Anil Seth How your brain invents your self TED
Transcriber:
Who am I? Who is anyone, really?
When I wake up in the morning
and open my eyes,
a world appears.
These days, since I’ve hardly
been anywhere,
it’s a very familiar world:
there’s the wardrobe
beyond the end of the bed,
the shuttered windows
and the shrieking of seagulls,
which drives Brighton residents
like me absolutely crazy.
But even more familiar
is the experience of being a self,
of being me,
that glides into existence
at almost the same time.
Now this experience
of selfhood is so mundane
that its appearance, usually,
just happens without us noticing at all.
We take our selves for granted,
but we shouldn’t.
How things seem is not how they are.
For most of us, most of the time,
it seems as though the self, your self,
is an enduring and unified entity –
in essence, a unique identity.
Perhaps it seems as though
the self is the recipient
of wave upon wave of perceptions,
as if the world just pours
itself into the mind
through the transparent
windows of the senses.
Perhaps it seems as though the self
is the decision-maker in chief,
deciding what to do next
and then doing it,
or, as the case may be,
doing something else.
We sense, we think and we act.
This is how things seem.
How things are is very different,
and the story of how and why this is so
is what I want to give you
a flavor of today.
In this story, the self is not the thing
that does the perceiving.
The self is a perception too,
or rather, it’s the collection
of related perceptions.
Experiences of the self and of the world
turn out to be kinds
of controlled hallucinations,
brain-based best guesses
that remain tied to the world and the body
in ways determined not by their accuracy,
but by their utility,
by their usefulness for the organism
in the business of staying alive.
Now the basic idea is quite simple,
and it goes back a very long way
in both science and philosophy –
all the way back, in fact, to Plato
and to the shadows cast by firelight
on the walls of a cave,
shadows which the prisoners within
took to be the real world.
Raw sensory signals,
the electromagnetic waves
that impinge upon our retinas,
the pressure waves
that assault our eardrums, and so on,
well, they’re always
ambiguous and uncertain.
Although they reflect
really existing things in the world,
they do so only indirectly.
The eyes are not transparent windows
from a self out onto a world,
nor are the ears,
nor are any of our senses.
The perceptual world that arises for us
in each conscious moment –
a world full of objects and people,
with properties like shape,
color and position –
is always and everywhere
created by the brain,
through a process
of what we can call “inference,”
of under-the-hood, neurally implemented
brain-based best guessing.
Now …
Here’s a red coffee cup.
When I see this red coffee cup,
when I consciously see it,
that’s because “red coffee cup”
is my brain’s best guess
of the hidden and ultimately unknowable
sensory signals that reach my eyes.
And just think about
the redness itself, for a moment.
Does the color red exist in the world?
No, it doesn’t.
And we don’t need neuroscience
to tell us this.
Newton discovered long ago
that all the colors we experience,
the rainbow of the visible spectrum,
are based on just a few wavelengths
of electromagnetic radiation,
which itself is, of course,
entirely colorless.
For us humans,
a whole universe of color is generated
from just three of these wavelengths,
corresponding to the three types
of cells in our retinas.
Color-wise, this thin slice of reality,
this is where we live.
Our experience of color –
indeed, our experience of anything –
is both less than and more than
whatever the real world really is.
Now what’s happening
when we experience color
is that the brain
is tracking an invariance,
a regularity in how objects
and surfaces reflect light.
It’s making a best guess,
a top-down, inside-out prediction,
about the causes
of the relevant sensory signals,
and the content of that prediction –
that’s what we experience as red.
Does this mean that red
is in the brain, rather than the world?
Well, no.
The experience of redness
requires both the world and a brain,
unless you’re dreaming,
but let’s not worry about that for now.
Nothing in the brain is actually red.
Cézanne, the great impressionist painter,
once said that color is where the brain
and the universe meet.
Now the upshot of all this
is that perceptual experience
is what I’ve come to call,
drawing on the words of others,
a “controlled hallucination.”
Now this is a tricky term,
prone to misunderstandings,
so let me be clear.
What I mean is that the brain
is continuously generating predictions
about the causes of sensory signals,
whether these come from the world
or from the body,
and the sensory signals themselves
serve as prediction errors,
reporting a difference
between what the brain expects
and what it gets,
so that the predictions
can be continuously updated.
