1
00:00:01,290 --> 00:00:13,450
So. Are. Hello and welcome to the Oxford Playhouse.

2
00:00:13,810 --> 00:00:20,920
My name is Mark, sister Sautoy. I'm the, uh, Simone professor for the Public Understanding of Science here at the University of Oxford.

3
00:00:21,310 --> 00:00:26,469
And this year, we've got not just one, but two events that we're bringing to the Oxford Playhouse here.

4
00:00:26,470 --> 00:00:36,430
So, uh, next week, on Monday, on the 11th and 12th of November, we've got a premiere of a new play that I've written called The Axiom of Choice,

5
00:00:36,730 --> 00:00:40,350
and which I've just come from rehearsals with a great team that we're putting on.

6
00:00:40,350 --> 00:00:44,169
And so I hope, uh, tickets will be available at the box office as you go out.

7
00:00:44,170 --> 00:00:48,850
So I hope you'll enjoy, uh, me for that's in a week and a bit time.

8
00:00:48,850 --> 00:00:53,979
The theme is all about free will, which is obviously very relevant to tonight's, uh, topic as well.

9
00:00:53,980 --> 00:01:00,070
War and mathematics. But tonight we've got an amazing Simone lecture lined up for you.

10
00:01:00,070 --> 00:01:06,040
Uh, testament to the wonderful speaker we have and the very interesting topic we're going to be talking about.

11
00:01:06,280 --> 00:01:12,190
Um, the theatre tonight is ram to the rafters. So thank you so much, uh, uh, for coming out in such numbers.

12
00:01:12,370 --> 00:01:17,020
Um, tonight's speaker annual. Seth actually grew up around here like myself.

13
00:01:17,050 --> 00:01:24,820
Um, and he said to me just before we came on that, uh, he hasn't actually been back to the Oxford Playhouse, uh, since he was at school here.

14
00:01:24,820 --> 00:01:29,530
So it's wonderful to have him back here, um, on, uh, home turf.

15
00:01:29,530 --> 00:01:37,599
Uh, uh, and he is now a professor of, uh, cognitive and computational neuroscience at the University of Sussex,

16
00:01:37,600 --> 00:01:41,830
where he is also director of the centre for Consciousness Studies.

17
00:01:42,070 --> 00:01:47,410
And he's also the author of this wonderful, uh, bestselling book, uh, Being You.

18
00:01:47,410 --> 00:01:52,809
And tomorrow he will actually be at Blackwell's, uh, at about 11:00, uh, to sign copies.

19
00:01:52,810 --> 00:01:59,320
If you would like to go and get a copy or bring your copy Well-thumbed copy all along and, uh, have a chat to him there.

20
00:01:59,320 --> 00:02:02,020
So that'll be another chance, uh, for you to talk to him.

21
00:02:02,020 --> 00:02:10,270
But tonight, um, he's here to give, um, his, uh, some only lecture entitled consciousness Consciousness in Humans and Other things.

22
00:02:10,270 --> 00:02:14,200
So please give a big Oxford Playhouse. Welcome to our Neil Smith.

23
00:02:23,660 --> 00:02:27,410
Thank you very much, Marcus. And yeah, it's lovely to almost see so many people here.

24
00:02:27,410 --> 00:02:31,940
I can't really see anybody at all because of the lights. But it is it is wonderful to be back.

25
00:02:31,940 --> 00:02:37,100
And indeed today I am going to be talking about this, this subject of consciousness.

26
00:02:37,610 --> 00:02:41,780
Now, consciousness is one of our greatest remaining mysteries.

27
00:02:42,290 --> 00:02:46,819
At the same time, it's a phenomenon that we are each intimately familiar with.

28
00:02:46,820 --> 00:02:54,740
We all know what consciousness is. It's what goes away when we go under something like deep general anaesthesia.

29
00:02:54,740 --> 00:02:57,770
How many people have had sort of deep general anaesthesia?

30
00:02:58,460 --> 00:03:02,270
Quite, quite a few. I can't quite. So for those of you who haven't had it, give it a go.

31
00:03:02,270 --> 00:03:05,569
It's really very interesting. I highly recommend it.

32
00:03:05,570 --> 00:03:08,629
Very existential experiment you can do on yourself.

33
00:03:08,630 --> 00:03:14,990
Of course, we also lose consciousness most nights when we go into a dreamless sleep, not dreaming, but dreamless sleep.

34
00:03:14,990 --> 00:03:21,200
And then consciousness is what returns when we wake up in the morning or come around in the recovery room,

35
00:03:22,610 --> 00:03:31,760
and when we are conscious and when we open our eyes in the morning or in the recovery room, our brains don't just process visual information.

36
00:03:32,360 --> 00:03:35,960
There's another dimension entirely. We see colours, shapes.

37
00:03:36,410 --> 00:03:41,899
We experience smells, sounds, emotions there's experiencing happening.

38
00:03:41,900 --> 00:03:52,130
And a world appears. And parts of this world, within this world, there is the experience of being a self, of being you or being me.

39
00:03:52,970 --> 00:04:00,830
This background experience of being somebody is probably the aspect of consciousness that we each cling to most tightly.

40
00:04:01,490 --> 00:04:05,930
But consciousness very simply, is any kind of experience whatsoever.

41
00:04:05,930 --> 00:04:10,550
It's what makes life worth living. That's the intuitive definition.

42
00:04:11,000 --> 00:04:17,930
I want to just give you a little bit more of a formal definition. This is from a philosopher, Thomas Nagel, and it's the definition that I prefer.

43
00:04:17,930 --> 00:04:22,700
I mean, there's still a lot of disagreement about this kind of thing. Now, Thomas Nagel put it like this.

44
00:04:22,700 --> 00:04:29,209
He said that an organism has conscious mental states if and only if there is something.

45
00:04:29,210 --> 00:04:31,820
It is like to be that organism.

46
00:04:31,820 --> 00:04:38,450
And I think what he means, Meyer, is that it feels like something to just to be made feels like something to be each one of you.

47
00:04:38,930 --> 00:04:48,590
But it doesn't feel like anything to be this, this table or this book or this shoe, or probably this laptop computer or this this wash.

48
00:04:48,830 --> 00:04:57,319
It does feel like something to be about. Although exactly what only a bat will know that, um, for these kinds of things,

49
00:04:57,320 --> 00:05:01,550
for some things in the universe there is experiencing going on and other things there isn't.

50
00:05:02,300 --> 00:05:06,050
Now, one reason I like this definition is for what it does not say.

51
00:05:06,320 --> 00:05:11,570
Consciousness is not the same thing as being intelligent or being able to speak,

52
00:05:11,570 --> 00:05:17,330
having language, or having even this explicit sense of personal identity.

53
00:05:17,330 --> 00:05:21,920
You know, to me that is just any kind of experience count.

54
00:05:22,670 --> 00:05:25,819
Now, putting it this way raises this problem,

55
00:05:25,820 --> 00:05:32,150
this challenge that's vexed scientists and philosophers for millennia, really, which is how does it happen?

56
00:05:32,690 --> 00:05:38,299
Now, on the one hand, we've got this mess of complex stuff inside our brains and bodies,

57
00:05:38,300 --> 00:05:42,020
the brain inside the skull, the brain, this electrified pathway.

58
00:05:42,350 --> 00:05:47,780
And on the other hand, we have the redness of red, the sharpness of pain.

59
00:05:47,780 --> 00:05:50,510
We have the world of experience. How do they relate?

60
00:05:50,960 --> 00:05:57,740
And probably the most influential way of putting this big overall challenge was from the philosopher David Chalmers.

61
00:05:58,340 --> 00:06:01,700
And he coined this idea of the hard problem of consciousness.

62
00:06:01,700 --> 00:06:02,479
He put it like this.

63
00:06:02,480 --> 00:06:13,460
He said it is widely agreed that experience arises from a physical basis, but we have no good explanation of why and how it so arises.

64
00:06:13,610 --> 00:06:17,209
Why should physical processing give rise to a rich inner life at all?

65
00:06:17,210 --> 00:06:21,290
It seems objectively unreasonable that it should. And yes, it does.

66
00:06:21,740 --> 00:06:25,960
We're all conscious. How does this happen? Well,

67
00:06:26,050 --> 00:06:30,790
the intuition sort of that David Chalmers is driving at here is that even if we had

68
00:06:30,790 --> 00:06:36,489
in our hands a complete explanation of how the brain works as a complex object,

69
00:06:36,490 --> 00:06:40,210
and it is a very complex object at most.

70
00:06:40,360 --> 00:06:48,099
Each brain in this room has about 86 billion neurones and about a thousand times more connections,

71
00:06:48,100 --> 00:06:52,780
so that if you counted one connection every second, it would take you about 3 million years to finish.

72
00:06:52,780 --> 00:06:57,459
It's a very, very complicated object. But even if we knew everything about it,

73
00:06:57,460 --> 00:07:05,350
we might still be completely in the dark as to how and why it has anything to do with consciousness seem to be like different things.

74
00:07:05,360 --> 00:07:07,390
That's that's the hard problem of consciousness.

75
00:07:08,770 --> 00:07:16,000
Now, addressing the hard problem, as Chalmers puts it head on, might not be the only or the right way to go about it.

