1
99:59:59,999 --> 99:59:59,999
Just over a year ago,

2
99:59:59,999 --> 99:59:59,999
for the third time in my life,

3
99:59:59,999 --> 99:59:59,999
I seized to exist.

4
99:59:59,999 --> 99:59:59,999
I was having a small operation,

5
99:59:59,999 --> 99:59:59,999
and my brain was filling with anesthetic.

6
99:59:59,999 --> 99:59:59,999
I remember a sense of detachment
and falling apart

7
99:59:59,999 --> 99:59:59,999
and a coldness.

8
99:59:59,999 --> 99:59:59,999
And then I was back,

9
99:59:59,999 --> 99:59:59,999
drowsy and disoriented,

10
99:59:59,999 --> 99:59:59,999
but definitely there.

11
99:59:59,999 --> 99:59:59,999
When you wake from a deep sleep,

12
99:59:59,999 --> 99:59:59,999
you might feel confused about the time
or anxious about oversleeping,

13
99:59:59,999 --> 99:59:59,999
but there's always a basic sense
of time having passed,

14
99:59:59,999 --> 99:59:59,999
of a continuity between then and now.

15
99:59:59,999 --> 99:59:59,999
Coming out from
anesthesia is very different.

16
99:59:59,999 --> 99:59:59,999
I could have been under for five minute,

17
99:59:59,999 --> 99:59:59,999
five hours,

18
99:59:59,999 --> 99:59:59,999
five years,

19
99:59:59,999 --> 99:59:59,999
or even 50 years.

20
99:59:59,999 --> 99:59:59,999
I simply wasn't there.

21
99:59:59,999 --> 99:59:59,999
It was total obliviion.

22
99:59:59,999 --> 99:59:59,999
Anesthesia --

23
99:59:59,999 --> 99:59:59,999
it's a modern kind of magic.

24
99:59:59,999 --> 99:59:59,999
It turns people into objects --

25
99:59:59,999 --> 99:59:59,999
and then we hope --

26
99:59:59,999 --> 99:59:59,999
back again into people.

27
99:59:59,999 --> 99:59:59,999
And in this process

28
99:59:59,999 --> 99:59:59,999
is one of the greatest remaining
mysteries in science and philosophy.

29
99:59:59,999 --> 99:59:59,999
How does consciousness happen?

30
99:59:59,999 --> 99:59:59,999
Somehow, within each or our brains,

31
99:59:59,999 --> 99:59:59,999
the combined activity
of many billions of neurons,

32
99:59:59,999 --> 99:59:59,999
each one a tiny biological machine,

33
99:59:59,999 --> 99:59:59,999
is generating a conscious experience.

34
99:59:59,999 --> 99:59:59,999
And not just any conscious experience --

35
99:59:59,999 --> 99:59:59,999
your conscious experience
right here and right now.

36
99:59:59,999 --> 99:59:59,999
How does this happen?

37
99:59:59,999 --> 99:59:59,999
Answering this question is so important

38
99:59:59,999 --> 99:59:59,999
because consciousness
for each of us is all there is.

39
99:59:59,999 --> 99:59:59,999
Without it, there's no world,

40
99:59:59,999 --> 99:59:59,999
there's no self,

41
99:59:59,999 --> 99:59:59,999
there's nothing at all.

42
99:59:59,999 --> 99:59:59,999
And when we suffer,

43
99:59:59,999 --> 99:59:59,999
we suffer conciously,

44
99:59:59,999 --> 99:59:59,999
whether it's through mental
illness or pain.

45
99:59:59,999 --> 99:59:59,999
And if we can experience
joy and suffering,

46
99:59:59,999 --> 99:59:59,999
what about other animals?

47
99:59:59,999 --> 99:59:59,999
Might they be conscious, too?

48
99:59:59,999 --> 99:59:59,999
Do they also have a sense of self?

49
99:59:59,999 --> 99:59:59,999
And as computers get faster and smarter,

50
99:59:59,999 --> 99:59:59,999
maybe there will come a point,

51
99:59:59,999 --> 99:59:59,999
maybe not too far away,

52
99:59:59,999 --> 99:59:59,999
when my iPhone develops a sense
of its own existence.

