and they're just in very rapid communication. We divide the barriers of four. OK, study on five, four. Yeah, that's kind of mind-bending, no? I mean, I thought when you came into the class, you thought you just had one mind, right? But now it turns out you actually have two minds that are just very rapidly talking to one another. This is your whole of your regular life. And you're suggesting, well, actually, it's eight or four? 16? 365? That's right, yep. There's no internal communication, yeah? But if you just keep moving your head, you could make sure that the two get the same information, yeah? If you just behave regularly, the two sides will get pretty much the same information, which is why in ordinary life, you're not going to be able to tell that there's anything unusual here. Yes? That's exactly right, yeah. That's the thing about that quote, yeah? He's got no idea, the language production center has got no idea why it chose the shovel, and it is just having to make something up. This is his thoughts, yeah, well, yeah, he's perfect. I mean, he's being sincere in this. And I can actually show you some more examples in a second of this kind of thing, yeah? This is a classic experiment, this one, a classic report, this one. But there are many other such reports, yeah? Uh-huh, yes. I strongly agree. I mean, animals are presumably conscious of stuff. We're not being able to verbalize at all, yeah? So we usually think that what we can verbalize is stuff that we're conscious of, but you could be conscious of stuff without being able to verbalize it. I mean, that's your point, I just mean to be playing back to what you just said. Is that right? He wouldn't say that sincerely if he'd been, where's it gone? He wouldn't say that sincerely to clean up the chicken coop if he was conscious of it. Yeah, I personally did, like, do his senses, but I don't think he was conscious of it. Very good, yeah, yeah. No, I absolutely see that. That's really good. Because what you're appealing to there is that consciousness is a unity. You have a single mental life. If you've got consciousness of the snow scene in there, then when you're doing your verbal report, you've got to be able to say it was because of the snow scene. If you honestly hunt for your conscious life and think what's there, this is really, you guys are really way ahead of me. This is, the thing is, what we were doing right now is if you just read off from what I was saying about the functional structure of the brain, yeah, the box and other diagram of the brain, then it's perfectly obvious that what you were just saying is wrong because this could be over here in the right hemisphere, and the snow scene could be right over here in the right hemisphere, and just not connected to the language output center, the right hemisphere on its own might be able to support sensory experience. That's to say, if you took someone and you just cleaned out their left hemisphere, then they'd be severely damaged, but they wouldn't be unconscious. They'd be able to do a lot of stuff more than the average animal, and you'd say that person is conscious. So although this is supporting consciousness, if you just look at the functional structure here, you can see that it might not be able to access the snow scene, yeah, the speech production center, but your point is also extremely good because when you think about it intuitively, and when you just think about it commonsensically, if you've got in your consciousness the snow scene, then when you're doing the verbal report, you must be able to access the snow scene. If you're being honest and you're not blocking it or whatever, yeah, yeah. So that is really puzzling, yeah. That is really the main point here. That is really the key point that when you think about this in terms of the functional structure of the brain, it's absolutely obvious that it's gonna have to make this report to clean up the chicken coop and that's gonna be the best he can do. But when you think about what's going on in his conscious life, it seems absolutely baffling that that could, I mean, it seems obvious that that couldn't be the best he could do. He must be able to verbally report the snow scene. And that was your point? Yeah, at the very least, I would say so. Yeah, there's something escaping me here, yeah. Okay, and so if you said, well, he was conscious of it, but he just couldn't in any way report it, that's kind of baffling. That's kind of incomprehensible. Yeah, yeah, I don't know how that could be. I saw there's a lot of people, someone who hasn't asked the question, yeah, yeah. Yes, I think so. I think that's what I'm going to do next, yeah. Wait a minute. I think this was the pipe example, but I think the pipe got missed out, if you see what I mean. So this is an abstract description of the pipe example. If a concealed object is placed in the left hand and the patient is asked to guess what's in it, okay, so you've got something in your left hand, you're being asked to guess, okay, so you put the dust on the left hand, you're being asked to guess what you've got in your left hand. Well, where's this information going to? To the right hemisphere, which doesn't do the language, right? So the left hemisphere, which is trying to do the language, is saying, well, I don't know. So, the right hemisphere