76
00:07:16,270 --> 00:07:19,960
And in my work over the last decade or so,

77
00:07:20,110 --> 00:07:26,360
I prefer to tackle on what I've been calling the real problem of consciousness just to annoy David Chalmers a little bit.

78
00:07:26,380 --> 00:07:29,770
The real problem, um, and it goes like this.

79
00:07:29,770 --> 00:07:36,940
It's it's to accept that consciousness exists and there will be some people, some philosophers that will tell you we were wrong about that,

80
00:07:36,940 --> 00:07:41,050
and that consciousness isn't this kind of special, distinctive phenomenon at all.

81
00:07:41,140 --> 00:07:45,250
But let's say that it exists. In fact, consciousness really is the only thing we can be sure of.

82
00:07:45,250 --> 00:07:49,690
Everything else is is sort of indirectly present, inferred through our consciousness.

83
00:07:49,810 --> 00:07:54,700
It exists, and it depends in some way on the brain and the body.

84
00:07:54,820 --> 00:08:00,070
So the question is how can mechanisms, this complex neural circuitry inside our skulls,

85
00:08:00,460 --> 00:08:06,490
in the brain and the body explain and predict and control properties of consciousness?

86
00:08:06,490 --> 00:08:14,410
Because that's in general what science does. It often doesn't have to tell you why a phenomenon is part of the universe in the first place.

87
00:08:14,410 --> 00:08:16,420
It's nice if it does, but often it doesn't.

88
00:08:16,420 --> 00:08:22,659
It just helps you explain the properties that it has, predict when they're going to happen, and ideally be able to you control.

89
00:08:22,660 --> 00:08:30,370
And that's the business of science. And the idea is that as we kind of try to do this and build bridges of explanation,

90
00:08:30,370 --> 00:08:36,670
I'll give you some examples and bridges of explanation between what's happening in the brain and what's happening in experience.

91
00:08:37,030 --> 00:08:43,419
This sense of mystery about how something is as apparently magical as consciousness

92
00:08:43,420 --> 00:08:49,840
can be so intimately associated with something as apparently mundane as mere stuff.

93
00:08:49,840 --> 00:08:57,970
That sense of mystery begins to dissolve away and may even disappear in a puff of metaphysical smoke.

94
00:08:58,000 --> 00:09:02,460
That's the hope. We're not there yet, but that's the overall strategy.

95
00:09:02,500 --> 00:09:08,379
So rather than solving this hard problem head on in one dramatic eureka moment of a solution where we say,

96
00:09:08,380 --> 00:09:15,730
ah, that's the that's where the magic happens. The hard problem of consciousness may in fact dissolve over time.

97
00:09:16,000 --> 00:09:19,660
And there is a historical precedent for this. Not a perfect one.

98
00:09:20,260 --> 00:09:29,800
But it wasn't that long ago. 150 years, 200 years, certainly, that people at the time thought that life was beyond the reach of science,

99
00:09:30,340 --> 00:09:35,820
that physics and chemistry could not account for the difference between the living and the non-living.

100
00:09:35,830 --> 00:09:43,120
At that time there was this philosophy of vitalism, the idea that there needed to be a special substance,

101
00:09:43,240 --> 00:09:49,930
and along B tau, a spark of life that would explain this difference, but was otherwise beyond the reach of science.

102
00:09:50,680 --> 00:09:56,200
Now we don't understand everything about life. Yet things like the origin of life is still fairly mysterious,

103
00:09:56,680 --> 00:10:07,510
but there's no sense of mystery that life is really something that fits in with our natural picture of the universe as as complicated stuff.

104
00:10:07,810 --> 00:10:10,959
The sense of mystery about life wasn't solved.

105
00:10:10,960 --> 00:10:12,730
People didn't find the spark of life.

106
00:10:12,730 --> 00:10:20,560
It was dissolved as biologists and chemists got on with the job of explaining properties of life in terms of physics and chemistry.

107
00:10:20,890 --> 00:10:23,890
So that's I mean, that's it's not a perfect historical parallel,

108
00:10:23,890 --> 00:10:30,160
but what I think is important is it tells us that what seems mysterious at one point in history,

109
00:10:30,490 --> 00:10:36,729
with the tools and the concepts that we have at this point. Doesn't always have to seem so mysterious,

110
00:10:36,730 --> 00:10:42,970
and we don't have to have a kind of revolution in physics or philosophy for that sense of mystery to dissipate.

111
00:10:43,910 --> 00:10:46,760
So life has many properties too. It's not just one thing.

112
00:10:47,710 --> 00:10:53,820
And so if we think about consciousness, instead of treating it as this one big scary mystery, what are its different aspects?

113
00:10:53,830 --> 00:10:58,420
What are its different properties? And I like to divide this into roughly three kinds of things.

114
00:10:58,630 --> 00:11:01,150
There's conscious level, which I already mentioned.

115
00:11:01,150 --> 00:11:08,590
This is the kind of global state of consciousness that goes away under anaesthesia and then comes back again and might be,

116
00:11:08,590 --> 00:11:13,090
might change in other states like sleep or hypnosis or things like that.

117
00:11:14,020 --> 00:11:16,810
Then when you are conscious, you're conscious of something.

118
00:11:16,840 --> 00:11:23,170
The sights and sounds and smells and colours and shape and people and places that populate your conscious experience.

119
00:11:23,350 --> 00:11:27,040
At any given time, we can think about that as conscious content.

120
00:11:27,700 --> 00:11:37,150
And then finally there's conscious self, the experience of being you or being me, the experience of being somebody that is probably,

121
00:11:37,360 --> 00:11:43,270
for many of us, the most important aspect of consciousness and the aspect we might take most for granted as well.

122
00:11:44,440 --> 00:11:51,910
So today I don't have time to talk about conscious level, but I want to focus a little bit unconscious content and conscious self.

123
00:11:52,270 --> 00:11:54,490
And then towards the end of the talk,

124
00:11:54,820 --> 00:12:01,600
explore some of the implications of what I've been saying for how we might think about consciousness beyond the human and especially,

125
00:12:01,900 --> 00:12:07,600
I think given the times we live in. What about consciousness in machines and artificial intelligence?

126
00:12:07,750 --> 00:12:12,639
What should we think about that? So that's where we're going. But where we're going to start is somewhere fairly simple.

127
00:12:12,640 --> 00:12:21,850
We're just going to start with colour. Now, colour is such a prominent, pervasive part of our conscious lives, especially our visual lives.

128
00:12:21,850 --> 00:12:26,420
It brings meaning and beauty to the way we visually experience the world.

129
00:12:26,440 --> 00:12:31,930
What could be simpler than colour? But of course, colour is far from straightforward.

130
00:12:32,710 --> 00:12:41,900
Now. The cells in our eyes. The photoreceptors in our eyes have long been known for most of us to be only sensitive to three,

131
00:12:42,440 --> 00:12:46,219
roughly three wavelengths in this whole electromagnetic spectrum,

132
00:12:46,220 --> 00:12:53,240
which goes all the way from radio waves at one end through infrared, ultraviolet, to x rays and gamma rays at the other end.

133
00:12:53,270 --> 00:12:58,190
So this thin slice of reality, that's where we live colour wise.

134
00:12:58,460 --> 00:13:04,920
And even within that thin slice, the cells in our eyes are only sensitive to just three wavelengths.

135
00:13:04,940 --> 00:13:11,090
Yet out of those three wavelengths, the brain is able to conjure millions of distinct colours.

136
00:13:12,090 --> 00:13:16,920
So what we experienced when we experienced colour is both less than what's really there,

137
00:13:16,950 --> 00:13:24,720
because it's just a sample of the electromagnetic spectrum, and the wavelengths within that spectrum aren't themselves coloured.

138
00:13:24,750 --> 00:13:28,860
They're just different wavelengths of of radiation, of energy.

139
00:13:29,550 --> 00:13:31,980
There's less than what's there, but it's also more than what's that?

140
00:13:31,980 --> 00:13:37,590
Because we can conjure millions of colours from just three out of three comes many.

141
00:13:38,790 --> 00:13:45,060
So what we see when we see colour is both less than and more than what's out there in the world.

142
00:13:45,980 --> 00:13:50,870
And I think that applies not just to colour, but to everything we experience.

143
00:13:51,470 --> 00:13:55,549
But let me stick with colour for a second. And here's just one. One illustration of this.

144
00:13:55,550 --> 00:14:02,440
This is one of my favourite visual illusions. The nice thing about talking about consciousness is you can use some of these fun illusions.

145
00:14:02,480 --> 00:14:05,629
How many people have seen this one before? I'm going to see if I can have a look.

146
00:14:05,630 --> 00:14:09,990
A few of you. Okay. This is one of my favourite. It's called the Lilac Chaser Illusion.

147
00:14:10,020 --> 00:14:18,950
I hope it's going to work in this theatre, but I'd like you to stare at the black cross in the middle and try not to blink or move your eyes.

148
00:14:20,370 --> 00:14:30,630
And then. I can hear a couple things. Let me know if something strange starts to happen and you start to see a a maybe a green disk.

149
00:14:31,230 --> 00:14:35,820
People saying that? Yes. And then if you now move your eyes and blink, what happens?

