9:59:59.000,9:59:59.000 Just over a year ago, 9:59:59.000,9:59:59.000 for the third time in my life, 9:59:59.000,9:59:59.000 I seized to exist. 9:59:59.000,9:59:59.000 I was having a small operation, 9:59:59.000,9:59:59.000 and my brain was filling with anesthetic. 9:59:59.000,9:59:59.000 I remember a sense of detachment[br]and falling apart 9:59:59.000,9:59:59.000 and a coldness. 9:59:59.000,9:59:59.000 And then I was back, 9:59:59.000,9:59:59.000 drowsy and disoriented, 9:59:59.000,9:59:59.000 but definitely there. 9:59:59.000,9:59:59.000 When you wake from a deep sleep, 9:59:59.000,9:59:59.000 you might feel confused about the time[br]or anxious about oversleeping, 9:59:59.000,9:59:59.000 but there's always a basic sense[br]of time having passed, 9:59:59.000,9:59:59.000 of a continuity between then and now. 9:59:59.000,9:59:59.000 Coming out from[br]anesthesia is very different. 9:59:59.000,9:59:59.000 I could have been under for five minute, 9:59:59.000,9:59:59.000 five hours, 9:59:59.000,9:59:59.000 five years, 9:59:59.000,9:59:59.000 or even 50 years. 9:59:59.000,9:59:59.000 I simply wasn't there. 9:59:59.000,9:59:59.000 It was total obliviion. 9:59:59.000,9:59:59.000 Anesthesia -- 9:59:59.000,9:59:59.000 it's a modern kind of magic. 9:59:59.000,9:59:59.000 It turns people into objects -- 9:59:59.000,9:59:59.000 and then we hope -- 9:59:59.000,9:59:59.000 back again into people. 9:59:59.000,9:59:59.000 And in this process 9:59:59.000,9:59:59.000 is one of the greatest remaining[br]mysteries in science and philosophy. 9:59:59.000,9:59:59.000 How does consciousness happen? 9:59:59.000,9:59:59.000 Somehow, within each or our brains, 9:59:59.000,9:59:59.000 the combined activity[br]of many billions of neurons, 9:59:59.000,9:59:59.000 each one a tiny biological machine, 9:59:59.000,9:59:59.000 is generating a conscious experience. 9:59:59.000,9:59:59.000 And not just any conscious experience -- 9:59:59.000,9:59:59.000 your conscious experience[br]right here and right now. 9:59:59.000,9:59:59.000 How does this happen? 9:59:59.000,9:59:59.000 Answering this question is so important 9:59:59.000,9:59:59.000 because consciousness[br]for each of us is all there is. 9:59:59.000,9:59:59.000 Without it, there's no world, 9:59:59.000,9:59:59.000 there's no self, 9:59:59.000,9:59:59.000 there's nothing at all. 9:59:59.000,9:59:59.000 And when we suffer, 9:59:59.000,9:59:59.000 we suffer conciously, 9:59:59.000,9:59:59.000 whether it's through mental[br]illness or pain. 9:59:59.000,9:59:59.000 And if we can experience[br]joy and suffering, 9:59:59.000,9:59:59.000 what about other animals? 9:59:59.000,9:59:59.000 Might they be conscious, too? 9:59:59.000,9:59:59.000 Do they also have a sense of self? 9:59:59.000,9:59:59.000 And as computers get faster and smarter, 9:59:59.000,9:59:59.000 maybe there will come a point, 9:59:59.000,9:59:59.000 maybe not too far away, 9:59:59.000,9:59:59.000 when my iPhone develops a sense[br]of its own existence. 9:59:59.000,9:59:59.000 I actually think the prospects[br]for a conscious AI are pretty remote. 9:59:59.000,9:59:59.000 And I think this because[br]my research is telling me 9:59:59.000,9:59:59.000 that consciousness has less to do[br]with pure intelligence 9:59:59.000,9:59:59.000 and more to do with our nature[br]as living and breathing organisms. 9:59:59.000,9:59:59.000 Consciousness and intelligence[br]are very different things. 9:59:59.000,9:59:59.000 You don't have to be smart to suffer, 9:59:59.000,9:59:59.000 but you probably do have to be alive. 9:59:59.000,9:59:59.000 In the story I'm going to tell you, 9:59:59.000,9:59:59.000 our conscious experiences[br]of the world around us, 9:59:59.000,9:59:59.000 and of ourselves within it, 9:59:59.000,9:59:59.000 are kinds of controlled hallucinations 9:59:59.000,9:59:59.000 that happen with, through[br]and because of our living bodies. 9:59:59.000,9:59:59.000 Now, you might have heard[br]that we know nothing 9:59:59.000,9:59:59.000 about how the brain and body[br]give rise to consciousness. 9:59:59.000,9:59:59.000 Some people even say it's beyond[br]the reach of science all together. 