has some control over movement of the hand for writing, yeah? So the right hemisphere is, suppose you're right-handed, yeah? The right hemisphere is going to be able to move the left hand and it will clumsily start, it was the pipe example, right? So the left thing writes out P, okay, so actually, I'm sorry, this is a bit confusing. I've now got a pipe in my left hand, okay? I don't have one with me, but picture if you will. So let us suppose that this is a pipe, this is a pipe, right? Then what I do is with the left hand, you start writing P. Yeah, right, I, and then suddenly the left, the right hand grabs the chalk. That was the example? Oh, actually the right center grabs control of the hand, yeah, the left center grabs control of the hand. Yeah, it just means on the other side here. I mean on the same side, yeah. I see, yeah. Okay, I don't remember it that way, but, okay. Suddenly the left hemisphere sees as control and says I see who you're gonna write here and writes pencil because that's obviously the start of the word pencil. My memory was that the other hand grabbed it, but you've probably read it more recently than I have. The point is that the speech production hemisphere is grabbing control of the situation and suddenly guessing. So it's like the chicken coop thing. Okay. Okay, that should be perfectly clear. Who hasn't raised a question yet? Yep. No, no, that's the thing here. You can write with your left hand. Yeah. So it's just responsible for speech? That's right. Yeah. Yes, that wasn't done in that example. Yeah, that just wasn't done there. I don't know what you'd get with writing output, yeah. Yes. Yes, he would, yes, yes. It's just that the left hemisphere is saying this is language production. This is my kind of thing. Let me do that. You see what I mean? Yeah, yeah. Is that the same point that it doesn't know what it doesn't know? Yeah, yeah. Yeah, I... The whole pipe. I don't know of a case just like that, but that would be the prediction. Yeah, you would get to complete the whole thing laboriously if you didn't have the other hemisphere trying to take charge. Okay, you guys have all last questions. Okay, yeah. Yes, right. Yes. That is not unreasonable. I think Nagel was thinking you start out PI. You see some, it's as if you see someone else writing out PI and then you say, oh, I know what that is and you're filling pencil. Right, but if you were writing with pencil, that's in the hand. Yeah, that is also possible. Yeah, that is also possible. The key point is it's an external cue to what you're seeing. Yeah, or to what you're feeling. It's an external cue that you're using to what you're feeling. Yeah, in your hand. Yep. Speech is one thing and language is another. Speech is a special thing you do with language. Comprehension is not confined to one hemisphere. Yes, I mean, it's not that you have to do it within that very brief timeframe of the flash. Okay, so then they have to... They do it, well, think about it as a strong word. They're just trying to do it right away, but they have more time than the flash. Well, my memory of this is quite different to yours. Right, so I may be completely wrong here, but my memory was that the pencil was literally snatched from the left hand by the right hand. If you see what I mean. And the old pencil completed. Yeah, yeah, yeah, one, two. Yes, that's right, that's right. That's exactly right. Yeah, okay. That's completely correct, and I'm happy to settle for a draw if it isn't specified which hand. Yes, that's right, yeah, yeah, yeah. Yeah, he, let's see. Oh, well, I'm gonna show you a picture of exactly that phenomenon in just a minute. But if you ask him to draw with the left hand, what he's looking at, he will draw the pipe. Yeah, it's speech that the left hemisphere is doing. Yes, no, I was trying to bring out how alarming it is. Yeah, I think it's completely astonishing, the idea that all of us are two minds. Yeah, that can't be right. Yes, that also is possible, yeah. That's right, and doesn't that show that we have two streams of consciousness? That's your question. Yeah, I mean, it would be a very strong result if that was so. I mean, there are many, many different visual processing areas. Either the last I heard it was in the high 30s is probably far more than that now. So if you're gonna say every time you've got a bit of the visual system that's doing something different to what another bit of the visual system is doing, that's a separate stream of consciousness. That's gonna be a whole lot of different streams of consciousness, and that's only for vision. You know, once we get onto the other senses and thinking in general, that's too many minds that, yeah, that can't be the right answer. At least I hope it's not the right answer, okay? It's clear why this is a puzzling phenomenon. I really encourage you to Google up SplitBren and see these guys talking and see these guys doing the experiments. So Nagel's basic point here is there's a kind of understanding that you can't have of those patients. There's a kind of understanding that we have of each other ordinarily, that we just take for granted, and you don't really see what it is that you're taking for granted until you think about these patients. I mean, just if I'm thinking right now, how does this scene look to you guys? I mean, I'm