150
00:14:39,730 --> 00:14:45,820
A lot of murmuring happens, apparently, but what should happen is that the magenta disks come back, right?

151
00:14:46,330 --> 00:14:49,870
Um, so there is no green disk in this illusion at all.

152
00:14:49,870 --> 00:14:54,460
There are only magenta disks that turn off one after the other.

153
00:14:54,580 --> 00:14:58,840
So what's happening here is actually three different things going on.

154
00:14:58,840 --> 00:15:02,229
The first thing that's going on is something called Traxler fading. In psychology.

155
00:15:02,230 --> 00:15:07,270
This is this phenomenon where if some things in the periphery of your vision and it has blurry borders,

156
00:15:07,570 --> 00:15:13,810
tends to fade away and be replaced by what's around it. The second thing that's happening is called apparent motion.

157
00:15:13,930 --> 00:15:19,450
So when things turn on and off next to each other, the brain tends to experience movement.

158
00:15:19,690 --> 00:15:26,890
That's how cinema works. How television works. We infer things as smoothly moving from series of static snapshots.

159
00:15:27,190 --> 00:15:30,549
And the third thing that's happening is colour opponents.

160
00:15:30,550 --> 00:15:36,340
See now for the brain. The opposite in the space of colour from magenta is green.

161
00:15:36,790 --> 00:15:47,830
And so when the brain uh, when, when the brain sort of is adapting to the absence of magenta, it, you end up perceiving green instead of magenta.

162
00:15:48,070 --> 00:15:51,399
So these three things together explain what's happening here.

163
00:15:51,400 --> 00:15:56,830
There's actually a fourth thing, which is that I've already told you that colours don't really exist out there in the world.

164
00:15:57,250 --> 00:16:04,420
They're they're a collaboration between the brain and the world. Now, magenta exists even less than other colours.

165
00:16:04,960 --> 00:16:11,140
And the reason for that is that if you think you make magenta by mixing usually red and blue light together,

166
00:16:11,140 --> 00:16:15,640
although the light isn't actually red and blue. But you mix these two lights together, you get magenta.

167
00:16:16,150 --> 00:16:26,410
And so when um, and that's because the red and blue wavelengths sort of either end of the, uh, of the extreme of this thin slice of reality.

168
00:16:26,410 --> 00:16:33,370
So when the brain gets those wavelengths of light, it's expecting something in the middle which would be experienced as green.

169
00:16:33,370 --> 00:16:38,290
So when it doesn't get it, it has to make something up. And what it makes up is magenta.

170
00:16:38,680 --> 00:16:43,240
So what you're seeing when you're seeing green here is you're seeing not not not green.

171
00:16:44,230 --> 00:16:51,500
I hope that makes sense. It didn't make any sense to me. So I thought example I think.

172
00:16:53,480 --> 00:16:56,000
Just underlines. Get put the details aside.

173
00:16:56,000 --> 00:17:03,020
What it what it underlines is that can be this big difference between how things seen in our experience and how they are.

174
00:17:03,650 --> 00:17:08,129
And there's one simple idea which I think can explain these experiences.

175
00:17:08,130 --> 00:17:14,360
And I've just zooming out from the details and can explain all our experiences in one way or another.

176
00:17:14,540 --> 00:17:18,020
And this is the idea that your brain is a prediction machine,

177
00:17:18,650 --> 00:17:28,940
and that everything that you experience is your brain's best guess about what's going on out there in the world or in here in the body.

178
00:17:29,180 --> 00:17:33,650
The brain's best guess about the causes of the sensory input that it gets.

179
00:17:34,460 --> 00:17:39,800
Now, this is a a very old idea, goes back in philosophy as long as you want.

180
00:17:40,160 --> 00:17:46,040
Certainly it goes back to, to Plato. And this is and is out in Plato's Allegory of the cave.

181
00:17:46,280 --> 00:17:55,490
Prisoners are chained to the wall of a cave, and all they can see, or they have access to are shadows cast on the walls by the light from a fire.

182
00:17:55,700 --> 00:18:01,070
And the prisoners take these shadows to be real, because that's all they have access to.

183
00:18:02,300 --> 00:18:08,000
Now, sort of bringing all this, skipping a few thousand years and coming up to the to the present day,

184
00:18:08,000 --> 00:18:13,430
a more modern version of this way of thinking is instead of prisoners trapped inside a cave,

185
00:18:13,820 --> 00:18:18,980
just try for a second to imagine what it's like to be your own brain.

186
00:18:19,640 --> 00:18:28,400
You are your brain. You're trapped inside this bony cave prison of a skull, trying to figure out what's going on out there in the world.

187
00:18:28,430 --> 00:18:31,910
Now there's no light in the skull. There's no sound. It's completely dark.

188
00:18:32,270 --> 00:18:34,219
It's completely silent.

189
00:18:34,220 --> 00:18:43,820
All the brain has to go on when trying to figure out what's there is noisy, ambiguous, uncertain, and unlabelled sensory information.

190
00:18:43,820 --> 00:18:46,639
Electrical signals that come in through the senses.

191
00:18:46,640 --> 00:18:52,040
Now, these electrical signals, these sensory inputs, they don't tell you they didn't come with labels on like,

192
00:18:52,040 --> 00:18:55,280
I'm from a hat or I'm from a table, or I'm from the kidneys.

193
00:18:55,700 --> 00:18:57,260
They're just electrical signals.

194
00:18:57,680 --> 00:19:08,330
So to make sense of them, the brain has to combine these sensory signals with its prior knowledge or expectations about what's going on in the world.

195
00:19:08,450 --> 00:19:14,989
And by combining this ambiguous sensory information with its prior expectations,

196
00:19:14,990 --> 00:19:23,569
the brain can make a best guess about what's going on, and that the idea here is that is what we perceive.

197
00:19:23,570 --> 00:19:26,570
The brain doesn't see light or hear sound.

198
00:19:27,110 --> 00:19:32,600
What we experience is the brain's best guess of the causes of those kinds of signals.

199
00:19:33,960 --> 00:19:40,800
I'll give you one more example of this. Just just so you might be familiar with this one, but we can think about this in this context.

200
00:19:40,810 --> 00:19:44,070
How many people have seen this one? This is a more common visual illusion.

201
00:19:44,070 --> 00:19:47,970
Still not everybody okay. So this is called Adelson's checkerboard.

202
00:19:48,750 --> 00:19:57,510
And. If you look at those two patches, A and B now, hopefully they should look to you to be different shades of grey.

203
00:19:57,540 --> 00:20:03,089
Is that everyone saying that different shades of grey okay, now because obviously it's an illusion.

204
00:20:03,090 --> 00:20:10,800
Obviously that's not true. If I put the thing up here, you can see that they are in fact exactly the same shade of grey.

205
00:20:10,820 --> 00:20:12,930
Everybody see that looks the same.

206
00:20:13,980 --> 00:20:20,790
And if you think I'm tricking you somehow, well, I'll just move this grey bar across and you can see it really is the same shade of grey.

207
00:20:20,790 --> 00:20:26,410
There's. There's no difference. And if I take it away, it looks different again.

208
00:20:28,310 --> 00:20:29,360
So what's going on here? Well,

209
00:20:29,360 --> 00:20:41,500
what's going on here is that your brain has baked into its visual circuits the knowledge that objects in shadow appear darker than they really are.

210
00:20:41,510 --> 00:20:48,130
And it also has this knowledge of how checkerboards work that they alternate between brightness and darkness.

211
00:20:48,740 --> 00:20:53,030
You don't necessarily know that your brain has this knowledge about the world, but it does.

212
00:20:53,570 --> 00:21:01,610
And that's why we see B as lighter than it really is, because it's in the shadow on the checkerboard from the cylinder.

213
00:21:01,880 --> 00:21:07,730
So the brain's expectations can really deeply shape what we consciously experience.

214
00:21:09,020 --> 00:21:15,440
Now I was going to skip this slide, but because I was introduced by by Marcus, I have to have at least one equation in the talk.

215
00:21:15,850 --> 00:21:18,590
That Mark is not efficient. And this is the only one.

216
00:21:19,160 --> 00:21:23,450
Uh, and it's just showing that there's a, there's like a kind of mathematical way to think about this,

217
00:21:23,450 --> 00:21:31,220
a mathematical way that describes this whole idea of the brain as making best guesses about what's out there in the world.

218
00:21:31,550 --> 00:21:35,270
And it's called Bayes theorem. And Bayes theorem goes back hundreds of years.

219
00:21:35,540 --> 00:21:42,020
And it's really about how one should optimally reason in the face of uncertainty.

220
00:21:42,230 --> 00:21:50,570
And the idea here is that, um, we can have we can have some starting situation, some prior belief about what's going on.

221
00:21:50,660 --> 00:21:54,810
And that's the dashed curve on the left. And we can get some new information.

222
00:21:54,830 --> 00:21:59,569
This could be sensory data coming into the brain. And Bayes theory you call that the likelihood.

223
00:21:59,570 --> 00:22:03,590
So that's the the other dashed curve to the right that the slightly broader one.

224
00:22:04,040 --> 00:22:05,479
And then the idea is Bayes theorem.

225
00:22:05,480 --> 00:22:12,830
You combine these two curves so you optimally integrate what you already know with what you what's what new information you get.