9:59:59.000,9:59:59.000 But in fact, 9:59:59.000,9:59:59.000 the last 25 years have seen an explosion[br]of scientific work in this area. 9:59:59.000,9:59:59.000 If you come to my lab [br]at the University of Sussex, 9:59:59.000,9:59:59.000 you'll find scientists[br]from all different disciplines, 9:59:59.000,9:59:59.000 and sometimes even philosophers. 9:59:59.000,9:59:59.000 All of us together trying to understand[br]how conscioussness happens 9:59:59.000,9:59:59.000 and what happens when it goes wrong. 9:59:59.000,9:59:59.000 The strategy is very simple. 9:59:59.000,9:59:59.000 I'd like you to think about consciousness 9:59:59.000,9:59:59.000 in the way that we've[br]come to think about life. 9:59:59.000,9:59:59.000 At one time, 9:59:59.000,9:59:59.000 people thought the property[br]of being alive could not be explained 9:59:59.000,9:59:59.000 by physics and chemisty. 9:59:59.000,9:59:59.000 That life had to be more[br]than just mechanism. 9:59:59.000,9:59:59.000 But people no longer think that. 9:59:59.000,9:59:59.000 As biologists got on with the job 9:59:59.000,9:59:59.000 of explaining the properties[br]of living systems 9:59:59.000,9:59:59.000 in terms of physics and chemistry -- 9:59:59.000,9:59:59.000 things like metabolism, reproduction,[br]homeostasis -- 9:59:59.000,9:59:59.000 the basic mystery of what life is[br]started to fade away, 9:59:59.000,9:59:59.000 and people didn't propose any more[br]magical solutions, 9:59:59.000,9:59:59.000 like a force of life or an élan vital. 9:59:59.000,9:59:59.000 So as with life, 9:59:59.000,9:59:59.000 so with consciousness. 9:59:59.000,9:59:59.000 Once we start explaining its properties 9:59:59.000,9:59:59.000 in terms of things happening[br]inside brains and bodies, 9:59:59.000,9:59:59.000 the apparently insoluble mystery[br]of what consciousness is 9:59:59.000,9:59:59.000 should start to fade away. 9:59:59.000,9:59:59.000 At least that's the plan. 9:59:59.000,9:59:59.000 So let's get started. 9:59:59.000,9:59:59.000 What are the properties of consciousness? 9:59:59.000,9:59:59.000 What should a science[br]of consciousness try to explain? 9:59:59.000,9:59:59.000 Well, for today I'd just like to think[br]of consciousness in two different ways. 9:59:59.000,9:59:59.000 There are experiences[br]of the world around us, 9:59:59.000,9:59:59.000 full of sights, sounds and smells, 9:59:59.000,9:59:59.000 there's multisensory, panoramic,[br]3D, fully immersive inner movie. 9:59:59.000,9:59:59.000 And then there's conscious self. 9:59:59.000,9:59:59.000 The specific experience[br]of being you or being me. 9:59:59.000,9:59:59.000 The lead character in this inner movie, 9:59:59.000,9:59:59.000 and probably the aspect of consciousness[br]we all cling to most tightly. 9:59:59.000,9:59:59.000 Let's start with experiences[br]of the world around us 9:59:59.000,9:59:59.000 with the important idea of the brain[br]as a prediction engine. 9:59:59.000,9:59:59.000 Imagine being a brain. 9:59:59.000,9:59:59.000 You're locked inside a bony skull, 9:59:59.000,9:59:59.000 trying to figure out what's[br]out there in the world. 9:59:59.000,9:59:59.000 There's no lights inside the skull. 9:59:59.000,9:59:59.000 There's no sound either. 9:59:59.000,9:59:59.000 All you've got to go on is streams[br]of electrical impulses 9:59:59.000,9:59:59.000 which are only indirectly related[br]to things in the world, 9:59:59.000,9:59:59.000 whatever they may be. 9:59:59.000,9:59:59.000 So perception -- 9:59:59.000,9:59:59.000 figuring out what's there -- 9:59:59.000,9:59:59.000 has to be a process of informed guess work 9:59:59.000,9:59:59.000 in which the brain combines[br]these sensory signals, 9:59:59.000,9:59:59.000 with its prior expectations or beliefs[br]about the way the world is 9:59:59.000,9:59:59.000 to form its best guess of what[br]caused those signals. 9:59:59.000,9:59:59.000 The brain doesn't hear sound or see light. 9:59:59.000,9:59:59.000 What we perceive is its best guess[br]of what's out there in the world. 9:59:59.000,9:59:59.000 Let me give you a couple[br]of examples of all this. 9:59:59.000,9:59:59.000 You might have seen this illusion before, 9:59:59.000,9:59:59.000 but I'd like you to think[br]about it in a new way. 9:59:59.000,9:59:59.000 If you look at those two patches, A and B, 9:59:59.000,9:59:59.000 they should look to you to be[br]very different shades of gray, right? 