Perception isn’t a process
of reading out sensory signals
in a bottom-up or outside-in direction.
It’s always an active construction,
an inside-out, top-down neuronal fantasy
that is yoked to reality
in a never-ending dance
of prediction and prediction error.
Now I call this process
controlled hallucination
to emphasize just this point.
All of our experiences
are active constructions
arising from within,
and there’s a continuity here,
between normal perception
and what we typically call hallucination,
where, for example, people might
see or hear things that others don’t.
But in normal perception,
the control is just as important
as the hallucination.
Our perceptual experiences
are not arbitrary.
The mind doesn’t make up reality.
While experienced colors
need a mind to exist,
physical things,
like the coffee cup itself,
exist in the world
whether we’re perceiving them or not –
it’s the way in which these things appear
in our conscious experience
that is always a construction,
always a creative act
of brain-based best guessing.
And because we all have different brains,
we will each inhabit our own distinctive,
personalized inner universe.
Now I’ve digressed quite far
from where we began,
so let me end by returning to the self,
to the experience of being you,
or being me.
They key idea here
is that the experience of being a self,
being any self,
is also a controlled hallucination,
but of a very special kind.
Instead of being about the external world,
experiences of selfhood are fundamentally
about regulating and controlling the body.
And what’s important here
is that the experiences of being a self
are composed of many different parts
that normally hang together
in a unified way,
but which can come apart in, for instance,
psychological or neurological disorders,
There are experiences of being
a continuous person over time,
with a name and a set of memories
shaped by our social
and cultural environments.
There are experiences of free will,
of intending to do something,
or of being the cause
of things that happen.
There are experiences
of perceiving the world
from a particular perspective,
a first-person point of view.
And then, there are deeply
embodied experiences,
for instance of identifying
with an object in the world
that is my body.
These hands, they’re my hands.
And then, of emotion and mood.
And at the deepest-lying,
most basal levels,
experiences of simply being a living body,
of being alive.
Now my contention
is that all these aspects of being a self
are all perceptual predictions
of various kinds.
And the most basic aspect
of being any self
is that part of perception
which serves to regulate the interior
of the body to keep you alive.
And when you pull on this thread,
many things follow.
Everything that arises in consciousness
is a perceptual prediction,
and all of our conscious experiences,
whether of the self or of the world,
are all deeply rooted in our nature,
as living machines.
We experience the world around us
and ourselves within it,
with, through and because
of our living bodies.
So who are you, really?
Think of yourself
as being like the color red.
You exist, but you might not be
what you think you are.
Thank you.
David Biello: A stand-in for the audience.
Anil Seth: David is clapping.
(Laughter)
AS: That makes me feel better.
DB: It was great. Thank you for that.
I have to say that the thought of my brain
floating around in a bony prison
is a disturbing one.
But how do all those billions
and trillions of neurons
give rise to this experience
of consciousness,
in your view?
AS: First, I mean,
consciousness is experience,
so I’d use the two terms
synonymously there.
It’s the same thing.
And by the way,
the idea of your brain wobbling around
in its bony vault of a skull
is presumably less disturbing
than it doing something else
and doing something
outside of the skull. (Laughter)
That would be the more worrying situation.
But the question, of course,
this is the big question.
You start off with a simple question,
“How does it all happen?”
And this is why there is
a long way to go here.
And there are, I think, two ways
to approach this mystery.
So the fundamental question here is …
What is it about a physical mechanism,
in this case, a neurobiological mechanism,
86 billion neurons
and trillions of connections,
that can generate
any conscious experience?
Put that way, it seems extremely hard,
because conscious experiences
seem to be the kinds of things
that cannot be explained
in terms of mechanisms,
however complicated
those mechanisms might be.
This is the intuition that David Chalmers
famously called “the hard problem.”
But my approach,
as hinted at in this talk,
is that we can characterize
different properties of consciousness –
what a perceptual experience is like,
what an experience of self is like,
what the difference between sleep
and wakefulness is like.
And in each of those cases,
we can tell a story
about how neural mechanisms
explain those properties.
In the part of the story
we’ve touched on today,
it’s all about predictive processing,
so the idea is that the brain
really does encode within it
a sort of predictive generative model
of the causes of signals from the world,
and it’s the content of those predictions
that constitutes
our perceptual experience.