226
00:22:13,130 --> 00:22:17,490
And you combine them and you come up with what Bayes called the posterior belief.

227
00:22:17,510 --> 00:22:23,390
So that's what I should believe, given what I already know and what what's coming in next.

228
00:22:24,200 --> 00:22:29,629
And so the idea is that it's really what the brain is trying to do when it's trying to perceive things out there in the world.

229
00:22:29,630 --> 00:22:33,290
It already knows stuff about the world, but it gets new information all the time.

230
00:22:33,500 --> 00:22:37,520
So it has to update what it knows on the basis of this new information.

231
00:22:38,060 --> 00:22:46,160
Now, the first person to my knowledge you really formalising wrote about perception in this way was a German polymath called Hermann von Helmholtz,

232
00:22:46,160 --> 00:22:54,170
and Hermann von Helmholtz said that perception was this process of unconscious inference, and he called it unconscious inference,

233
00:22:54,770 --> 00:23:00,160
to make the point that we're not aware of all this probabilistic wizardry going on under the hood.

234
00:23:00,170 --> 00:23:03,829
We're only aware of the result of it. We're only aware of the output.

235
00:23:03,830 --> 00:23:13,520
We don't know that our brain is doing all this clever stuff, but if it is, it really casts perception, I think, in a very different light.

236
00:23:13,700 --> 00:23:20,330
It flips how we think about things, even if we have never really thought about these things all that much before.

237
00:23:21,140 --> 00:23:25,680
Now, the classical view of how the brain does perception, and this is something of the sort, this,

238
00:23:25,700 --> 00:23:30,350
this kind of picture I would see in textbooks when I was a student some years ago, many years ago.

239
00:23:30,800 --> 00:23:36,410
And the idea in this sort of old classical view is that perception is this kind of outside in,

240
00:23:36,410 --> 00:23:42,170
bottom up process where signals come into the brain from the retina and they progress.

241
00:23:42,170 --> 00:23:48,440
They sort of marched deeper and deeper into the brain, and more complex features are picked out as the signals go further into the brain.

242
00:23:48,440 --> 00:23:55,220
So simple things like edges and colours early on, more complex things like faces later on, the monkey face because this is a monkey brain.

243
00:23:55,700 --> 00:24:02,149
Um, now there may be some activity going in the other direction, but all the heavy lifting is done in this bottom up,

244
00:24:02,150 --> 00:24:06,710
outside in direction, as if the brain is reading the world through the senses.

245
00:24:07,310 --> 00:24:11,990
And that seems right. I mean, it seems kind of how things are that there's a world,

246
00:24:11,990 --> 00:24:18,230
and my brain is sort of just soaking it in through the transparent windows of my eyes and my ears and my other senses.

247
00:24:18,830 --> 00:24:23,480
Now the prediction machine view turns this completely on its head.

248
00:24:23,810 --> 00:24:30,170
Instead of perception being this business of reading out sensory signals from the outside in.

249
00:24:30,890 --> 00:24:38,629
It's much more about perceptual predictions which flow in the opposite direction from the top down and the inside out.

250
00:24:38,630 --> 00:24:43,550
These green arrows here, the brain is always making predictions about the causes of sensory signals,

251
00:24:43,550 --> 00:24:47,480
and then using the sensory signals to update the predictions.

252
00:24:47,790 --> 00:24:57,889
Turns out if the brain does this and always tries to update its predictions to minimise the error that it gets, then it approximates.

253
00:24:57,890 --> 00:25:03,980
It starts to do this, this process of Bayesian inference. Um, but what it means for perception is that.

254
00:25:05,000 --> 00:25:13,340
What we experience is an active generation, rather than a passive registration of the world around us.

255
00:25:14,150 --> 00:25:18,590
So this theory is known by by kind of many names in neuroscience and psychology.

256
00:25:19,100 --> 00:25:24,580
Predictive processing is probably the most common. And the core idea, at least the way I think about this theory.

257
00:25:24,590 --> 00:25:32,510
The core idea is that perceptual content, what we perceive comes from the inside out just as much, if not more, than from the outside in.

258
00:25:32,510 --> 00:25:41,030
And these sensory signals mainly serve to keep the brain's predictions tied to the world in ways that are not necessarily accurate,

259
00:25:41,300 --> 00:25:46,520
but which are most useful in how we and guiding our behaviour.

260
00:25:47,390 --> 00:25:53,840
Now, William James, who was one of the fathers, uh, the first people founding figures in psychology,

261
00:25:54,530 --> 00:25:58,459
said something very similar over 100 years ago in the late 19th century.

262
00:25:58,460 --> 00:26:04,310
He said that was part of what we perceive comes through our senses from the object before us.

263
00:26:04,490 --> 00:26:09,650
Another part, and it may be the larger part, always comes out of our own heads.

264
00:26:10,610 --> 00:26:14,150
He had the same idea. If you didn't, even if you didn't put it in the same way.

265
00:26:15,470 --> 00:26:19,730
Now we can see echoes and shadows of this process in our everyday lives.

266
00:26:19,910 --> 00:26:27,590
There's a phenomenon called pareidolia, which means seeing patterns in fact, faces a very powerful stimuli.

267
00:26:28,130 --> 00:26:34,160
Uh, we, you know, we're very sensitive to the presence of faces because we're very social creatures.

268
00:26:35,580 --> 00:26:45,440
And, um, what this means is the brain is always casting out the prediction of face into, uh, the world to see where it sticks.

269
00:26:45,450 --> 00:26:47,670
And so we can see faces and clouds,

270
00:26:47,850 --> 00:26:54,060
and we can even see faces in things like the arrangements of windows on a building faces a very, very, very prominent.

271
00:26:55,230 --> 00:27:01,470
And, um, one of the things we've been doing at Sussex is taking this idea and playing with it a little bit in the lab.

272
00:27:01,860 --> 00:27:08,879
So we've been combining virtual reality with some machine learning or AI methods to, uh,

273
00:27:08,880 --> 00:27:17,430
to try to simulate what it would be like if the brain had two strong, overly strong predictions to see faces everywhere.

274
00:27:17,640 --> 00:27:21,360
So this is like this is now quite an old school neural network.

275
00:27:21,360 --> 00:27:27,150
It's very good at telling you what's an image, what's in an image if you present it with that image.

276
00:27:27,870 --> 00:27:32,970
Um, but what we did was we, we used a tweak of this called Deep Dream, which runs it backwards.

277
00:27:33,120 --> 00:27:38,729
And what happens in this, uh, this manipulation is instead of the network telling you what's in an image,

278
00:27:38,730 --> 00:27:46,010
you fix the output to something like dog, and you give it an image as input, and then you update the image until the whole thing settles down.

279
00:27:46,020 --> 00:27:54,000
So it's a bit of a brute force way of saying, how can we simulate what it would be like if the brain had a strong prediction to see dog?

280
00:27:54,630 --> 00:28:02,520
Um, and what we did with, uh, my postdoc Casa Katie Zuki is we took this idea and we took some panoramic video of Sussex campus,

281
00:28:02,670 --> 00:28:06,840
and we applied this method to every frame within the video.

282
00:28:06,840 --> 00:28:14,880
And then, um, gave people a VR headset, which they could wear, and then they experience Sussex Campus in a very unusual way.

283
00:28:15,090 --> 00:28:18,330
So I mean, it is different from Oxford, but it's not this different normally.

284
00:28:19,760 --> 00:28:26,180
There's a few too many dogs. But, um, what's interesting about this for me is that it's it's a it's a sort of computational model,

285
00:28:26,180 --> 00:28:31,100
but it's a not not of what people do or any kind of cognition.

286
00:28:31,100 --> 00:28:39,140
It's a model of a different kind of experience. It's a way of using computational models to to model how we experience the world.

287
00:28:39,560 --> 00:28:47,420
Um, what we've been doing just this week actually was, um, because computers have got faster and faster, we can now do this in real time.

288
00:28:47,600 --> 00:28:50,960
So if you visit my my lab, we can put this headset on.

289
00:28:51,080 --> 00:28:58,250
And right then in the moment, you know, you can have this, this very strange, almost psychedelic like experience of what's going on around you.

290
00:28:58,250 --> 00:29:01,430
And of course, we can tweak it in various, various different ways.

291
00:29:01,580 --> 00:29:05,090
We're also taking the same method. And this isn't just fun.

292
00:29:05,090 --> 00:29:08,389
I mean, it is fun. And a lot of science starts off just by it, to be honest.

293
00:29:08,390 --> 00:29:13,580
Just by playing around to see what you can do, to see what kinds of things you can explore.

294
00:29:13,790 --> 00:29:19,579
But we've also been taking this same method now and applying it to try to understand how and why

295
00:29:19,580 --> 00:29:23,809
different kinds of visual hallucinations are actually the way they are and how they're different.

296
00:29:23,810 --> 00:29:29,240
So people with Parkinson's disease have visual hallucinations quite often people with Charles Bonnet syndrome,

297
00:29:29,240 --> 00:29:32,960
which is where people lose a lot of vision through macular degeneration.

298
00:29:33,080 --> 00:29:37,790
They also sometimes have hallucinations. Psychedelics involve hallucinations as well.