9:59:59.000,9:59:59.000 But they are in fact[br]exactly the same shade. 9:59:59.000,9:59:59.000 And I can illustrate this. 9:59:59.000,9:59:59.000 If I put up a second version[br]of the image here, 9:59:59.000,9:59:59.000 and join the two patches[br]with a gray-colored bar, 9:59:59.000,9:59:59.000 and you can see there's no difference. 9:59:59.000,9:59:59.000 It's exactly the same shade of gray. 9:59:59.000,9:59:59.000 And if you still don't believe me, 9:59:59.000,9:59:59.000 I'll bring the bar across[br]and joing them up. 9:59:59.000,9:59:59.000 It's a single colored block of gray, 9:59:59.000,9:59:59.000 there's no difference at all. 9:59:59.000,9:59:59.000 So this isn't any kind of magic trick. 9:59:59.000,9:59:59.000 It's the same shade of gray, 9:59:59.000,9:59:59.000 but take it away again, 9:59:59.000,9:59:59.000 and it looks different. 9:59:59.000,9:59:59.000 So what's happening here 9:59:59.000,9:59:59.000 is that the brain is using[br]its prior expectations 9:59:59.000,9:59:59.000 built deeply into the circuits[br]of the visual cortex 9:59:59.000,9:59:59.000 that a cast shadow dims[br]the appearance of a surface, 9:59:59.000,9:59:59.000 so that we see B as lighter[br]than it really is. 9:59:59.000,9:59:59.000 Here's one more example, 9:59:59.000,9:59:59.000 which shows just how quickly[br]the brain can use new predictions 9:59:59.000,9:59:59.000 to change what we consciously experience. 9:59:59.000,9:59:59.000 Have a listen to this. 9:59:59.000,9:59:59.000 ([Sound]) 9:59:59.000,9:59:59.000 Sounded strange, right? 9:59:59.000,9:59:59.000 Have a listen again and see[br]if you can get anything. 9:59:59.000,9:59:59.000 ([Sound]) 9:59:59.000,9:59:59.000 Still strange. 9:59:59.000,9:59:59.000 Now listen to this. 9:59:59.000,9:59:59.000 Recording: I think breakfast[br]is a really terrible idea. 9:59:59.000,9:59:59.000 (Laughter) 9:59:59.000,9:59:59.000 Which I do. 9:59:59.000,9:59:59.000 So you heard some words there, right? 9:59:59.000,9:59:59.000 Now listen to the first sound again. 9:59:59.000,9:59:59.000 I'm just going to replay it. 9:59:59.000,9:59:59.000 ([Recording]) 9:59:59.000,9:59:59.000 Yeah? 9:59:59.000,9:59:59.000 (Laughter) 9:59:59.000,9:59:59.000 So you can now hear words there. 9:59:59.000,9:59:59.000 One more more for luck. 9:59:59.000,9:59:59.000 ([Recording]) 9:59:59.000,9:59:59.000 OK, so what's going on here? 9:59:59.000,9:59:59.000 The remarkable thing is the sensory[br]information coming into the brain 9:59:59.000,9:59:59.000 hasn't changed at all. 9:59:59.000,9:59:59.000 All that's changed is your[br]brain's best guess 9:59:59.000,9:59:59.000 of the causes of that sensory information. 9:59:59.000,9:59:59.000 And that changes what you[br]consciously hear. 9:59:59.000,9:59:59.000 All this puts the brain[br]basis of perception 9:59:59.000,9:59:59.000 in a bit of a different light. 9:59:59.000,9:59:59.000 Instead of perception depending largely[br]on signals coming into the brain 9:59:59.000,9:59:59.000 from the outside world, 9:59:59.000,9:59:59.000 it depends as much, 9:59:59.000,9:59:59.000 if not more, 9:59:59.000,9:59:59.000 on perceptual predictions flowing[br]in the opposite direction. 9:59:59.000,9:59:59.000 We don't just passively[br]perceive the world, 9:59:59.000,9:59:59.000 we actively generate it. 9:59:59.000,9:59:59.000 The world we experience comes[br]as much if not more 9:59:59.000,9:59:59.000 from the inside out 9:59:59.000,9:59:59.000 as from the outside in. 9:59:59.000,9:59:59.000 Let me give you one more[br]example of perception 9:59:59.000,9:59:59.000 as this active, constructive process. 9:59:59.000,9:59:59.000 Here we've combined immersive[br]virtual reality with image processing 9:59:59.000,9:59:59.000 to simulate the effects of overly[br]strong perceptual predictions 9:59:59.000,9:59:59.000 on our experience. 9:59:59.000,9:59:59.000 In this panoramic video, 9:59:59.000,9:59:59.000 we've tranformed the world -- 9:59:59.000,9:59:59.000 which is in this case Sussex Campus -- 9:59:59.000,9:59:59.000 into a psychedilic playground. 9:59:59.000,9:59:59.000 We've processed the footage using[br]an alogrithm based on Google's Deep Dream