53
99:59:59,999 --> 99:59:59,999
I actually think the prospects
for a conscious AI are pretty remote.

54
99:59:59,999 --> 99:59:59,999
And I think this because
my research is telling me

55
99:59:59,999 --> 99:59:59,999
that consciousness has less to do
with pure intelligence

56
99:59:59,999 --> 99:59:59,999
and more to do with our nature
as living and breathing organisms.

57
99:59:59,999 --> 99:59:59,999
Consciousness and intelligence
are very different things.

58
99:59:59,999 --> 99:59:59,999
You don't have to be smart to suffer,

59
99:59:59,999 --> 99:59:59,999
but you probably do have to be alive.

60
99:59:59,999 --> 99:59:59,999
In the story I'm going to tell you,

61
99:59:59,999 --> 99:59:59,999
our conscious experiences
of the world around us,

62
99:59:59,999 --> 99:59:59,999
and of ourselves within it,

63
99:59:59,999 --> 99:59:59,999
are kinds of controlled hallucinations

64
99:59:59,999 --> 99:59:59,999
that happen with, through
and because of our living bodies.

65
99:59:59,999 --> 99:59:59,999
Now, you might have heard
that we know nothing

66
99:59:59,999 --> 99:59:59,999
about how the brain and body
give rise to consciousness.

67
99:59:59,999 --> 99:59:59,999
Some people even say it's beyond
the reach of science all together.

68
99:59:59,999 --> 99:59:59,999
But in fact,

69
99:59:59,999 --> 99:59:59,999
the last 25 years have seen an explosion
of scientific work in this area.

70
99:59:59,999 --> 99:59:59,999
If you come to my lab 
at the University of Sussex,

71
99:59:59,999 --> 99:59:59,999
you'll find scientists
from all different disciplines,

72
99:59:59,999 --> 99:59:59,999
and sometimes even philosophers.

73
99:59:59,999 --> 99:59:59,999
All of us together trying to understand
how conscioussness happens

74
99:59:59,999 --> 99:59:59,999
and what happens when it goes wrong.

75
99:59:59,999 --> 99:59:59,999
The strategy is very simple.

76
99:59:59,999 --> 99:59:59,999
I'd like you to think about consciousness

77
99:59:59,999 --> 99:59:59,999
in the way that we've
come to think about life.

78
99:59:59,999 --> 99:59:59,999
At one time,

79
99:59:59,999 --> 99:59:59,999
people thought the property
of being alive could not be explained

80
99:59:59,999 --> 99:59:59,999
by physics and chemisty.

81
99:59:59,999 --> 99:59:59,999
That life had to be more
than just mechanism.

82
99:59:59,999 --> 99:59:59,999
But people no longer think that.

83
99:59:59,999 --> 99:59:59,999
As biologists got on with the job

84
99:59:59,999 --> 99:59:59,999
of explaining the properties
of living systems

85
99:59:59,999 --> 99:59:59,999
in terms of physics and chemistry --

86
99:59:59,999 --> 99:59:59,999
things like metabolism, reproduction,
homeostasis --

87
99:59:59,999 --> 99:59:59,999
the basic mystery of what life is
started to fade away,

88
99:59:59,999 --> 99:59:59,999
and people didn't propose any more
magical solutions,

89
99:59:59,999 --> 99:59:59,999
like a force of life or an élan vital.

90
99:59:59,999 --> 99:59:59,999
So as with life,

91
99:59:59,999 --> 99:59:59,999
so with consciousness.

92
99:59:59,999 --> 99:59:59,999
Once we start explaining its properties

93
99:59:59,999 --> 99:59:59,999
in terms of things happening
inside brains and bodies,

94
99:59:59,999 --> 99:59:59,999
the apparently insoluble mystery
of what consciousness is

95
99:59:59,999 --> 99:59:59,999
should start to fade away.

96
99:59:59,999 --> 99:59:59,999
At least that's the plan.

97
99:59:59,999 --> 99:59:59,999
So let's get started.

98
99:59:59,999 --> 99:59:59,999
What are the properties of consciousness?

99
99:59:59,999 --> 99:59:59,999
What should a science
of consciousness try to explain?

100
99:59:59,999 --> 99:59:59,999
Well, for today I'd just like to think
of consciousness in two different ways.