trying to think, is this an effective presentation or whatever, and I'm trying to imagine what it looks like to you, or you're trying to imagine what I'm seeing, how I can possibly be thinking the things I'm saying and so on, then that seems so easy. That seems so effortless. But with these patients, there's some sense in which you just can't imagine what their visual experience is like. And it's subtle, but it really seems like, think of this visual experience of this guy looking at the snow scene in the chicken claw. What is he seeing? What is his experience? He can't be seeing that whole scene the way you or I are seeing it, because then he could put the two things together, then he'd know he's getting these two different things there. That's not what he's getting. He doesn't seem to be getting just one of them, because either of these can support experience, either hemisphere can support experience of the scene. He seems to be having both experiences. It's not that he's having no experience at all, but how can that be? What does it look like to him? Can you imagine that? Can you imagine what he's getting when he stares at that scene? It seems completely impossible. And saying there are two minds there is really a way of giving up. You're saying, well, I can imagine seeing that and I can imagine seeing that, and there are two different minds. I mean, maybe that's the best you can do, but that really seems to lead to this absurd idea that all of us right now have got many different minds sitting there inside the same body, just talking to each other very fast. That's the wrong answer. So there's some sense in which you just cannot visualize what he's getting when he looks at the screen. Sperry said, many people have said, instead of the normally unified single stream of consciousness, what you've got with these patients is two independent streams of conscious awareness, one in each hemisphere. But as Nego says, these are people who can drive a truck, these are people who can play tennis. How can it be right to say they've got two independent streams of consciousness? Everything about them in everyday life is functionally highly integrated, just as integrated as you or me. It doesn't seem right to say it's only, as came up earlier and as someone was raising earlier, it doesn't seem right to say it's only the left hemisphere, the language hemisphere, that's got the conscious experience. So he's having conscious experience of the thing on the right, but no conscious experience of the snow scene. That doesn't seem to be the right answer because without, if he didn't have the language hemisphere, you'd say he's got experience of the snow scene. He'd be reacting appropriately to it. He'd be shivering, he'd be doing whatever. Yeah, you would say he has experience of the stuff in the left. So it doesn't seem right to say you've got a mind related to just the left hemisphere. The right hemisphere has got all these complex, emotional, effective things going on with it that seem to belong to visual experience. And on the other hand, it would just be hard to believe if you said he can report the chicken claw and so on, but he's not conscious of it because that's the only way we have it, usually of knowing what other people are conscious of is by looking at what they say, yeah. So there's a kind of understanding that we ordinarily have of each other that isn't functionalist. I mean, from a functionalist's perspective, these people are fully functionally integrated. So you can't, you could describe every functional connection they have. What we were doing at the start is just working through, it's pretty simple functionally what is going on. Yeah, and that's when you guys are all predicting what he's gonna say, yeah, you could do that. But that doesn't let you imagine from the inside what it would be like to be a patient like that. You don't know what kind of perspective you'd have in the world if you were such a patient. You don't know what your experiences would be like. So there's a kind of understanding that we ordinarily have of one another that we don't have of these patients and that's not a matter of knowing how things are functionally for them. We know all the functional connections this guy has, but we don't understand his mind. We don't know what's going on there. And that's our limitation in functionalism. Here's one other example. There are these paintings by Archambaldo of faces and people made of fruit, yeah? Now, the right hemisphere is thought to do faces. The left hemisphere is thought to do relatively detailed things like fruit, yeah? Yes, that makes sense. There's that specialization in the brain of what does what. So let me just check. Can you see some, can you see vegetables here? Fruit, yeah? Can you see the face? Okay, very good. I mean, there are many, many such paintings. So you show this to the split brain patient and you say, you put up two words on the screen, just one above or the other, and you say, can you point to the word that describes what you're seeing? So this is not asking for speech production, just can you point to the word that describes what you're seeing? What finger, okay, now point with your right hand. What's he gonna point to with his right hand? I said the, I said the left side does relatively low scale things like