299
00:29:37,790 --> 00:29:38,990
They're all kind of different.

300
00:29:39,170 --> 00:29:45,709
But through this method, we can start to understand how and why different kinds of hallucinations are different from each other,

301
00:29:45,710 --> 00:29:50,600
and therefore understand a bit more about perception in the here and now as well.

302
00:29:51,050 --> 00:29:57,200
But there's a sort of single take home from all this, which is that we can think of hallucination.

303
00:29:57,200 --> 00:30:00,290
Here is a kind of uncontrolled perception.

304
00:30:00,290 --> 00:30:04,549
It's what happens when the brain loses its grip.

305
00:30:04,550 --> 00:30:08,690
The brain's predictions lose their grip on their causes in the world.

306
00:30:09,140 --> 00:30:11,870
And now, by the same token,

307
00:30:11,870 --> 00:30:19,550
we can then think of normal perception in the here and now as a kind of controlled hallucination where the brain's best guess is,

308
00:30:19,850 --> 00:30:24,710
uh, reined in by, controlled by that causes in the world.

309
00:30:26,160 --> 00:30:29,580
And I think this way of putting it is important because when we think about hallucination,

310
00:30:29,580 --> 00:30:33,899
we often think of it as, you know, something completely different from how we do things.

311
00:30:33,900 --> 00:30:37,350
Normally. It's another category. People see things here, things that aren't there.

312
00:30:37,710 --> 00:30:44,490
But when we experience things without hallucinating, we have this kind of direct vertical access to how things really are.

313
00:30:44,700 --> 00:30:50,160
I don't think it's like that. I think there's a continuity, a spectrum we can for various parts of the spectrum.

314
00:30:50,460 --> 00:31:00,180
All of our perceptual experience comes from the inside out, and it's all calibrated in some way by sensory input from the outside in.

315
00:31:01,920 --> 00:31:08,930
Now, one implication of this idea is that since we all have different brains, we will all have different experiences.

316
00:31:08,940 --> 00:31:12,090
We will all differ on the inside, just as we do on the outside.

317
00:31:12,270 --> 00:31:17,370
The novelist Anais Nin put this very nicely in her 1961 book, The Seduction of the Minotaur,

318
00:31:17,370 --> 00:31:23,819
when she said we do not see things as they are, we see them as we are and as one.

319
00:31:23,820 --> 00:31:28,810
One last example of this I want to show. I think you've probably seen this before, right?

320
00:31:28,830 --> 00:31:33,239
Remember this. This is almost ten years ago now. This image first exploded across the internet.

321
00:31:33,240 --> 00:31:40,020
So this is a photo of a dress. How many people see this as a white and gold dress?

322
00:31:41,420 --> 00:31:45,470
Quite a few. How many people see it as a blue and black dress?

323
00:31:46,100 --> 00:31:50,270
Many more. How many people don't know what the [INAUDIBLE] I'm talking about? Okay.

324
00:31:50,280 --> 00:31:53,639
No it's not. I mean, this is. Time has passed, so one never knows.

325
00:31:53,640 --> 00:31:57,990
And the lighting in here is strange. See, you know, this came in 2015.

326
00:31:57,990 --> 00:32:04,080
What I think is amazing about this is that those people who see it one way, you know,

327
00:32:04,080 --> 00:32:10,250
the white and gold people out there, it's very hard to imagine what it would be like to see it in a different way.

328
00:32:10,260 --> 00:32:15,260
Right. And you see it the way you see it on. But of course it's the same.

329
00:32:15,260 --> 00:32:19,999
It's the same picture. And the reason we see it differently, we can come back to that later.

330
00:32:20,000 --> 00:32:25,729
It has to do. It probably has to do with how our brains take into account the, you know, the ambient light,

331
00:32:25,730 --> 00:32:30,469
which in this room is quite yellowish, by the way, those people who say it's blue and black, you're right.

332
00:32:30,470 --> 00:32:33,590
The real dress is blue and black. Um, so well done you.

333
00:32:35,080 --> 00:32:41,920
Um but the point and gold people. You might be wrong, but but your brains typically assume that you're outdoors and happy, so, you know, lucky you.

334
00:32:45,010 --> 00:32:51,940
This example is, you know, it exploded into the public consciousness because the difference was so big

335
00:32:51,970 --> 00:32:55,570
that it became noticeable when people started arguing about what do you see?

336
00:32:56,350 --> 00:33:02,679
But that obscures, I think, a deeper point, which is that we will all experience things differently.

337
00:33:02,680 --> 00:33:08,380
And most of the time those differences won't be large enough that they'll surface into our language and behaviour.

338
00:33:08,410 --> 00:33:12,640
You know, we all differ on the outside in terms of body shape, skin colour and so on.

339
00:33:12,970 --> 00:33:17,020
And those differences don't have to be very large. And we can still see them because we can see them.

340
00:33:17,530 --> 00:33:24,580
But differences on the inside a much, much harder to measure because that private my I have my experience and you don't.

341
00:33:24,790 --> 00:33:31,719
We use language to kind of paper over the differences, and it also just seems as though I see the world as it is, you know?

342
00:33:31,720 --> 00:33:37,810
And so why should anybody see it differently? And for me, this has been a very interesting challenge.

343
00:33:37,810 --> 00:33:43,910
We don't know all that much about the diversity of of perceptual experience in this way.

344
00:33:43,930 --> 00:33:50,290
So one project that I've been involved with over the last 2 or 3 years is become the perception senses.

345
00:33:50,500 --> 00:34:00,040
And this has been a very ambitious study involving so far, only 40,000 people each doing hours of experiments to try to understand,

346
00:34:00,370 --> 00:34:04,659
you know, how we each experience the world in our own unique way.

347
00:34:04,660 --> 00:34:12,310
And we've so far had people from, um, 40,000 people from over 100 countries and ages from 18 to 80,

348
00:34:12,970 --> 00:34:18,010
uh, to try to paint a picture of what I've been calling perceptual diversity.

349
00:34:18,340 --> 00:34:21,639
And I use that term because I want to emphasise that it applies to all of us,

350
00:34:21,640 --> 00:34:30,250
and it's not something that's specific to people with so-called neurodivergent conditions like autism or ADHD, who want to study that, too.

351
00:34:30,430 --> 00:34:33,430
But we all differ in how we experience the world.

352
00:34:33,850 --> 00:34:38,610
And there's a kind of I'm dwelling on this because I think there's an important implication.

353
00:34:38,620 --> 00:34:42,219
We haven't analysed the data very much yet, so I don't have any results to show you.

354
00:34:42,220 --> 00:34:46,540
But even just the examples that you've seen,

355
00:34:47,110 --> 00:34:55,629
I think one consequence of thinking about things this way is that it can help us cultivate a bit of humility about our own take on things,

356
00:34:55,630 --> 00:34:59,830
like the way I see things is not the only way other ways are possible.

357
00:35:00,040 --> 00:35:09,220
And so my hope is, and it is very much a hope that by revealing a bit more about how we differ in our perceptual experience of the world,

358
00:35:09,370 --> 00:35:15,970
we will be able to build some some new platforms that will allow better understanding and communication between people,

359
00:35:16,300 --> 00:35:23,830
because we live in perceptual echo chambers. And the first step to getting out of an echo chamber is to realise that you're in one.

360
00:35:25,320 --> 00:35:31,170
Okay, so in the next part of the talk, I want to move on from perception of the world to perception of the self.

361
00:35:31,920 --> 00:35:36,150
And it's easy to take the self for granted, but we should not.

362
00:35:36,690 --> 00:35:43,650
And it's also easy to. So I think make a simple mistake about where the self fits in to this picture of consciousness.

363
00:35:44,100 --> 00:35:47,819
You know the easy how things seem view is something like this. There's a world out there.

364
00:35:47,820 --> 00:35:50,850
We perceive the world. Sensory inputs come into our eyes.

365
00:35:51,310 --> 00:35:57,210
And the self in this view is the is the thing that does the perceiving the essence of you or me.

366
00:35:57,390 --> 00:36:04,980
And that receives that the perception of the world makes and plans decide what to do next and then does that thing.

367
00:36:05,130 --> 00:36:08,580
We make some actions in the world, and the world changes, and round and round we go.

368
00:36:08,580 --> 00:36:12,840
We sense, we think we act. That might be the house, how things seem view.

369
00:36:13,110 --> 00:36:16,200
But how things are is, I think, quite different.

370
00:36:17,300 --> 00:36:24,020
In this view, both experiences of the world and experiences of the self are kinds of perception.

371
00:36:24,020 --> 00:36:29,780
The self is not the thing, the essence, the universe, or the meanness that does the perceiving.

372
00:36:30,020 --> 00:36:39,860
The self is itself a kind of perception, or rather a bundle, a collection of related but different perceptions.

373
00:36:40,640 --> 00:36:45,960
Um. So the self two can be thought of as a kind of controlled hallucination.

374
00:36:46,650 --> 00:36:50,550
The purpose of which is to keep the body alive.

375
00:36:51,270 --> 00:36:56,479
Now, thinking about it this way. First thing that comes up is there are many aspects.

376
00:36:56,480 --> 00:36:59,840
There are many different ways in which we each experience being a self.