101
99:59:59,999 --> 99:59:59,999
There are experiences
of the world around us,

102
99:59:59,999 --> 99:59:59,999
full of sights, sounds and smells,

103
99:59:59,999 --> 99:59:59,999
there's multisensory, panoramic,
3D, fully immersive inner movie.

104
99:59:59,999 --> 99:59:59,999
And then there's conscious self.

105
99:59:59,999 --> 99:59:59,999
The specific experience
of being you or being me.

106
99:59:59,999 --> 99:59:59,999
The lead character in this inner movie,

107
99:59:59,999 --> 99:59:59,999
and probably the aspect of consciousness
we all cling to most tightly.

108
99:59:59,999 --> 99:59:59,999
Let's start with experiences
of the world around us

109
99:59:59,999 --> 99:59:59,999
with the important idea of the brain
as a prediction engine.

110
99:59:59,999 --> 99:59:59,999
Imagine being a brain.

111
99:59:59,999 --> 99:59:59,999
You're locked inside a bony skull,

112
99:59:59,999 --> 99:59:59,999
trying to figure out what's
out there in the world.

113
99:59:59,999 --> 99:59:59,999
There's no lights inside the skull.

114
99:59:59,999 --> 99:59:59,999
There's no sound either.

115
99:59:59,999 --> 99:59:59,999
All you've got to go on is streams
of electrical impulses

116
99:59:59,999 --> 99:59:59,999
which are only indirectly related
to things in the world,

117
99:59:59,999 --> 99:59:59,999
whatever they may be.

118
99:59:59,999 --> 99:59:59,999
So perception --

119
99:59:59,999 --> 99:59:59,999
figuring out what's there --

120
99:59:59,999 --> 99:59:59,999
has to be a process of informed guess work

121
99:59:59,999 --> 99:59:59,999
in which the brain combines
these sensory signals,

122
99:59:59,999 --> 99:59:59,999
with its prior expectations or beliefs
about the way the world is

123
99:59:59,999 --> 99:59:59,999
to form its best guess of what
caused those signals.

124
99:59:59,999 --> 99:59:59,999
The brain doesn't hear sound or see light.

125
99:59:59,999 --> 99:59:59,999
What we perceive is its best guess
of what's out there in the world.

126
99:59:59,999 --> 99:59:59,999
Let me give you a couple
of examples of all this.

127
99:59:59,999 --> 99:59:59,999
You might have seen this illusion before,

128
99:59:59,999 --> 99:59:59,999
but I'd like you to think
about it in a new way.

129
99:59:59,999 --> 99:59:59,999
If you look at those two patches, A and B,

130
99:59:59,999 --> 99:59:59,999
they should look to you to be
very different shades of gray, right?

131
99:59:59,999 --> 99:59:59,999
But they are in fact
exactly the same shade.

132
99:59:59,999 --> 99:59:59,999
And I can illustrate this.

133
99:59:59,999 --> 99:59:59,999
If I put up a second version
of the image here,

134
99:59:59,999 --> 99:59:59,999
and join the two patches
with a gray-colored bar,

135
99:59:59,999 --> 99:59:59,999
and you can see there's no difference.

136
99:59:59,999 --> 99:59:59,999
It's exactly the same shade of gray.

137
99:59:59,999 --> 99:59:59,999
And if you still don't believe me,

138
99:59:59,999 --> 99:59:59,999
I'll bring the bar across
and joing them up.

139
99:59:59,999 --> 99:59:59,999
It's a single colored block of gray,

140
99:59:59,999 --> 99:59:59,999
there's no difference at all.

141
99:59:59,999 --> 99:59:59,999
So this isn't any kind of magic trick.

142
99:59:59,999 --> 99:59:59,999
It's the same shade of gray,

143
99:59:59,999 --> 99:59:59,999
but take it away again,

144
99:59:59,999 --> 99:59:59,999
and it looks different.

145
99:59:59,999 --> 99:59:59,999
So what's happening here

146
99:59:59,999 --> 99:59:59,999
is that the brain is using
its prior expectations

147
99:59:59,999 --> 99:59:59,999
built deeply into the circuits
of the visual cortex

148
99:59:59,999 --> 99:59:59,999
that a cast shadow dims
the appearance of a surface,

149
99:59:59,999 --> 99:59:59,999
so that we see B as lighter
than it really is.