fruit, vegetables and so on. The right side does larger scale things like is it a face, yeah? So with the left hand, he points to the word face. With the right hand, he points to the word. Very good, right? So what is it? You guys can simultaneously get it that this is a face and that this is fruit, right? What in the world is he getting when he looks at this kind of scene? He's somehow getting both all right, but he's not getting both at once yet. How can that be? You can make sense of just getting one or just getting the other, but how can you visualize what he gets when he looks at that scene, yeah? This is not using, it's not really eyes, it's the visual field, remember, yeah? But this is not really using the visual field phenomenon. This is just using that the two hemispheres are doing different kinds of processing, yeah. Yeah, yeah, I don't know if that being done, but that would be the prediction. Yeah, that would be the prediction. Oh, yeah, but you can't do it both at once. Yes, the idea of switching attention here is really important, yeah. Myself, I feel like I get this both simultaneously, but yeah, what do people think? But it's often very difficult to know whether you're switching attention or whether you're really getting two things simultaneously, one, two. Yes, right, yeah, that is a very good example. Yeah, that really seems to be switching, yeah, yeah. Yeah, yeah, yeah. You know that kind of example, yeah. So you can see it as an old lady, or you can see it as a young woman, yeah. You can't see them both at the same time, yeah. Okay, so the point is that these, the general abstract point is with these patients, it's unfunctionally very easy to describe what is going on. At the same time, there is something truly mind-bending about them. You have really no, there's some sense in which you have no understanding what's going on with our minds at all. So I said this is a way of interpreting Descartes' argument. Descartes' argument was the mind, as we ordinarily think of it, has a kind of unity. There's a single perspective from which the world is being viewed, but you can't explain that in materialist terms, what kind of unity we've got here, because any functionalist account you would give of the unity here. The patients meet that, but there's some sense in which you don't have a single perspective in the world here. There's nothing coherent you can imagine here about what the patient is getting, yeah. So this is the phenomenon that someone just raised. I think the person who's asking about pipes just raised that you're looking at, you've got a fixation point here and you're asked to say what word are you encountering? And you say face, right? It's going to the left hemisphere, the left hemisphere, there's a language production or the speech production. And so you say face. Now you put the word face on the left hand side and you're asked to say what you're seeing and you say, well, I can't see anything. But if you're asked to draw with your left hand what you're seeing, you can draw the face just fine. Yep, yep. No, I'm saying this is a way of proving his argument right, that there's something about our understanding of each other that uses imagination or something like that to get hold of the other person's perspective in the world, what the world is like from their point of view and saying that's important to our ordinary understanding of the world. And it's so easy usually that you don't even notice it. You don't even notice you're making that presupposition. But the thing about these patients is you don't have that unity and that's really bizarre when you don't have it. And you certainly say, well there's a kind of hanging together that experiences don't have but I don't see any way of explaining what that is in materialist terms. That's the idea. So that's a way of elaborating Descartes' argument. I'm not putting that forward as exactly what Descartes had in mind but it's a way of elaborating the idea. Yeah? I mean, to say the mind is indivisible, if you say what's going on here what is he experiencing when he looks at this display? One, if the mind was divisible you could say, well of course we know what's going on there. He has two half minds. One half of the mind is getting the word face. The other half of the mind is not getting the word face. That doesn't make it go away, right? You have no idea what you're talking about when you say half a mind there. That's the sense in which the mind is indivisible. You can talk about two different minds but two half minds makes no sense. How should I put this? You can multiply minds but you can't divide them. It's hard to say, it's not, yeah. You could say that. You could say the right hand side of the brain is like a zombie, yeah? It does lots of complex stuff but it's really just a zombie. It doesn't have experiences. The left hand side by the language that's where you get the experience. The trouble is the right hand side of the, and you see this is a cheery face, right? This is a happy face. The patient's emotions, the patient's moods might all really be affecting how the stimulus is processed in the right hand side. Most of the things, many of the things that we think of as involved in the conscious life might be being sustained, are being sustained by the right hand side of the brain. Face