And as we sort of develop and test
explanations like this,
the intuition is that this hard problem
of how and why neurons,
or whatever it is, in the brain,
can generate a conscious experience,
won’t be solved directly –
it will be dissolved.
It will gradually fade away
and eventually vanish
in a puff of metaphysical smoke.
DB: Katarina wants to talk
about anesthesia,
that experience of having
your consciousness kind of turned off.
What do we know about this ability
to switch a person off,
in a matter of seconds?
What is actually happening
there, do you think?
AS: Firstly, I think it’s one of the best
inventions of humanity, ever.
The ability to turn people into objects
and then back again into people –
I wouldn’t want to live
at a time in history without it.
Whenever we have this, like,
“Wouldn’t it be nice to live
in Greek antiquity or something,
when people swum around,
philosophizing, drinking wine?”
Yes, but what about anesthesia?
(Laughs)
That’s my response.
It does work, this is a fantastic thing.
How?
Here’s an enormous opportunity
for consciousness science,
because we know what anesthetics do
at a very local level.
We know how they act on different
molecules and receptors in the brain.
And of course, we know
what ultimately happens,
which is that people get knocked out.
And by the way,
it’s not like going to sleep.
Under general anesthesia,
you’re really not there.
It’s an oblivion comparable
with the oblivion before birth
or after death.
So the real question is,
“What is happening?”
How is the local action of anesthetics
affect global brain dynamics
so as to explain this disappearance
of consciousness?
And to cut a long story very short,
what seems to be happening
is that the different parts of the brain
become functionally disconnected
from each other,
and by that I mean,
they speak to each other less.
The brain is still active,
but communication between brain areas
becomes disrupted in specific ways.
and there’s still a lot we need to learn
about the precise ways
in which this disconnection happens –
what are the signatures
of the loss of consciousness?
There are many different
kinds of anesthetic,
but whichever variety
of anesthetic you take,
when it works, this is what you see.
DB: I think some folks such as Jasmine
and more anonymous folks
are troubled by this idea
that what I call red
might be a different color for you
and for everyone else.
Is there a way of knowing
if we’re all hallucinating reality
in a similar way or not?
AS: Again, this is a lovely topic,
and it really gets to the heart
of how I’ve been thinking
about perception,
because one of the aspects of perception
that I think is easy to overlook
is that the contents of perception
seem real, right?
The redness of this coffee cup,
it seems to be a mind-independent,
really existing property
of the external world.
Now, certain aspects of this coffee cup
are mind-independent.
Its solidity is mind-independent.
If I throw it at you, David,
across the Atlantic,
and you don’t see it coming,
it will hit you in the head, it will hurt.
That doesn’t depend on you seeing it,
but the redness does depend on a mind.
And to the extent
that things depend on a mind,
they’re going to be different
for each of us.
Now, they may not be that different.
In philosophy, there’s this argument
of the inverted spectrum,
so if I see red, is that the same
as you seeing green or blue, let’s say?
And we might never know.
I don’t have that much truck
with that particular thought experiment.
Like many thought experiments,
it pushes things a little bit too far.
I think the reality is that we see
things like colors,
maybe we see them similar,
but not exactly the same,
and we probably overestimate
the degree of similarity
between our perceptual worlds,
because they’re all filtered
through language.
I mean, I just used the word “red,”
and there are many shades of red;
painters would say, “What red?”
I remember when I was decorating my house,
it’s like, “I want to paint
the walls white.”
How many shades of white are there?
This is too many.
And they have weird names,
which doesn’t help.
We will overestimate
the similarity of our universe.
And I think it’s a really
interesting question,
how much they do indeed diverge.
You will probably remember
this famous dress,
this photo of a dress
half the world saw as blue and black,
and the other half saw as white and gold.
AS: You’re a white and gold person?
DB: Yeah, yeah.
AS: I’m a blue and black person.
I was right, the real dress
is actually blue and black.
(Laughter)
AS: Never mind …
DB: We could argue about that.
AS: We couldn’t.
It really is blue and black.
I talked to the dress designer.
The actual one is blue and black.
There’s no argument there.
But the thing that made that so weird
is that it’s not that we vaguely see it
as one color or the other,
we really see that blueness and blackness
or whiteness and goldness
as really existing in the world.
And that was an interesting lever
into a recognition of how different
our perceptual universes might be.