377
00:36:59,840 --> 00:37:01,850
It might feel like the self is one thing,

378
00:37:02,150 --> 00:37:08,060
but it breaks down in many ways that the experience of being and having a particular object in the world, the body.

379
00:37:08,090 --> 00:37:14,450
Now this is my body and that isn't. There's the experience of perceiving the world from a particular first person point of view.

380
00:37:15,470 --> 00:37:20,840
There's the volitional self, the experience of being the cause of particular actions,

381
00:37:21,440 --> 00:37:24,750
or the author of my own thoughts when people talk about free will.

382
00:37:24,770 --> 00:37:30,350
This is one of the things they talk about, and only then things like the narrative in the social self.

383
00:37:30,380 --> 00:37:37,140
This is where personal identity comes in. So there's a sense of self in me that's bound to a name and identity.

384
00:37:37,160 --> 00:37:44,780
Memories of the past and plans for the future. Now all of these aspects of self might seem unified intrinsically.

385
00:37:44,780 --> 00:37:52,100
Maybe necessarily so, but we know they aren't. There's many examples in the lab and also in psychiatry, in neurology,

386
00:37:52,400 --> 00:37:56,960
where these different aspects of self come apart in all sorts of different ways.

387
00:37:57,470 --> 00:38:04,310
And I think what this tells us is that the experience of being a self, being you, is not something to take for granted.

388
00:38:04,550 --> 00:38:09,560
It's a fragile construction of the brain, for the brain and the body.

389
00:38:11,020 --> 00:38:19,060
Now I want to focus just on one aspect of this, which is the bodily self, the experience of being and having a particular body.

390
00:38:19,360 --> 00:38:22,570
Now again, we don't really think about this very much, right? The body is just that.

391
00:38:23,050 --> 00:38:26,260
It's this kind of meat robot that takes me from one meeting to another.

392
00:38:27,730 --> 00:38:33,670
But if you think about it from the brain's perspective, the body is also inaccessible.

393
00:38:33,670 --> 00:38:38,799
The brain only gets electrical signals that in this case, come from the body rather than the world.

394
00:38:38,800 --> 00:38:44,290
But it's always having to make a best guess about what is and what is not the body.

395
00:38:44,500 --> 00:38:48,850
And that's a lovely demonstration of this I love this. This is called the rubber hand illusion.

396
00:38:48,850 --> 00:38:56,770
You've probably seen this before. I won't start it just yet. And this shows how easily our experience of what is the body can be altered.

397
00:38:57,520 --> 00:39:02,440
Now, in the rubber hand illusion, what happens is the guy in blue, his real hand is hidden from sight.

398
00:39:02,440 --> 00:39:07,720
Behind this put partition and then a fake rubber hand is placed in front of him.

399
00:39:08,470 --> 00:39:09,820
Um, and he's looking at that.

400
00:39:09,940 --> 00:39:17,710
Then the experiment in green takes two paintbrushes and [INAUDIBLE] stroke both hands simultaneously while the guy's looking at the fake hand.

401
00:39:18,070 --> 00:39:20,500
And what happens, um, for most people,

402
00:39:20,830 --> 00:39:29,200
is that they start to experience a rather uncanny sensation that maybe this rubber hand is in some way part of the body.

403
00:39:30,110 --> 00:39:32,000
And that's the best way to test whether it's working or not.

404
00:39:35,770 --> 00:39:40,270
Um, now, the standard story told about this is that I can't resist a bit of a diversion here.

405
00:39:40,270 --> 00:39:46,839
The standard story told about this is that the bright. It's to do with integration of senses from different modalities.

406
00:39:46,840 --> 00:39:51,700
So you've got vision and you've got touch, and the brain sees this hand and it feels the touch.

407
00:39:51,700 --> 00:39:57,070
So it puts them together and, and comes to the conclusion that the rubber hand is in your hand.

408
00:39:57,460 --> 00:40:01,630
Um, but there's another story actually, which is, which is also part of it.

409
00:40:01,630 --> 00:40:09,040
My colleague at Sussex, Peter Lush, for a number of years has been pointing out that, um, in the rubber hand illusion,

410
00:40:09,040 --> 00:40:14,319
you're basically in a situation where you're strongly encouraged that you should experience something weird.

411
00:40:14,320 --> 00:40:18,309
You know, you've given a fake hand, ask to stare at it, and then asked, is it your hand?

412
00:40:18,310 --> 00:40:22,990
It's a very strong, um, example of what psychologists call demand characteristics.

413
00:40:22,990 --> 00:40:28,150
You're in a situation which is implicitly encouraging you to have a particular kind of experience.

414
00:40:28,420 --> 00:40:35,190
So to test this for Pete, did, uh, the rubber hand illusion on over 350 people at Sussex, uh,

415
00:40:35,200 --> 00:40:44,409
a couple of years ago and found that the degree to which people experienced it correlated with the, um, how hypnotised they were.

416
00:40:44,410 --> 00:40:47,440
We're all hypnotised, able uh, to some degree or other.

417
00:40:47,440 --> 00:40:52,150
It's not a good thing. It's not a bad thing. It's just it's just a thing. It's a stable psychological trait.

418
00:40:52,450 --> 00:40:58,689
And those people who were more suggestible, uh, experienced the rubber hand illusion to a stronger extent.

419
00:40:58,690 --> 00:41:02,139
So I think that tells us that that's at least part of the story.

420
00:41:02,140 --> 00:41:04,480
And it's very compatible with what I've been saying, too,

421
00:41:04,480 --> 00:41:10,930
because what it shows is that that kind of experimental context of the rubber hand allusion, it's a kind of expectation.

422
00:41:10,930 --> 00:41:14,380
You're giving the brain an expectation about what to experience.

423
00:41:14,620 --> 00:41:23,500
And so it does. So talks a bit about having a body and how that is actually something the brain constructs on the fly.

424
00:41:23,510 --> 00:41:32,240
There's also this experience of being a body, of being a living flesh and blood organism with emotions and moods.

425
00:41:32,690 --> 00:41:43,370
And I think at the base of all experience of self and possibly of all experience at all, this simple background feeling of being alive.

426
00:41:44,380 --> 00:41:51,430
Um, this experience of being a body. And this brings up another form of perception entirely, which is called interception.

427
00:41:51,430 --> 00:41:58,770
Interception is rather overlooked in in science, psychology, neuroscience, but is very important.

428
00:41:59,090 --> 00:42:08,380
Interception is all about how the brain senses and controls the interior of the body because again, from the brain's perspective, the interior,

429
00:42:08,410 --> 00:42:17,260
interior, physiological states, the internal physiological state that's also not directly accessible, the brain locked away in its bony skull.

430
00:42:18,040 --> 00:42:22,180
And if it's trying to figure out what the heart is doing, what how the how the lungs are doing,

431
00:42:22,660 --> 00:42:31,510
it has to infer that make a best guess about it on the basis of, um, sensory input and its prior expectations.

432
00:42:31,510 --> 00:42:42,729
So now we have the same dance of prediction and prediction error, but now it's all taking place or largely taking place inside the body itself.

433
00:42:42,730 --> 00:42:47,650
The brain is making predictions about what's happening in the body and updating those predictions.

434
00:42:48,400 --> 00:42:55,040
So what happens when it does this? What? When the brain does this out there in the world, we might experience objects and people and places.

435
00:42:55,040 --> 00:43:03,930
But what happens when the brain is making predictions about the heart or the lungs, or the overall physiological condition of the body itself?

436
00:43:03,950 --> 00:43:10,010
Basically, how good a job it's doing is staying alive. Well, the idea here is that that's what emotion is.

437
00:43:11,240 --> 00:43:17,150
Now again, we tend or there's been a tendency to think of emotion is very different kind of thing.

438
00:43:17,180 --> 00:43:25,100
Now we have thought, we have perception. We have emotion. The the overall picture that that's emerging here is that these are all aspects

439
00:43:25,100 --> 00:43:28,910
of the same underlying process of the brain making and updating predictions.

440
00:43:29,210 --> 00:43:37,880
And when it comes to emotion, these predictions are about the interior of the body, that that's what an emotion is on this view.

441
00:43:38,330 --> 00:43:43,520
William James again said something very similar and sort of slightly flowery Victorian language.

442
00:43:43,520 --> 00:43:48,230
He said bodily changes followed directly the perception of the exciting fact,

443
00:43:48,410 --> 00:43:52,670
and there are feeling of these same changes as they occur is the emotion.

444
00:43:54,950 --> 00:43:57,060
The intuition here is that here's the key.

445
00:43:57,080 --> 00:44:05,180
And the example that William James famously gave was if somebody sees a bear and they feel the frightened run away, what's happening?

446
00:44:05,420 --> 00:44:12,800
It could be that they see the bear that causes them to feel afraid, and the feeling of fear causes them to run away.

447
00:44:13,430 --> 00:44:17,720
But what James said and what what's what I think is happening also in this story,

448
00:44:18,050 --> 00:44:23,420
is that the person sees the bear that immediately induces all kinds of changes in the body.

449
00:44:23,600 --> 00:44:26,930
Adrenaline starts coursing. Cortisol shoots around.

450
00:44:27,320 --> 00:44:31,250
Heart rate goes up. And it's the perception of those changes.