processing, looking at the face of someone you know well in an autumn evening, remembering all those years, right? You really want to say the face processing there, that's not conscious. That's just a zombie doing that stuff. I mean, things that we think are very important to the conscious life are going on in the right hemisphere. Oh, there are actually advantages to being a split brain patient. You can try this, right? If you have two pens, you can try this right now. Suppose you look at these two figures, right? If you're asked to copy them, if you're asked to draw them right now, if you have a piece of paper, you try to copy them right now, you can do that for each of them, yes? That make sense? Yeah. But I put it to you, you can try this for yourself. But suppose you take a pen or a pencil in your left hand and a pen or a pencil in your right hand and you try and draw both of them simultaneously. This is very difficult, right? Yeah, I mean, try this yourself. It's very, very hard to do that. You can't, well, I can't anyway, yeah? Split brain patients can do that just fine. They can copy the two things simultaneously. Yeah, and if you think about it, it's obvious why that is. You or I trying to do this, this is the corpus callosum at work. You or I trying to do this, have this traffic trying to coordinate your information, trying to coordinate your movements across the two hands, trying to pull them together to make a unified action. And that's what's so confusing. The patient who has the corpus callosum cut doesn't have that. Here are regular people on the left trying to copy, I mean, if you try to copy things that are mirror images of one another with the two hands, then that's pretty easy. You can do this simultaneously or if they're exactly the same, you can do that. But look at here, here is two images to be copied by each of the two hands and a regular person, there's something pretty much like what I did, right? Yeah, that's like a regular, that's a regular person. If you can do it, that means that there's something wrong with your corpus callosum, so I wouldn't get too high and mighty about this. Whereas as you can see, patients manage both things just fine, yeah? So this is, it's not all bad news being a split brain patient, yeah? There are some things that actually helps you with. And this actually connects to the thing about attention. One question about the unity of consciousness, when you try to, I think one of the most interesting ideas about the unity of consciousness is that it has to do with attention, that you can't attend to two different things at once, yeah? And you might wonder with patients, isn't it that they switch attention between say, the chicken and the snow scene, they're switching attention. The alien I began by talking about, the weird thing about the alien who's reading two different books at once is that they're attending to two quite different things at once, yeah? And it's so hard to do that usually. I mean, you can do two different things at once, you can, I'm not that good at it, but you can pat your head and rub your stomach, right? But usually you take it that if you're doing that, then one of these things is being done automatically. Almost one of them is what you're attending to. You've got to set one of them to run an automatic pilot, even if you're attending to the other one. You usually think, well, maybe I can only attend to two different things at once. And Tim Bain has suggested this with split brain patients, but what they've got is they can attend to the snow scene, they can attend to the chicken, but they just can't attend to both of them at once. Yeah, they kind of switch and temporarily, but whoa. But the trouble with that kind of diagnosis is exactly this kind of case. Well, it seems like the patient doing these two things is really attending to both shapes simultaneously, yeah? So it's not like with the archambaldo, the face made out of fruits and vegetables. It's not like that the patient switches but can't really hold it, because there you see the patient, he's doing what the alien does. He is attending to two quite different tasks simultaneously. How can that be? Yeah, I mean, both of these are relatively, they're not that hard, there is not as hard as reading a book, but it's relatively demanding to do that kind of drawing of a shape, yeah? So how could he be attending to two different things simultaneously? That's another way of putting it, that's what one of the things that makes you say there are two different minds here, because if it was only one mind, how could you do that, yeah? The mind is, just a single mind is a single set of attentional resources. Now, I hope it's relatively clear what the general point is here, that you've got this theoretical functionalist knowledge of how the split-print patient is working. That's, okay, I don't need to go over that again, that's absolutely clear at this point, yeah? Okay, if this isn't playing his day at this point, I'm not explaining this very well, okay? Okay, or the patient who's shown pencil on the left hand and is picking, sorry, it's shown spoon on the left hand and is saying I didn't see anything while picking up the spoon. There's another kind of case, incidentally, where the control of facial expressions is contralateral, so your left hemisphere is