And in fact, a study we’re doing at Sussex
over the next year or two,
we’re trying to characterize
the amount of perceptual diversity
that is just there to be discovered.
We’re usually only aware of it
at the extremes,
people call things like neurodiversity,
where people have experiences
that are so different,
they manifest in different behaviors.
But I think there’s this,
sort of, big dark matter
of individual diversity in perception
that we know very little about,
but it’s there.
DB: I’m glad we could put to rest
a major internet debate
and come down firmly
on the blue and black side of things.
Daniella wants to know,
“Could you explain how memory is involved
in this perception of a self?”
AS: Just as there are many
different aspects of selfhood,
there are many different
kinds of memory, too.
I think colloquially,
in everyday language,
when we talk about memory,
we often talk about autobiographical
memory or episodic memory,
like “What did I have for breakfast?”
“When did I last go for a walk?”
These kinds of things.
“When did I last have the pleasure
of talking to David?”
These are the memories
of things that pertain to me
as a continuous individual over time.
That’s one way in which memory
plays into self,
and that part of memory can go away,
and self remains –
back to the earlier point.
There’s a famous case
I talk about in the book,
of a guy called Clive Wearing,
who had a brain disease,
an encephalopathy,
which basically obliterated his ability
to lay down new autobiographical memories.
He lost his hippocampus,
which is a brain region
very important for this function.
His wife described it as him living
in a permanent present tense,
of between seven to 30 seconds.
And then, everything was new.
It’s very, very difficult to put yourself
in the shoes of somebody like that.
But other aspects of his self remained.
But then, there are all sorts
of other aspects of memory
that probably also play into what it is
to be you or to be me.
We have semantic memory.
We just know things,
like we know what the capital
of France is, who the president is,
I hope so, I don’t know.
Sometimes, that’s a good thing.
Sometimes, that’s not a good thing.
And all of these things
that get encoded in memory
shape our self too.
And then finally,
there’s perceptual memory.
It’s not that experience is like a video
recording that we can replay,
but everything we experience changes
the way we perceive things in the future,
and the way we perceive things
is also, in my view,
part of what it is to be a self.
Actually, I just want to say,
one of the really interesting
questions here,
and one of the things we’re working on –
Imagine a typical day.
You go through your typical day,
you’re experiencing
a continuous stream of inputs.
Now you blink, of course,
and so on, but more or less,
there’s this continuous stream of inputs.
Yet when we remember a day,
it’s usually in chunks,
these autobiographical chunks:
“I did this, I did that,
I did the other, this happened.”
So a really important question
is, “How does this chunking
process happen?”
“How does the brain extract
meaningful episodes
from a relatively continuous
flow of data?”
And it’s kind of disturbing,
how little of any given day we remember.
So it’s a very selective process,
and that’s something
that I think is going to be useful
not only for basic neuroscience,
but, for instance, in helping people
with memory loss and impairments,
because you could, for instance,
have a camera,
and then, you could predict what aspects
of their day would constitute a memory,
and that can be very, very useful
for them and for their carers.
DB: The brain clearly has a good editor.
You call us, people,
“feeling machines” in your book.
Care to expand on that?
AS: Yeah, that’s right.
Well, we’re not cognitive computers,
we are feeling machines.
And I think this is true
at the level of making decisions,
but for me, it’s really at the heart
of how to understand life,
mind and consciousness.
And this, really, is the idea that –
In consciousness science,
we tended to think things like vision –
Vision as being the royal road
to understanding consciousness.
Vision is easy to study,
and we’re very visual creatures.
But fundamentally,
brains evolved and develop and operate
from moment to moment
to keep the body alive,
always in light of this deep
physiological imperative
to help the organism persist
in remaining an organism,
in remaining alive.
And that fundamental role of brains,
that’s what, in my view,
gave rise to any kind of perception.
In order to regulate something,
you need to be able to predict
what happens to it.
It’s this whole apparatus
of prediction and prediction error
that undergirds all
of our perceptual experiences,
including the self,
has its origin in this role
that’s tightly coupled
to the physiology of the body.
And that’s why, I think,
we’re feeling machines,
we’re not just computers
that happen to be implemented
on meat machines.
DB: Thank you, Anil,
for chatting with us today.
AS: Really enjoyed it.
AS: Thanks a lot, David.
DB: Thank you.