451
00:44:31,760 --> 00:44:37,700
That is the emotion of fear. So it's kind of flipping things around.

452
00:44:38,090 --> 00:44:42,380
Once again, things between how things seem and how they are.

453
00:44:43,880 --> 00:44:49,210
Now there's another. Final aspect of this story, which I think sort of fleshes out a little bit.

454
00:44:49,230 --> 00:44:55,890
So why do emotions feel the way they are and sort of visual experience feels a different way?

455
00:44:56,250 --> 00:44:59,280
Well, these predictions about the interior of the body.

456
00:45:00,200 --> 00:45:04,070
You know that they don't care where things are. They're not about figuring out what's out there in the world.

457
00:45:04,100 --> 00:45:07,310
They really care about controlling and regulating the body.

458
00:45:07,670 --> 00:45:13,639
That that's that's what, um, this process is fundamentally, um, doing.

459
00:45:13,640 --> 00:45:17,510
It's for keeping the body in the States compatible with being alive,

460
00:45:17,510 --> 00:45:22,430
keeping heart rate where it needs to be, keeping blood pressure right where it needs to be, and so on.

461
00:45:23,000 --> 00:45:27,170
So introspective predictions are about controlling things rather than finding things out.

462
00:45:27,170 --> 00:45:29,750
When you can predict something, you can control it pretty well.

463
00:45:30,380 --> 00:45:35,390
So the idea here is that's actually why the brain is a prediction machine in the first place,

464
00:45:35,390 --> 00:45:43,880
because that basic process evolved to keep the body alive, to provide an effective way of regulating the body.

465
00:45:44,210 --> 00:45:49,210
Now, there are many other kind of lines of work that support that, which I'll just skip over.

466
00:45:49,220 --> 00:45:55,340
But it's it's sort of has ancestry in many different areas of psychology and neuroscience.

467
00:45:56,280 --> 00:46:02,440
But I think it explains quite nicely why different experiences are the way they are and not some other way.

468
00:46:02,460 --> 00:46:08,820
Visual predictions underpin visual experiences with objects and people, because that's what those predictions are trying to do.

469
00:46:08,820 --> 00:46:12,360
They're trying to figure out where things are, how they're moving, what they are,

470
00:46:12,810 --> 00:46:21,360
but intercept if predictions underpin emotions and this simple feeling of being alive, because that's what these predictions are all about.

471
00:46:21,600 --> 00:46:24,600
They're about controlling, regulating the body.

472
00:46:25,380 --> 00:46:31,950
Now I'm cutting a long story very short here, but if you pull this thread long enough, I at least for me,

473
00:46:31,950 --> 00:46:41,250
you get to this kind of picture where conscious experience and consciousness itself is intimately related to our nature as living systems.

474
00:46:41,550 --> 00:46:51,480
Because these, this, this whole, um, edifice of the brain is a prediction machine evolved over many millions of years,

475
00:46:51,480 --> 00:46:59,490
develops in each of us, and operates moment to moment in light of this fundamental biological imperative to stay alive.

476
00:46:59,490 --> 00:47:02,969
The reason the brain makes predictions about the world and updates them is

477
00:47:02,970 --> 00:47:07,980
because that circuitry has been there from the get go to keep the body going.

478
00:47:07,980 --> 00:47:13,830
So consciousness in this case, less to do with something like intelligence, more to do with something like being alive.

479
00:47:15,370 --> 00:47:22,029
And this brings me to René Descartes. René Descartes, one of the most famous philosophers of all time,

480
00:47:22,030 --> 00:47:27,540
and cause all sorts of mischief in the philosophy of mind by separating the mind and the body.

481
00:47:27,580 --> 00:47:34,450
And we've struggled to put them back together ever since. But he also separated life from consciousness.

482
00:47:35,110 --> 00:47:39,930
And, um, it's called being a beast machine because he was listening to what he wrote.

483
00:47:39,940 --> 00:47:44,739
He was quite uncharitable about whether non-human animals were conscious.

484
00:47:44,740 --> 00:47:48,820
He called them beast machines. He said, without minds to direct their bodily movements.

485
00:47:49,210 --> 00:47:54,610
Animals must be regarded as unthinking, unfeeling machines that move like clockwork.

486
00:47:55,120 --> 00:48:02,290
So for Descartes, being alive was irrelevant to consciousness or to the kind of consciousness that that matters.

487
00:48:02,950 --> 00:48:07,120
And I've come to think almost the opposite is the case,

488
00:48:07,750 --> 00:48:16,270
that being alive is why we are also conscious that we perceive and experience the world around us and ourselves within it,

489
00:48:16,540 --> 00:48:21,000
with, through, and because of our living bodies.

490
00:48:21,010 --> 00:48:25,810
We are not kind of meat based computers. We are feeling machines.

491
00:48:27,760 --> 00:48:36,459
So I want to finish just the next five minutes. By talking about consciousness in other things, and especially in artificial intelligence,

492
00:48:36,460 --> 00:48:43,420
because I think this view of consciousness is intimately tied to our natures living systems has seen some interesting things to say about us.

493
00:48:44,080 --> 00:48:47,260
So the idea of AI has been with us for a long time.

494
00:48:47,260 --> 00:48:49,420
All those are very, very much more prominent now.

495
00:48:49,990 --> 00:48:56,740
And the idea that I could become not only smart but also conscious has also been around for a long time.

496
00:48:56,740 --> 00:49:03,400
Alan Turing, who basically gave us the many of ideas about computation as we use them now,

497
00:49:03,790 --> 00:49:11,380
also seeded the idea that I could be conscious when he asked the famous question whether machines can think, um.

498
00:49:11,800 --> 00:49:18,730
And in doing this, he also tied consciousness in AI to something that we might call intelligence,

499
00:49:18,880 --> 00:49:22,990
thinking, you know, if an AI can think, maybe it's conscious.

500
00:49:22,990 --> 00:49:27,819
We see this also in a lot of science fiction, whether it's how from 2001,

501
00:49:27,820 --> 00:49:34,330
in intelligence here and consciousness are bound up not with a body, but with this kind of disembodied mind.

502
00:49:34,750 --> 00:49:36,940
Ex Machina, a brilliant film by Alex Garland,

503
00:49:36,940 --> 00:49:45,100
also plays beautifully with this idea of artificial intelligence becoming conscious and for a long time, these.

504
00:49:46,190 --> 00:49:56,180
These ideas, these these possibilities of building machines that had experience, that were sentient was the realm of literature and science fiction.

505
00:49:56,630 --> 00:50:00,470
But now it seems we might actually be able to do that.

506
00:50:00,470 --> 00:50:02,660
And in fact, some people think we're already there.

507
00:50:02,660 --> 00:50:09,680
A couple of years ago, a Google engineer called Blake Lemoine got fired from Google because he claimed that the language model,

508
00:50:09,680 --> 00:50:12,830
the chat bot he was working on, was actually conscious.

509
00:50:13,310 --> 00:50:21,590
Not that many people took him that seriously, but the fact that he even, you know, raised the question with was itself pretty interesting.

510
00:50:21,680 --> 00:50:27,680
So there is this question here. Can artificial intelligence lead to real consciousness?

511
00:50:29,300 --> 00:50:34,610
Answering this question is fundamentally important because it has a huge number of ethical and moral implications,

512
00:50:34,610 --> 00:50:41,270
not only for how we treat AI systems, but for how we understand and deal with our own interactions with them.

513
00:50:41,780 --> 00:50:46,219
And the ground here is really muddy. I read this in the New Statesman last year.

514
00:50:46,220 --> 00:50:50,690
It was something just when there was a lot of fuss and bother about open AI,

515
00:50:51,200 --> 00:50:57,259
and in this paragraph talks about artificial general intelligence and says that, um,

516
00:50:57,260 --> 00:51:02,089
company documents state that the board's purpose is to decide when the company has developed highly

517
00:51:02,090 --> 00:51:07,819
autonomous artificial general intelligence that outperforms humans at most economically valuable work.

518
00:51:07,820 --> 00:51:12,410
And to ensure this technology reshaped society in a in a manner that's safe and benevolent.

519
00:51:12,530 --> 00:51:21,830
In other words, the board exists to decide when the machine is sentient, when it is alive, and to ensure the new consciousness is moral.

520
00:51:22,220 --> 00:51:26,180
So this is mixing all kinds of things together, which are actually very different.

521
00:51:26,180 --> 00:51:35,570
Consciousness is having an experience. Intelligence is doing the right thing at the right time, and being alive is something else altogether.

522
00:51:36,500 --> 00:51:45,260
So we get confused. I think talking about consciousness in AI, when we mix consciousness and intelligence together, they are very different things.

523
00:51:45,260 --> 00:51:51,980
They may correlate quite often in living creatures. The more intelligent you are, the more ways you have of being conscious.

524
00:51:52,460 --> 00:52:02,270
But fundamentally they're different concepts, and I think we confuse them because we're very susceptible to particular psychological biases.

525
00:52:02,270 --> 00:52:04,520
We tend to be very anthropocentric creatures.

526
00:52:04,760 --> 00:52:11,570
You know, we see the world through a human lens, and we think we're intelligent and we know we're conscious,

527
00:52:11,840 --> 00:52:15,440
so we tend to put the two together and confound them always.