controlling what goes on in the right side of your face, your right hemisphere is controlling what goes on in the left side of your face. So if you flash up on the right side of the screen, the right side of the screen, smile, you really get a very peculiar expression because only the left, only the right side of the face is trying to smile. The other half has no idea that it's meant to be smiling. Yeah, sorry. I was talking about the face, the tongue is a further area, right? And when I smile, I don't usually bring my tongue into it frankly, right? But there are all kinds of variations, I guess, yeah. Okay, yeah, I said this thing with the chicken and the coop, there are lots of cases like this. There was a patient who's shown, he's asked to show the, what's the movement, what's the action you'd associate with the word we're going to show you? And so you flash up telephone on the left-hand side and so does the speech center get that? No, so is he going to say telephone? Is he going to say phoning or something like that? Do a phone movement? No, and what this patient said was clap. Why clap? I don't know, and the experimenter said to him, well, I'll hopefully actually flashed up with telephone. Do you know why you said clap? What does clap have to do with telephone? And he said, I don't know, I guess it's all these pills I'm taking. They make you kind of high and people will not just say, I didn't know what was going on. You see what I mean? People make up stories. This patient was flashed up bell on the left and music on the right. And I can't remember, let me see if I can get this. And I think maybe drew a bell, yeah? And they said, well, what word did you see? They said music. He said music, the patient, I can't remember if a male or a female said music. And then so why did you draw a bell? Well, it's all kind of music you hear around here is these dumb bells, morning till night. So whatever I think of music, I naturally think of bells. Or this, again, this was a woman patient who gave very, when she was shown a scene on the right and could describe it, she gave a very elaborate description of it. This is an athlete jumping over a hurdle, going pretty fast, arms pointing in different directions. We give very full descriptions of what she saw. Given a presentation on the left, so she couldn't do a speech for it, she got a little bit, she said, this is an athlete. And then went on to give a very full, verbal description of what she was seeing. It's some kind of athlete, a basketball player, I think, running right towards me. The whole thing entirely made up, bearing no relation in the details to what she was actually seeing. So that thing with the chicken and the coop is really very common. So what's missing in all these cases is something like this. You don't have any grasp of the patient's point of view on the scene. You don't have any grasp of their perspective on the scene. You can't put yourself in the patient's shoes and visualize what kind of experience is there having. So that means that your knowledge of other people's minds, the kind of understanding that we have and use all the time, every moment, right in this class right now, you're using it the whole time, your understanding of how things are from other people's point of view. That's not just knowledge of a theory. That's not just knowledge of a box and arrow diagram of how the other person works because you can have a box and arrow diagram of how the other person works, but not have any idea what it's like from their perspective. So if you ask, what's that thing that you're missing here? Functionalism can't explain what the missing knowledge is. You're not missing anything about these patients functionally. You know the whole story functionally. Behaviorism can't explain what you're missing here because you know how the patient's going to behave. In fact, what we've been working through is that you can actually really predict pretty well the kind of, as well as you can with other people ordinarily, what these patients are going to say or how they're going to respond to these experimental situations. So behaviorism doesn't explain what's missing because the knowledge of behavior we have of those patients is pretty good. Dualism doesn't seem to explain what we're missing because it's not as if you could say, well, if only I knew what was going on with this patient's ectoplasm, then I'd be able to fill it in. You could give a complete description of what's going on with this patient's ectoplasm and still not be able to visualize how the world is for them. And it can't be that what's missing is something that Central State Materialism describes because we actually know a lot about the anatomy and physiology of these patients. You know exactly that it was a corpus callosum that was severed. You know a lot about what the corpus callosum does. You know all that stuff, but you still don't know anything about what their visual experience is like. That is still completely baffling. That is still a real puzzle. So there is something about the mind, something about your conscious visual experience that is alluding all these perspectives. Behaviorism, Central State Materialism, functionalism, dualism, and on that bombshell, we'll pack it up for today and carry on with the Chinese room argument on Thursday.