150
99:59:59,999 --> 99:59:59,999
Here's one more example,

151
99:59:59,999 --> 99:59:59,999
which shows just how quickly
the brain can use new predictions

152
99:59:59,999 --> 99:59:59,999
to change what we consciously experience.

153
99:59:59,999 --> 99:59:59,999
Have a listen to this.

154
99:59:59,999 --> 99:59:59,999
([Sound])

155
99:59:59,999 --> 99:59:59,999
Sounded strange, right?

156
99:59:59,999 --> 99:59:59,999
Have a listen again and see
if you can get anything.

157
99:59:59,999 --> 99:59:59,999
([Sound])

158
99:59:59,999 --> 99:59:59,999
Still strange.

159
99:59:59,999 --> 99:59:59,999
Now listen to this.

160
99:59:59,999 --> 99:59:59,999
Recording: I think breakfast
is a really terrible idea.

161
99:59:59,999 --> 99:59:59,999
(Laughter)

162
99:59:59,999 --> 99:59:59,999
Which I do.

163
99:59:59,999 --> 99:59:59,999
So you heard some words there, right?

164
99:59:59,999 --> 99:59:59,999
Now listen to the first sound again.

165
99:59:59,999 --> 99:59:59,999
I'm just going to replay it.

166
99:59:59,999 --> 99:59:59,999
([Recording])

167
99:59:59,999 --> 99:59:59,999
Yeah?

168
99:59:59,999 --> 99:59:59,999
(Laughter)

169
99:59:59,999 --> 99:59:59,999
So you can now hear words there.

170
99:59:59,999 --> 99:59:59,999
One more more for luck.

171
99:59:59,999 --> 99:59:59,999
([Recording])

172
99:59:59,999 --> 99:59:59,999
OK, so what's going on here?

173
99:59:59,999 --> 99:59:59,999
The remarkable thing is the sensory
information coming into the brain

174
99:59:59,999 --> 99:59:59,999
hasn't changed at all.

175
99:59:59,999 --> 99:59:59,999
All that's changed is your
brain's best guess

176
99:59:59,999 --> 99:59:59,999
of the causes of that sensory information.

177
99:59:59,999 --> 99:59:59,999
And that changes what you
consciously hear.

178
99:59:59,999 --> 99:59:59,999
All this puts the brain
basis of perception

179
99:59:59,999 --> 99:59:59,999
in a bit of a different light.

180
99:59:59,999 --> 99:59:59,999
Instead of perception depending largely
on signals coming into the brain

181
99:59:59,999 --> 99:59:59,999
from the outside world,

182
99:59:59,999 --> 99:59:59,999
it depends as much,

183
99:59:59,999 --> 99:59:59,999
if not more,

184
99:59:59,999 --> 99:59:59,999
on perceptual predictions flowing
in the opposite direction.

185
99:59:59,999 --> 99:59:59,999
We don't just passively
perceive the world,

186
99:59:59,999 --> 99:59:59,999
we actively generate it.

187
99:59:59,999 --> 99:59:59,999
The world we experience comes
as much if not more

188
99:59:59,999 --> 99:59:59,999
from the inside out

189
99:59:59,999 --> 99:59:59,999
as from the outside in.

190
99:59:59,999 --> 99:59:59,999
Let me give you one more
example of perception

191
99:59:59,999 --> 99:59:59,999
as this active, constructive process.

192
99:59:59,999 --> 99:59:59,999
Here we've combined immersive
virtual reality with image processing

193
99:59:59,999 --> 99:59:59,999
to simulate the effects of overly
strong perceptual predictions

194
99:59:59,999 --> 99:59:59,999
on our experience.

195
99:59:59,999 --> 99:59:59,999
In this panoramic video,

196
99:59:59,999 --> 99:59:59,999
we've tranformed the world --

197
99:59:59,999 --> 99:59:59,999
which is in this case Sussex Campus --

198
99:59:59,999 --> 99:59:59,999
into a psychedilic playground.

199
99:59:59,999 --> 99:59:59,999
We've processed the footage using
an alogrithm based on Google's Deep Dream