528
00:52:15,440 --> 00:52:18,500
We're also very anthropomorphic creatures.

529
00:52:18,710 --> 00:52:26,450
We tend to project human like qualities into things on the basis of what might turn out to be superficial similarities,

530
00:52:26,750 --> 00:52:33,620
and that's become very prominent with this explosion of language models that we have.

531
00:52:33,860 --> 00:52:40,790
Because language, it seems to us, is something that is very distinctively human and very much associated with intelligence.

532
00:52:41,240 --> 00:52:43,820
So when something is able to speak to us fluently.

533
00:52:44,960 --> 00:52:52,760
It's very compelling for us to infer not only that it can speak to us fluently, which it can, but also that it is conscious.

534
00:52:52,770 --> 00:52:55,159
There's a conscious mind behind that,

535
00:52:55,160 --> 00:53:03,590
and I think that is much more a reflection of our biases than an accurate insight into what's going on inside these systems.

536
00:53:03,860 --> 00:53:07,190
By the way, it's often said that language models hallucinate when they make stuff up.

537
00:53:07,700 --> 00:53:12,860
That's part of the problem, too. When we say that we're already assuming something like having an experience.

538
00:53:13,130 --> 00:53:18,950
I think it's much more accurate to say they can. Fabulous. They make stuff up without knowing what they're doing.

539
00:53:20,810 --> 00:53:28,730
There's a deeper reason there, and a deeper reason why. I'm very sceptical of the whole idea that AI or computers could be conscious.

540
00:53:28,970 --> 00:53:34,820
And that's because the more you look at it, the more different brains are from computers.

541
00:53:35,180 --> 00:53:39,650
Now, in a in a computer, there's a very sharp distinction. Give you just one example.

542
00:53:40,670 --> 00:53:45,770
In a computer, there's a sharp distinction by design between the hardware and the software.

543
00:53:46,100 --> 00:53:50,370
What a computer does is independent of what it is.

544
00:53:50,390 --> 00:53:55,879
That's why computers are useful. And you can run the same program on different ones, and they do the same thing in a brain.

545
00:53:55,880 --> 00:54:00,830
There is no distinction between what we might call the mind where and the wetware.

546
00:54:01,040 --> 00:54:07,580
There's no sort of sharp threshold. You can't say what's in my brain and run it on somebody else's brain.

547
00:54:08,060 --> 00:54:12,710
Brains are very much more complicated than computers.

548
00:54:13,040 --> 00:54:22,670
And this this just. And when we reduce ourselves to a computer, I think we just really do a massive disservice to the to how rich,

549
00:54:22,940 --> 00:54:26,750
um, human brains and other animal brains really are.

550
00:54:27,940 --> 00:54:33,459
Now, if these ideas are a little bit on the right track, then it means that what we can do with computers and AI,

551
00:54:33,460 --> 00:54:40,300
we can certainly simulate consciousness, simulate intelligence and so on, but we can't necessarily can't implement it.

552
00:54:40,870 --> 00:54:46,239
And this is this is taken for granted in other things, like if we have computer simulations of weather systems,

553
00:54:46,240 --> 00:54:50,500
we never expect it to get wet or windy inside a computer simulation of a storm.

554
00:54:50,500 --> 00:54:52,270
Right? It just always a simulation.

555
00:54:53,050 --> 00:55:00,700
But for some reason we think that when we have a computer simulation of a brain, we will actually get consciousness out of it.

556
00:55:00,730 --> 00:55:03,760
And I think that's actually very unlikely.

557
00:55:04,270 --> 00:55:08,469
Um, now to finish, I might be wrong.

558
00:55:08,470 --> 00:55:09,790
There are still things to worry about.

559
00:55:09,790 --> 00:55:15,279
Many people disagree with me on this, and think that consciousness is the kind of thing that computers could have.

560
00:55:15,280 --> 00:55:22,250
There are many theories of consciousness. Many of them provide blueprints for how one might build a conscious machine.

561
00:55:22,290 --> 00:55:26,649
I think they're all on the wrong track in this sense. But I might be wrong.

562
00:55:26,650 --> 00:55:34,810
They might be right. And I just want to end by saying there are many reasons why we should not build conscious AI, even if it is very unlikely.

563
00:55:35,500 --> 00:55:39,160
Many reasons. But I think the main reason is that if for some reason we were able to,

564
00:55:39,700 --> 00:55:43,600
we would risk an ethical catastrophe because we would have introduced into the world

565
00:55:43,840 --> 00:55:48,790
a vast new potential for forms of suffering that we might not even recognise.

566
00:55:48,790 --> 00:55:56,589
It would be a very immoral, unethical thing to do. And even AI that seems conscious is also problematic.

567
00:55:56,590 --> 00:56:01,570
It is also bad. And that's almost already here, as we've seen with these language models.

568
00:56:01,990 --> 00:56:08,139
There's many other examples which which I'll skip, but we get ourselves into all kinds of moral quandaries.

569
00:56:08,140 --> 00:56:14,140
If we build technologies that seem conscious, even if they are not, because either we end up caring about them,

570
00:56:14,440 --> 00:56:18,610
even though they're just lifeless hunks of silicon and code, or we don't,

571
00:56:18,610 --> 00:56:24,309
and we treat them badly, even though we can't help feeling that they are conscious,

572
00:56:24,310 --> 00:56:28,900
there's this kind of potential for cognitively impenetrable illusions of consciousness here.

573
00:56:28,900 --> 00:56:32,950
You know, these two lines are different lengths, but you'll never be able to see them.

574
00:56:33,400 --> 00:56:36,610
Sorry, they're the same length, but you will never be able to see them as the same length.

575
00:56:36,610 --> 00:56:46,419
It's a cognitively impenetrable illusion. Same might go for I have a hunch we know we might not be able to avoid experiencing AI systems as conscious,

576
00:56:46,420 --> 00:56:52,659
and that gets us into these really difficult problems. One of my former mentors, the philosopher Daniel Dennett,

577
00:56:52,660 --> 00:56:59,080
who I think gave the first of these lectures 25 years ago, gives a nice thought, I think, which should guide us.

578
00:56:59,080 --> 00:57:02,740
Sadly, we lost Daniel Dennett this year. He died around April.

579
00:57:03,090 --> 00:57:10,450
Um, but he said we should treat AI as tools rather than colleagues and always remember the difference.

580
00:57:11,460 --> 00:57:15,690
I think that's very wise. We are much more than machines. We shouldn't sell ourselves so cheaply.

581
00:57:16,050 --> 00:57:18,840
Do you think that we can be replaced by a language model?

582
00:57:19,560 --> 00:57:24,389
But I want to finish on a more positive note and just point out that consciousness is not just this,

583
00:57:24,390 --> 00:57:29,780
um, this intellectual mystery that fascinates people like me for many years.

584
00:57:29,790 --> 00:57:38,339
It's also a mystery that matters. And that's why I think it's a particularly and important subject to study in medicine,

585
00:57:38,340 --> 00:57:42,510
a better understanding of consciousness to help us deal with conditions in psychiatry,

586
00:57:42,510 --> 00:57:49,770
in neurology, to address the mechanisms rather than just treating the symptoms in technologies not just AI, but also virtual reality.

587
00:57:49,770 --> 00:57:57,060
How we develop and interact with these technologies needs a deeper understanding of how we perceive and experience the world and the self.

588
00:57:57,510 --> 00:58:00,510
Society, which is facing all kinds of challenges, of course,

589
00:58:00,510 --> 00:58:07,830
will benefit from the ability to understand build bridges of empathy between people who experience things in different ways.

590
00:58:08,310 --> 00:58:16,800
We need to make decisions about how we treat non-human animals, um, and even how we treat people before birth.

591
00:58:16,980 --> 00:58:22,980
And at the end of life, too, all of these turn on what we can say about the possibility for consciousness in

592
00:58:23,010 --> 00:58:28,770
non-human animals and unborn humans and in people towards the end of life in law,

593
00:58:28,890 --> 00:58:32,760
when we hold people responsible, depends on what we think about free will.

594
00:58:33,150 --> 00:58:37,860
Now, do we have some consciousness that floats above the brain that makes us do things?

595
00:58:37,860 --> 00:58:41,720
No we don't. So it's a graded, more complex phenomenon.

596
00:58:41,730 --> 00:58:46,170
But of course, it matters when and how we hold people responsible for their actions.

597
00:58:46,800 --> 00:58:52,800
We can also think about how to make life better for those of us who aren't particularly ill or suffering,

598
00:58:52,800 --> 00:58:59,760
but just to cultivate more positive forms of conscious experience by understanding how they might arise.

599
00:59:00,300 --> 00:59:05,220
And again, to understand that we are much more than meat based computers.

600
00:59:05,550 --> 00:59:08,960
But fundamentally, consciousness is worth studying.

601
00:59:08,970 --> 00:59:11,730
It's a bit like the Everest of intellectual problems, really.

602
00:59:11,880 --> 00:59:21,410
It matters because it is there, and for me, it's a real privilege to try to understand this most deep, profound, but also personal of mysteries.

603
00:59:21,420 --> 00:59:22,920
So thank you very much for your attention.